Immunological tolerance in chickens hatching from eggs injected with cell-associated herpesvirus of Turkey (HVT)

Cell-associated herpesvirus of turkeys (HVT) was inoculated in ovo at various stages of incubation. Chickens hatching from these eggs were tested for anti-HVT antibodies by several serologic procedures including enzyme-linked immunosorbent assay, indirect immunofluorescence assays, and western blot. Viremic chickens that remained free of detectable antibodies were considered tolerant to HVT. Chickens exposed to HVT at embryonation day 14 or earlier had 6-33% incidence of tolerance. Tolerant chickens developed persistent HVT viremia. A preliminary challenge experiment provided circumstantial evidence that tolerant to HVT may be associated with reduced resistance to virulent Marek's disease virus. Tolerance to HVT did not influence the ability of the chickens to produce antibodies against an extraneous antigen or respond to a T cell mitogen.