Lymphotoxin-α-Deficient Mice Can Clear a Productive Infection with Murine Gammaherpesvirus 68 but Fail To Develop Splenomegaly or Lymphocytosis

Respiratory challenge with murine gammaherpesvirus 68 (MHV-68) leads to an acute productive infection of the lung and a persistent latent infection in B lymphocytes, epithelia, and macrophages. The virus also induces splenomegaly and an increase in the number of activated CD8 T cells in the circulation. Lymphotoxin- α-deficient (LTα(−/−)) mice have no lymph nodes and have disrupted splenic architecture. Surprisingly, in spite of the severe defect in secondary lymphoid tissue, LTα(−/−) mice could clear a productive MHV-68 infection, although with delayed kinetics compared to wild-type mice, and could control latent infection. Cytotoxic T-cell activity was comparable in the lungs and spleens of LTα(−/−) and wild-type mice. However, splenic gamma interferon responses were substantially reduced in LTα(−/−) mice. Furthermore, LTα(−/−) mice failed to develop splenomegaly or lymphocytosis. Although germinal centers were absent, LTα(−/−) mice were able to class switch and showed significant virus-specific antibody titers. This work demonstrates that organized secondary lymphoid tissue is not an absolute requirement for the generation of immune responses to viral infections.