Detection of mouse thymic virus (MTLV) antigens in infected thymus by competition immunoassay

Mouse thymic virus (MTLV; murid herpesvirus 3) causes T lymphocyte depletion, thymic necrosis and immunosuppression in acutely infected neonatal mice. Infected animals shed virus persistently in saliva for prolonged periods of time. The standard procedure for detection of MTLV in infected mice is an in vivo infectivity assay. A sensitive enzyme linked immunosorbent assay (ELISA) recently has been developed for the detection of antibodies to MTLV. However, a direct test for viral antigen would be desirable in order to identify animals shedding virus, in the event that some infected animals may remain seronegative. For this purpose, we developed and assessed the feasibility of a competition ELISA to detect viral antigens in MTLV infected tissue. In competition ELISA, unknown tissue samples possibly containing antigen are mixed with a known quantity of antibody. Subsequent measurement of unbound antibody by ELISA is used to determine the presence of MTLV antigen in the samples. By competition ELISA we were able to detect MTLV in thymuses of acutely infected animals at a level of approximately 16 ID50 per sample. This technique shows promise as an alternative to infectivity testing methods and is also useful for confirmatory tests in MTLV serology.