Vaccines and other immunological antimicrobial therapy 1

Transcription

1 Vaccines and other immunological antimicrobial therapy 1

2 Vaccines Vaccine: a biological preparation that provides active acquired immunity to a particular disease. Vaccine typically contains an agent that resembles a disease-causing micro-organisms. Vaccines are often made from weakened or killed forms of the microbes. Vaccines can be prophylactic (example: to prevent or ameliorate the effects of a future infection by any natural or "wild" pathogen), or therapeutic (e.g., vaccines against cancer are also being investigated). The administration of vaccines is called vaccination.

3 History of Vaccines Variolation: Inoculation of smallpox into skin (18th century) Vaccination: Inoculation of cowpox virus into skin (Edward Jenner) Inoculation with rabies virus (Louis Pasteur) In 1881, to honour Jenner, Pasteur proposed that the terms should be extended to cover the new protective inoculations then being developed. Herd immunity: results when most of a population is immune to a disease.

4 Vaccines for Persons Aged 0 6 Years Hepatitis B Rotavirus Diphtheria-tetanuspertussis (DTP) Haemophilus influenzae b (Hib) Pneumococcal vaccine (PCV; pneumococcal conjugate vaccine) Inactivated poliovirus Influenza Measles-mumps-rubella (MMR) Varicella Hepatitis A Meningococcal vaccine (MCV; meningococcal conjugate vaccine)

5 Dream vaccine Cheap and high protection rate Oral administration Life-long immunity by single administration Stability without refrigerator Safe

6 Nightmare of vaccine development Safety issue: litigation Bad profit: high cost but low profit Limitation in growing antigen: virus Bad storage: in refrigerator

7 Principal Vaccines Attenuated whole-agent vaccines; live vaccines Inactivated whole-agent vaccines Toxoids Subunit vaccines, Recombinant vaccines, Acellular vaccines Conjugated vaccines Nucleic acid vaccines

8 Types of Vaccines Inactivated whole-agent vaccines Usually killed by formalin or phenol. Rabies (animals sometimes receive a live vaccine), Salk polio, influenza, pneumococcal pneumonia, cholera Long-used inactivated vaccines, but now being replaced by newer more effective types; pertussis and typhoid

9 Types of Vaccines Attenuated whole-agent vaccines Better mimic an actual infection Lifelong immunity is often achieved without boosting (effectiveness is 95%) Attenuated viruses replicate in body increasing the original dose and acting as a series of 2 nd immunizations Usually derived from mutations accumulated during long-term artificial culture. Safety issue: Back mutation to a virulent form. Not recommended for people whose immune systems are compromised. MMR (Measles, mumps, rubella), Sabin polio vaccine, tuberculosis bacillus (BCG), oral-administration typhoid vaccines BCG (bacillus of Calmette and Guerin): a live culture of M. bovis made avirulent by long cultivation on artificial media. Uneven effectiveness (young children: fairly effective, adolescents and adults: bad effectiveness, HIV-infected children: often develop fatal infection)

10 Types of Vaccines Toxoids Inactivated toxin. Against toxin Toxoids for tetanus and diphtheria: long used, require a series of injections for full immunity and boosters every 10 years. Subunit vaccines Only antigenic fragments of pathogen. Produced by genetic engineering (recombinant vaccine). Safer and fewer adverse effects. But limitation in effectiveness Cf. acellular vaccine: antigen-containing fraction of a disrupted bacterial cells. Acellular pertussis Recombinant hepatitis B (coat protein): produced form yeast

11 Types of Vaccines Conjugated vaccine Developed to deal with the poor immunity to capsular polysaccharide Polysaccharides: T-independent antigen Children s immune systems do not respond well to these antigens until the age of 15 to 24 month Hib (haemophilus influenza type b) vaccine, MCV (meningococcal conjugate vaccine), PCV (pneumococcal conjugate vaccine)

12 The immune system 3 rd edition, p268, Peter Parham, Garland Science

13 Types of Vaccines Nucleic acid (DNA) vaccines Newest and most promising (?) vaccine. Injection of naked DNA by gene gun to express antigenic protein for long time period. Two DNA vaccines are approved for animal: West Nile virus (for horses), a salmon virus (for domestically reared salmon) Hopefully eliminate the cost and need for large supplies of syringes, needles, refrigerators, and vaccines

14 Kuby immunology, 6 th edition, p482, T. J. Kindt, R. A. Goldsby, B. A. Osborne, W. H. Freeman and Company

15 Principal Vaccines Used in US to Prevent Bacterial Diseases in Humans DtaP Diphtheria: Purified diphtheria toxoid Pertussis: Acellular fragments of B. pertussis Tetanus: Purified tetanus toxoid Meningococcal meningitis: Purified polysaccharide from N. meningitidis Haemophilus influenzae type b meningitis: Polysaccharides conjugated with protein Pneumococcal conjugate vaccine: S. pneumoniae antigens conjugated with protein

16 Principal Vaccines Used in US to Prevent Viral Diseases in Humans Smallpox: Live vaccinia virus Poliomyelitis: Inactivated virus Rabies: Inactivated virus Hepatitis A: Inactivated virus Influenza: Inactivated or attenuated virus Measles: Attenuated virus Mumps: Attenuated virus Rubella: Attenuated virus Chickenpox: Attenuated virus Hepatitis B: Antigenic fragments (recombinant vaccine)