Absence of splenic latency in murine gammaherpesvirus 68-infected B cell-deficient mice

Murine gammaherpesvirus 68 (MHV-68) is a natural pathogen of mice which causes an acute lung infection and establishes a latent infection in B lymphocytes. In this paper we describe the infection in transgenic B cell-deficient (mu MT) mice, to determine whether a latent infection can be established in a mouse lacking circulating B lymphocytes. Little difference was observed in the acute lung infection, although there was a slight delay in virus clearance in the mu MT mice. This indicates that antiviral antibody is of little importance in the resolution of the lung infection. Neither free nor latent virus could be detected in the spleen in the mu MT mice. In addition, these mice did not develop MHV-68-induced splenomegaly. These data suggest that within the lymphoid compartment B lymphocytes are the sole reservoir for MHV-68 infection in vivo, confirming earlier work which identified B cells as the site of latent infection based on cell fractionation studies. In addition, our study shows that CD4-driven lymphocyte expansion leading to splenomegaly is dependent on the presence of MHV-68-infected B cells in the spleen. Although no free virus was detected (using conventional biological assays) in the lung after the resolution of the acute infection, MHV-68 genome was detected in the lungs of both control and mu MT mice by PCR analysis. This suggests that cells in the lung may act as a reservoir of latent virus which is independent of the B lymphocyte infection.