TUMOR-NECROSIS-FACTOR-ALPHA INHIBITS ENTRY OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INTO PRIMARY HUMAN MACROPHAGES - A SELECTIVE ROLE FOR THE75-KILODALTON RECEPTOR

The proinflammatory cytokine tumor necrosis factor alpha (TNF alpha) i s readily detected after human immunodeficiency virus type 1 (HIV-1) i nfection of primary macrophages in vitro and is present in plasma and tissues of patients with AIDS. Previous studies have shown that human recombinant TNF alpha (hrTNF alpha) enhances HIV replication in both c hronically infected promonocytic and T-lymphoid cell lines in vitro. W e report here that in contrast to untreated tissue culture-differentia ted macrophages (TCDM), in which the proviral long terminal repeat (LT R) could be detected as soon as 8 h postinfection by a PCR assay, TCDM pretreatment for 3 days by hrTNF alpha markedly delayed its appearanc e until 72 h after infection with the HIV-1 Ada monocytotropic strain, Moreover the inhibition of formation of the proviral LTR in HIV-1-inf ected TCDM was directly proportional to the concentration of hrTNF alp ha used, To determine if the inhibition of LTR formation results from blockade of viral entry, we performed a reverse transcription PCR assa y to detect intracellular genomic viral RNA as early as 2 h after infe ction, Pretreatment of primary TCDM by hrTNF alpha for 3 days and even for only 2 h inhibits 75% of the viral entry into the cells, The inhi bition of viral entry by hrTNF alpha was totally abolished by the use of anti-human TNF alpha monoclonal antibody, By using TNF alpha mutant s specific for each human TNF alpha receptor, we showed that the inhib ition of HIV-1 entry into TCDM was mediated not through the 55-kDa TNF receptor but through the 75-kDa TNF receptor, Although prolonged (1 t o 5 days) TNF alpha treatment can downregulate CD4 expression in prima ry human TCDM, surface CD 1 levels were not reduced by 2 h of treatmen t and was therefore not a limiting step For HIV-1 entry, In contrast t o the inhibition of viral entry into primary TCDM, pretreatment with h rTNF alpha did not modify HIV-1 entry into phytohemagglutinin A-activa ted peripheral blood lymphocytes, TNF alpha-pretreatment inhibited HIV -1 replication in primary TCDM but not in phytohemagglutinin A-activat ed peripheral blood lymphocytes as assessed by decreased reverse trans criptase activity in culture supernatants. These results demonstrate t hat TNF alpha is able to enhance host cellular resistance to HIV-1 inf ection and that selective inhibition of HIV-1 entry into primary TCDM by TNF alpha involves the 75-kDa TNF receptor but not the 55-kDa TNF r eceptor.