IMMUNOPHENOTYPIC CHARACTERIZATION OF SIMIAN IMMUNODEFICIENCY VIRUS-INFECTED DENDRITIC CELLS IN CERVIX, VAGINA, AND DRAINING LYMPH-NODES OF RHESUS-MONKEYS

Significant progress has been made in understanding the biology of het erosexual transmission of HIV by utilizing the simian immunodeficiency virus (SIV)/rhesus monkey animal model. Our previous studies have sho wn that SIV-infected cells within the stratified squamous epithelium o f the vagina have a dendritic morphology. However, the type of cell in fected was not conclusively determined. The purpose of the present stu dy was to immunophenotype the SIV-infected cells in the lower reproduc tive tract and genital lymph nodes of the female rhesus monkey. Vagina , cervix, and iliac lymph node from eight chronically SIV-infected adu lt female monkeys were examined for this study. None of the animals ha d histologic evidence of opportunistic infections or genital tract pat hogens other than SIV. Combined in situ hybridization and immunohistoc hemistry were used to detect SIV RNA and to determine the immunophenot ype of SIV-infected cells in tissue sections and cytospin preparations of cells from the tissues. We now show that SIV-infected cells were m ost common in iliac lymph node and that the majority of infected cells in the lymph node were T lymphocytes. SIV-infected macrophages, Lange rhans' cells, and dendritic cells were also found in the lymph node. S IV-infected cells were found within the epithelium and lamina propria of the vagina. Although most of the infected cells were T cells, a sig nificant proportion (approximately 40%) of the SIV-infected cells in c ytospin preparations from explant cultures of vagina and cervix were L angerhans' cells. SIV-infected T cells in the lower genital tract were commonly associated with focal mononuclear cell infiltrates. SIV-infe cted macrophages were rarely found in the genital tract. The present s tudy provides the first direct demonstration that Langerhans' cells an d dendritic cells in the genital tract and lymph nodes are infected wi th SIV in vivo. Thus, dendritic cells, in general, and Langerhans' cel ls, in particular, are important reservoirs for HIV/SIV replication in vivo.