HIV infection is active and progressive in lymphoid tissue during the clinically latent stage of disease

Abnormalities in subset distribution, activation, and differentiation of T cells isolated from large intestine biopsies in HIV infection. The Berlin Diarrhoea/Wasting Syndrome Study Group

Intestinal T cells have a unique state of activation and differentiation which might specifically affect or be affected by HIV infection. Lymphocyte subsets in the peripheral blood are well characterized, but our knowledge about intestinal lymphocytes in HIV infection is incomplete. We therefore analysed lymphocytes isolated from large intestine biopsies of AIDS patients and controls by three-colour cytofluorometry. In the large intestine of HIV-infected patients CD4 T cells were reduced and CD8 T cells were increased compared with controls. Most of the CD8 T cells in the colorectal mucosa of AIDS patients were of the cytotoxic phenotype. Activated and resting CD4 T cells were similarly reduced, the expression of CD25 and HLA-DR of CD8 T cells was unaltered and increased, respectively. In intestinal CD4 T cells the expression of CD29 was decreased, but the expression of CD45RO and HML-1 was normal. CD8 T cells had a decreased expression of all these differentiation markers. Our findings demonstrate substantial alterations in subset distribution, activation, and differentiation of large intestine T cells, which may contribute to the secondary infections and malignancies commonly observed in the gut of AIDS patients.

Analysis of long-term viral expression in CEM cells persistently infected with non syncytium-inducing HIV-1 strains

CEM cells were infected with three HIV-1 non syncytium-inducing (NSI) strains obtained from AIDS patients or seropositive individuals. The surviving cells were followed for several months in the persistently infected cultures designated 65870/CEM, 65871/CEM and 3929/CEM, and analyzed for virus expression using light and electron microscopy, immunofluorescence, reverse transcriptase assay, polymerase chain reaction amplification (PCR), nucleic acid hybridization and flow cytometry. The virus isolates induced relatively few syncytia and other cytopathic effects in the corresponding cell lines and the number of cells positive for virus expression never rose above 44%. Distinct peaks of antigen-positive cells were obtained, coincident with high levels of reverse transcriptase activity. The cultures were strongly resistant to superinfection by laboratory strain Lai, with the exception of 65870/CEM which expressed HIV antigens in up to 15% of the cells for a few days. However, cell lysis was minimal in all cases. After long-term cultivation of the three cultures, no antigen-positive cells were detected and no trace of virus expression could be observed. The remaining cells consisted entirely of CD4-negative cells. PCR analyses indicated that cells harboring a provirus were progressively eliminated from the cultures, leaving only virus-free cells. In this system, cells carrying a latent provirus survive for a limited period of time before virus activation induces cell lysis. These results suggest that at least three types of cells exist in the CEM cell line: CD4-positive cells which are rapidly killed by the virus, a second type harboring a latent viral genome after the infection and which grow normally until activation of the resident genome by external or internal signal(s), and a third type which represents rare CD4-negative cells present in the initial CEM population and which are selected for by the NSI isolates. This is the first study documenting specific interactions between NSI strains of HIV-1 and distinct subpopulations of CEM cells grown as a single cell culture.

Characterization of a family of related cellular transcription factors which can modulate human immunodeficiency virus type 1 transcription in vitro

LBP-1 is a cellular protein which binds strongly to sequences around the human immunodeficiency virus type 1 (HIV-1) initiation site and weakly over the TATA box. We have previously shown that LBP-1 represses HIV-1 transcription by inhibiting the binding of TFIID to the TATA box. Four similar but distinct cDNAs encoding LBP-1 (LBP-1a, -b, -c, and -d) have been isolated. These are products of two related genes, and each gene encodes two alternatively spliced products. Comparison of the amino acid sequence of LBP-1 with entries in the available protein data bases revealed the identity of LBP-1c to alpha-CP2, an alpha-globin transcription factor. These proteins are also homologous to Drosophila melanogaster Elf-1/NTF-1, an essential transcriptional activator that functions during Drosophila embryogenesis. Three of the recombinant LBP-1 isoforms show DNA binding specificity identical to that of native LBP-1 and bind DNA as a multimer. In addition, antisera raised against recombinant LBP-1 recognize native LBP-1 from HeLa nuclear extract. Functional analyses in a cell-free transcription system demonstrate that recombinant LBP-1 specifically represses transcription from a wild-type HIV-1 template but not from an LBP-1 mutant template. Moreover, LBP-1 can function as an activator both in vivo and in vitro, depending on the promoter context. Interestingly, one isoform of LBP-1 which is missing the region of the Elf-1/NTF-1 homology is unable to bind DNA itself and, presumably through heteromer formation, inhibits binding of the other forms of LBP-1, suggesting that it may function as a dominant negative regulator.

Human immunodeficiency virus type 1 (HIV-1) and human hematopoietic progenitor cells

Besides a progressive depletion of CD4+ T-lymphocytes, other peripheral blood cytopenias, (granulocytopenia, anemia and thrombocytopenia) are frequently observed in HIV-1 seropositive individuals, especially in patients with overt AIDS. Various experimental evidences suggest that HIV-1 could play a direct role in the pathogenesis of HIV-1 related peripheral blood cytopenias, affecting the survival/proliferation capacity of hematopoietic progenitors. CD34+ human hematopoietic progenitors, however, are substantially not susceptible to HIV-1 infection either in vitro and in vivo and their defects seem rather related to an alteration of bone marrow and peripheral blood microenvironments due to the presence of soluble HIV-1 specific products.

Mucosal model of genital immunization in male rhesus macaques with a recombinant simian immunodeficiency virus p27 antigen

Human immunodeficiency virus (HIV) can be transmitted through infected seminal fluid or vaginal or rectal secretions during heterosexual or homosexual intercourse. To prevent mucosal transmission and spread to the regional lymph nodes, an effective vaccine may need to stimulate immune responses at the genitourinary mucosa. In this study, we have developed a mucosal model of genital immunization in male rhesus macaques, by topical urethral immunization with recombinant simian immunodeficiency virus p27gag, expressed as a hybrid Ty virus-like particle (Ty-VLP) and covalently linked to cholera toxin B subunit. This treatment was augmented by oral immunization with the same vaccine but with added killed cholera vibrios. Polymeric secretory immunoglobulin A (sIgA) and IgG antibodies to p27 were induced in urethral secretions, urine, and seminal fluid. This raises the possibility that the antibodies may function as a primary mucosal defense barrier against SIV (HIV) infection. The regional lymph nodes which constitute the genital-associated lymphoid tissue contained p27-specific CD4+ proliferative and helper T cells for antibody synthesis by B cells, which may function as a secondary immune barrier to infection. Blood and splenic lymphocytes also showed p27-sensitized CD4+ T cells and B cells in addition to serum IgG and IgA p27-specific antibodies; this constitutes a third level of immunity against dissemination of the virus. A comparison of genito-oral with recto-oral and intramuscular routes of immunization suggests that only genito-oral immunization elicits specific sIgA and IgG antibodies in the urine, urethra, and seminal fluid. Both genito-oral and recto-oral immunizations induced T-cell and B-cell immune responses in regional lymph nodes, with preferential IgA antibody synthesis. The mucosal route of immunization may prevent not only virus transmission through the genital mucosa but also dissemination and latency of the virus in the draining lymph nodes.

Nevirapine resistance mutations of human immunodeficiency virus type 1 selected during therapy

Drug susceptibility and mutations in the reverse transcriptase (RT) gene were analyzed with 167 virus isolates from 38 patients treated with nevirapine, a potent nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) RT. Resistant isolates emerged quickly and uniformly in all patients administered nevirapine either as monotherapy or in combination with zidovudine (AZT). Resistance developed as early as 1 week, indicating rapid turnover of the virus population. The development of resistance was associated with the loss of antiviral drug activity as measured by CD4 lymphocyte counts and levels of HIV p24 antigen and RNA in serum. In addition to mutations at amino acid residues 103, 106, and 181 that had been identified by selection in cell culture, mutations at residues 108, 188, and 190 were also found in the patient isolates. Sequences from patient clones documented cocirculating mixtures of populations of different mutants. The most common mutation with monotherapy, tyrosine to cysteine at residue 181, was prevented from emerging by coadministration of AZT, which resulted in the selection of alternative mutations. The observations documented that, under selective drug pressure, the circulating virus population can change rapidly, and many alternative mutants can emerge, often in complex mixtures. The addition of a second RT inhibitor, AZT, significantly altered the pattern of mutations in the circulating population of HIV.

The presence of tat protein or tumor necrosis factor alpha is critical for herpes simplex virus type 1-induced expression of human immunodeficiency virus type 1

Tat-independent transcription of human immunodeficiency virus type 1 (HIV-1) plays an important role in virus life cycle before biologically significant levels of Tat protein have been accumulated. Using a latently infected T-cell line containing an integrated Tat-defective HIV-1 provirus, we examined whether factors known to up-regulate the HIV-1 expression in vitro can replace the requirement for a functional Tat protein and induce the expression of the Tat-defective HIV-1 provirus. Both tumor necrosis factor alpha (TNF-alpha) and herpes simplex virus type 1 (HSV-1) infection stimulated transcription of the Tat-defective HIV-1 provirus to comparable levels, but in HSV-1-infected cells, the cytoplasmic HIV-1 transcripts were not efficiently translated in the absence of Tat protein and were excluded from the large polysomes. However, HSV-1 infection did not affect the distribution of cellular gamma-actin RNA or 28S RNA in the polysomal fractions. The translational block of HIV-1 RNA was not mediated by the virion-associated host cell shutoff protein (vhs); dissociation of HIV-1 transcripts from the polysomes and inefficient translation was also observed in cells infected with the vhs-defective mutant of HSV-1 (vhs-1). Overexpression of Rev protein did not rescue the synthesis of HIV-1 proteins in these cells; however, the observed inhibition of HIV-1 RNA translation was efficiently overcome in the presence of Tat protein or TNF-alpha. These findings suggest that, in contrast to TNF-alpha, HSV-1 infection is not able to induce a full cycle of HIV-1 replication and that cytokines and Tat have a critical role in the activation of HIV-1 provirus by HSV-1.

CD8+ cytolytic T lymphocytes become infected in vitro in the process of killing HIV-1-infected target cells

In the present study the requirements for in vitro infection of antigen-specific CD8+ cytotoxic T lymphocytes (CTL) with human immunodeficiency virus -1(HIV-1) were investigated. CD3+CD8+CD4- HIV-1 nef-specific CTL become infected with HIV-1 after short-term co-culture with HLA-matched HIV-1-infected CD20+ B lymphoblastoid cells (B-LCL) which are specifically killed. Similar results were observed with an allospecific CD8+ CTL population. In addition, co-culture experiments showed that once infected with HIV-1, these CD8+ CTL could spread the infection further to uninfected CD4+ lymphocytes. In contrast, CD8+ CTL did not become infected with HIV-1 when co-cultured with HLA-mismatched HIV-1-infected B-LCL which are not killed. These observations in vitro could have relevance in peripheral lymphoid organs contributing to the progressive decrease of HIV-specific CD8+ CTL activity that is associated with the progression to AIDS.

Redistribution of HIV outside the lymphoid system with onset of AIDS

The basis for many of the symptoms and pathological changes found in patients with the acquired immunodeficiency syndrome (AIDS) remains poorly understood. We have used a quantitative polymerase chain reaction technique to investigate the extent to which direct infection with human immunodeficiency virus (HIV) produces the disease manifestations of AIDS. In five patients who died with AIDS-defining illnesses (Centers for Disease Control and Prevention class IV), we found variable, but in many cases extensive, infection by HIV at various sites, including brain, lung, colon, and liver. By contrast, in three HIV-positive subjects who died without HIV-related disease (CDC class II), we found no evidence of significant infection of any non-lymphoid organ. In both groups of patients there were high levels of infection in cells of the spleen, lymph nodes, and peripheral blood. Pathological examination of tissues from the AIDS patients revealed many abnormalities, of which some, such as giant-cell encephalitis in the brain, were specifically associated with the presence of high levels of HIV infection. These findings suggest that spread of HIV outside cells of the immune system is a late event in HIV infection and is extremely sensitive to the degree of immunosuppression in the patient.

Disseminated human immunodeficiency virus 1 (HIV-1) infection in SCID-hu mice after peripheral inoculation with HIV-1

A small animal model that could be infected with human immunodeficiency virus 1 (HIV-1) after peripheral inoculation would greatly facilitate the study of the pathophysiology of acute HIV-1 infection. The utility of SCID mice implanted with human fetal thymus and liver (SCID-hu mice) for studying peripheral HIV-1 infection in vivo has been hampered by the requirement for direct intraimplant injection of HIV-1 and the continued restriction of the resultant HIV-1 infection to the human thymus and liver (hu-thy/liv) implant. This may have been due to the very low numbers of human T cells present in the SCID-hu mouse peripheral lymphoid compartment. Since the degree of the peripheral reconstitution of SCID-hu mice with human T cells may be a function of the hu-thy/liv implant size, we increased the quantity of hu-thy/liv tissue implanted under the renal capsule and implanted hu-thy/liv tissue under the capsules of both kidneys. This resulted in SCID-hu mice in which significant numbers of human T cells were detected in the peripheral blood, spleens, and lymph nodes. After intraimplant injection of HIV-1 into these modified SCID-hu mice, significant HIV-1 infection was detected by quantitative coculture not only in the hu-thy/liv implant, but also in the spleen and peripheral blood. This indicated that HIV-1 infection can spread from the thymus to the peripheral lymphoid compartment. More importantly, a similar degree of infection of the hu-thy/liv implant and peripheral lymphoid compartment occurred after peripheral intraperitoneal inoculation with HIV-1. Active viral replication was indicated by the detection of HIV-1 gag DNA, HIV-1 gag RNA, and spliced tat/rev RNA in the hu-thy/liv implants, peripheral blood mononuclear cells (PBMC), spleens, and lymph nodes of these HIV-1-infected SCID-hu mice. As a first step in using our modified SCID-hu mouse model to investigate the pathophysiological consequences of HIV-1 infection, the effect of HIV-1 infection on the expression of human cytokines shown to enhance HIV-1 replication was examined. Significantly more of the HIV-1-infected SCID-hu mice expressed mRNA for human tumor necrosis factors alpha and beta, and interleukin 2 in their spleens, lymph nodes, and PBMC than did uninfected SCID-hu mice. This suggested that HIV-1 infection in vivo can stimulate the expression of cytokine mRNA by human T cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Potential pitfalls on the road to an effective HIV vaccine

Experimental vaccines for AIDS prophylaxis are being tested in larger and higher-risk populations. Here, David Schwartz, an advocate of HIV-vaccine research and development, highlights some of the concerns that have been voiced about this strategy and presents a simple mathematical model that considers the drawbacks to vaccine-induced expansion of HIV-specific CD4+ T cells.

Fusion from without directed by human immunodeficiency virus particles

Fusion from without is the process through which particles of some enveloped viruses can direct fusion of target cells in the absence of viral replication. We demonstrate here that human immunodeficiency virus (HIV) particles can efficiently promote fusion from without. Using HeLa-CD4 cells carrying a Tat-inducible lacZ gene, we observed syncytia as early as 6 h after exposure to HIV particles, before HIV gene expression could be detected. Efficient syncytium formation could be obtained when cells were treated with zidovudine, which prevented HIV replication and expression but not cell-cell fusion. Fusion was also observed when cells were exposed to particles of a replication-defective HIV integrase mutant. Fusion from without by HIV particles could be blocked by a monoclonal antibody specific for the V3 loop of the HIV-1 envelope glycoprotein and by soluble CD4. This mechanism of cytopathicity, which can involve cells that do not actively replicate HIV and can be directed by replication-defective particles, could participate in the pathogenicity of the CD4 cell depletion that characterizes HIV infection.

Kinetics of primary SIV infection in lymph nodes

The very early stages of SIV infection in lymph nodes of rhesus monkeys were characterized by in situ hybridization. Massive viral replication was detected in macrophages and lymphocytes during the first week of infection. In a second phase, SIV RNA concentrated in the developing germinal centers, and colocalized with the follicular dendritic cells. The down-regulation of the viral load in lymph nodes varied depending on the animal, indicating early differences in the susceptibility to SIV infection.

Human immunodeficiency virus type 1 mRNA expression in peripheral blood cells predicts disease progression independently of the numbers of CD4+ lymphocytes

To address the significance of human immunodeficiency virus (HIV) replication in peripheral blood mononuclear cells (PBMCs), we have used reverse transcriptase-initiated PCR to measure HIV-1 mRNA expression in PBMC specimens collected from a cohort of HIV-infected individuals during a long-term prospective study. We found dramatic differences in HIV mRNA expression among individuals with very similar clinical and laboratory indices, and this variation strongly correlated with the future course of the disease. No evidence of viral replication was detected in PBMCs from asymptomatic individuals who, thereafter, had normal levels of CD4+ cells for at least 5 years. Irrespective of whether the CD4+ cell numbers were normal at the time of sampling, abundant expression of HIV-1 mRNA in PBMCs predicted accelerated disease progression within the next 2 years. Thus, independently of what may be the rate of HIV replication in other viral reservoirs, such as lymphatic tissue, the amount of HIV mRNA in PBMCs appears to reflect the subsequent development of HIV disease. We have also used the reverse transcriptase-initiated PCR assay to demonstrate a transient response to 3'-azido-3'-deoxythymidine treatment. Determination of HIV-1 mRNA expression in the PBMCs of infected individuals could, therefore, have significant clinical utility as a prognostic indicator and as a means to guiding and monitoring antiviral therapies.

Modulation of the effector function of human monocytes for Mycobacterium avium by human immunodeficiency virus-1 envelope glycoprotein gp120

Disseminated Mycobacterium avium infection in AIDS is associated with high tissue burdens (10(9)-10(10) mycobacteria/g tissue) of organism. The basis for the extraordinary susceptibility of AIDS to M. avium infection is unclear. HIV or its constituents may alter mononuclear phagocyte functions resulting in enhanced intracellular M. avium growth. The effects of an envelope glycoprotein (gp120), a transmembrane protein (p121), and core proteins of HIV-1 on M. avium infection of human monocytes were examined. Preculturing monocytes with gp120 inhibited M. avium phagocytosis and consistently enhanced intracellular growth of six M. avium strains. Pretreatment with p121, gag5, or p24 did not inhibit phagocytosis nor enhance intracellular growth of M. avium. Incubation of gp120 with soluble CD4 before addition to monocyte cultures or pretreatment of monocytes with OKT4A abrogated gp120 effects on M. avium phagocytosis and intracellular growth. gp120 also augmented cytokine production by infected monocytes. These results suggest that gp120, but not p121 or core proteins, modulate monocyte phagocytosis and enhance intracellular growth of M. avium at least in part through monocyte CD4 receptors. Direct effects of HIV-1 products may, therefore, contribute to the diathesis of AIDS to develop disseminated M. avium infection and to the extensive replication of the organisms within tissue macrophages.

Human transcription factor YY1 represses human immunodeficiency virus type 1 transcription and virion production

The transcriptional activity of human immunodeficiency virus type 1 (HIV-1) is affected by many cellular factors. Homologies near the HIV-1 initiator region to the DNA-binding sequences of YY1, a multifunctional transcription factor known to regulate diverse viral and cellular promoters, suggested that YY1 might regulate HIV-1. Antibody to YY1 blocked the formation of complexes by HeLa cell nuclear extract and a DNA oligonucleotide encoding the HIV-1 initiator region. HIV-1 long terminal repeat (LTR) expression, as measured the expression of a transfected LTR-CAT reporter gene, was repressed more than 12-fold by the cotransfection of a YY1 expression vector. HIV-1 production by both COS-1 and CEM cells after transfection of an infectious molecular HIV-1 clone was repressed 7- to 20-fold by cotransfection of a YY1 expression vector. HIV-1 production was also decreased threefold in a CD4-positive lymphocyte cell line chronically infected with HIV-1 (8E5) after transfection of YY1. In situ hybridization studies confirmed that YY1 reduced HIV-1 RNA expression. YY1 may play an important role in the regulation of HIV-1 LTR expression in vivo and virus production by infected cells.

MT-2 cell tropism as prognostic marker for disease progression in human immunodeficiency virus type 1 infection

The ability of human immunodeficiency virus type 1 (HIV-1) isolates to replicate in MT-2 cells was investigated as a prognostic marker for disease progression and CD4+ lymphocyte depletion in 53 HIV-1-infected, asymptomatic individuals. MT-2-negative viruses were isolated from 49% of the patients both early and late during the follow-up period; 38% converted from being MT-2 negative to MT-2 positive, while 11% were MT-2 positive throughout the study. One individual showed a fluctuating virus phenotype. The loss of CD4+ lymphocytes was significantly more rapid in MT-2-positive patients. We found a broad spectrum of CD4+ lymphocyte changes in patients whose virus changed its MT-2 tropism. Our data suggest that the changes could be divided into three general patterns. A stable or slowly decreasing CD4+ lymphocyte count changed into a more rapid fall in 44% of the patients, no significant change in rate of decline could be noted in 44% of the patients, while a stable CD4+ lymphocyte level after a change in MT-2 tropism was noted in 12% of the patients. A correlation between MT-2 tropism and clinical symptoms was also noted. Half of the patients with MT-2-negative virus throughout the study were still asymptomatic after a mean follow-up time of 80 months, while only 15% of those who converted remained asymptomatic. All patients with MT-2-positive viruses at the time of inclusion in the study developed HIV-1-related symptoms, and half of them died during the study. The MT-2 status of 16 patients, could be determined at the time of AIDS diagnosis; 50% were Mt-2 positive, while 50% were MT-2 negative. No difference in AIDS-defining diagnoses or CD4+ lymphocyte counts at the time of diagnosis was noted. Knowledge of the HIV-1 phenotype may improve the early recognition of progressive disease.

Interleukin 1 induces expression of the human immunodeficiency virus alone and in synergy with interleukin 6 in chronically infected U1 cells: inhibition of inductive effects by the interleukin 1 receptor antagonist

In the present study we have observed that interleukin (IL) 1 alpha or IL-1 beta directly induced expression of human immunodeficiency virus (HIV) in the latently infected human promonocytic cell line U1. In addition, IL-1 synergized with IL-6, but not with tumor necrosis factor, in the upregulation of virus expression in U1 cells as measured by accumulation of steady-state mRNAs and production of reverse transcriptase activity. The HIV inductive effect of IL-1 was blocked by transforming growth factor beta, anti-IL-1 antibodies, or monoclonal antibodies directed to the type 1, but not to the type 2, cell surface receptor for IL-1; the latter actually caused enhancement of the IL-1-mediated effect. Unlike tumor necrosis factor alpha, IL-1 either alone or in combination with IL-6 did not induce activation of the transcription activating factor NF-kappa B above the constitutive levels of unstimulated U1 cells. Finally, the IL-1 receptor antagonist effectively blocked IL-1-mediated direct and synergistic inductive effects on virus production. Thus, IL-1 may be an important mediator of HIV expression, and blocking of IL-1 expression and/or its effects may have a potential therapeutic role in the inhibition of HIV expression in infected individuals.

Antiretroviral therapy for human immunodeficiency virus infection: hope and despair

While considering AIDS as an infectious disease with a direct relation between the etiologic agent and the deep immunodeficiency, antiretroviral drugs created much hope. The only transient effect observed with AZT treatment may not be due only to resistance occurrence but to effects that AZT does not target. These effects seem to be related to cytokines secretion which major the immunodepression. Efficient treatment should restore a normal cytokines network.

Persistence of four related human immunodeficiency virus subtypes during the course of zidovudine therapy: relationship between virion RNA and proviral DNA

Human immunodeficiency virus (HIV) virion RNA and proviral DNA sequences have been examined over a 1-year period in an HIV-seropositive patient, commencing with the start of zidovudine treatment. By characterizing the variable V3 and V4 env domains, four related but structurally discrete genotypes could be identified prior to the start of therapy and during the subsequent 60-week period of therapy. Each of the four subtypes showed a unique pattern in the preservation of glycosylation sites. A comparison of the V3 amino acid sequences in peripheral blood mononuclear cell proviral DNA and plasma virion RNA at 0, 24, 36, and 60 weeks demonstrated that proviral DNA did not serve as a predictor of the structure of virion RNA. HIV virion RNA subtype 3 was the most prevalent virion RNA subtype at three of the four periods studied, yet no corresponding proviral DNA was detected. Other virion subtypes have been observed, but only on a transient basis. The present data are consistent with a model of HIV infection in which related but different HIV substrains coexist and evolve independently within an individual. Characterization of virion RNA may be required to identify the unique properties of the virus involved in disease progression; characterization of proviral DNA will not yield this information.

Apoptosis induced in CD4+ cells expressing gp160 of human immunodeficiency virus type 1

In a previous study (Y. Koga, M. Sasaki, H. Yoshida, H. Wigzell, G. Kimura, and K. Nomoto, J. Immunol. 144:94-102, 1990), we demonstrated that the expression of gp160, a precursor form of envelope glycoprotein of human immunodeficiency virus type 1, in CD4+ cells causes the downregulation of surface CD4 and single-cell killing by forming intracellular gp160-CD4 complex. In the present study we investigated the events that lead to cell death in CD4+ cells expressing gp160. We found that apoptosis is induced in cells undergoing single-cell death. Moreover, even the cell clone, which expresses so little gp160 that it does not exhibit any apparent cytopathic effects, such as the inhibition of cell growth, was found to be highly susceptible to the apoptosis induction by the anti-Fas monoclonal antibody.

Management of antiretroviral drug therapy in human immunodeficiency virus infection

Nucleoside analog reverse transcriptase inhibitors, including zidovudine, didanosine, and zalcitabine, remain the cornerstone of therapy against human immunodeficiency virus (HIV) infection, the cause of AIDS. Although therapeutic regimens have been designed that are effective in slowing the progression of disease, therapy with these agents has not been optimized. Ultimately, therapy is destined to fail in most patients. Decisions regarding when to begin therapy and the course of action to take when failure of therapy occurs are largely in the hands of the patient's physician, and currently must be made without the support of conclusive clinical data. In addition to an understanding of the recommended dosing guidelines, proper management of AIDS therapy requires a fundamental knowledge of the disease process, the pharmacology and limitations of the agents employed against the virus, and close cooperation with the clinical laboratory. Therefore, this article reviews the pharmacology of the three drugs currently approved for treatment of HIV infection, and the current guidelines for their use. The article also reviews the clinical and laboratory management of these agents, including the use of surrogate markers and the potential for pharmacokinetic optimization of therapy.

Persistence of multiple maternal genotypes of human immunodeficiency virus type I in infants infected by vertical transmission

The extent of nucleotide variation within the HIV-1 env hypervariable domains serves as a marker of virus genotypes within infected individuals and as a means to track transmission of the virus between individuals. We analyzed env V1 and V2 sequences in longitudinal samples from two HIV-1-infected mothers, each with three children infected by maternal transmission of the virus. Sequences in samples that were obtained from two infants at 2 d and 4 wk after birth displayed more variation in V1 and V2 than maternal samples obtained at the same times. Multiple HIV-1 genotypes were identified in each mother. In each family, multiple maternal HIV-1 genotypes were transmitted to the infants. Specific amino acid residues in the hypervariable domains were conserved within sequences from each family producing a family-specific amino acid signature pattern in V1 and V2. Viruses that were highly related to maternal viruses in signature pattern persisted for as long as 4 yr in the older children. Results support a model of transmission involving multiple HIV-1 genotypes with development of genetic variation from differential outgrowth and accumulation of genetic changes within each individual.

Markers of immune stimulation in the cerebrospinal fluid during HIV infection: a longitudinal study

Markers of immune stimulation were studied in 76 sequential cerebrospinal fluid (CSF) samples from 19 patients infected with HIV-1 without antiretroviral treatment during observation periods ranging from 22 months to 6 years. Eight of these patients were further followed with 14 CSF samples for 3-24 months of zidovudine treatment. During the course of HIV-1 infection, the mean CSF neopterin and beta 2-microglobulin (beta 2M) concentrations increased from 12.7 to 20.4 nmol/l (p < 0.01) and from 1.93 to 2.17 mg/l (p < 0.05), respectively, while the mean peripheral CD4 + T cell count decreased from 624 to 320 cells x 10(6)/l (p < 0.001). The IgG index, reflecting intrathecal immunoglobulin production, increased from 0.72 to 0.92 (p = 0.08). The number of patients with CSF pleocytosis did not change significantly during follow-up (8/19 at baseline, 7/19 at endpoint). In the 8 patients followed up during antiretroviral treatment, a significant reduction in mean CSF levels of neopterin and beta 2M (-48% and -32%, respectively, p < 0.01) was seen after 3-12 months on zidovudine. We suggest that gradual increase in immune stimulation reflected by the rising CSF concentrations of neopterin and beta 2M indicates that HIV-1 infection in the central nervous system is progressive even in neurologically asymptomatic stages.

The importance of nef in the induction of human immunodeficiency virus type 1 replication from primary quiescent CD4 lymphocytes

The viral regulatory gene, nef, is unique to the human immunodeficiency viruses (HIV) and their related primate lentiviruses. Expression of the nef gene has been shown to be essential to the maintenance of high levels of virus replication and the development of pathogenesis in the animal model of simian immunodeficiency virus (SIV) infection. In contrast to this in vivo model, the use of standard T cell culture systems to study nef function in vitro has produced a spectrum of contradictory results, and has failed to demonstrate a significant positive influence of nef on viral life cycle. We have developed a cell model to study regulation of HIV-1 replication that we believe reflects more accurately virus-cell interactions as they occur in vivo. Our experimental system used acute virus infection of purified, quiescent CD4 lymphocytes and subsequent induction of viral replication through T cell activation. With this cell model, NL4-3 virus clones with open and mutated nef reading frames were compared for replication competence. The clones with nef mutations showed reproducible and significant reductions in both rates of growth and maximal titers achieved. The degree of reduced replication was dependent on initial virus inoculum and the timing of T cell activation. The influence of nef was highly significant for induction of virus replication from a latent state within resting CD4 cells. Its effect was less apparent for virus infection of fully proliferating CD4 cells. This study demonstrates that nef confers a positive growth advantage to HIV-1 that becomes readily discernable in the primary cell setting of virus induction through T cell activation. The experimental cell model, which we describe here, provides not only a means to study nef function in vitro, but also provides important clues to the function of nef in HIV infection in vivo.

Novel indolocarbazole protein kinase C inhibitors prevent reactivation of HIV-1 in latently infected cells

Suppression of human immunodeficiency virus-1 (HIV-1) reactivation in latently infected cells by protein kinase C (PKC) inhibitors has been described. Based on an initial finding with the indolocarbazole inhibitor Gö 6976 we have examined several members of this new class of potent and specific PKC inhibitors with respect to their ability to prevent the PKC-mediated induction of HIV-1 replication in the latently infected U1 cell line. Two of these compounds strongly inhibited not only PMA-induced release of p24-antigen and infectious virus particles into the supernatant (50% inhibition at 0.04-0.35 microM) but also TNF-alpha-mediated HIV-1 reactivation in the same concentration range. Significant lower toxicities compared to Gö 6976 were observed for the new compounds, with 50% cytotoxic concentrations at 5.2 microM for Gö 7775 and 3.4 microM for Gö 7716. This resulted in selectivity indices which were 10-20-times higher compared to the reference compound Gö 6976 and were comparable to those of registered anti-AIDS drugs. No anti-HIV-1 activity was observed for a closely related indolocarbazole analogue with no inhibitory activity in the PKC in vitro enzyme assay. This study demonstrates the important role of PKC in reactivation of HIV-1 in latently infected cells and points to the potential of indolocarbazoles to preserve the latent state of HIV-1 infection.

High viral load in lymph nodes and latent human immunodeficiency virus (HIV) in peripheral blood cells of HIV-1-infected chimpanzees

We have examined human immunodeficiency virus type 1 (HIV-1) infection in chimpanzees by analyzing HIV-1 DNA and RNA in lymph nodes and peripheral mononuclear cells (PBMCs). Like certain asymptomatic HIV-infected persons, these chimpanzees had no detectable viral replication in their PBMCs. However, viral replication and a high viral load were observed in the lymphatic tissue. Despite the absence of viral replication in PBMCs, 1/1,000 to 1/10,000 of the PBMCs contained HIV-1 proviral DNA, and HIV transcription could be rapidly induced in these cells in vitro. These results provide direct evidence of cellular latency of HIV in vivo and suggest that HIV infection in chimpanzees may be a useful model for clinical latency of HIV infection in humans.

In vivo footprinting analysis of constitutive and inducible protein-DNA interactions at the long terminal repeat of human immunodeficiency virus type 1

The regulation of the rate of transcription of human immunodeficiency virus type 1 is mainly exerted through the long terminal repeat (LTR) at the 5' end of the provirus. A large number of cis-acting regulatory elements have been identified in the LTR by in vitro binding studies; the biological role of these sites within living infected cells, however, is still not clear. We have studied the interactions of nuclear proteins with the LTR in the U1 monocytic cell line by in vivo dimethylsulfate footprinting, using the ligation-mediated polymerase chain reaction technique. In this cell line, transcription of the virus, which is very low under basal conditions, is highly inducible by treatment with phorbol esters; therefore, this system is likely to represent a suitable cellular model to study viral latency. Independently of the level of viral transcription, major in vivo footprints appear at the two Sp1 sites adjacent to the enhancer, the downstream-positioned enhancer repeat, the NFAT binding site, and one of the purine-rich sites of the negative regulatory element. Upon transcriptional activation by phorbol myristate acetate, the only perturbation in the footprinting pattern is a dramatic increase in dimethylsulfate sensitivity of guanine at position -92 in the downstream enhancer repeat. This modification is correlated with the transient induction of two enhancer-binding activities, as determined by gel retardation assays. While the transcriptional rate is still increasing and the in vivo footprinting pattern is unchanged at up to 24 h postactivation, these enhancer-binding factors are considerably reduced at this time. Therefore, further levels of regulation have to be considered to explain the maintenance of the induced state.

The fastest genome evolution ever described: HIV variation in situ

Human immunodeficiency virus is an RNA virus in which the degree of genetic variation observed is phenomenal--up to 20% within an infected individual. This is essentially due to remorseless cycles of viral replication, most probably due to chronic activation of the immune system. It can be estimated that the number of variants in existence worldwide must be in excess of 10(14)-10(18), and given the nature of RNA viruses even more novel variants should emerge.

An individual with a high prevalence of a tat-defective provirus in peripheral blood

The first exon of tat was sequenced from 23 provirus genomes randomly amplified directly from an HIV-1-infected individual's peripheral blood. Twelve of the 23 sequences constituted a distinct subset of the quasi-species detected. This subset had in common two inactivating mutations in the tat gene. In addition, two of these defective genomes each had a unique mutation. This is the second instance of a defective early gene being present in a high percentage of the proviruses present in the PBMCs of an HIV-1-infected individual, (the first reported by Martins LP et al.: J Virol 1991;65:4502-4507), and suggests that genomes defective in an early gene can participate in the infectious spread of HIV-1 in vivo.

Multifactorial nature of human immunodeficiency virus disease: implications for therapy

The immunopathogenic mechanisms underlying human immunodeficiency virus (HIV) disease are extremely complex; the disease process is multifactorial with multiple overlapping phases. Viral burden is substantial and viral replication occurs throughout the entire course of HIV infection. Inappropriate immune activation and elevated secretion of certain cytokines compound the pathogenic process. Profound immunosuppression ultimately occurs together with a disruption of the microenvironment of the immune system, which is probably unable to regenerate spontaneously. Thus, therapeutic strategies in HIV disease must not be unidimensional, but rather must be linked to the complex pathogenic components of the disease and must address where feasible each of the recognized pathogenic processes for the possibility of therapeutic intervention.

HIV gene expression enhances T cell susceptibility to hydrogen peroxide-induced apoptosis

A human T cell lineage was used to determine the possible effects of HIV infection on T cell antioxidant status. On inoculation into serum-free culture, 8E5, a constitutive HIV-expressing T cell line, underwent apoptosis whereas cell death was not observed with the uninfected A3.01 or latently HIV-infected 8E5L T cell lines. 8E5 survival was markedly prolonged by supplementing the serum-free medium with either A3.01-conditioned medium, catalase, vitamin E, or 2-mercaptoethanol, but supplementation with ascorbic acid, glutathione, or N-acetylcysteine had no effect. Consistent with their being in a state of oxidative stress, 8E5 cells displayed reduced levels of catalase activity, and were more susceptible to killing by exogenous hydrogen peroxide (H2O2) than A3.01 and 8E5L cells. These results demonstrate an inverse correlation between HIV gene expression and antioxidant status in human T cells. Enhanced cytotoxicity of HIV-infected, antioxidant-deficient CD4 T cells following exposure to H2O2 in lymphoid tissues responding to opportunistic pathogens may contribute to the depletion of CD4 T cells in AIDS.

Alternative splicing of human immunodeficiency virus type 1 mRNA modulates viral protein expression, replication, and infectivity

Multiple RNA splicing sites exist within human immunodeficiency virus type 1 (HIV-1) genomic RNA, and these sites enable the synthesis of many mRNAs for each of several viral proteins. We evaluated the biological significance of the alternatively spliced mRNA species during productive HIV-1 infections of peripheral blood lymphocytes and human T-cell lines to determine the potential role of alternative RNA splicing in the regulation of HIV-1 replication and infection. First, we used a semiquantitative polymerase chain reaction of cDNAs that were radiolabeled for gel analysis to determine the relative abundance of the diverse array of alternatively spliced HIV-1 mRNAs. The predominant rev, tat, vpr, and env RNAs contained a minimum of noncoding sequence, but the predominant nef mRNAs were incompletely spliced and invariably included noncoding exons. Second, the effect of altered RNA processing was measured following mutagenesis of the major 5' splice donor and several cryptic, constitutive, and competing 3' splice acceptor motifs of HIV-1NL4-3. Mutations that ablated constitutive splice sites led to the activation of new cryptic sites; some of these preserved biological function. Mutations that ablated competing splice acceptor sites caused marked alterations in the pool of virus-derived mRNAs and, in some instances, in virus infectivity and/or the profile of virus proteins. The redundant RNA splicing signals in the HIV-1 genome and alternatively spliced mRNAs provides a mechanism for regulating the relative proportions of HIV-1 proteins and, in some cases, viral infectivity.

A short-term clinical evaluation of L-697,661, a non-nucleoside inhibitor of HIV-1 reverse transcriptase. L-697,661 Working Group

BACKGROUND

The non-nucleoside reverse transcriptase inhibitors are novel antiretroviral agents with selective activity in vitro against human immunodeficiency virus type 1 (HIV-1). They act through direct inhibition of reverse transcriptase and are not incorporated into DNA.

METHODS

We evaluated a pyridinone non-nucleoside reverse transcriptase inhibitor, L-697,661, in separate six-week double-blind trials in patients with HIV-1 infection whose CD4 counts ranged from 200 to 500 cells per cubic millimeter (68 patients) or less than 200 cells per cubic millimeter (67 patients). Eligible patients were randomly assigned to receive L-697,661 orally in one of three doses (25 mg twice a day, 100 mg three times a day, or 500 mg twice a day) or zidovudine (100 mg five times a day). Clinical and laboratory assessments were performed weekly. Viral isolates were obtained from a subgroup of patients before and after treatment and were evaluated for in vitro sensitivity to L-697,661.

RESULTS

Both L-697,661 and zidovudine were well tolerated. Transient increases in CD4 counts were noted in the patients with fewer than 200 CD4 cells per cubic millimeter who received the two higher doses of L-697,661, but not in those who received the lowest dose or zidovudine. Patients who received L-697,661 had rapid, dose-related decreases in plasma p24 antigen levels. However, this response virtually disappeared after six weeks in some patients receiving L-697,661, coincidently with the emergence of resistant viruses. This change in susceptibility was more frequent among patients receiving the higher doses of L-697,661 and was associated with amino acid substitutions at positions 103 and 181 in the HIV-1 reverse transcriptase gene.

CONCLUSIONS

L-697,661 is safe and well tolerated and has significant dose-related activity against HIV-1. However, resistant strains of the virus emerge rapidly and may limit the effectiveness of non-nucleoside reverse transcriptase inhibitors as monotherapy for HIV-1 infection.