DIFFERENCES IN THE IMMUNE-RESPONSE DURING THE ACUTE-PHASE OF E-55-VIRUS INFECTION IN PROGRESSOR BALB AND LONG-TERM NONPROGRESSOR C57BL MICE( MURINE LEUKEMIA)

E-55+ murine leukemia virus infection of both progressor (BALB) and lo ng term nonprogressor (C57BL) mouse strains is characterized by an acu te and a persistent phase of infection. During the acute phase, progre ssor strains require CD8(+) T cells to decrease virus burden, whereas the long term nonprogressor strains do not. In the present studies the immune response in BALE and C57BL mice during the acute phase of E-55 + murine leukemia virus infection was examined. The results demonstrat e that BALE mice produce both IL-4 and IFN-gamma, in contrast to C57BL mice, which produce only IFN-gamma, In BALE mice, IL-4 production res ults in the absolute requirement for CD8(+) T cells to reduce the viru s burden during the acute phase of infection. The anti-virus immune re sponse in these mice is IFN-gamma dependent. On the other hand, C57BL mice do not produce IL-4 and, in the absence of both CD8+ T cells and IFN-gamma, still generate an effective anti-virus immune response. Gen etic studies suggest that these distinct immune responses are regulate d by more than one non-MHC-linked gene. Two candidate regions that may encode this gene(s), located on chromosomes 7 and 19, respectively, w ere identified by recombinant inbred strain linkage analysis.