Relation between the neutralization of herpesvirus of turkeys and the antibody to late-appearing membrane antigen induced by the virus.

The relation between the neutralization of herpesvirus of turkeys HVT) and the antibodies to early appearing membrane antigen (EMA), late appearing membrane antigen (LMA) and intracellular antigen (IA) induced by the virus was examined by blocking of direct immunofluorescence using 38 sera from chickens infected with HVT. Our results provide evidence that anti-LMA is significant in the neutralization of the infectivity (P less than 0.001) since the neutralizing capacity of the serum was related to its blocking index (BI) and not to its anti-EMA titre (BI). Furthermore, the anti-IA titres (BI) of the sera were also related to their neutralizing activity to a lesser extent (P less than 0.025). However, no relationships among any two of the titres of EMA, LMA and IA were observed. The implication of these results of the relationship of LMA to infectious virus particles is discussed.