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Knowing others is intelligence; knowing yourself is true wisdom. Mastering others is strength; mastering yourself
is true power.
— Lao Tzu
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FOREWORD
As a foreword, I would like to express that the source of inspiration behind the crea- tion of this book is Prof. K. Sambamurthy. He is among those pioneers who started the Biotechnology Department in Andhra University, Visakhapatnam. He also held the most coveted status of being the Emeritus Fellow, University Grants Commission, New Delhi.
His first book Pharmaceutical Engineering was a great success in India and abroad. The great response from the students and professors encouraged him to initiate another book on Pharmaceutical Biotechnology but unfortunately his sudden untimely demise stopped the progress of the book half way through.
His dreams are being fulfilled by Prof. Asuthosh Kar who has taken a lot of trouble and interest in the development and completion of the book.
My heart felt thanks and gratitude to Prof. Asuthosh Kar for making my husband’s dream a reality.
I hope and believe that this book would be of great help to the students in the disci- pline of pharmaceutical sciences.
Smt. K. Sambamurthy
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PREFACE
Biotechnology essentially and predominantly deals with the meticulous application of living organisms or their corresponding products in a variety of large-scale industrial processes. Besides, biotechnology is extremely multidisciplinary in nature ; it has its foundations and domain prominently spread in a wide spectrum of fields, such as : pharmaceutical sciences, microbiology, biology, biochem- istry, molecular biology, genetics, genomics, genetic engineering, chemistry, and chemical and process engineering. Therefore, it may be genuinely and rightly regarded as a series of ‘enabling technologies’ embracing the practical application of host specific organisms and their respective cellular components to either environmental management or to manufacturing and service industries.
Interestingly, from a historical aspect biotechnology could be regarded as a pragmatic, realistic, and tangible strategy to an ‘art’ more than a ‘science’, which may be enormously exemplified and duly expatiated in the commercial production of wines, beers, cheeses, and the like, whereby the modus operandi of various techniques involved were well-known and reproducible, but the exact molecular mechanisms were not known adequately. Nevertheless, at present biotechnology is passing through an amazing growth phase whose ultimate destiny is not too far in sight. With the advent of major advances in the better in-depth knowledge of ‘microbiology’ and ‘biochemistry’, these molecular mechanisms (viz., processes) have been rendered more logically understandable.
Pharmaceutical Biotechnology, based entirely on modern biotechnological techniques, as to date encompass a wider range of altogether newer medicinal compounds, e.g., antibiotics, vaccines, and monclonal antibodies (MABs) that may now be produced commercially using well-defined, optimized, and improved fermentative methodologies. In fact, genetic engineering has brought in a sea change by virtue of the directed construction of microorganisms resulting in a plethora of newer life-saving drugs.
The present textbook on ‘Pharmaceutical Biotechnology’ is strictly developed, structured, ex- panded, and expatiated along the guidelines provided by AICTE syllabus for B. Pharmacy–2000. It essentially consists of five main chapters, namely : Immunology and Immunological Preparations ;
Genetic Recombination ; Antibiotics ; Microbial Transformations ; and Enzyme Immobilization.
In addition to this, there are five auxilliary chapters, namely : Advent of Biotechnology ; Biosensor
Technology ; Bioinformatics and Data Mining ; Regulatory Issues in Biotechnology ; and Safety
in Biotechnology, which have been duly included so as to stimulate the students’ interest and expand their knowledge.
Each chapter has been carefully and adequately supported with a brief introductory note, fol- lowed by theoretical aspects, graphics, neat well-labeled diagrams, explanations, discussions, and pro- fusely supplemented with appropriate examples to make the relevance of each topic more comprehensi- ble to the students of Pharmacy both in India and abroad.
It is earnestly believed that students, learning Pharmaceutical Biotechnology will certainly find this text not only useful but also a good companion for further pursuit of higher knowledge. Besides, research scientists, teachers, food technologists, industrial technical personnels, postgraduate students involved in ‘industrial microbiology’ shall definitely be benefitted from this practical approach to the broader horizons of biotechnology.
The authors solemnly believe that this modern, well documented, lucid and easy presentation of topics contained in the textbook on ‘Pharmaceutical Biotechnology’ will prove to be of immense value to students, teachers, and practising researchers.
K. SAMBAMURTHY
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CONTENTS
1. Immunology and Immunological Preparations ...
1. Introduction ...
2. Principles ...
3. Antigens and Haptens ...
3.1. Antigens ...
3.2. Haptens ...
4. Immune Systems ...
4.1. Manipulation of Immune System ...
4.2. Types of Immunity ...
4.2.1. Humoral Immunity ...
4.2.1.1. B Lymphocytes
4.2.1.2. Immunological Peptides (IDPs)
4.2.1.3. Antigen Presenting Cell (APC)
4.2.1.4. T Cell Subsets
4.2.1.5. Class II MHC (Major histocompatibility complex) proteins
4.2.2. Cell-Mediated Immunity (CMI) ...
4.2.2.2. Privileged graft Sites
4.2.2.3. Graft-Vs-Host Disease (GVHD)
4.2.3. Innate (or Natural Immunity) ...
4.2.4. Acquired Immunity ...
4.2.4.1. Actively Acquired Immunity
4.2.4.2. Passively Acquired Immunity
4.2.5. Non-Specific Immunity ...
5. Antigen Antibodies Reactions and their Applications ...
5.1. Antigen Antibodies Reactions ...
5.1.3. Immunoglobulins as Antigens ...
5.1.4. Structure of Antibody ...
g 5.1.4.1. I
A Molecule
g 5.1.4.2. I
G Molecule
5.1.4.3. Glycosylation of Antibody (IgG)
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5.1.5. Monoclonal Antibodies (MABs) ...
5.1.5.1. MABs in Diagnostics ...
5.1.5.2. MABs in Imaging and Therapy ...
5.1.5.3. Production of Monoclonal Antibodies (MABs) ...
5.1.5.4. Application of Monoclonal Antibodies (MABs) ...
6. Hypersensitivity Reaction ...
6.1. Types of Hypersensitivity Reaction ...
6.1.1. Type-I : Anaphylactive Hypersensitivity ...
6.1.2. Type-II : Antibody Dependent Cytotoxic Hypersensitivity ...
6.1.3. Type-III : Complex Mediated Hypersensitivity ...
6.1.4. Type-IV : Cell-mediated or Delayed Type Hypersensitivity ...
6.1.5. Type-V : Stimulatory Hypersensitivity ...
7. Vaccines : Preparation, Standardization and Storage ...
7.3. Classification of Vaccines ...
7.3.1. Synthetic Peptide Vaccines ...
7.3.2. Multivaccine System ...
7.3.3. Bacterial Vaccines ...
7.3.5. Typhoid-Paratyphoid A and B Vaccine (TAB-Vaccine) ...
7.3.6. Other Bacteria Vaccines ...
7.3.7. Typhoid and Tetanus Vaccine ...
7.3.8. Anthrax Vaccine ...
7.3.9. Q-Fever Vaccine ...
7.3.10. Leprosy Vaccines ...
7.3.11. Whooping Cough Vaccine (Pertussis Vaccine) ...
7.3.12. Diphtheria Vaccines ...
7.3.13. Varicella-Zoster Vaccine ...
7.3.14. Viral and Rickettsial Vaccines ...
7.3.15. Smallpox Vaccine ...
7.3.16. Vaccines for Special Protection ...
7.3.17. Rabies Vaccines ...
7.3.18. Influenza Vaccine (Flu Fever Vaccine) ...
7.3.19. Inactivated Influenza Vaccine ...
7.3.19.1. Inactivated Influenza Vaccine (Split-Virion) ... 100
7.3.19.2. Inactivated Influenza Vaccine (Surface Antigen)
7.3.20. Polio Vaccine ... 101
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7.3.20.2. Sabin Type Polio Vaccine
7.3.20.3. Sabin Type Polio Vaccine
7.3.20.4. Inactivated Poliomyelitis Vaccine
7.3.20.5. Poliomyelitis Vaccine, Live (Oral)
7.3.21. Cancer Vaccine ... 106
7.3.22. Birth Control Vaccine for Women ... 106
7.3.23. AIDS-Vaccine ... 107
7.3.24. Pneumococcal Vaccine ... 109
7.3.25. Measles Vaccine, Live ... 109
7.3.25.1. Measles, Mumps and Rubella (MMR) Vaccine
7.3.25.2. Germanal Measles (Rubella) Vaccine
7.3.26. Meningococcal Polysaccharide Vaccine ... 111
7.3.27. Future Development Scope of Vaccines ... 112
7.3.27.1. Vaccine against Alzheimeir’s Disease
7.3.27.2. Vaccine for Meningitis C
7.3.27.3. Super Vaccine
7.3.27.5. Vaccination with Gas Lighter
7.3.27.6. Vaccine against Cervical Cancer
7.3.27.7. Vaccination without Needles
2. Genetic Recombination ... 119
1. Introduction ... 119
2. Transformation ... 122
2.1. Agrobacterium-Mediated Gene Transfer ... 122
2.1.1. Co-culture with Tissue Explants ... 122
2.1.2. In Planta Transformation ... 124
2.2. Agroinfection ... 125
2.3. Direct Gene Transfers ... 125
2.3.1. Chemical Methods ... 126
2.3.2. Electroporation ... 126
2.3.3. Particle Gun Delivery ... 128
2.3.7. Pollen Transformation ... 132
2.3.8. DNA Delivery via Growing Pollen Tubes ... 132
2.3.9. Laser-Induced Gene Transfer ... 133
2.3.10. Fibre-Mediated Gene Transfer ... 133
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2.3.11. Transformation by Ultrasonication ... 134
5. Protoplast Fusion ... 141
5.1. Spontaneous Fusion ... 141
5.2. Induced Fusion ... 142
5.2.1. Sodium Nitrate (NaNO 3 ) Treatment
5.2.2. Calcium Ions (Ca 2+ ) Treatment at High pH ... 145
5.2.3. Propylene Glycol (PEG) Treatment ... 145
5.2.4. Electrical Impulse (Fusion) ... 145
6. Gene Cloning ... 146
6.1. Cloning Process ... 147
6.1.1. DNA-Cloning ... 148
6.1.2. Cloning Larger DNA Fragments in Specified Cloning Vectors
6.1.3. Cloning Eukaryotic DNAs in Bacterial Plasmids ... 149
6.1.4. Cloning Eukaryotic DNAs Phase Genomes ... 151
6.1.5. Cloning cDNAs ... 153
6.1.6. Expression Cloning ... 155
6.1.7. Amplifying DNA : The Polymerase Chain Reaction (PCR) ... 155
7. Development of Hybridoma for Monoclonal Antibodies (MABs) ... 157
7.1. The Principle of Monoclonal Antibody Production ... 158
7.2. Cell Fusion ... 158
8. Drugs Produced by Biotechnology ... 161
8.1. Alteplase ... 162
8.2. Humulin ... 164
8.3. Humatrope : Growth Hormone ... 168
8.4. Hepatitis B [Recombinant HB (Merck)—A Hepatitis B Vaccine] ... 169
3. Antibiotics ... 173
1. Historical Development of Antibiotics ... 173
2. Antimicrobial Spectrum and Methods Used for their Standardization ... 174
2.1. Cylinder-Plate Method ... 179
2.2. Turbidimetric Method ... 179
3. Screening or Soil for Organisms Producing Antibiotics ... 179
3.1. Screening ... 181
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3.2. Secondary Screening ... 183
3.2.1. Methodology ... 183
3.2.2. Salient Features of Secondary Screening ... 184
4. Fermentors [or Bioreactors] ... 186
4.1. Salient Features of Bioreactors ... 188
4.2. Classifications ... 189
4.2.1. Solid State Fermentation ... 189
4.2.2. Anaerobic Fermentation ... 191
4.2.3. Aerobic Fermentation ... 192
4.2.3.1. Stirred-tank Type Fermentors (or Stirred Bioreactors)
4.2.3.2. Air-lift Type Fermentors ... 194
4.2.4. Immobilized Cell Bioreactors ... 194
4.2.4.1. Immurement Cultures ... 195
4.2.4.2. Entrapment Cultures ... 195
4.3. Design and Bioreactors (Fermentor Variants) ... 196
4.3.1. Fermacell (Laboratory) Fermentor ... 196
4.3.2. Bubble-Cap Fermentor ... 198
4.3.3. Loop (Recycle) Bioreactor ... 200
4.3.4. Tower Bioreactor ... 200
4.3.5. Activated Sludge Bioreactor ... 201
4.3.6. Continuous Flow Stirred Tank Bioreactor ... 202
4.3.7. Packed Bed Bioreactor ... 202
4.3.8. Trickling Film Bioreactor ... 203
4.3.9. Mist Bioreactor ... 204
4.3.10. Rotating Drum Bioreactor ... 205
4.3.11. Bubble Column Bioreactor ... 206
4.3.12. Commercial Fermentation Plant ... 207
5. Mutants ... 209
5.1. Isolation of Mutants ... 209
5.1.1. Method of Causing a Mutation ... 210
5.1.2. Somaclonal Variation ... 210
5.1.2.1. Isolation of Somaclonal Variants ... 210
5.2. Factor Influencing Rate of Mutation ... 214
5.2.1. Conditional Mutation ... 214
5.2.2. Radiation Induced Mutations ... 214
5.2.3. Effect of UV Radiation ... 215
5.2.4. Chemically Induced Mutations ... 216
5.2.5. Beneficial Mutation ... 219
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6. Design of Fermentation Processes ... 220
6.1. Quality of Water ... 220
6.2. Quality Control of Raw Materials ... 220
6.3. Nutritional Requirements ... 220
6.4. Sterilization Practices ... 221
6.5. Media Preparation ... 221
6.5.1. Solid Substrate Fermentation ... 222
6.5.2. Submerged Fermentation ... 222
6.5.3. Downstream Processing ... 224
6.5.4. Technology of Mammalian and Plant-cell Culture ... 225
6.5.5. Cell Recycle Technique ... 228
7. Production of Antibiotics (Isolation of Fermentation Products) ... 228
7.1. The Penicillins ... 230
7.1.1. Genes in Penicillin Biosynthesis ... 230
7.1.2. The Penicillin Variants ... 234
7.1.3. Production of Benzylpenicillins [Penicillin G] ... 235
7.1.3.1. Inoculum ... 235
7.1.3.2. Production Media ... 237
7.1.3.3. Biomass Production ... 237
7.1.3.4. Course of Typical Penicillin Fermentation ... 238
7.1.3.5. Penicillin Nucleus : Two Amino Acids ... 240
7.1.3.6. Role of Enzyme Penicillinase ... 241
7.1.3.7. Penicillin Production and Recovery ... 241
7.2. Streptomycin ... 244
7.2.1. Chemical Structure ... 245
7.2.2. Choicest Medium ... 246
7.2.3. Inoculum ... 247
7.2.4. Streptomycin Production ... 247
7.3. The Tetracyclines ... 248
7.3.1. Salient Features of the Tetracyclines ... 248
7.3.2. Nomenclatures ... 249
7.3.3. General Characteristics of the Tetracyclines ... 249
7.3.3.1. Tetracycline ... 251
7.4. Vitamin B 12 (Cyanocobalamine; Cobamide) ... 253
7.4.1. Vitamin B 12 from Propionobacterium Shermanii
7.4.2. Vitamin B 12 from Pseudomonas Denitrificans
8. Future Prospects ... 257
(xvii)
4. Microbial Transformations ... 261
1. Introduction ... 261
2. Types of Reactions Mediated by Microorganisms ... 262
2.1. Vinegar (Acetic Acid) Production ... 263
2.1.1. Traditional Method ... 263
2.1.2. Aerobic Fermentation Process ... 264
2.1.3. Orleans Process ... 265
2.1.4. Packed-Generator Process ... 265
2.1.5. Trickling Generator ... 269
2.1.6. Submerged Fermentor ... 271
2.2. Gluconic Acid Production ... 273
2.3. Antibiotic Production ... 275
2.4. Single-Cell Proteins (SCPs) from Methanol ... 275
2.5. Lactic Acid Production ... 278
2.6. Kojic Acid ... 281
2.7. Itaconic Acid ... 282
3. Design of Biotransformation Processes ... 283
3.1. Methodologies for Biotransformation ... 289
3.1.1. Growing Cultures ... 289
3.1.2. Resting Cells ... 291
3.1.3. Immobilized Cells ... 291
4. Selection of Organisms ... 291
5. Biotransformation Process and Its Improvements with Special Reference to Steroids
5.1. Biotransformation of Steroids ... 296
5.1.1. Types of Transformations/Biotransformations ... 298
5.1.2. Cost-Effective Viable and Important Transformations ... 298
5.1.3. Microbial Cleavage of Sterol-Side Chains (at C-17) ... 303
5.1.4. Mycobacterial Cleavage of Steroid Nucleus (Ring ‘B’) ... 303
5.2. Steroid Bioconversion via Fermentative Procedures ... 304
5. Enzyme Immobilization ... 309
1. Introduction ... 309
1.1. Salient Features ... 309
1.2. Carrier Matrices ... 310
2. Methods of Immobilization ... 310
2.1. Adsorption Method ... 310
2.2. Covalent Bonding ... 312
3. Factors Affecting Enzyme Kinetics ... 323
3.1. Enzyme Activity ... 324
3.2. Michaelis-Menten Constant [K m ] ... 326
3.2.1. Kinetics of ES-Complex Formation ... 326
3.2.2. Determination of K m ... 328
3.2.3. Kinetic Characteristic Features ... 329
3.2.4. Parameters Governing Enzymatic Reactions ... 330
3.2.4.1. Maximum Reaction Velocity (V max ) ... 331
3.2.4.2. pH Activity ... 331
3.2.4.3. Optimum Temperature (T opt ) ... 332
3.2.4.4. Stability ... 332
3.2.4.5. Dissociation Constants of Substrate (K s ) and Product (K p )
3.2.4.6. Turnover Number or Rate Constant [K cat ] ... 333
3.2.4.7. Michaelis Constant [K m ] ... 333
3.2.4.8. Specificity Constant [K cat /K m ] ... 333
3.2.4.9. Rate Enhancement [K cat /K non ] ... 333
3.2.4.10. Catalytic Proficiency [(K cat /K m )/K non ] ... 334
4. Profile of Some Important Enzymes ... 334
4.5.1. α -Amylases [Diastase] ... 339
4.5.2. β -Amylases ... 344
4.6. Proteases [Proteolytic Enzymes] ... 344
4.6.1. Alkaline Proteases ... 345
4.6.2. Neutral Proteases ... 346
4.6.3. Acid Proteases ... 347
4.6.4. Fungal Proteases ... 347
4.6.5. Bacterial Proteases ... 348
5. Immobilization of Bacteria and Plant Cells ... 351
5.1. Immobilization of Bacteria ... 352
5.2. Immobilization of Plant Cells ... 353
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6. Advent of Biotechnology ... 359
1. Introduction ... 359
2. Advances in Biotechnology ... 360
2.1. Alcohol Production ... 360
2.2. Algal Biotechnology (Food) ... 363
2.3. Biological Fuel Generation ... 364
2.4. Bioengineered Plant Materials ... 366
2.5. Bioextractive Metallurgy ... 367
2.6. Biopharmaceuticals (Pharmacobiotechnology Based Drugs) ... 368
2.7. Cheese Production ... 369
2.8. Indonesian Temph ... 370
2.9. Immunotoxins ... 370
2.10. Japanese Enzymes ... 371
2.11. Vegetative Products ... 372
2.12. Newer Approaches to Sewage Treatment ... 373
2.12.1. Classical Aerobic Activated Sludge Process ... 373
7. Biosensor Technology ... 377
1. Introduction ... 377
2. Types of Electrodes Used in Biosensors ... 380
2.1. Electrochemical Electrodes [Enzyme Electrodes] ... 380
2.2. Microbial Electrodes ... 381
3. Biosensor Variants ... 383
3.1. Alcohol Biosensor ... 383
3.2. Amorphous Silicon Biosensor ... 384
3.3. Glucose and Carbon Dioxide (CO 2 ) Biosensor
3.4. Hypoxanthine Biosensor ... 385
3.5. Inosine Biosensor ... 386
3.6. Image Biosensor ... 386
3.7. Integrated Multi-Biosensor ... 387
3.8. Urea Biosensor ... 388
3.9. Thermistor Containing Biosensor ... 389
3.10. Bioaffinity Sensor ... 389
3.11. Opto-Electronic Biosensor ... 390
4. Biochips (or The Biological Computer) ... 390
8. Bioinformatics and Data Mining ... 393
1. Introduction ... 393
2. Sequential Growth in Bioinformatics ... 395
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3. Web Services ... 397
4. Alignment Tools ... 399
4.1. Local Sequence Alignment Tools ... 399
4.2. Multiple Sequence Alignment Tools ... 402
5. Data Mining ... 403
5.1. Applications of Data Mining ... 404
6. Selected Organization vis-a-vis Interest in Bioinformatics ... 405
7. Wonders of Bioinformatics and Data Mining ... 405
8. Bioinformatics Information Centres in India ... 406
9. Regulatory Issues in Biotechnology ... 408
1. Introduction ... 408
1.1. Biosafety ... 409
1.2. Topic of Concern [Website of ICGEB] ... 411
1.3. Biosafety Guidelines and Regulations ... 412
1.4. Operation/Function of Biosafety Guidelines and Regulations ... 412
1.5. Development of Herbicide Resistant Crops ... 413
2. Intellectual Property Right (IPR) and Protection (IPP) ... 414
2.1. Types of IPR-Protection ... 416
2.1.1. Patents ... 416
2.1.2. Copyrights ... 417
2.1.3. Trade Secrets (Know-how) ... 417
2.1.4. Trade Marks ... 417
2.2. Status and Implication of IPR ... 418
2.3. Protection of Biotechnological Inventions ... 421
10. Safety in Biotechnology ... 423
1. Introduction ... 423
1.1. Biological Precautions ... 423
1.2. Chemical Precautions ... 424
1.3. Personal Precautions ... 425
2. Biosafety ... 426
3. Pathogenic Microorganisms and Fungi ... 427
3.1. Pathogenic Microorganisms ... 427
3.2. Pathogenic Fungi ... 427 Glossary
... 430 Index
CHAPTER IMMUNOLOGY AND IMMUNOLOGICAL PREPARATIONS
1. INTRODUCTION
The ‘science of immunology’ virtually saw the light of the day through the earnest efforts of Edward Jenner in 1798 who assumed to be true on the basis of reasoning that the value of ‘vaccination’ as a probable means of protection against the cowpox (vaccinia) ailment. In fact, it was Jenner who first and foremost suggested the protective means of ‘vaccination’ with non-virulent cowpox against small- pox infection. It is, however, pertinent to mention here that the science of immunology ultimately got its legitimate recognition as a branch of knowledge requiring systematic study and method only in 1881 when the entire universe witnessed an epoch making spate of progress put forward by two eminent scientists Louis Pasteur and Robert Koch. In reality, Pasteur’s development of a vaccine for anthrax i.e., an acute infectious disease caused by Bacillus anthracis, using attenuated organisms was enor- mously hailed by many scientists across the globe.
Elie Metchnikoff (1833)*, a noted Russian scientist spotted the pivoted role of phagocytes** in causing immunity in the course of an extensive and intensive research due to infection of the popular waterflea, Daphnia, by a specific fungus. Metchinkoff’s observations and findings put forward the well- known phagocytic theory, which essentially postulated that the prevailing ‘inflammatory responses’ in the human body were, in fact, the very outcome of numerous on-going cellular reactions instead of the vasculogenic reactions as suggested earlier by Julius Cohnhein. In short, the preliminary as well as the pioneering work of Metchinkoff not only proved adequately but also established the justified role of the cellular substances present in the blood in accomplishing pathogenic microorganisms to a significant extent.
Interestingly, Metchinkoff’s articulated concept and belief that ‘inflammation produced’ happen to be a ‘protective’ rather than a ‘destructive’ phenomenon. As on date, it has been recognized beyond any reasonable doubt that the phagocytic activity of human WBC designates the primary line of defence against invasion on the body by a host of pathogenic organisms. Virchow and Pfeiffer vehemently opposed Metchinkoff’s phagocytic theory based on their claim that the entire process caused solely due
* Metchinkoff E., (1893) : Comparative Pathology of Inflammation, Transl FA et. al., Trübner and Co., Lon- don.
** A cell e.g. leukocyte or microphage having the ability to ingest and destroy particulate substances, such as : bacteria, protozoa, cells and cell debris.
PHARMACEUTICAL BIOTECHNOLOGY
to the action of antibodies, which they ultimately laid as the fundamental foundation of the very under- standing of the ensuing immume bacteriolysis.
Salient Features of Metchnikoff’s Doctrine : The various salient features of Metchnikoff’s doctrine are, namely :
(a) importance of activated microphage, (b) latest concept that certain diseases are controlled by circulating antibodies, (c) ‘phagocytes’ (specialized cells) active participation in causing protection against other preva-
lent diseases, (d) ‘humoral antibodies’ responsible for the pathogenesis of autoimmune plus other immunogenic
ailments , and (e) certain diseases are also produced by cell-mediated reactions. Later on in 1890 Vohn Behring, duly recognized ‘antibodies’ present in serum to diphtheria
toxin. Denys and Leclef (1895) observed that phagocytosis invariably get enhanced by immunization to
a substantial extent. Bordet in 1899 observed that the lysis of cells by antibody essentially requires the earnest cooperation of various serum factors that are now collectively known as ‘complement’. Landsteiner in 1900, discovered the ABO antigens, a magnificent invention that eventually laid the foundation stone of the ‘science of serology’. Richet and Portier (1902) introduced the terminology ‘anaphylaxis’ i.e., opposite of prophylaxis. In 1903, Almorth Wright based on the clue derived from the ‘humoral theory’ propounded another theory termed as the ‘theory of opsonization’ in relation to opsonic activity to phagocytosis. In other words, it explains that antibodies as well as phagocytes are equally important and necessary to cause infectious diseases, and supplement each other in the com- plete eradication of pathogenic organisms. His remarkable research outputs conferred on him the Noble Prize in 1908. Almost after a lapse of 22 long years, Zinsser (1925) put forward a well-defined and explicite contrast between immediate and delayed-type hypersensitivity. Lastly, Heidelberger and Kendall (1930-35) carried out an elaborated ‘precipitin* studies’ an antigen-antibody interactions.
2. PRINCIPLES
The ‘science of immunology’ categorically deals with the specific mechanisms by which the living tissues invariably react to the so called foreign biological materials, such as : invading pathogenic microorganisms, so that ultimately either immunity or resistance gets developed in vivo to combat the dreadful diseases in the humans and animals. The credibility as well as the integrity of the defence mechanism system of the host, and in turn its ability to undergo critical and specific reaction(s) thereby counteract the possible invasion by microorganisms seems to be of prime and vital importance for the ultimate survival of the individual.
Obviously, the ‘foreign biological materials’ quite often gain entry into a living body through such barriers as : hair, skin or ruptured spaces. Consequently, the innate immune mechanisms of the body trigers its action to offer adequate protection required spontaneously, which is actually carried out by WBC or leucocytes. It has been duly observed that this particular mechanism is absolutely insuffi- cient to afford full protection in most of the instances commonly encountered ; and, therefore, the body does respond through an immune system.
* An antibody formed in the blood serum of an animal owing to the presence of a soluble antigen, usually a protein. When added to a solution of the antigen, it brings about precipitation. The injected protein is known
IMMUNOLOGY AND IMMUNOLOGICAL PREPARATIONS
In fact, the entire prevailing ‘immune system’ is essentially made up of cells and macromolecules that usually give rise to a rather complex network of cellular and molecular interactions so designed to negate the adverse effect caused by microorganisms and parasites. In other words, one may explain this intricate immune response as a mechanism explicitely exhibited either by humans or higher organisms, whereby a very critical as well as specific response is invariably drawn out against the probable inva- sion of well-defined pathogenic microorganisms and other foreign substances. Besides, it may also be regarded as a ‘specific physiological response’ which protects human beings against a plethora of dreadful diseases. Interestingly, the ensuing immune response is appreciably signified by memory, specificity and above all the capability to differentiate between ‘self’ from ‘non-self ’ at the molecular level even.
3. ANTIGENS AND HAPTENS
The two terminologies viz., antigens and haptens are intimately associated with immunology ; and, hence one may understand and have a clear concept about them as far as possible.
3.1. Antigens
An antigen is either a cell or molecule which will bind with preexiting antibody but will not definitely cause induction of antibody production.
Antigen may also be defined as — ‘a macromolecular entity that essentially elicits an immune response via the formation of specific antibodies in the body of the host’.
In a broader perspective the antigen (or immunogen*) is invariably regarded as the afferent branch of the prevailing immune system, as illustrated in Fig. 1.1 below, and is any cell or molecule which would provoke an immune response** very much in an immunologically viable and competent individual. Generally, immunogens (antigens) must fulfil the following two cardinal characteristic fea- tures, namely :
(a) should be larger than 2000 in molecular weight, e.g., protein, glycoprotein and carbohy- drates, and
(b) must be absolutely foreign to the individual into whom they have been introduced appropri- ately.
Fig. 1.1. Immune Mechanism.
* Sometimes, the term antigen is used synonymously with immunogen, although this usage is incorrect. ** Production of antibodies and/or sensitization of lymphoid cells.
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Example : The most befitting example of an ‘antigen’ is ones own erythrocytes (WBC). Be- cause, they will not induce antibody formation in oneself but will definitely react with an antibody essentially contained in an improperly matched blood transfusion.
It is, however, pertinent to state here that quite often an antigen is a protein, but it could also be
a polysaccharide or nucleic acid or any other substance. Importantly, it may also be possible that a foreign substance (e.g., protein)-not necessarily belonging to a pathogenic microorganism, may act as an antigen so that on being injected into a host, it may induce antibody formation. Besides, they may turn out to be antigenic and thereby cause stimulation of antibody production, incase they are intimately and lightly get bound to certain macromolecules, for instance : proteins, carbohydrates and nucleic acids.
3.2. Haptens
In usual practice, the relatively smaller, less rigid or rather less complex molecules usually are not immunogenetic in their purest form, but may be made so by simply linking them strategically to either larger or more complex structures. Consequently, the smaller molecules are invariably termed as haptens ; whereas, the larger molecules or cells are known as carriers.
Hapten may also be defined—‘as a substance that normally does not act as an antigen or stimu- late an immune response but that can be combined with an antigen and, at a later time, initiate a
specific antibody response on its own’. Furthermore, small molecules (micromolecular), such as : drug substances, that may serve as
‘haptens’ and can normally be made antigenic by coupling them chemically to a macromolecular substance e.g., protein, polysaccharide, carbohydrate etc. The hapten is obtained from a non-antigenic compound (micromolecule) e.g., morphine, carteolol etc., which is ultimately conjugated*, covalently to a carrier* macromolecule to render it antigenic.
Morphine should be first converted to the corresponding 3-o-carboxymethyl derivative prior to carbodiimides (CCD) coupling with albumin to provide a functional coupling moiety in the hapten.
Another glaring example is of gastrin (hapten) which is duly coupled to albumin (i.e., protein- carrier) by treatment with carbodiimides (CCD), which couple functional carboxyl, amino, alcohol, phosphate or thiol moieties.
Importantly, the hapten-conjugate thus obtained is normally subjected to emulsification in a highly refined ‘mineral oil’ preparation containing-killed Mycobacterium (Complete Freund’s
* Conjugate : The combined ‘hapten’ and ‘carrier’. ** Carrier : A protein, polypeptide, or inert matrix that is coupled to the hapten to form an antigen.
IMMUNOLOGY AND IMMUNOLOGICAL PREPARATIONS
Adjivant*), and subsequently injected intradermally either in healthy rabbits or guinea pigs on several occassions at intervals. Evidently, the serum antibody should have not only high degree of specificity but also a reasonably strong affinity for the prevailing antigens.
It has been observed that a relatively large variety of low molecular-weight chemical substances may cater for as allergenic haptens (partial immunogens) and induce allergy after combining covalently with an appropriate protein carrier. On one hand this serves as a vital and important phenomenon spe- cifically in drug allergy ; however, the most widely found ‘environmental allergens’. Perhaps the most notable exception in the instance of common allergic contact dermatitis produced by a variety of plants, drugs, clothing additives and other similar substances.
Examples : (a) Urshiols : The allergenic constituents i.e., the oleoresin fraction, derivatives of pentadecycatechol or heptadecylcatechol, that are solely responsible for causing contact dermatitis in North America usually belong to the natural order Anacardiaceae, the genus Toxicodendron (Rhus), and quite often include oak, sumac and poison ivy.
(b) Several plants which essentially belong to the natural order compositae viz., ragweeds, also responsible for causing contact dermatitis, and the allergens have been duly isolated and characterized as sesquiterpinoid lactones.
4. IMMUNE SYSTEMS
Immunology, the generation of an immune response or the defence mechanism exclusively depends upon the interaction of the three most vital components of the immune mechanism, namely : (a) immunogen stimulation ; (b) humoral immune system ; and (c) cellular immune system. Since 1901 and 1984 an enormous and substantial research inputs, were made by various scientists across the globe which have enabled the inhabitants of the world to lead a better and safer quality of life through the evolution of ‘immunotechnology’ i.e., conglomeration of various immune systems. During the said long period (1901-1984) the wonderful findings of scientists and researchers not only brought them wide recognition through most coveted Noble Prizes but also paved the way towards the introduction of remarkable and most trustworthy remedies for complicated not-so-easy diseases of the present day.
It would be worthwhile to make a brief and comprehensive illustration of some of these meaning- ful contributions in a chronological manner as stated below :
• Emil von Behring (1901) : Awarded with Noble Prize for his interesting discovery that quite a few diseases are caused due to the expression of toxins, which he demonstrated by inoculating healthy animals with diphtheria tetanus toxins to generate antitoxins.
• Jules Bordet (1919) : Bagged the Nobel Prize for proving that erythrocytes may be haemolyzed with particular antibody and complement accordingly. His work further demonstrated quite successfully the strategical involvement of certain biological processes taking place in vivo, namely : bacterial ag-
glutination**, neutralization of the precipitin reaction, and complementary mediated immune haemolysis.
* [Jules Thomas Freund, Hungarian-born US immunologist 1890-1960] A mixture of killed microorganisms, usually mycobacteria, in an oil and water emulsion. The material is adiministered to induce antibody forma- tion. Because the oil retards absorption of the mixture, the antibody response is much greater than if the killed microorganisms were administered alone.
** A type of antigen-antibody reaction in which a solid antigen clumps together with a soluble antibody. It requires a cell with antigenic markers close to the surface, available for interaction with the antibody. The
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• Karl Landsteiner (1930) : Became the Nobel Laureate for his epoch making findings for a deeper and vivid immunological concepts with regard to the discovery of blood group antigens i.e., A- B-O blood groups, that was eventually used for successful transfusions in humans.
• Ehrlich’s Selection Theory : It is directly associated with antibody production, and it was amply revealed that during the intricate phenomenon of acquiring ‘immunity’, the critical substances that are exclusively responsible for the fine specificity of recognition were revealed to be the globular proteins that are strategically located in the γ -fraction of blood serum. Subsequently, Landsteiner ex-
perimentally demonstrated the aforesaid theory to be ‘false’, based on blood transfusions. In other words, Ehrlich failed to substantiate his assumption that traces of each individual kind of antibody are carried out in the organism specifically ; whereas, Landsteiner adequately proved that antibodies may only be generated under the influence of foreign substances, i.e., via an instructive process.
• Linus Pauling’s Instructive Theory (1940s) : Pauling was pioneer in assigning a ‘helical structure’ to the protein molecules ; and, soon after proposed the instructive theory. He even went a step ahead and postulated a ‘template theory’ particularly for the synthesis of antibody molecules that could have a relativeily broad range of diversity in shapes. However, at a later stage a renowned immu- nologist Sir Macfarlane Burnet heavily criticized the ‘template theory’ on logical grounds.
• Natural Selection Theory (1955) : Niels Kaj Jerne put forward the ‘natural selection theory’ for the production of antibody. In fact, his proposed theorization revolves round his logical explanation that — ‘the antigen neither serves as a template nor as an enzyme modifier’. In other words, the antigen
is exclusively a highly selection carrier closely associated with a spontaneously circulating antibody to
a ‘system of cells’ that is capable of reproducing this antibody. It has been duly observed that globulins* are being synthesized in a large variant of different configuration. At this juncture the introduction of an antigen into the blood stream essentially gives rise to the selective attachment onto the surface of the antigen only such globulin molecules that should exhibit a complementary configuration. In short, Niels Kaj Jarne brought back a new lease of life to the ‘Ehrlich’s Selection Theory’ almost after a long gap of six decades.
• Clonal Selection Theory : Burnet in 1957, put forward clonal selection theory with regard to ‘antibody formation’ that vehemently offered a positive clue that each cell following an usual contact with an antigen yields a clone** of cells that would be exclusively engaged in the production of anti- body of a particular kind. Importantly, Burnet’s theory suggests two responses taking place, namely : primary and secondary, of which the latter one seems to be more powerful by virtue of the fact that ‘antigenic memory ultimately gives rise to colossal clonal expansion in an extraordinarily rapid man- ner in the course of subsequent exposure to antigen. Hence, the said theory has not only been accepted across the globe but also attracted enormous glory, fame and recognition which enabled Burnet to bag the Nobel Prize in 1960 (also shared by Sir Peter Medawar).
It is, however, pertinent to mention here that Niel’s Kaj Jerne also overwhelmingly was honoured with the Nobel Prize in 1984 i.e., almost after a gap of 24 long years for his ever enlightening and wonderful discovery of the following two aspects in the immunological concepts, namely :
* One of a group of simple proteins insoluble in pure water but soluble in neutral solutions of salts of strong acids e.g., serum globulin, fibrinogen, and lactoglobulin.
** A group of organisms or cells produced asexually from one ancestor.
IMMUNOLOGY AND IMMUNOLOGICAL PREPARATIONS
(a) clonal expansion concept, and (b) evaluation of idiotype* network in regulatory mechanism of immune responses.
• Rodney R Porter and Gerald M Edelman (1972) : The pioneering discovery made by Porter and Edelman with regard to the elucidation of the structure of antibody molecule, which is extremely vital and important in the elaborated study of antigen-antibody interactions, helped them to be hon- oured with the most coveted and prestigeous Nobel Prize in 1972. Importantly, their findings not only proved but also established the most glaring fact that the four polypeptide chains comprising of each immunoglobulin molecule may be enzytmetically cleaved into three distinct segments, such as : two
antibody fragements (Fab) ; and one crystalline fragment (Fc).
• Wu and Kabat’s Observations : In 1970, these researchers adequately demonstrated the pres- ence of specific ‘hypervariable regions’ strategically located on the ‘antibody molecule’. These criti- cal observations, in fact, virtually paved the way towards the rapid and tremendous progress in the field of immunology ; and, therefore, legitimately caused a geometrical development equally stretched over the two most virulant segments of medicine as well as modern biology, for instance : organ and tissue transplantation, vaccinology, and molecular biology.
• Identification of HLA-Complex : The structure and eventually the specialized role and func- tions of the human leucocyte antigens (HLA) complex were scientifically revealed by Snell, Dausset and Benacerraf in late seventies earned them the Nobel Prize in 1980.
• Somatic Hybridization : The ever sensational production of immunologically homogeneous
monoclonal antibodies was accomplished through a wonderful major historical breakthrough by two immunologists : George Kohler and Ceasar Milstein in the year 1975, which bagged them the Nobel Prize in 1982.
• S. Tonegawa’s Immunoglobulin Gene Rearrangement : The evolution of somatic recombi- nation theory logistically suggesting the individual coding in fragments of the ensuing variable and
constant regions that are ultimately ressembled to generate an enormous quantum of binding sites ; and, therefore, various binding sites may be adequately obtained due to the different combinations and permutations of relatively lighter and heavier chains. At this material time Tonegawa’s remarkable epoch making discovery of the most plausible mechanism of shuffling of several gene segments in the plasma cells (i.e., antibody secreting cells) producing a huge variety of antiody molecules. In short, Tonegawa’s spectacular and superb scientific observations on the immunoglobulin gene rearrangement made an appreciable contribution both in the fields of immunology and molecular biology. Tonegawa was rightfully awarded with the prestigious Nobel Prize in the year 1987.
In a nut-shell, one may interestingly observe and access the tremendous sea-change in the most scientific and logistic progress and development during the period 1901-1987 and even after that in the fields of immunology and molecular biology which, of course, have enormously improved upon the
quality of life of humans across the globe irrespective of their caste and creed. However, the ‘immune systems’ may be viewed from the following two aspects critically, such
as : (a) Manipulation of immune system, and (b) Types of immunity.
* In immunology, the set of antigenic determinants (idiotopes) on an antibody that make that antibody unique. It is associated with the amino acids of immunoglobulin light and heavy chains.
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4.1. Manipulation of Immune Systems
The ‘immune system’ or the ‘immune defence mechanism’ in an individual person may be sub- jected to a wide spectrum of articulated well-planned manipulation against a host of dreadful and even fatal infectious diseases, caused by highly dangerous and most pathogenic microorganisms, such as : cholera, polio, chicken-pox, small-pox, diphtheria, measles, whooping cough, Hongkong Flu, anthrax, jaundice, hepatitis A, B and C and the like by immunization squarely and effectively. The underlying principle of immunization is solely based on injecting an individual subject with an appropriate dosage with a sterilized and pre-tested/evaluated preparation of a pathogenic microorganism (disease-causing microorganism) that has been rendered harmless absolutely.
It has been duly proved and established beyond any reasonable doubt that immune system pre- dominantly and essentially possess two extremely special characteristic features which not only enable the body in preventing the individual from the dreadful infection but also ensure that he must not suffer from the same infection once again i.e., one normally suffers from certain infectious ailments only once in one’s life-time (small-pox, measles etc.,). Interestingly, the said two special characteristic features are, namely : (a) Memory : and (b) adaptibility.
More explicitely one may understand that the very first encounter of an infections agent, the body starts to learn whether it is either a foreign entity or a nonself entity : and subsequently gets adapted to fight back the caused infection (MEMORY). But, the same individual on being exposed to the infect- ing agent, the body in turn exhibits a substantially increased agent, the body in turn exhibits a substan- tially increased immune response that is actually dependent on the earlier encounter. In the science of immunology these are invariably termed as primary and secondary immune responses. Consequently, as a fundamental characteristic features one may proclaim that the immune system has acquired ad- equate adaptibility.
4.2. Types of Immunity
The various types of immunity that are commonly identified, characterized and studied at length are as stated below : (i) Humoral Immunity
(ii) Cell-mediated Immunity, (iii) Innate (or Natural Immunity), (iv) Acquired Immunity, and
(v) Non-specific Immunity. These different types of immunities shall now be treated individually in the sections that follows :
4.2.1. Humoral Immunity
Antibodies are immunoglobulin (I g ) molecules (e.g., serum proteins) and they are usually com-
G, and I g M respectively. However, it is pertinent to state here that each category essentially possesses certain specific characteristic features, such as : size, carbohydrate content, electrophoretic-migration velocity, quantum of antigen-combining sites, im- munological response, and immunological objective.
prised of several categories designated as I g g A, I
g D, I g E, I
Examples : (a) I g M : Almost always enjoys the reputation of being the first class of antibody generated
invariably in most humoral responses but normally gets switched over to the corresponding
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(b) I g G : Most versatile important and abundantly available class of antibodies taking part in largest humoral immune reactions. Besides, it happens to cross the placenta thereby pro- viding a newly born baby absolute temporary immunity against whatever immunogens the
mother has earlier against I g G.
(c) I g A : Antibodies are invariably found in a plethora of such secretions as : tears, saliva and mucous membranes. These are quite frequently termed as our first-line-of-defense mecha- nism by virtue of the fact that most bacteria, viruses and fungi that eventually gain entry
into the body do cross a mucous membrane. (d) I g E : Antibodies are equally important in our body’s defense against the parasitic worm
infections specifically. Prominently and predominantly several allergic manifestations give rise to the release of histamines e.g., allergy due to pollens, house dust, dust mite, human hair, food allergens etc., which in turn afford the apparent discomforts resulting into extrin- sic asthma, hay fever, or hives, or excessive sneezing (during changes of season due to pollens in the air).
(e) Antibodies normally serve as surface receptors strategically located on certain immunologically active cells so as to enable them to bind immunogen.
Importantly, the different types of cells or entities that are held responsible for contributing im- mensely to the humoral immunity are as follows :
(i) B Lymphocytes (or B Cells), (ii) Immunodominant peptides (IDPs), (iii) Antigen-presenting cell (APC), (iv) T Cell subsets
(v) Class II MHC (major histocompatibility complex) proteins. It would be worthwhile to have a closer and detailed description and functionalities of each of the
cell or entity cited above in the selections that follows :
4.2.1.1. B Lymphocytes [or B cells]
The B lymphocytes or B cells are so named because they were first and foremost found in the Bursa* of Fabricius of birds . It has been observed that in ‘birds’ the multipotent stem cells actually originate in the bone marrow usually migrate to the bursa, and here they virtually get differentiated into
specific antibody synthesizing cells. In fact, antibody molecules are normally generated by the plasma cells which are vividly differentiated from B cells. It has been found that B cells are concentrated in various parts of the body, such as : spleen, mucous-associated lymphoid tissue, and regional lymph nodes, where they actually await contact by the foreign epitopes** which promptly initiate the process of conversion into the plasma cells.
Interestingly, the characteristic features of B cells may be enumerated as stated below :
1. B cells possess essentially surface immunoglobulins (sI g s) plus a number of receptors.
2. The sI g form an integral part of B cells ; and, therefore, act as receptor for antigens. * A padlike sae or cavity found in connective tissue usually in the vicinity of joints.
** Any component of an antigen molecule that functions as an antigen determinant by permitting the attach- ment certain antibodies. (Syn : Antigenic determinant).
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3. B cells may also have immunoglobulines (I g ) in their cytoplasm.
4. Intially, when B cells are ‘immature’, sI g molecules which are exhibited specially belong to
I g M category that do not cross link with other I g Ms.
5. I g D molecules appear prominently on the surface showing extremely high levels with B cell marching ahead to its developmental pathway.
6. Activation of B cell initiates loss of I g Ds together with other receptors appearing in the membrane that eventually enhance the phenomenon of activation.
7. B cells may undergo activation by the aid of lipopolysaccharide preparations from Gram- negative organisms e.g., E. coli, Salmonlla. Besides, activation may be followed by the ap-
pearance of a plethora of surface receptors for I g s, ocystalline fragment (Fc) component of heavy I g chain, and also for Epstein-Barr virus*.
8. Antigen critically trigers selection of an appropriate antibody-producing cell and this selec- tion is exclusively based upon the surface receptors.