5 Viral and Bacterial Vaccines Flashcards
vaccine
suspension of live (usually attenuated) or inactivated microorganisms
(e.g., bacteria or viruses) or fractions administered to induce immunity and prevent infectious disease
Mechanisms of acquiring immunity
Vaccines can induce acquired side of the immune system
Passive and active immunity can be induced by vaccination, as well as being naturally acquired in response to contact with pathogens or other bacteria with cross-reactive antigens
Passive immunisation types
- Natural
2. Artificial
natural passive immunisation
- placental transfer of IgG
- colostral transfer of IgA
artificial passive immunisation
- immunoglobulin
- immune cells
disease examples of vaccine-induced passive immunity
tetanus
antibody source - human, horse
use - prophylaxis therapy
Pros of passive immunisation
immediate protection
Active immunisation types
natural
artificial
natural active immunisation
- exposure to sub-clinical infections
- exposure to cross-reaction non-pathogens
artificial active immunisation
- attenuated organisms
- killed organisms
- heterologous organisms
Natural acquisition of immunity
Develops from infection - may be transient or persistant, leading to acute or chronic disease,
Infection may be sub-clinical (which may also cause disease at a later timepoint)
Disease may result in death or morbidity, or it may resolve; in the latter cases this can result in immunity
Types of immunity
- Cell-mediated
2. Humoral
Cell-mediated
TH1 response, mediated by cytotoxic cells such as cytotoxic T-cells, as well as phagocytic cells such as polymorphonuclear leukocytes and macrophages
- important for resistance to intracellular pathogens including viruses or intracellular bacteria
Humoral
TH2 response is likely to lead to a less controlled form of the disease (DTH response suppressed, antibody levels raised but unable to control the infection, there are large numbers of organisms and tissues invasion
Bacterial vaccine targets
number of surface and secreted molecules can form the basis of vaccines, including proteins, capsular polysaccharide and lipo-oligosaccharide
Viral vaccine targets
Like bacterial targets, tend to be surface exposed proteins
Proteins expressed during the viral life cycle in the host cell and presented by T cells on the host cell surface may also be targeted
Ideal vaccine
- Given orally (or nasally)
- Generates long-lasting protective immunity
- Stimulates both T and B cells to generate immunological memory and class switching
- Provides cross-protective immunity
- Is effective in all age groups
- Safe, cheap to make, stable
Criteria for vaccine development: the organism
- disease severity
- prevalence
- mortality
- availability of treatments
Criteria for vaccine development: the antigen
Conservation
accessibility
generation of functional immunity
cross-protective
Conservation
should be well-conserved and expressed in vivo
Accessibility
should be accessible to immune system
Generation of functional immunity
should generate functional (e.g. bactericidal) antibodies and/or cell-mediated immunity
Cross-protective
should ideally provide protection across serogroups/serotypes and serosubtypes
Safety of vaccines
Risks from natural disease must outweigh risks of vaccination
Strict ‘good manufacturing practice’ observed
Records kept of administration and manufacturing details
Bacterial vaccines based on
may be based on whole cells, which may be live and attenuated to reduce their virulence or killed
Attenuated strain
may be target organism, a closely related but less (or non-) pathogenic organism, or a distantly related organism expressing heterologous recombinant proteins derived from the target organism
Subunits types
protein or non-protein
subunits - proteins
proteins can be purified from target organism or expressed as a recombinant
> recombinant administered as engineered attenuated vaccine strain in a heterologous organism
subunits - non-proteins
non-protein antigens conjugated to proteins to provide better immunogens
Bacterial vaccines: examples - whole cell
cholera
Bacterial vaccines: examples - live attenuated
BCG, typhoid
Bacterial vaccines: examples - protein
diphtheria
Viral vaccines: examples
- whole cell
polio
Viral vaccines: examples
- live attenuated
MMR
Viral vaccines: examples
- protein
influenza A
Viral vaccines: examples
- recombinant virus
rabies
anti-idiotype vaccines
antibody is used as an immunogen to generate additional antibodies which mimic the antigen; these in turn can be used as immunogens
Immunodominant/subdominant peptides
based on the peptide sequence of an immunogen can be chemically synthesised. Immunodominant peptides based on the meningococcal PorA gene have been used in experimental vaccines
what does BCG vaccine protect you against
Mycobacterium tuberculosis (and thus TB >70%) and leprosy
what is the BCG vaccine strain
live attenuated Mycobacterium bovis strain
what is BCG
Bacillus Calmette-Guerin
Meningococcal vaccines groups
6 major serogroups responsible for most human disease (A, B, C, W, X, Y)
meningococcal vaccines type and effect
polysaccharide vaccines are safe and effective but do not induce class switching or immunological memory
who cant have meningococcal vaccines
young children
what are the meningococcal vaccine - polysaccharide based on
serogroup B polysaccharide
Conjugate vaccines
Capsular polysaccharide can be chemically conjugated to protein antigens (e.g. tetanus toxoid)
what was introduced to conjugate vaccines thats made them efficious
Introduction of Serogroup C conjugate vaccines proven highly efficious
what are conjugate vaccines dependent on
T cell-dependent antigens
