The responses of normal an athymic mice to infections by togaviruses: strain differentiation in active and adoptive immunization.

Strains of yellow fever virus (YFV), Venezuelan equine encephalomyelitis virus (VEEV) and Semliki Forest virus (SFV) have been used to compare the stimulations of regulatory immunity (pre-challenge), antibody synthesis and protective immunity (post-challenge) in athymic-nude and normal mice. Similarly, direct assessments have been extended to athymic recipients of normal spleen cells and to adoptively immunized mice. The results indicate that the responses of mice to different togaviruses or strains of togaviruses may be differentially T-lymphocyte dependent at any one or more of the above three stages of host response. T-cell reconstitution or adoptive immunization may be effective only for the virus strains of highest immunogenicity. These results suggest a resolution of T-lymphocytes dependence at three levels of host response to virus infections. This approach may be of value in the similarly direct in vivo differentiation of other virus strains and as a practical framework for the consideration of the in vivo significance of the variety of in vitro lymphocytes markers.