Reconstitution of immunosuppression mice with mononuclear cells from donors sensitized to foot-and-mouth disease virus (FMDV).

Passive transfer experiments were performed to serve as a basis for analyzing the immune response of adult mice to FMDV infection. Animals were irradiated (750 rad: 1 lethal dose 50%) and reconstituted with allogeneic mononuclear cells from blood, spleen, thymus and peritoneal cavity from donors 2 and 8 days post-inoculation (p.i.). Donors were primed with 10 000 suckling mouse 50% lethal doses of FMDV strain O1 Campos. The following parameters were studied in recipient mice challenged with 10 000 suckling mouse 50% lethal doses of the same virus: (1) viremia; (b) FMDV neutralizing antibody titres; (c) sheep red blood cell (SRBC) hemagglutinating antibody titres. Viremia was substantially prolonged in irradiated control mice, which did not produce detectable antibodies to FMDV or SRBC. In contrast, the span of viremia was markedly shorter in animals reconstituted with cells obtained 8 days p.i. and its eclipse coincided with the onset of neutralizing antibody production. An equally efficient antibody response to the inoculation of SRBC was observed in these animals. No effect was detected after the transfer of cells obtained 2 days p.i. It is concluded that the humoral immune response plays a predominant role in the recovery from FMDV experimental infection in adult mice.