ASSESSMENT OF THE CELL-MEDIATED-IMMUNITY IN CATTLE INFECTION AFTER BOVINE HERPESVIRUS-4 INFECTION, USING AN IN-VITRO ANTIGEN-SPECIFIC INTERFERON-GAMMA ASSAY

The cell-mediated immunity (CMI) following bovine herpesvirus 4 (BHV4) infection has been poorly investigated in cattle. The in vivo respons e measured by a delayed type of hypersensitivity (DTH) assay has been reported to be positive in only few animals showing serological eviden ces of BHV4 infection. We have investigated the CMI following BHV4 inf ection by an in vitro antigen-specific interferon gamma (IFN-gamma) re lease assay, as an indicator of an actively acquired immunity to BHV4. Our preliminary results using a partially purified antigen suggest th at there was a measurable CMI in 75 out of 168 animals (44.4%) origina ting from a farm with a clinical history and serological evidences (76 .3% seropositivity) of BHV4 infection. If the results of serological t ests and BHV4 IFN-gamma test are interpreted in parallel, 81.5% of the animals are classified positive, demonstrating the complementarity of these tests. The specificity of the BHV4 IFN-gamma test was supported by the absence of a measurable CMI in 41 animals originating from a f arm with no clinical history or serological evidence of BHV4 infection . In an allied study, we developed a bovine herpesvirus 1 (BHV1) IFN-g amma test. This allowed us to measure the antigen specific IFN-gamma r elease after stimulation with a mixture of BHV1 and BHV4 antigens. Ani mals that were classified negative by the BHV4 IFN-gamma test and by t he BHV1 IFN-gamma test, were classified negative after stimulation wit h a mixture of both antigens. Animals that were classified positive by the BHV4 IFN-gamma test or the BHV1 IFN-gamma test, were classified p ositive after stimulation with a mixture of both antigens. Taken toget her these results suggest that the in vitro assessment of the CMI afte r BHV4 infection should be further investigated as a specific and valu able alternative to the DTH assay.