CD4(+) T-cells are required for the establishment of maedi-visna virus infection in macrophages but not dendritic cells in vivo

The role of CD4(+) lymphocytes in the establishment of lentivirus infection in macrophages has been studied in an in vivo system of lentivirus infecti on where CD4(+) lymphocytes are not the targets for infection. Using the no n-T-cell-tropic lentivirus, maedi-visna virus (MVV), in CD4-depleted sheep, we have found that CD4(+) T cells were required for MW infection in macrop hages but not dendritic cells. CD4-depleted sheep had significantly lower l evels of MVV-infected cells in lymph nodes and efferent lymph after MW chal lenge in the drainage area of the lymph node. Due to the absence of virus i n combination with the lack of CD4(+) T helper cells, virus-specific immune responses were reduced. There was delayed induction of cytotoxic T cell pr ecursors, a marked reduction in virus-specific in vitro proliferative respo nses, and a delay in the appearance of MW-specific antibodies. By contrast, CD4 depletion had no effect on the establishment of MW infection in affere nt lymph dendritic cells migrating from the skin infection site to the lymp h node, (C) 1999 Academic Press.