Evolutionary pattern of human immunodeficiency virus (HIV) replication and distribution in lymph nodes following primary infection: implications for antiviral therapy.

Evolutionary patterns of virus replication and distribution in lymphoid tissue during the early phases of HIV infection have not been delineated. Lymph node (LN) biopsies were excised from patients at different times after the estimated time of primary infection. Within 3 months of the acute viral syndrome, HIV was mostly present in individual virus-expressing cells in LNs; trapping of virions in the follicular dendritic cell (FDC) network was minimal or absent, but was the predominant form of HIV detected in LNs of subjects with chronic infection, either recent (4-20 months after primary infection) or long-term (>2-3 years after primary infection). Plasma viremia was significantly higher in patients during the first 3 months than in those recently infected; however, there were no significant differences in the number of virus-expressing cells per square millimeter of LN tissue in these two groups. Numbers of virus-expressing cells in lymphoid tissue were significantly lower in the subjects with long-term infection than in the other two groups. Therefore, during the transition from primary to chronic HIV infection, the level of HIV replication in lymphoid tissue remains elevated despite the fact that viremia is significantly downregulated. These findings have implications for therapeutic strategies in primary HIV infection and in recent seroconvertors.

Human immunodeficiency virus (HIV) infection in CD4+ T lymphocytes genetically deficient in LFA-1: LFA-1 is required for HIV-mediated cell fusion but not for viral transmission.

In the present study, we demonstrated that expression of the LFA-1 molecule is necessary for cell fusion and syncytia formation in human immunodeficiency virus (HIV)-infected CD4+ T lymphocytes. In contrast, the lack of expression of LFA-1 does not influence significantly cell-to-cell transmission of HIV. In fact, LFA-1- T lymphocytes obtained from a leukocyte adhesion deficiency patient were unable to fuse and form syncytia when infected with HIV-1 or HIV-2, despite the fact that efficiency of HIV infection (i.e., virus entry, HIV spreading, and levels of virus replication) was comparable with that observed in LFA-1+ T lymphocytes. In addition, we provide evidence that LFA-1 by mediating cell fusion contributes to the depletion of HIV-infected CD4+ T lymphocytes in vitro.

Direct polyclonal activation of human B lymphocytes by the acquired immune deficiency syndrome virus.

When B lymphocytes from normal human peripheral blood were incubated for 1 hour with the retrovirus that causes the acquired immune deficiency syndrome (AIDS), the B cells showed marked proliferation and differentiation. Proliferative responses to the virus peaked on day 4 and appeared to be independent of accessory cells. This finding was repeated with three separate viral isolates, one of which was from a patient from Zaire. The magnitude of the observed responses was comparable to that seen with standard polyclonal B-cell activators. This phenomenon may be at least partially responsible for the polyclonal B-cell activation seen in patients with AIDS.

The reservoir for HIV-1 in human peripheral blood is a T cell that maintains expression of CD4.

Human immunodeficiency virus type 1 (HIV-1) selectively infects cells expressing the CD4 molecule, resulting in substantial quantitative and qualitative defects in CD4+ T lymphocyte function in patients with acquired immunodeficiency syndrome (AIDS). However, only a very small number of cells in the peripheral blood of HIV-1-infected individuals are expressing virus at any given time. Previous studies have demonstrated that in vitro infection of CD4+ T cells with HIV-1 results in downregulation of CD4 expression such that CD4 protein is no longer detectable on the surface of the infected cells. In the present study, highly purified subpopulations of peripheral blood mononuclear cells (PBMCs) from AIDS patients were obtained and purified by fluorescence-automated cell sorting. They were examined with the methodologies of virus isolation by limiting dilution analysis, in situ hybridization, immunofluorescence, and gene amplification. Within PBMCs, HIV-1 was expressed in vivo predominantly in the T cell subpopulation which, in contrast to the in vitro observations, continued to express CD4. The precursor frequency of these HIV-1-expressing cells was about 1/1000 CD4+ T cells. The CD4+ T cell population contained HIV-1 DNA in all HIV-1-infected individuals studied and the frequency in AIDS patients was at least 1/100 cells. This high level of infection may be the primary cause for the progressive decline in number and function of CD4+ T cells in patients with AIDS.

Experience with a cross-study endpoint review committee for AIDS clinical trials. Terry Beirn Community Programs for Clinical Research on AIDS.

OBJECTIVES: To describe the methods and results of a standardized system for clinical endpoint determination for defining and reviewing endpoints in clinical trials for HIV-infected individuals. DESIGN: A system was developed utilizing standard definitions for the 24 diagnoses or clinical events that serve as trial endpoints and together define the combined endpoint 'progression of HIV disease. A common set of case report forms were used for all trials. Thus, an event of Pneumocystis carinii pneumonia (PCP), for example, for a subject co-enrolled in an antiretroviral trial and a PCP prophylaxis trial was only reported once. METHODS: A central committee was established to define clinical events and review endpoints across all studies. Events were classified according to established criteria for confirmed, probable and possible levels of certainty. RESULTS: This report describes the methods used to ascertain and review endpoints, and summarized 2299 clinical events for 8097 subjects enrolled in one or more of nine clinical trials. Data on the diagnostic certainty of events and agreement between site clinicians and the endpoint committee are presented. CONCLUSIONS: Uniform classification of endpoints across AIDS clinical trials can be accomplished by multicenter, multitrial organizations with standardized definitions and review of endpoint documentation. Our experience suggests that nurse coordinators reviewing all submitted endpoints for every trial are warranted and the need for external review by a clinical events committee may depend on the type of trial conducted.

Preliminary evidence for partial restoration of immune function in HIV type 1 infection with potent antiretroviral therapies: clues from the Fourth Conference on Retroviruses and Opportunistic Diseases.

Critical advances in understanding the pathogenesis and treatment of HIV-1 infection have been made. These include the following: delineation of the replication kinetics of HIV in all stages of disease, underscoring the role of viral replication in disease pathogenesis; development of highly sensitive quantitative assays to determine viral load in infected individuals; and potent new antiretroviral drugs, the availability of which has provided a tool for the investigation of viral pathogenesis and immunopathogenesis, and has permitted the demonstration of the clinical efficacy of combination therapies. The results of studies of potent antiretroviral combination therapies presented at the Fourth Conference on Retroviruses and Opportunistic Infections (January 22-26, 1997, Washington, D.C.) demonstrate that such therapies are capable of at least partially restoring the immune system that is damaged by infection with HIV-1. This includes evidence for the ability of potent therapies to begin to reverse the abnormalities of maturation, activation, and function that are attributable directly or indirectly to the CD4+ helper T lymphocyte population.

Summary of the National Institutes of Health workshop on primary human immunodeficiency virus type 1 infection.

A Workshop on primary human immunodeficiency virus type 1 (HIV-1) infection sponsored by the National Institute of Allergy and Infectious Diseases (NIAID) and the Office of AIDS Research (OAR) of the National Institutes of Health (NIH) was held February 25-26, 1993 in Bethesda, Maryland. The major goals of this scientific meeting were to bring together researchers and infectious disease specialists who have expertise in primary HIV-1 infection (PHI) to review the pathogenesis of PHI, the treatment experience of PHI in humans and of early retroviral infection in animal models, and to devise theoretical and operational strategies for future clinical trials relating to therapeutic intervention of PHI. The proceedings of this workshop are timely and serve to further the development of innovative strategies for the treatment of HIV-1 infection.

Frequent detection of HIV-1-specific mRNAs in infected individuals suggests ongoing active viral expression in all stages of disease.

It has been shown that only a small fraction of CD4+ T cells are infected with human immunodeficiency virus type 1 (HIV-1) in vivo, particularly early in the course of infection. An even smaller proportion of cells have been shown to be expressing virus. Recent studies suggest that plasma viremia in asymptomatic HIV-infected individuals, representing active viral replication, is more common than was previously believed (range 23-100% of patients). To determine the in vivo state of HIV expression, samples of peripheral blood of 49 HIV-infected individuals at all stages of disease were examined. All subjects were positive for viral DNA by standard polymerase chain reaction (PCR), and a modified PCR was utilized to detect HIV-specific mRNAs (gag, major splice junction, env, and tat/rev). Patient's plasma was also assayed for p24 antigen and viremia. The results were as follows: (formula: see text) Overall, the findings suggest that active viral expression occurs at all stages of HIV infection. In particular, the presence of gag mRNA was determined in only 2 of 14 patients with T4% greater than 30% but in 20 of 35 patients with T4% less than or equal to 30% (p less than 0.05), demonstrating a direct association between the presence of message for a structural protein, and more advanced immunosuppression. Determination of the expression of certain HIV-specific messages from within a patient's cells adds a new dimension to understanding the pathogenesis of HIV infection. The presence of HIV-specific mRNAs, and in particular gag message, in many healthy seropositives may further argue for early initiation of antiviral therapy.

Treatment research priorities for human immunodeficiency virus infection.

Viral infections such as with the human immunodeficiency virus (HIV) present difficult challenges for the development of effective antiviral therapies. These viruses depend on the host cell machinery for their existence, and interference with these processes typically interferes with other important host physiology. HIV presents other challenges as well because of its inherent pathogenic destruction of the immune system. It is the goal of HIV therapeutics to attempt to cure HIV infection, or if that is not possible, to stop HIV disease progression while preserving a high quality of life for HIV-infected individuals. This may be achieved through an effective combination of interference with the viral life cycle and the pathogenic processes, and by slowing or reversing the immunologic dysfunction that leads to the complications of HIV infection. Unprecedented progress has been made in understanding the virus and HIV disease pathogenesis. This knowledge has led to the identification of viral features that have become targets for therapeutic intervention. This article reviews the most important priorities of HIV treatment research for adult HIV-infected patients for the immediate future. These priorities include the following: development of new antiretroviral compounds and their application as both monotherapies and in combination therapy approaches; immune-based therapeutic approaches; and research and treatment for acute or primary HIV infections.

Human immunodeficiency virus and acquired immunodeficiency syndrome: an update.

Research progress in the understanding of HIV and its effects on the human immune system continues at a rapid pace. Such research is yielding new ideas for chemotherapeutic agents, immunologic stimulators and modifiers, and potential vaccines. Clinical trials to test these approaches are under way. Despite the accomplishments, the epidemic progresses unchecked, resulting in continued suffering and death and enormous demands on the health care system of many nations. Clinicians have had to deal with new and difficult opportunistic infections. Yet advances in the treatment and prevention of these illnesses have benefited many AIDS victims. In the United States, the AIDS epidemic is now concentrating in the inner cities, involving injection drug users, minorities, heterosexuals, women and their offspring. In the developing world, AIDS continues to be predominantly a heterosexually transmitted disease, where more than one third of prostitutes in central African cities are infected. The major burden of the AIDS epidemic in the remainder of this and the next century will be in India and Southeast Asia, again predominantly via heterosexual spread. A great deal is now understood concerning the life cycle of HIV. More light has been shed on the interaction of HIV and CD4+ T cells, the cellular and viral factors involved in viral expression vs. latency, the function of the viral regulatory and structural proteins and the role of cytokines in regulation of HIV expression. Our understanding of the precise mechanisms whereby HIV causes a loss of CD4+ T cells remains incomplete. The direct infection and cell killing of CD4+ T cells is important and is supported by recent evidence demonstrating a high viral burden in these cells in the lymphoid tissue of patients. Over the last 1 to 2 years, there has been new evidence for indirect mechanisms of CD4+ T-cell depletion and/or dysfunction including: autoimmune reactions, perturbations of specific V beta T-cell receptor populations, infection of T-cell precursors in bone marrow and thymus, immunosuppression and dysregulation by viral proteins, possible super-antigen effects, and antigen-induced apoptosis or programmed cell death. New information has come forth in our understanding of B-cell abnormalities in HIV pathogenesis, including the putative role of IL-6 in B-cell activation and the identification of EBV in B-cell lymphomas in the CNS of patients with AIDS. It is expected that these and future discoveries concerning immunopathogenesis of HIV infection will help steer the therapeutic effort. Major strides continue to be made in the therapeutic arena for HIV infection and its complications.(ABSTRACT TRUNCATED AT 400 WORDS)

Primary human immunodeficiency virus type 1 infection: review of pathogenesis and early treatment intervention in humans and animal retrovirus infections.

Primary human immunodeficiency virus type 1 (HIV-1) infection can present clinically as the abrupt onset of a febrile illness resembling acute mononucleosis. The symptoms coincide with high titers of culturable plasma viremia, cell-associated virus, and antigenemia, which rapidly decrease coincident with the emergence of detectable HIV-specific antibody and HIV-specific cytotoxic T lymphocytes. This article reviews the human and animal model data on the virologic and immunologic events that occur during primary HIV-1 and animal retrovirus infections, evaluates the prophylactic treatment experience of retrovirus infections in the animal model, and provides a plausible rationale for treatment intervention of primary HIV-1 infection in humans. Recent work delineating the pathogenesis of primary HIV-1 infection provides insight into the major mechanisms of viral dissemination and host immune response. The results from retrovirus-infected animal models treated with antiviral agents suggests that therapy at the time of viral dissemination may be an effective strategy that may modify disease progression. Clinical trials to evaluate this approach are in progress.

Emergence of unusual opportunistic pathogens in AIDS: a review.

Opportunistic infections are a major cause of morbidity and death among patients infected with the human immunodeficiency virus (HIV), particularly late in the disease, when immunosuppression is severe. Some pathogens, such as Pneumocystis carinii and Toxoplasma gondii, are extremely common in this population and are readily recognized by clinicians caring for these patients. However, many other organisms occasionally cause conditions that clinically mimic the more commonly encountered pathogens. Clinicians must be alert to the threat posed by these less frequently occurring organisms and of the broader differential diagnosis that must be considered for infections in patients with HIV infection.

A phase I study of interferon-alpha 2b in combination with interleukin-2 in patients with human immunodeficiency virus infection.

Interferon-alpha (IFN-alpha) can inhibit human immunodeficiency virus (HIV-1) replication and is effective in treating Kaposi's sarcoma; interleukin-2 (IL-2) can increase circulating lymphocytes in HIV-1-infected patients. The safety of combination treatment with recombinant (r)IFN-alpha 2b and IL-2 was evaluated in HIV-1-infected patients with > 200 CD4+ T cells/mm3. A maximal tolerated dose of rIFN-alpha 2b was determined for 17 patients; then they received in combination 3, 6, or 12 x 10(6) IU/day rIL-2, given intravenously over 21 days. Twelve patients ultimately received the combination, 9 for the full 21 days. Significant toxicities included flu-like symptoms, anemia, transaminemia, and depression. Transient increases in CD4+ T cell percentages and spontaneous lymphocyte blast transformation were observed. Quantitative microcultures demonstrate a decline in HIV titers in patients receiving rIFN-alpha 2b (5/9) with a further decline on addition of rIL-2 (7/9). In summary, continuous rIL-2 at 6 x 10(6) IU/day in combination with rIFN-alpha 2b was reasonably tolerated and provided preliminary evidence of immunomodulatory and antiviral activity.

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.

Zidovudine treatment in patients with primary (acute) human immunodeficiency virus type 1 infection: a randomized, double-blind, placebo-controlled trial. DATRI 002 Study Group. Division of AIDS Treatment Research Initiative.

A multicenter, double-blind, placebo-controlled trial randomized 28 patients with primary (acute) human immunodeficiency virus (HIV)-1 infection (PHI) to receive zidovudine, 1000 mg daily, or placebo for 24 weeks. At week 48, compared with placebo patients, zidovudine-treated patients had significantly higher CD4 cell counts (zidovudine, 666 cells/mm3; placebo, 362; P = .004) and lower peripheral blood mononuclear cell (PBMC) culture titers (zidovudine, 0.58 log infectious units per million cells; placebo, 1.68; P = .02) but no difference in plasma RNA (zidovudine, 3.93 log copies/mL; placebo, 4.00; P = .83). Serious adverse events and minor clinical events were infrequent and comparable in both arms. There were two deaths: 1 patient died of sepsis and renal disease (zidovudine arm), and 1 patient died of sepsis and tension pneumothorax (placebo arm). Six months of high-dose zidovudine initiated during PHI results in higher CD4 cell counts and lower PBMC culture titers but no difference in plasma HIV-1 RNA. Further studies with more potent antiretroviral combination therapies are warranted.

NIH conference. Immunopathogenic mechanisms in human immunodeficiency virus (HIV) infection.

An understanding of the immunopathogenic mechanisms of infection with human immunodeficiency virus (HIV) is fundamental in developing successful approaches to designing effective therapeutic and vaccine strategies. In this regard, we have investigated the mechanisms by which HIV inserts itself into the human immune system and uses the elaborate cytokine network to its own replicative advantage. We have also shown that the burden of HIV in CD4+ T cells is directly associated with a decline in this cell population in vivo and a progression to disease. Mononuclear phagocytes may play a role in the pathogenesis of HIV infection by serving as reservoirs of the virus. Of note is the fact that monocytes in the peripheral blood of HIV-infected individuals are rarely infected in vivo, whereas infected-tissue macrophages may play a role in organ-specific HIV-related pathogenesis. The role of HIV-specific humoral and cell-mediated immunity in HIV infection is not well understood. However, fine specificity of responses against HIV have been delineated in some in-vitro systems. It is unclear why these responses, particularly HIV-specific cytolytic T-cell responses, diminish over the course of infection and are unable to contain progression of infection.

Immune-based therapeutics: scientific rationale and the promising approaches to the treatment of the human immunodeficiency virus-infected individual.

The primary approach to therapy for infection with human immunodeficiency virus (HIV) continues to be centered around antiretroviral agents that have conferred significant clinical benefits. The considerable degree of immunologic dysfunction in HIV infection, however, has led to intense interest in methods of immune stimulation and reconstitution. Immunomodulatory intervention in HIV infection is highly controversial. Over the years a number of immunomodulatory agents--many with only a poor rationale for their clinical use--have been evaluated. In this review we concentrate on immunomodulatory approaches that are currently being investigated. We group these interventions, reviewing the rationale and clinical data for each category: passive immunity (administration of immunoglobulins and use of apheresis), thymic hormone treatment, cytokine treatment (administration of interleukins, tumor necrosis factor, and interferons), adoptive cellular immunity, and therapeutic vaccination. At present, the only interventions supported by data from well-controlled studies are the parenteral administration of interferon alpha to patients with HIV-associated Kaposi's sarcoma and the administration of pooled immunoglobulin (to decrease the rate of bacterial infections) to children who cannot take trimethoprim-sulfamethoxazole. However, several other approaches under development show promise in reversing some of the immune deficits of HIV infection. Clinical evaluation of these approaches should yield valuable insights into the immunopathogenesis of HIV infection, and these insights should facilitate the formulation of new modalities of treatment.

Epidermal Langerhans cells are not principal reservoirs of virus in HIV disease.

Several reports implicate Langerhans cells of skin as susceptible targets, reservoirs, and vectors for transmission of HIV: 1) numbers of Langerhans cells in skin of HIV-infected patients were decreased about 50% of that in control skin; 2) as many as 30% of Langerhans cells in the skin of HIV-infected patients were morphologically abnormal; 3) viral particles typical for HIV were identified in or around 2 to 5% of these cells; and 4) infectious HIV was isolated from skin biopsies of infected patients. These results were consistent with similar observations of HIV-infected macrophages in such tissues as brain, lung, and lymph node. Despite these findings, other investigators find no evidence for virus infection in the epidermis of HIV-infected patients by any of several immunohistochemical or ultrastructural criteria. To address this controversy, we obtained skin from 28 HIV-seropositive subjects at various clinical stages by full thickness biopsy or suction blister. Samples were analyzed by transmission electron microscopy for presence of HIV virions, by immunofluorescent staining for viral proteins, by in situ hybridization for HIV-specific mRNA, by polymerase chain reaction amplification of virus-specific DNA, and by direct virus isolation by coculture of epidermis onto monocyte target cells. By any of these techniques, demonstration of HIV in the epidermis of infected patients was equivocal and even then, infrequent. In contrast, viral DNA was detected from the dermis of the same skin samples (26 of 28 samples). Moreover, the number and morphology of Langerhans cells in skin of infected patients were within normal limits, regardless of stage of disease. These studies in toto suggest that a role for Langerhans cells as a principal viral reservoir or vector of transmission is highly unlikely.

Relationship between event rates and treatment effects in clinical site differences within multicenter trials: an example from primary Pneumocystis carinii prophylaxis.

The results of multicenter clinical trials may differ across participating clinical sites. We present a diagnostic approach for evaluating this diversity that emphasizes the relationship between the observed event rates and treatment effects. We use as an example a trial of sequential strategies of Pneumocystis prophylaxis in human immunodeficiency virus infection with 842 patients randomly allocated to start prophylaxis with trimethoprim/sulfamethoxazole, dapsone, or pentamidine. Prophylaxis failure rates varied significantly across the 30 clinical sites (0-30.3%, p = 0.002 by Fisher's exact test) with prominent variability in the pentamidine arm (0-63.6%). Starting with oral regimens was better than starting with pentamidine in sites with high rates of events, whereas the three strategies had more similar efficacy in other sites. Sites enrolling fewer patients had lower event rates and had more patients who withdrew prematurely or were lost to follow-up. In a hierarchical regression model adjusting for random measurement error in the observed event rates, starting with trimethoprim/sulfamethoxazole was predicted to be increasingly better than starting with aerosolized pentamidine as the risk of prophylaxis failure increased (p = 0.01), reducing the risk of failure by 47% when the failure rate of pentamidine was 30%, whereas the two regimens were predicted to be equivalent when the failure rate was 17%. Differences in event rates could reflect a combination of heterogeneity in diagnosis, administration of treatments, and disease risk in patients across sites. The evaluation of clinical site differences with a systematic approach focusing on event rates may give further insight in the interpretation of the results of multicenter trials beyond an average treatment effect.

Preferential infection of CD4+ memory T cells by human immunodeficiency virus type 1: evidence for a role in the selective T-cell functional defects observed in infected individuals.

CD4+ T cells of patients with AIDS exhibit a qualitative defect in their ability to respond to soluble antigen while their responses to mitogens remain normal. CD4+ T cells can be broadly divided phenotypically into "naive" [CD45RA+ (2H4+)] and "memory" [CD29+ (4B4+) or CD45RO+ (UCHL1+)] cell subpopulations, which represent distinct maturation stages. To determine the human immunodeficiency virus type 1 (HIV-1) infectability of memory and naive CD4+ T-cell subsets in vitro and to determine the in vivo preference of HIV-1 in these subpopulations, we obtained highly purified CD4+ T-cell subsets from normal and HIV-1-infected individuals and studied them by viral cultivation, quantitative polymerase chain reaction, and functional assays. Polymerase chain reaction studies demonstrated that the memory cell subset of CD4+ T cells is preferentially infected (4- to 10-fold more than naive T cells) by HIV-1 in vitro, and these memory cells are the principal reservoir for HIV-1 within CD4+ T cells obtained from infected individuals. Functional abnormalities attributable to CD4+ T cells in HIV-infected individuals (failure to respond in vitro to soluble antigen or to anti-CD3 monoclonal antibodies) were shown to reside primarily within these memory cells. Thus, the present study suggests that the selective functional defects present in the memory CD4+ T-cell subset of HIV-infected individuals may be a direct result of the preferential infection and consequently greater viral burden within these cells.