HOST-VIRUS INTERACTION AS DEFINED BY AMPLIFICATION OF VIRAL-DNA AND SEROLOGY IN LENTIVIRUS-INFECTED SHEEP

To correlate the presence of ovine lentivirus (OvLV) as detected by po lymerase chain reaction (PCR) with detection of antibody, 42 sheep fro m a flock with enzootic OvLV infection were studied. The results of ag ar gel immunodiffusion (AGID), ELISA, and immunoblotting assays were c ompared, and leukocytes (blood, bone marrow, lymph node, and lung cell s) were assessed for viral DNA by PCR using pol and LTR primers; ampli fied products were detected by specific DNA and RNA probes. Based on t he number of animals that had detectable viral DNA, the specificities of AGID, ELISA, and immunoblotting were 77%, 92%, and 95 or 100% (depe nding on which criterion was used to interpret immunoblot results), re spectively. Only in animals with OvLV-associated disease was OvLV DNA detected in leukocyte DNA prior to the amplification of virus in cultu re and only, in this group was high titer antibody detected to the OvL V major surface (gp 105) and transmembrane (gp 55) antigens. Animals t hat were both antibody and PCR-negative lacked histopathologic evidenc e of disease. From this study there was no indication that OvLV infect ion without the development of antibody occurs, and detection of OvLV DNA in animals with weak or partial serological reactions likely indic ates early OvLV infection rather than false-positive PCR results.