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To determine the effects of immunomodulatory agents upon HIV replication in macrophages, cultured monocyte-derived macrophages were treated with various substances and then infected with a macrophage-tropic strain of HIV-1. Pretreatment with rIFN-alpha, IFN-beta, and IFN-gamma, or bacterial LPS prevented viral replication in macrophages. In treated cultures, little or no infectious HIV or p24 core antigen was released into the supernatant, no virions were seen by electron microscopy, no viral RNA or DNA was detectable in the cell lysates, and no cytopathology (as determined by multinucleated giant cell formation) occurred. In contrast, pretreatment with a wide dose range of recombinant IL-1 beta, IL-2, IL-4, IL-6, M-CSF, TNF, or lymphotoxin failed to protect macrophages from productive infection by HIV. A consistent effect of granulocyte/macrophage-CSF on HIV replication in macrophages was not observed. In dose response studies, pretreatment with approximately 100 U/ml of IFN-alpha, approximately 10 U/ml of IFN-beta, or approximately 100 U/ml of IFN-gamma was sufficient to prevent virion release maximally and to prevent cytopathology completely. In kinetic studies, IFN-alpha, IFN-gamma, or LPS were added to the macrophage cultures either before or after infection with HIV. Even when added 3 d after infection with a multiplicity of 1 50% tissue-culture infectious dose per cell, all three treatments markedly reduced virion release, suggesting that these agents act at a point in the viral life cycle beyond the early events of virus binding, penetration, and uncoating. These data indicate that HIV replication in previously uninfected macrophages may be regulated by an inducible host cell mechanism. These findings may explain the restricted replication of HIV in macrophages in vivo and suggest an antiviral role for interferons in the therapy of HIV infection.

The mechanisms by which HIV-1 infection kills T lymphocytes are not clearly established. Apoptosis is an internally programmed cell death pathway that may regulate both T cell development and senescence, and that is characterized by cleavage of DNA at internucleosomal regions. The present experiments show that acute HIV-1 infection of MT2 lymphoblasts and activated normal peripheral blood mononuclear cells induces apoptosis.

Conventional assays based on infection of T-cell lymphoblastoid lines with tissue culture-adapted strains of human immunodeficiency virus (HIV)

A series of dipyridodiazepinones have been shown to be potent inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. The lead compound, BI-RG-587, had a 50% inhibitory concentration of 84 nM against HIV-1 reverse transcriptase activity. This compound reduced plaque formation of HIV-1 in HeLa cells expressing the CD4 receptor by 50% at 15 nM. BI-RG-587 at comparable concentrations inhibited the production of p24 antigen following the acute infection of CEM T-lymphoblastoid cells or primary human monocyte-derived macrophages with HIV-1. No inhibitory effects against HIV-2 or against three picornaviruses were detected. Zidovudine (3'-azido-3'-deoxythymidine [AZT])-susceptible and AZT-resistant isolates of HIV-1 were equally susceptible to BI-RG-587. AZT and BI-RG-587 exhibited synergistic inhibition of HIV-1BRU at all concentrations examined.

SummaryHigh levels of unintegrated viral DNA accumulate during human immunodeficiency virus type 1 (HIV 1) infection of CEM T cells. Reinfection of already infected cells is required to attain these levels and reinfection also promotes the development of HIV-induced cytopathology. Rates of virus production, however, are independent of the accumulation of unintegrated viral DNA . Neutralizing antibody added soon after infection reduced viral DNA levels without appreciably affecting the production of cell-free viral p24 antigen or reverse transcriptase activity. Only 50 pM AZT were required to reduce the accumulation of unintegrated viral DNA by 50% in contrast to the 25 nM required to inhibit virus production by 50%. Cytopathology,-as measured by number of syncytia in infected cell cultures, was correlated with highly elevated levels of unintegrated viral DNA . The minimal levels of unintegrated viral DNA present constitutively in the persistently infected HCEM cell line were consonant with the absence of cytopathic effects in these cells. These data demonstrate that inhibiting the reinfection of already infected cells modulates cytopathic HIV-1 infection to a form that is persistent and noncytopathic.Depletion of CD4 T lymphocytes is an important feature of the natural history of HIV-1 infection (1, 2). Reduced numbers in this cell population predict disease progression (1-3) and are likely to contribute to immunodeficiency (4) . HIV-1 infection in vitro is rytopathic for T lymphocytes (5-7) and T lymphoid cell lines (8,9). This cytopathology occurs by the formation of syncytia when infected and uninfected CD4+ cells are admixed (8, 9) and direct cell killing by a mechanism independent of cell fusion (10) . Based on the cytopathic effects of HIV-1 infection of T cells in vitro, this mechanism was proposed to be a crucial feature of viral pathogenesis in AIDS (6,5,11, 12) . In this study, we have examined the role of reinfection and viral DNA accumulation in cytopathic and persistent HIV-1 infection of the CEM cell line.Host-pathogen interactions leading to cytopathology have been characterized extensively in avian retrovirus models. The accumulation of high levels of unintegrated viral DNA is a recognized feature of rytopathic infection by these retroviruses (13, 14) and was also shown to be an important marker of pathogenesis in the case of feline leukemia virus infection of cats (15) and equine infectious anemia virus infection of horses (16).Unintegrated viral DNA is generated by reverse transcription of infecting viral RNA . A linear viral DNA molecule 1035 flanked at both ends by long terminal repeat (LTR)t sequences (17) is generally found to be the most abundant form of unintegrated viral DNA . Intramolecular recombination between the LTR sequences then generates a circular molecule with one LTR that is of intermediate abundance . A circular DNA form with two LTR seems to arise via direct ligation of the ends of a linear molecule and is the least abundant species . Importantly, these DNA species are pro...

Changing treatment from zidovudine to 500 mg per day of didanosine appears to slow the progression of HIV disease.

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