Immune mechanisms against canine distemper. II. Role of antibody in antigen modulation and prevention of intercellular and extracellular spread of canine distemper virus.

Specific antibody was shown to be highly effective in neutralizing extracellular canine distemper virus (CDV) as well as preventing the intercellular spread of this virus. Thus, relatively low levels of antibody neutralized 1 x 10(5) TCID50 of extracellular CDV and the development of plaques or CPE in Hep-2 and Vero cells respectively could be prevented even when up to 5% of the cells were infected. This inhibition of CPE and virus spread was most pronounced when antibody was added early but could still limit the degree of CPE if added as late as 48 h post-infection. This anti-viral activity was observed in different cell types including canine macrophages, cells normally infected with CDV in vivo. Prolonged exposure of infected target cells to high concentrations of antibody led to redistribution of surface viral antigens and their subsequent disappearance. The possible role of antibody in the defence against, and/or recovery from CDV and the mechanism(s) by which antibody may aid in recovery are discussed.