MD5: Influenza Vaccines Flashcards
what is orthomyxovirus
ssRNA, enveloped, recognises sialic acid receptors
what are three envelope proteins
hemagglutinin, neuraminidase, M2
what is hemagglutin
envelope protein
functions in attachment and penetration
what is neuraminidase
envelope protein
cleaves sialic acid from glycoconjugates, facilitates elutiokn of progeny virions from infected cells
what is M2
envelope protein
functions in uncoating and virus maturation
what is the structure of heamagglutinin
globular head and fibrous stem
globular head binds to cell surface receptor sialic acid
what is the function of neuraminidase
an enzyme that breaks down the sialic acid receptor on the cell surface
pathogens have acquired neuramididases to facilitate infection/propagation
once sialic acid is removed from the receptor by neuraminidase, the heamagglutinin protein no longer binds
what is the initial innate response to influenza infection
NFkB transcription leads to pro-inflammatory cytokine gene expression of TNFalpha, IFNbeta and IL-8
what do chemokines and cytokines do in the innate response to influenza infection
increase inflammatory response by attracting NK, B and T cells to the infection site
these cells produce more inflammatory cytokines to keep the Th1 response cycle going
what is the long term response to influenza infection
IFNgamma boosts chemokine gene expression, activation of macrophages, antigen presentation and continual development of specific cell-mediated immunity Th2 response T cell stimulation antigen presentation B cell mutation antigen specific IgG production
what infections do influenza A and B viruses cause
seasonal epidemics of disease every year
what do influenza C viruses cause
mild respiratory illness but do not cause epidemics
what do influenza D viruses cause
primarily affect cattle and do not infect people
what are the influenza A sub-types
based on the two proteins on the surface of the virus
hemagglutinin and neuraminidase
how many different subtypes of hemagglutinin are there
18
how many different subtypes of neuraminidase are there
11
what is antigenic drift
gradual accumulation of amino acid mutations that allow the hemagglutinin to escape neutralising antibodies
epidemic strains of influenza have changes in three or more antigenic sites
what is the result of antigenic drift
reduced ability of circulating antibodies to recognise the ‘new’ virus
how are influenza vaccines produced
growing the bacteria or virus in culture media then inactivating it with heat/chemicals
inactivated vaccines cannot replicate; entire dose of antigen is administered in the injection
first dose primes the immune system, does not give immunity
what are the advantages of inactivated vaccines
generally safer, improved stability
what are the disadvantages of inactivated vaccines
can be costly, hypersensitivity
