Development of specific immune response in mice infected with Junin virus

Different parameters of specific immune response involved in the resistance to intracerebral Junin virus (JV) infection were studied in adult BALB/c mice. The relationship of virus replication to production of antiviral antibodies, to occurrence of cytotoxic T cells and to development of delayed-type hypersensitivity response was evaluated. Spleen cytotoxic T cells were assayed by 51Cr-release method on virus-infected H2 compatible targets. Effector T cells were detected on day 2, reached peak concentrations by day 6 and declined on day 10. These cells seemed responsible, at least in part, for virus clearance from the infected target organ, since virus could not be recovered from the brain in any sample taken on days 2, 5, 6, 8, 10, 15 and 20 post infection (p.i.). All three main antibody classes common in viral infection were present. Serum antibodies appeared later than the T cell cytotoxic response. Neutralizing antibodies and those detected by immunofluorescence prevailed in the IgG fraction, whereas the IgM antibody class was reactive in complement fixation assay. Challenge of infected mice with JV did not result in production of delayed-type hypersensitivity as measured by footpad swelling irrespective of the route of sensitization. The possible interpretations of these findings are discussed in connection with the resistance of adult mice to JV infection.