Antigenic variation

Antigenic variation is of considerable importance in foot-and-mouth disease. There are seven distinct serotypes of the virus. These are the European or classical types 0, A and G, the Southern African Territories types SAT1, SAT2 and SATJ, and Asia 1. An animal recovering from infection with one type of the virus is not protected against infection with any of the remaining six 

The variation measured by these tests is expressed on the virus capsid proteins which are coded for by the 30 to 40 6 of the virus BRA at the 5 iid (28). It is not known, however, vdiether variation is limited to this region of the genome. e have been studying the biochemical basis for variation by analysing the ERA and primary products of several isolates of the virus. 

Dietzschold at (50) demonstrated by saturation hybridisation that the sequence homology between the ERAs of isolates of each of the European types of the virus was between 44 said 65% The homology between sub-types of type 0 was only very slightly greater (51)  

Using a competition hybridisation test, however, Eobson al. (32) have found sequence homologies of 60 to 70% between types 0, A, C and Asia 1 These viruses form a group distinct from the SAT serotypes because the homology between the two groups is 25 to 40% Homology between the individual SAT serotypes is also 60 - 70% 

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Composition and Methods of Manufacture. Two types of influen2a vimses, A and B, are responsible for causing periodic outbreaks of febrile respiratory disease. The manufacture of an effective vaccine is compHcated by antigenic variation or drift, which can occur from year to year within the two vims types, making the previous year s vaccine less effective. Each year, antigenic characteri2ation is important for selecting the vims strains to be included in the vaccine. 

Compared to bacterial cells, which are identical within a given cell type (except for O antigen variations), animal cells display a wondrous diversity of structure, constitution, and function. Although each animal cell contains, in its genetic material, the instructions to replicate the entire organism, each differentiated... 

Vickerman, K. (1974). Antigenic variation in African trypanosomes. Ciba Found. Symp. 25, 53-80. 

Phase and antigenic variation in bacteria. These may be mediated by slipped-strand mispairing of repeat sequences that occur in these phase variable genes or by gene duplication events. 

Trypanasoma brucei causes sleeping sickness in humans. These flagellated parasites are directly exposed to immune defences as they circulate in the mammalian host bloodstream but maintain persistent infections by undergoing antigenic variation. These parasites have been reported to have certain unusual histone modifications where the N-terminal alanine of H2A, H2B, H4 get... 

B7. Brown, K. N., and Brown, I. N., Immunity to malaria. Antigenic variation in chronic infections of Plasmodium knowlesi. Nature (London) 208, 1286-1288 (1965). 

Antigenic variation (trypanosomes) Varies Nonreciprocal gene conversion Successive expression of different genes encoding the variable surface glycoproteins (VSGs) allows evasion of host immune response. 

In addition to these issues, it would be useful to investigate the potential impact of antigenic variation in the parasite population in relation to resistance to vaccine-induced immune responses. Having now undertaken many of the studies for the T. ovis, T. saginata and f. granulosus vaccines, there may be aspects of what has been learnt along the way that may be useful for others in the future who are faced with a similar vaccine development task. 

Webster, R.G. Laver, W.G. (1975). Antigenic variation of influenza viruses. In The Influenza Viruses and Influenza (Kilboume, E.D., Ed.), pp. 269-314, Academic Press, New York. 

France LL, Piatti PG, Newman JFE, Toth I, Gibbons WA, Brown F (1994) Circular dichro-ism, molecular modeling, and serology indicate that the structural basis of antigenic variation in foot-and-mouth disease virus is a-helix formation. Proc Natl Acad Sci U S A 91(18) 8442-8446... 

A second example of O antigen variation caused by nucleotide substitutions involves E. coli 0107 and 0117. They differ in substitution of only a few amino acid residues, but the glycosyltranferases have different specificities resulting in the presence of different sugars as the third residue in the 0107 and Ol 17 structures (Wang et al., 2009). 

Owing to the strength of the avidin-biotin complex, the immunochemical bond can be preferentially severed, permitting selective elution of the antigen. Variations on this same theme allow the immunoaffinity isolation of other components of the immune system, such as tmtibodies, complements, blood cell receptors, and the like. 

RNA viruses Myxovi ruses Influenza virus Enveloped particles, 100nm in diameterwith a helically symmetric These viruses are capable of extensive antigenic variation, producing new types against which the human population does not have effective immunity. These new antigenic... 

The antigenic variation of blood group substances is due to specific glycosyltransferases (the primary gene products) responsible for synthesis of the oligosaccharide determinants (the secondary gene products). 

Proft T, Moffatt S, Weller K, Paterson A, Martin D, Fraser J The streptococcal superantigen SMEZ exhibits wide allelic variation, mosaic stmcture, and significant antigenic variation. J Exp Med 2000 191 1765-1776. 

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