Immunology - Viral Diseases Flashcards
Immunisation
The process whereby a susceptible individual is rendered immune to an infection
Can be passive or active
Aims of immunisation can range from eradication to preventing symptoms
Passive immunisation
Transfer of pre-formed antibodies to a susceptible individual giving temporary protection from infection
Natural, passive immunisation
Mother to baby via the placenta and breast milk
Diseases requiring normal immunoglobulins - passive immunisation
Hep A
Measles
Diseases requiring spp immunoglobulins - passive immunisation
Hep B
Rabies
Varicella Zoster
Tetanus
Diseases requiring monoclonal immunoglobulins - passive immunisation
RSV
Molecules used in active immunisation
Live attenuated Inactivated whole cell Toxoid Subunit Polysaccharides Conjugated polysaccharide
Live attenuated vaccines
Traditionally generated by serial passage in tissue culture
Examples of live attenuated vaccines
TB (BCG) Measles Mumps Rubella Varicella Zoster Rotavirus
Pros of live attenuated vaccines
Replicates in recipients = excellent immune response
More closely resembles natural infection = mucosal immunity as appropriate
Cons of live attenuated vaccines
Potential for reversion
Potential for sustained vaccine strain infection
Not suitable for all
Inactivated whole cell vaccines
Pathogen killed by chemical or physical processes
Examples of inactivated whole cell vaccines
Inactivated polio (Salk)
Hep A
Rabies
Toxoid vaccine
Inactivated toxin
Toxins chemically treated to eliminate toxicity whilst maintaining immunogenicity e.g. w/ formaldehyde
Examples of toxoid vaccines
Diphtheria
Tetanus
Types of subunit vaccines
Recombinant proteins
Chemically purified
Subunit vaccines - recombinant proteins
Spp viral protein produced in a heterologous expression system
Recombinant proteins examples
Hep B
Papillomavirus
Subunit vaccines - chemically purified
Certain components of a pathogen are purified for use in a vaccine
Examples of chemically purified subunit vaccines
Acellular pertussis
Influenza
Polysaccharide vaccines
Purified bacterial polysaccharide
T cell independent and poorly immunogenic in young children
Examples of polysaccharide vaccines
Some meningococcal vaccines
Some pneumococcal vaccines
Salmonella
Conjugated polysaccharide vaccines
Purified bacterial polysaccharide linked to a protein
Examples of conjugated polysaccharides
H. influenzae
Pneumococcal
Meningococcal
Adjuvants
Agents that stimulate the immune system
Thought to sequester antigen and cause infl
Commonly used adjuvants
Aluminium phospahte
Aluminium hydroxide
Pre exposure vaccines in adults
65 yrs of age - pneumococcal polysaccharide vaccines
65 yrs of age - annual influenza vaccine
70 yrs of age - varicella zoster (shingles)
Pre exposure vaccines in pregnant women
Influenza vaccine in any trimester prior to start of flu season
Pertussis vaccine from 16 weeks’ gestation
Childhood vaccines at 2 months
Diphtheria/ tetanus/ pertussis/ polio/ haemophilus/ hep B
Meningococcal B
Rotavirus
Childhood vaccines at 3 months
Diphtheria/ tetanus/ pertussis/ polio/ haemophilus/ hep B
Rotavirus
Pneumococcal conjugate
Childhood vaccines at 4 months
Diphtheria/ tetanus/ pertussis/ polio/ haemophilus/ hep B
Meningococcal B
Childhood vaccines at 12-13 months
Haemophilus/ meningococcal C conjugate
Meningococcal B
Pneumococcal conjugate
MMR
Childhood vaccines at 2 years
Influenza - annually to age 16 (in process of being rolled out)
Childhood vaccines at 3yr 4 months
Diphtheria/ tetanus/ pertussis/ polio
MMR
Childhood vaccines at 12-13 yrs
Papillomavirus (2 doses 6 months apart)
Childhood vaccines at 14 years
Tetanus/ diphtheria/ polio
Meningococcal ACWY conjugate
Post-exposure vaccines
Ig and some vaccines can be given after exposure to reduce the chance of an individual developing a disease of reducing disease severity
Examples of post-exposure vaccines
Wounds at risk of tetanus - spp Ig
Potential rabies exposure - course of vaccine +/- -spp Ig
Unvaccinated contact w/ confirmed measles case - vaccine, in contraindicated - consider normal Ig
Adverse effects to immunisations
Related to either immunogenicity or other component of the vaccine
Most commonly local reactions - pain, swelling and redness
General systemic effects - fever, headaches and malaise
Examples of adverse effects to immunisations
Yellow fever - encephalitis
Rubella - thrombocytopenia
BCG - osteitis
Rotavirus - potential increased risk of intussusception
Contraindications considerations for immunisations
Hx of anaphylaxis to previous vaccine/ vaccine component
Immunosupression
Pregnancy
When may an immunisation need to be deferred
Acutely unwell
Other vaccines given recently
Ig therapy
Immunisation failure
Primary vaccine failure
Secondary vaccine failure
Primary vaccine failure
Failure to mount an immune response to a vaccine
Causes of primary vaccine failure
Vaccine factors
Host factors
Inappropriate vaccine schedule
Vaccine factors leading to primary vaccine failure
Administration error
Manufacturing error
Incomplete strain coverage
Host factors leading to primary vaccine failure
Immunodeficiency
Immunological issues
Secondary vaccine failure
Immunity develops initially following immunisation but w/ time immunity wanes
What does the innate immune system rely on
Interaction between PRR’s and PAMPs
What does the innate immune system comprise
Mechanical barrier
Proteins (enzymes, complement)
Cells (macrophages, neutrophils, NK cells)
What does the adaptive immune system comprise
B cells - antibody production T cells (CD4 - 'helper' cels and CD8 - 'cytotoxic' cells)
Why do we need 2 vaccines for live attenuated virus vaccines
We go from sero-ve to seroprotective but the virus-app antibody titre drops so we become sero+ve, therefore requiring a booster
Sero+ve
Partial or no protection
Why don’t wild - type viruses require a booster
Despite virus-app antibody titre drops, it is still enough to be seroprotective
Why might a child not have been vaccinated
Parents may have refused
Vaccination may have been accidentally missed
Examples of misinformation about immunisations
Polio (a Western plot to make African women infertile)
HPV (a cause of promiscuity in teenagers)
