Antigenic relationships among five reovirus-like (RVL) agents by complement fixation (CF) and development of new substitute CF antigens for the human RVL agent of infantile gastroenteritis.

The human reovirus-like (HRVL) agent, Nebraska calf diarrhea virus (NCDV), epizootic diarrhea of infant mice (EDIM) virus, simian agent (SA)-11, and the "O" (offal) agent were found to be similar, if not identical, in reciprocal complement fixation (CF) tests employing hyperimmune animal sera. In addition, in CF tests with paired sera from 35 diarrhea patients who shed the HRVL agent, 74% developed serologic evidence of infection with the HRVL antigen, 43% with NCDV, 51% with EDIM virus, 57% with SA-11, and 71% with the "O" agent. Thus, in addition to the NCDV, which had previously been described as a suitable substitute CF antigen for the HRVL agent, the SA-11, "O", and EDIM viruses may also be utilized as substitute antigens for the HRVL agent. However, the "O" agent appears to be the most efficient of the four substitute CF antigens and thus should be used preferentially when the HRVL agent is not available. The "O" agent was about as efficient as the HRVL agent and significantly more efficient than the NCDV for detecting seroresponses. The greatest efficiency for detecting infection with the HRVL agent resulted when sera were tested with both the HRVL and "O" agents as 31 (89%) of the patients developed serologic evidence of infection with one or both antigens. The finding of additional substitute CF antigens for the HRVL agent may have implications in the immunoprophylaxis against human disease.