[Experimental infection of guinea pigs with Tacaribe virus: effect on the functioning of the immunocompetent system]

Tacaribe virus is the member most closely related to Junín virus within the Tacaribe complex. It has been demonstrated that both viruses are indistinguishable by complement-fixation, due to the high cross-reactivity. However, adult guinea pigs are highly sensitive to infection with the XJ pathogenic strain of Junín virus whereas Tacaribe virus is nonpathogenic for this species. Furthermore this last virus protects them against Junín virus. The XJ strain reduces the immune response of guinea pigs to many antigens. Both the humoral response and the hypersensitivity of the Arthus type have been reduced in infected animals. Considering that Tacaribe virus could be used as vaccine antigen, the purpose of the present study was to investigate the effect of Tacaribe infection on the immune system of guinea pigs. The data reported here supports earlier findings showing that the XJ strain of Junín virus suppresses humoral immune response as indicated by lower precipitating antibody titers to ovoalbumin (which contributed to milder Arthus cutaneous reactivity) and a significant depression of plaque-forming cells to sheep erythrocytes. In contrast, Tacaribe-infected guinea pigs did not show detectable immunosuppression employing the same models. Similar results were found when the cell-mediated immunity was investigated. Tacaribe-infected guinea pigs had a normal immune response to contact sensitivity to 2-4 dinitro-1-fluorobenzene as demonstrated by measuring ear swelling and unmodified tuberculin reaction, after injection with complete Freund's adjuvant. Our results and those of previous investigations justify the consideration of Tacaribe immunization as an approach to the prophylaxis of Argentine Hemorrhagic Fever.