Immune cell tropisms of attenuated MHV3 viruses isolated from brains of chronically infected mice

Effect of adoptive transfer of CD4, CD8 and B cells on recovery from MHV3-induced immunodeficiencies

A chronic viral infection can occur when the host fails to mount an effective immune response to clear the virus. Mouse hepatitis virus type 3 (MHV3) appears to be an excellent model for the study of the relationship between viral-induced immunodeficiency and chronic disease development. (C57BL/6 x A/J)F1 mice surviving acute hepatitis develop a chronic disease characterized by T- and B-cell immunodeficiencies, viral persistence in various organs including the brain, spleen and thymus, and death within 3 months postinfection (p.i.). We have reported that T- or B-cell deficiencies, observed in MHV3 chronically infected (C57BL/6 x A/J)F1 mice, can be partially or totally thwarted by adoptive transfer of CD4+, CD8+ and/or B cells, at 15 days p.i. in mice surviving the acute phase of the disease. Adoptive transfer of syngeneic CD4+ and/or CD8+ allowed a partial restoration of the T-cell deficiencies, as characterized by thymic atrophy, decrease in splenic T cells, and in all thymocyte subpopulations. B-cell immunodeficiency, as defined by a decrease in splenic B cells, as well as in the bone marrow pre-B- and B-cell compartments, and the occurrence of abnormally larger forms of bone marrow pre-B and B cells, were partially thwarted by B-cell treatment only. Splenic B cells and the bone marrow B-cell compartment, respectively, returned partially or totally to normal values, whereas the pre-B-cell compartment remained depleted in infected mice treated with B cells. Levels of all immunoglobulin classes returned to normal values in MHV3 chronically infected mice when treated with CD4+ in combination with CD8+ cells. All T- and/or B-cell treatments, however, were sufficient to thwart the process of the chronic disease, and favoured the survival of mice for up to 6 months p.i.