Human intestinal lamina propria lymphocytes are naturally permissive to HIV-1 infection

The presence of HIV-1 in the intestinal mucosa of AIDS patients has been re ported and human intestinal lamina propria lymphocytes (LPL) have been prop osed as important targets for HIV-1 infection. However, little information is available concerning the permissiveness of human intestinal CD4(+) T lym phocytes to HIV-1 infection. Here, we show that human LPL, in contrast to a utologous peripheral blood lymphocytes (PBL), are permissive to both X4 T-t ropic and R5 M-tropic strains of HIV-I, as well as to clinical isolates, in the absence of exogenous stimuli. Flow cytometry showed that the vast majo rity of T LPL were CD45RO(+) and CD69(+), and that CD4(+) T LPL highly expr essed CG chemokine receptor 5 (CCR5) as compared to PBL, while CX chemokine receptor 4 was equally expressed on LPL End PBL. Exogenous RANTES and macr ophage inflammatory protein-1 alpha (natural CCR5 ligands) virtually abolis hed the entry of the R5 M-tropic strain HIV-1 into human LPL. Thus, we infe r that human intestinal CD4(+) T lymphocytes are naturally susceptible to H IV-1 infection, due to their physiological state of activation and to marke d expression of HIV-1 coreceptors, independently of the route of primary (e ither mucosal or parental) infection and the shifts of the virus phenotype occurring during the course of AIDS.