Multiple effects of interferon on HIV-1 replication

Several cell-intrinsic effectors drive type I interferon-mediated restriction of HIV-1 in primary CD4+ T cells

Type I interferon (IFN) upregulates proteins that inhibit HIV within infected cells. Prior studies have identified IFN-stimulated genes (ISGs) that impede lab-adapted HIV in cell lines, yet the ISG(s) that mediate IFN restriction in HIV target cells, primary CD4+ T cells, are unknown. Here, we interrogate ISG restriction of primary HIV in CD4+ T cells by performing CRISPR-knockout screens with a custom library that specifically targets ISGs expressed in CD4+ T cells. Our investigation identifies previously undescribed HIV-restricting ISGs (HM13, IGFBP2, LAP3) and finds that two factors characterized in other HIV infection models (IFI16 and UBE2L6) mediate IFN restriction in T cells. Inactivation of these five ISGs in combination further diminishes IFN's protective effect against diverse HIV strains. This work demonstrates that IFN restriction of HIV is multifaceted, resulting from several effectors functioning collectively, and establishes a primary cell ISG screening model to identify both single and combinations of HIV-restricting ISGs.

Several cell-intrinsic effectors drive type I interferon-mediated restriction of HIV-1 in primary CD4 + T cells

Type I interferon (IFN) upregulates proteins that inhibit HIV within infected cells. Prior studies have identified IFN-stimulated genes (ISGs) that impede lab-adapted HIV in cell lines, yet the ISG(s) that mediate IFN restriction in HIV target cells, primary CD4 + T cells, are unknown. Here, we interrogate ISG restriction of primary HIV in CD4 + T cells. We performed CRISPR-knockout screens using a custom library that specifically targets ISGs expressed in CD4 + T cells and validated top hits. Our investigation identified new HIV-restricting ISGs (HM13, IGFBP2, LAP3) and found that two previously studied factors (IFI16, UBE2L6) are IFN effectors in T cells. Inactivation of these five ISGs in combination further diminished IFN’s protective effect against six diverse HIV strains. This work demonstrates that IFN restriction of HIV is multifaceted, resulting from several effectors functioning collectively, and establishes a primary cell ISG screening model to identify both single and combinations of HIV-restricting ISGs.

Current status of gene therapy strategies to treat HIV/AIDS

Progress in developing effective gene transfer approaches to treat HIV-1 infection has been steady. Many different transgenes have been reported to inhibit HIV-1 in vitro. However, effective translation of such results to clinical practice, or even to animal models of AIDS, has been challenging. Among the reasons for this failure are uncertainty as to the most effective cell population(s) to target, the diffuseness of these target cells in the body, and ineffective or insufficiently durable gene delivery. Better understanding of the HIV-1 replicative cycle, host factors involved in HIV-1 infection, vector biology and application, transgene technology, animal models, and clinical study design have all contributed vastly to planning current and future strategies for application of gene therapeutic approaches to the treatment of AIDS. This review focuses on the newest developments in these areas and provides a strong basis for renewed optimism that gene therapy will have an important role to play in treating people infected with HIV-1.

Interferon-induced exonuclease ISG20 exhibits an antiviral activity against human immunodeficiency virus type 1

Interferons (IFNs) encode a family of secreted proteins that provide the front-line defence against viral infections. It was recently shown that ISG20, a new 3'-->5' exoribonuclease member of the DEDD superfamily of exonucleases, represents a novel antiviral pathway in the mechanism of IFN action. In this report, it was shown that ISG20 expression is rapidly and strongly induced during human immunodeficiency virus type 1 (HIV-1) infection. In addition, it was demonstrated that the replication kinetics of an HIV-1-derived virus expressing the ISG20 protein (HIV-1(NL4-3ISG20)) was delayed in both CEM cells and peripheral blood mononuclear cells. No antiviral effect was observed in cells overexpressing a mutated ISG20 protein defective in exonuclease activity, suggesting that the antiviral effect was due to the exonuclease activity of ISG20. Paradoxically, despite the antiviral activity of ISG20 protein, virus rescue observed in HIV-1(NL4-3ISG20)-infected cells was not due to mutation or partial deletion of the ISG20 transgene, suggesting that the virus was able to counteract the cellular defences. In addition, HIV-1-induced apoptosis was significantly reduced in HIV-1(NL4-3ISG20)-infected cells suggesting that emergence of HIV-1(NL4-3ISG20) was associated with the inhibition of HIV-1-induced apoptosis. Altogether, these data reflect the ineffectiveness of virus replication in cells overexpressing ISG20 and demonstrate that ISG20 represents a new factor in the IFN-mediated antiviral barrier against HIV-1.

Structure of the mitochondrial ATP synthase by electron cryomicroscopy

We have determined the structure of intact ATP synthase from bovine heart mitochondria by electron cryomicroscopy of single particles. Docking of an atomic model of the F1-c10 subcomplex into a major segment of the map has allowed the 32 A resolution density to be interpreted as the F1-ATPase, a central and a peripheral stalk and an FO membrane region that is composed of two domains. One domain of FO corresponds to the ring of c-subunits, and the other probably contains the a-subunit, the transmembrane portion of the b-subunit and the remaining integral membrane proteins of FO. The peripheral stalk wraps around the molecule and connects the apex of F1 to the second domain of FO. The interaction of the peripheral stalk with F1-c10 implies that it binds to a non-catalytic alpha-beta interface in F1 and its inclination where it is not attached to F1 suggests that it has a flexible region that can serve as a stator during both ATP synthesis and ATP hydrolysis.

Trans-activated interferon-alpha2 delivered to T cells by SV40 inhibits early stages in the HIV-1 replicative cycle

Several lines of evidence suggest a potential major role for interferon (IFN) in controlling HIV-1 replication. However, this inhibition is moderate and is reversible upon IFN removal. To achieve prolonged high concentrations of IFN at the site of infection, we devised an SV40-based vector, SV[HIVLTR]IFN, to direct the synthesis of human IFN-alpha2, by employing a virus-trans-activated human IFN-alpha2 gene to be transcribed in response to HIV-1 infection. Expression of IFN-alpha2 was confirmed by Northern and Western blotting, in SV[HIVLTR]IFN-transduced, HIV-1-challenged human lymphocyte lines and primary human lymphocytes. SV[HIVLTR]IFN-transduced cells showed no evidence of HIV-1-related cytophatic effects when challenged with high doses of HIV-1(NL4-3). As measured by supernatant HIV-1 p24 antigen concentration, IFN-alpha2-expressing cell lines and peripheral blood lymphocytes (PBL) were protected from high-dose challenges of HIV-1. rSV40-delivered IFN-alpha2 inhibited gp120 protein synthesis and expression of HIV-1 mRNAs. Finally, Southern analysis revealed that levels of proviral DNA were markedly reduced in SV[HIVLTR]IFN-transduced cells compared to control cultures. IFN-alpha2 expression driven by HIVLTR delivered by an rSV40 vector thus strongly inhibits HIV-1 replication, probably by blocking a preintegration step in HIV-1 infection. Targeted expression of IFN-alpha2 delivered by SV40 can thus repress HIV-1 replication, and may be a useful approach to HIV-1 treatment.

Immunologic profile of highly exposed yet HIV type 1-seronegative men

The host immune factors that determine susceptibility to HIV-1 infection are poorly understood. We compared multiple immunologic parameters in three groups of HIV-1-seronegative men: 14 highly exposed (HR10), 7 previously reported possibly to have sustained transient infection (PTI), and a control group of 14 low risk blood bank donors (BB). Virus-specific cellular immune assays were performed for CD4(+) T helper cell responses, CD8(+) cytotoxic T lymphocyte activity, CD8(+) cell chemokine release, and CD8(+) cell-derived antiviral soluble factor activity. General immune parameters evaluated included CCR5 genotype and phenotype, interferon alpha production by PBMCs, leukocyte subset analysis, and detailed T lymphocyte phenotyping. Comparisons revealed no detectable group-specific differences in measures of virus-specific immunity. However, the HR10 group differed from the BB group in several general immune parameters, having higher absolute monocyte counts, higher absolute CD8(+) T cell counts and percentages, lower naive and higher terminal effector CD8(+) cells, and lower levels of CD28(+)CD8(+) cells. These changes were not associated with seropositivity for other chronic viral infections. The PTI men appeared to have normal levels of monocytes and slightly elevated levels of CD8(+) T cells (also with increased effector and decreased naive cells). Although we cannot entirely exclude the contribution of other chronic viral infections, these findings suggest that long-lived systemic cellular antiviral immunity as detected by our assays is not a common mechanism for resistance to infection, and that resistance may be multifactorial. General immune parameters reflected by CD8(+) T cell levels and activation, and monocyte concentrations may affect the risk of infection with HIV-1, and/or serve as markers of exposure.

Low-dose IFN-alpha monotherapy in treatment-naive individuals with HIV-1 infection: evidence of potent suppression of viral replication

To evaluate the safety and antiviral action of interferon-alpha (IFN-alpha) in HIV-1 infection, we undertook a proof of concept study in 27 treatment-naive patients. Eligible patients comprised two groups: the IFN-alphaT group (n = 17), which received 5 MIU IFN-alpha s.c. daily for 32 consecutive days, and the IFN-alphaNT group (n = 10), which did not receive IFN-alpha prior to highly active antiretroviral therapy (HAART), which was commenced on day 28 in both groups. IFN-alphaTreatment was well tolerated in 14 of the 17 patients of the IFN-alphaT group who completed the study. The mean HIV RNA reduction in the IFN-alphaT group on day 14 was 1.1 log(10). Viral load suppression was inversely associated with baseline viral load (p = 0.031). Four weeks after initiation of HAART, IFN-alphaT and IFN-alphaNT group patients had 2.40 and 1.82 log(10) HIV RNA reduction from baseline, respectively (p < 0.001). There was no evidence of cross-resistance with existing antiretrovirals in patients with HIV-RNA rebound after initial plasma viral load decline > or = 1 log(10) during IFN-alpha monotherapy. Thus, low daily IFN-alpha exhibits potent anti-HIV-1 activity in vivo without serious adverse effects. These properties render IFN-alpha an attractive candidate for further assessment as a constituent of HAART.

A randomized trial of interferon alpha therapy for HIV type 1 infection

The immunologic and virologic efficacy and safety of interferon a (IFN-alpha) administered in combination with zidovudine (ZDV) and zalcitabine (ddC) was evaluated in HIV-infected subjects with CD4+ cell counts between 300 and 500 cells/ml and no more than 14 weeks of prior antiretroviral therapy. A total of 256 subjects enrolled in an open-label, randomized controlled trial. Subjects were randomized equally into treatment groups. All subjects received ZDV and ddC, while half also receive IFN-alpha (3 MU subcutaneously every 24 hr). At 48 weeks the median average area under the curve minus baseline (AAUCMB) for plasma HIV-1 RNA for the two-drug group was -0.68 versus -0.75 log10 copies/ml for the IFN-alpha group (p = 0.046). Mean HIV-1 RNA changes from baseline to 48 weeks for these groups were -0.65 and -1.12 log10 copies/ml, respectively (p = 0.010). The median AAUCMB for CD4+ cell count for the two-drug group was 28 versus -1 cells/mm3 for the IFN-alpha group (p = 0.011). Neutropenia, anemia, and drug intolerance were more common in the IFN-alpha group. This study demonstrates that IFN-alpha inhibits HIV-1 replication but attenuates the CD4+ cell response to dual therapy with ZDV and ddC.

Phase II, randomized, open-label, community-based trial to compare the safety and activity of combination therapy with recombinant interferon-alpha2b and zidovudine versus zidovudine alone in patients with asymptomatic to mildly symptomatic HIV infection. HIV Protocol C91-253 Study Team

OBJECTIVES

To compare, in a community-based therapeutic setting, the safety, tolerance, and efficacy of combination therapy with recombinant interferon-alpha2b (rIFN-alpha2b) and zidovudine (ZDV) to ZDV monotherapy.

DESIGN

Open-label, two-armed, randomized study.

PATIENTS AND METHODS

Asymptomatic or minimally symptomatic HIV-infected adults without an AIDS-defining illness, a CD4 count of 200 to 500 cells/microl, and < or = 6 months of prior ZDV therapy received ZDV 100 mg orally five times daily. Patients randomized to rIFN-alpha2b received 3 million IU subcutaneously three times weekly for 2 weeks and 5 million IU three times weekly thereafter. The groups were compared with respect to adverse events (AEs), dosing modifications, treatment discontinuation, clinical endpoints and changes in CD4 count. A virology substudy compared the treatments with respect to HIV viral load and development of ZDV resistance.

RESULTS

Between October, 1991 and January, 1993, 139 patients were randomized to combination therapy and 117 to ZDV alone. Of AEs reported at any grade, fatigue, myalgias, and sweating occurred significantly more often with combination therapy (p < .001). Study subjects receiving combination therapy showed modest but significantly greater weight loss (p = .0001), a significantly higher frequency of any abnormal laboratory test result (p = .002), neutropenia (p = .002), and leukopenia (p = .02), and also required dosage reduction for hematologic toxicity significantly more often (p < .05) than those in the ZDV monotherapy arm. No statistically significant differences were found between the groups with respect to development of specific AIDS-defining events, overall event rate, time to events, or change in performance status or CD4+ counts, or percentages or development of ZDV resistance. Viral burden, reflected by serum p24 antigen and quantitative peripheral blood mononuclear cell (PBMC) microcultures, was greater at baseline in the combination therapy group. Baseline SI phenotype predicted progression to AIDS (p = .004, chi2), whereas intermediate susceptibility to ZDV predicted development of ZDV resistance (p < .005, chi2). The annual rate of development of phenotypic resistance to ZDV was 16.8% and was not affected by administration of rIFN-alpha2b.

CONCLUSIONS

At the doses and schedule used in this study, the combination of ZDV with rIFN-alpha2b was not therapeutically superior to ZDV alone and was less well tolerated. The addition of rIFN-alpha2b to ZDV did not prevent or delay the development of ZDV resistance.

Norepinephrine Accelerates HIV Replication Via Protein Kinase A-Dependent Effects on Cytokine Production

To explore the role of sympathetic nervous system activation in HIV pathogenesis, we examined the effect of the neuroeffector molecule norepinephrine (NE) on HIV-1 replication in quiescently infected PBMCs that were subsequently activated with Abs to CD3 and CD28. NE accelerated HIV-1 replication at concentrations ranging from 10−8 to 10−5 M. This effect could be mimicked by protein kinase A (PKA) activators (forskolin or dibutyryl-cAMP) and abrogated by β-adrenoreceptor antagonists or the PKA inhibitor rp-cAMP, indicating transduction via the adrenoreceptor signaling pathway. NE reduced cellular activation and altered the production of several HIV-modulating cytokines: IL-10 and IFN-γ were markedly suppressed; TNF-α, IL-1β, IL-2, IL-4, and IL-6 were mildly suppressed; and levels of IL-12 were not significantly altered. The addition of either exogenous IFN-γ or IL-10 abrogated the effect of NE on virus production. Thus PKA-dependent suppression of cytokine production appears to mediate the enhancement of HIV-1 replication by NE.

Modulation of cytokine-induced HIV gene expression by competitive binding of transcription factors to the coactivator p300

The host response to viral infection involves the secretion of multiple cytokines which alter immune function and viral replication. These proteins activate several signal transduction pathways in infected cells which must be integrated to regulate cellular and viral gene expression. In this report, we demonstrate that specific transcription factors induced by distinct cytokines regulate HIV transcription by competitive binding to the p300 coactivator. Interferon-alpha (IFN-alpha) was found to inhibit NF-kappaB-dependent HIV gene expression stimulated by tumor necrosis factor-alpha (TNF-alpha). This inhibition was mediated by binding of the IFN-alpha signal transducer and activator of transcription 2, Stat2, to a specific domain of p300 which also binds to the RelA (p65) subunit of NF-kappaB. p300 was found to be limiting with respect to RelA (p65) and Stat2, and this effect was reversed by overexpression of p300. Inhibition by Stat2 was specific for NF-kappaB and was not mediated by Stat1, which is also induced by IFN-alpha. Gene activation induced by the Stat2 transcription domain was also inhibited by expression of RelA. These results demonstrate that HIV transcription can be regulated in the nucleus by competitive binding of specific cytokine-induced transcription factors to a discrete domain of a transcriptional coactivator.

Molecular mechanisms of interferon resistance mediated by viral-directed inhibition of PKR, the interferon-induced protein kinase

The interferon (IFN)-induced cellular antiviral response is the first line of defense against viral infection within an animal host. In order to establish a productive infection, eukaryotic viruses must first overcome the IFN-induced blocks imposed on viral replication. The double-stranded RNA-activated protein kinase (PKR) is a key component mediating the antiviral actions of IFN. This IFN-induced protein kinase can restrict viral replication through its ability to phosphorylate the protein synthesis initiation factor eukaryotic initiation factor-2 alpha-subunit and reduce levels of viral protein synthesis. Viruses, therefore, must block the function of PKR in order to avoid these deleterious antiviral effects associated with PKR activity. Indeed, many viruses have developed effective measures to repress PKR activity during infection. This review will focus primarily on an overview of the different molecular mechanisms employed by these viruses to meet a common goal: the inhibition of PKR function, uncompromised viral protein synthesis, and unrestricted virus replication. The past few years have seen exciting new advances in this area. Rather unexpectedly, this area of research has benefited from the use of the yeast system to study PKR. Other recent advances include studies on PKR regulation by the herpes simplex viruses and data from our laboratory on the medically important hepatitis C viruses. We speculate that IFN is ineffective as a therapeutic agent against hepatitis C virus because the virus can effectively repress PKR function. Finally, we will discuss briefly the future directions of this PKR field.

Regulation of human immunodeficiency virus replication by 2',5'-oligoadenylate-dependent RNase L

Activation of RNase L by 2',5'-linked oligoadenylates (2-5A) is one of the antiviral pathways of interferon action. To determine the involvement of the 2-5A system in the control of human immunodeficiency virus type 1 (HIV-1) replication, a segment of the HIV-1 nef gene was replaced with human RNase L cDNA. HIV-1 provirus containing sense orientation RNase L cDNA caused increased expression of RNase L and 500- to 1,000-fold inhibition of virus replication in Jurkat cells for a period of about 2 weeks. Subsequently, a partial deletion of the RNase L cDNA which coincided with increases in virus production occurred. The anti-HIV activity of RNase L correlated with decreases in HIV-1 RNA and with an acceleration in cell death accompanied by DNA fragmentation. Replication of HIV-1 encoding RNase L was also transiently suppressed in peripheral blood lymphocytes (PBL). In contrast, recombinant HIV containing reverse orientation RNase L cDNA caused decreased levels of RNase L, increases in HIV yields, and reductions in the anti-HIV effect of alpha interferon in PBL and in Jurkat cells. To obtain constitutive and continuous expression of RNase L cDNA, Jurkat cells were cotransfected with HIV-1 proviral DNA and with plasmid containing a cytomegalovirus promoter driving expression of RNase L cDNA. The RNase L plasmid suppressed HIV-1 replication by eightfold, while an antisense RNase L construct enhanced virus production by twofold. These findings demonstrate that RNase L can severely impair HIV replication and suggest involvement of the 2-5A system in the anti-HIV effect of alpha interferon.

Interferon-alpha and -gamma differentially reduce rapid immature T-cell death by contact with HIV-1 carrier cell clones in vitro

The non-antigen specific rapid cytotoxic (CT) death of immature TdT+CD4+CD8+ T cells due to contact with HIV-1 carrier T-cell clones we have found recently is a novel phenomenon. The effects of interferons (IFN) on this CT reaction were studied in vitro. Treatment of the HIV-1 carrier clones, referred to as "effectors," with IFN-alpha but not IFN-gamma, or of the susceptible immature TdT+CD4+CD8+ T cells, referred to as "targets," with IFN-gamma but not IFN-alpha, for 24 hr prior to CT testing was found to reduce the CT reaction. Simultaneously, a down-regulated CD8 expression and an up-regulated antigen expression of both major histocompatibility antigen complex class I (MHC-I) and HIV-1 gp120/gp160 in the IFN-alpha treated effector (gp120+CD8+ HPB-ALL/HIV), and/or simultaneously up-regulated antigen expression of both CD8 and MHC-I in the IFN-gamma treated target (CD4+CD8+ HPB-ALL) were found to be associated with reduced CT reaction. However, altered antigen expression in the IFN-gamma treated effectors or IFN-alpha treated targets did not affect the ultimate degree of CT reaction. This study thus suggests a possible therapeutic efficacy of IFN by reducing the direct elimination of the T-cell precursors in HIV-1 infection.

What happens inside lentivirus or influenza virus infected cells: insights into regulation of cellular and viral protein synthesis

Efficient manipulation of the regulatory mechanisms controlling host cell gene expression provides the means for productive infection by animal viruses. Upon infecting the host cell, viruses must: (i) bypass the cellular antiviral defense mechanisms to prevent the translational blocks imposed by the interferon pathway; and (ii) effectively "hijack" the host protein synthetic machinery into mass production of virion protein components. The multicomponent regulatory nature of cellular gene expression has provided the means of selecting for a diverse range of mechanisms utilized by animal viruses to ensure that replication efficiency is maintained throughout the virus life cycle. One important research component of the careful examination of gene regulation is those studies that focus on elucidating the mechanisms by which viruses control mRNA translation during host cell infection. Much of the work in our laboratory has focused on elucidating the strategies by which human immunodeficiency virus type 1 and influenza virus regulate protein synthesis during infection. Here we describe the ways in which these two distinctly different RNA viruses ensure the selective and efficient translation of their viral mRNAs in infected cells. These strategies include circumvention of the deleterious effects associated with activation of the interferon-induced protein kinase, PKR. Herein we describe our methodologies designed to elucidate the translational regulation in cells infected by these viruses. We conclude with a brief summary of new directions, utilizing these methods, taken toward understanding the translational control mechanisms imposed by these viral systems, and how our studies of virally infected cells have allowed us to identify growth-regulating components of normal, uninfected cells.

Anti-HIV potential of a new interferon, interferon-tau (trophoblastin)

Antiretroviral effects of a new class of interferon (IFN), IFN-tau, were compared with those of IFN-alpha in primary peripheral blood lymphocytes (PBLs) and monocyte-derived macrophages (MDMs), infected in vitro by human immunodeficiency viruses type 1, HIV-1/LAI, and HIV-1/DAS isolates, respectively. Cells were treated with recombinant IFN 24 h before or after HIV infection and then continuously exposed. Viral replication was monitored twice a week by quantifying the reverse transcriptase activity in cell culture supernatants. Integrated proviral DNA was monitored 24 h after infection in IFN-tau-pretreated MDMs, using specific gag gene amplification by the polymerase chain reaction. IFN-tau inhibited HIV-1 replication in both PBLs and MDMs as well as in peripheral blood mononuclear cells (PBMCs). IFN-tau was 35-fold more potent than IFN-alpha in PBLs and 100-fold more potent in MDMs. Differences were observed in the amount of integrated proviral DNA between untreated and 10 IU/ml IFN-tau-treated HIV-infected MDMs. IFN-tau exhibits significant anti-HIV activity in comparison to IFN-alpha, and like other IFNs, it seems to interact with several steps of HIV replication cycle.

Regulation of human immunodeficiency virus type 1 and cytokine gene expression in myeloid cells by NF-kappa B/Rel transcription factors

CD4+ macrophages in tissues such as lung, skin, and lymph nodes, promyelocytic cells in bone marrow, and peripheral blood monocytes serve as important targets and reservoirs for human immunodeficiency virus type 1 (HIV-1) replication. HIV-1-infected myeloid cells are often diminished in their ability to participate in chemotaxis, phagocytosis, and intracellular killing. HIV-1 infection of myeloid cells can lead to the expression of surface receptors associated with cellular activation and/or differentiation that increase the responsiveness of these cells to cytokines secreted by neighboring cells as well as to bacteria or other pathogens. Enhancement of HIV-1 replication is related in part to increased DNA-binding activity of cellular transcription factors such as NF-kappa B. NF-kappa B binds to the HIV-1 enhancer region of the long terminal repeat and contributes to the inducibility of HIV-1 gene expression in response to multiple activating agents. Phosphorylation and degradation of the cytoplasmic inhibitor I kappa B alpha are crucial regulatory events in the activation of NF-kappa B DNA-binding activity. Both N- and C-terminal residues of I kappa B alpha are required for inducer-mediated degradation. Chronic HIV-1 infection of myeloid cells leads to constitutive NF-kappa B DNA-binding activity and provides an intranuclear environment capable of perpetuating HIV-1 replication. Increased intracellular stores of latent NF-kappa B may also result in rapid inducibility of NF-kappa B-dependent cytokine gene expression. In response to secondary pathogenic infections or antigenic challenge, cytokine gene expression is rapidly induced, enhanced, and sustained over prolonged periods in HIV-1-infected myeloid cells compared with uninfected cells. Elevated levels of several inflammatory cytokines have been detected in the sera of HIV-1-infected individuals. Secretion of myeloid cell-derived cytokines may both increase virus production and contribute to AIDS-associated disorders.

Selective decrease in human immunodeficiency virus type 1 (HIV-1)-induced alpha interferon production by peripheral blood mononuclear cells during HIV-1 infection

We previously reported that human immunodeficiency virus type 1 (HIV-1), herpes simplex virus (HSV), and Sendai virus induce higher levels of alpha interferon (IFN-alpha) in blood dendritic cells than in monocytes of healthy donors. In the present study, the levels of IFN-alpha induced by T-cell tropic (IIIb and RF) and monocytotropic (BaL) strains of HIV-1 and by HSV were significantly decreased in peripheral blood mononuclear cells (PBMCs) derived from subjects with asymptomatic and symptomatic HIV-1 infection. In contrast, Sendai virus, a paramyxovirus that induces proportionally more IFN-alpha in monocytes and B cells than do either HIV-1 or HSV, stimulated normal levels of IFN-alpha in PBMCs from the HIV-1-infected men. The IFN-alpha produced by PBMCs from the HIV-1-seropositive subjects was partially acid labile, whereas the IFN-alpha produced by PBMCs from the HIV-1-seronegative donors was acid stable. We hypothesize that there is a selective defect in IFN-alpha production by peripheral blood dendritic cells, whereas the host retains the IFN-alpha-producing capacity of monocytes and B lymphocytes. The loss of IFN-alpha production in response to HIV-1, herpesviruses, and possibly other pathogens could contribute to the progression of HIV-1 infection and to the development of AIDS.

Alpha interferon-induced antiretroviral activities: restriction of viral nucleic acid synthesis and progeny virion production in human immunodeficiency virus type 1-infected monocytes

Alpha interferon (IFN-alpha) restricts multiple steps of the human immunodeficiency virus type 1 (HIV-1) life cycle. A well-described effect of IFN-alpha is in the modulation of viral nucleic acid synthesis. We demonstrate that IFN-alpha influences HIV-1 DNA synthesis principally by reducing the production of late products of reverse transcription. The magnitude of IFN-alpha-induced downregulation of HIV-1 DNA and/or progeny virion production was dependent on the IFN-alpha concentration, the duration of cytokine administration, the multiplicity of infection, the viral strain, and the cycles of viral infection. Interestingly, reductions in viral DNAs could not fully account for the observed IFN-alpha-induced abrogation of progeny virion production. These data, by our investigation of both single-cycle and spreading viral infections, support a predominant but not exclusive effect of IFN-alpha on viral DNA synthesis.

Further evaluation of soluble CD4 as an anti-HIV type 1 gene therapy: demonstration of protection of primary human peripheral blood lymphocytes from infection by HIV type 1

We previously reported on the construction of retroviral vectors that produce a secreted form of the HIV-1 receptor, T cell antigen CD4 (Morgan et al., AIDS Res Hum Retroviruses 1990;6:183-191). In this article we test the ability of these sCD4-expressing retroviral vectors to protect human T-cell lines or primary T cells from HIV-1 infection. To demonstrate that protection from HIV-1 infection is mediated by the soluble nature of this protein, two coculture protection experiments were conducted. In these experiments, sCD4-expressing retroviral vectors were used to engineer mouse NIH 3T3 cells. In one coculture experiment the human SupT1 cell line was added directly to the culture of sCD4-producing NIH 3T3 cells, and in another experiment the two cell types were separated physically by a semipermeable membrane. In both coculture configurations, the T cell line was protected from HIV-1 challenge as measured by syncytium formation and indirect immunofluorescent assays. In addition, the SupT1 line was directly engineered with sCD4-expressing retroviral vectors and shown to be protected from HIV-1 challenge. As a prelude to further preclinical studies, we tested the ability of retroviral vectors to transduce primary human peripheral blood lymphocytes (PBLs). Conditions used to stimulate T cell growth resulted in significant shifts in the CD4/CD8 cell in favor of CD8 cells. Retroviral-mediated gene transfer under these conditions resulted in low levels of gene transfer (< 5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased efficacy of human natural interferon alpha (IFN-alpha n3) versus human recombinant IFN-alpha 2 for inhibition of HIV-1 replication in primary human monocytes

Natural IFN-alpha n3, a purified mixture of many different natural IFN alpha species, was 10- to 100-fold more effective than equal concentrations of human rIFN-alpha 2b or rIFN-alpha 2a for inhibition of HIV replication in primary human monocytes. This difference was highly reproducible in multiple side-by-side experiments using the identical HIV-1 inoculum and the same monocyte target cells: natural IFN-alpha n3 was more effective than rIFN-alpha 2b at lower concentrations for protection against a constant HIV-1 inoculum; cells treated with natural IFN-alpha n3 were protected against a greater HIV-1 challenge than were cells treated with the same concentration of rIFN-alpha 2b. Fractionation of natural IFN-alpha n3 by reversed-phase high-pressure liquid chromatography (RP-HPLC) showed that most antiviral activity for HIV localized to discrete and reproducible peaks. The RP-HPLC peak that contained purified natural IFN-alpha 2b was the least effective fraction. These data suggest heterogeneity among IFN-alpha species for antiviral activity against HIV and may provide a molecular basis for more effective IFN-alpha therapy.

Preclinical evaluation of antiviral activity and toxicity of Abbott A77003, an inhibitor of the human immunodeficiency virus type 1 protease

A synthetic, symmetry-based inhibitor of the human immunodeficiency virus type 1 (HIV-1) protease, A77003, was evaluated for antiviral activity and cytotoxicity in vitro in human peripheral blood lymphocytes or cell lines H9, CEM, and U937. Toxicity and antiviral activity of the HIV-1 protease inhibitor were compared with those of the reverse transcriptase inhibitors zidovudine and 2',3'-dideoxy-2',3'-didehydrothymidine and human recombinant alpha and beta interferons. Production of infectious virus particles, cell-free p24 antigen, and cell-associated viral proteins was reduced 50% by the HIV-1 protease inhibitor at concentrations of 0.12 to 0.26 microM (50% effective concentration [EC50]) in acute infection and 0.2 to 1.7 microM (EC50) in persistent infection. Fluorescence-activated cell sorter analysis of U937 cells persistently infected with HIVIIIB using a monoclonal antibody to HIV also showed a reduction of cell-associated viral protein in A77003-treated cells. Furthermore, toxicity of A77003 assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay was not observed at greater than 100 times the EC50. A77003 was more effective in persistent HIV-1 infection than alpha and beta interferons (1,000 U/ml), while zidovudine and 2',3'-dideoxy-2',3'-didehydrothymidine were not active.

Loss of infectivity by progeny virus from alpha interferon-treated human immunodeficiency virus type 1-infected T cells is associated with defective assembly of envelope gp120

Levels of human immunodeficiency virus (HIV) DNA, RNA, or p24 antigen and reverse transcriptase activity in T-cell cultures treated with 500 IU of recombinant alpha interferon (rIFN alpha) per ml were comparable to those in control cultures. Radioimmunoprecipitation analysis of proteins in lysates of IFN-treated T cells documented a marked accumulation of HIV proteins. Localization of gp120 by immunofluorescence showed a diffuse pattern in IFN-treated cells quite distinct from the ring pattern in untreated control cells. That large quantities of gp120 in aberrant cell compartments might affect HIV morphogenesis was confirmed in infectivity studies: virions from IFN-treated cells were 100- to 1,000-fold less infectious than an equal number of virions from control cells. Direct examination of IFN-treated and control HIV-infected cells by transmission electron microscopy showed little difference in the number or distribution of viral particles. However, quantitation of gp120 by immunogold particle analysis revealed a marked depletion of envelope glycoprotein in virions released from IFN-treated cells. This defect in gp120 assembly onto mature viral particles provides a molecular basis for this loss of infectivity.