Effects of formalin inactivation on bovine herpes virus-1 glycoproteins and antibody response elicited by formalin-inactivated vaccines in rabbits

The possibility of using a radioimmune assay (RIA) to measure the retention of antigenic determinants on gI, gIII, and gIV, the three major bovine herpes virus 1 (BHV-1) glycoproteins, during the formalin inactivation and aluminium hydroxide adsorption commonly used in the manufacture of killed virus vaccines was investigated. Monoclonal antibodies were used to measure thirteen previously identified glycoprotein epitopes in experimental vaccines containing live BHV-1 or formalin-killed BHV-1 and a commercial formalin-inactivated BHV-1 vaccine. All four epitopes on gI lost 80–97% of their ability to bind monoclonal antibodies. Two of five epitopes on gIII were preserved but the other three epitopes on gIII and five on gIV were reduced as much as 88%. To show that the measured loss of epitopes was biologically relevant, the vaccines were administered to rabbits and the resulting antibody responses against the same epitopes were evaluated by competition RIA. Little correlation was found between the measured antigenic site destruction and the rabbit response against those antigenic sites, suggesting that monoclonal antibody reactivity of a formalin-inactivated vaccine could not provide a meaningful measure of antigenic activity.