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              Review
              
              
              9.   
                  
                  
                              
                              Antigenic variation of foot and mouth disease 
                              virus - An overview - Neeta longjam, Tilling Tayo
                              Vet World. 2011; 4(10): 475-479
               
              
              
              doi: 10.5455/vetworld.2011.475-479
              
              
               
              
              
              
   
 
              
               
               
               
              
              
              Abstract
              
                              
                              
                              
                              Foot and mouth disease (FMD) is a highly 
                              contagious viral diseases of cloven-hoofed 
                              animals, caused by FMD virus, a single molecule of 
                              linear positive sense, with single stranded RNA of 
                              size 7.2– 8.4 kb. Antigenic variation is one of 
                              the striking characters of FMD virus. It is a 
                              process by which an infectious organism alters its 
                              surface proteins in order to evade a host immune 
                              response and is associated with mutation leading 
                              to amino acid replacement. These changes may 
                              result either in the field or in the laboratory 
                              leading to the development of a new strain of 
                              virus which totally differs from the circulating 
                              field strain challenging the vaccine strains use 
                              for controlling the diseases. The high sequence 
                              variability found in VP1 region of this virus 
                              accounts for the low cross-reactivity observed 
                              among different serotypes of FMDV and also due to 
                              high degree of antigenic variation may be 
                              attributed to different reasons like high rate of 
                              mutation, genetic recombination, quasispecies 
                              nature of the virus and continuous circulation of 
                              the virus in the field, which is a main loophole 
                              for severe economic loss in livestock productions. 
              
              
                              
                              Keywords: antigenic variation, quasispecies, 
                              FMD.