The immunopathogenesis of human immunodeficiency virus infection

HIV-specific lymphoproliferative responses in asymptomatic HIV-infected individuals

In vitro lymphoproliferative responses to HIV-1 recombinant antigens (gp160, p24, and Rev protein) were studied in 83 patients with asymptomatic HIV-1 infection (CDC groups II and III) and circulating CD4 lymphocyte numbers > 400/mm3. Significant response to at least one of the three antigens was detected in 52.4% of the subjects, but the responses were weak, and concordance of the response to the three antigens was rare, the frequency of individuals responding to each antigen not exceeding 22.4%. Increasing frequencies of response were observed when recall antigens (tetanus toxoid and Candida albicans glycomannoprotein) (65.5%) and anti-CD3 MoAb (76.6%) were used as stimuli. Although a significant association between lymphocyte response to p24, but not gp160, and steadiness of CD4 lymphocyte numbers before the assay was observed, no predictive value for lack of CD4 cell decrease was confirmed for either antigen, and fluctuation of the responses to HIV antigens was seen during subsequent follow up. The panel of T cell assays used could be regarded as appropriate for monitoring both HIV-specific responses and T lymphocyte function during immunotherapy with soluble HIV antigens.

HIVgp120 activates autoreactive CD4-specific T cell responses by unveiling of hidden CD4 peptides during processing

T cells are made tolerant only to those self-peptides that are presented in sufficient amounts by antigen-presenting cells. They ignore cryptic self-determinants, such as either those not generated by processing machinery or generated in insufficient amounts. It is anticipated that mechanisms that either change antigen processing or increase the yield of previously "invisible" peptides may be capable of inducing T cell priming and, if they are self-maintained, may sustain autoimmune diseases. Herein, we demonstrate for the first time a mechanism by which the gp120 human immunodeficiency virus-I, by downregulating plasma membrane CD4 and increasing its processing, unveils hidden CD4 epitopes, inducing an autoimmune-specific T cell response.

Peripheral lymphocytes of clinically non-progressor patients harbor inactive and uninducible HIV proviruses

The HIV viral burden and RNA expression in a selected group of infected, clinically non-progressor patients were investigated. Five fast-progressor patients and 10 AIDS cases were included as controls. The HIV viral load was investigated by semiquantitative polymerase chain reaction (PCR) in adherent macrophages and in genomic and extragenomic fractions of lymphocytes. HIV DNA was not found in macrophages in the non-progressor subjects, was weakly positive in 2 of 5 fast-progressors and strongly positive in most of the AIDS patients. The number of HIV proviruses found in lymphocytes of the non-progressor subjects varied from 5 to 160 copies/microgram DNA, values ten times lower than those recorded in fast-progressors and AIDS patients. The extragenomic HIV DNA (2 LTR forms) was absent or barely detectable in the lymphocytes from non-progressors and abundant in the other groups. HIV RNA was not found in the lymphocytes of all non-progressors. This may indicate that a latent state of HIV provirus exists in the lymphocytes of these subjects. To investigate this point, cultivation and stimulation with PHA (phytohemoagglutinin) and PMA (phorbol 12-myristate 13-acetate) of lymphocytes from these subjects were attempted but after 6 days HIV RNA (RT-PCR for gag region) was still absent or barely detectable in these patients. There are no other reports of the absence of HIV provirus induction in lymphocytes from infected individuals. If confirmed in a larger number of patients, such non-inducibility might serve as a predictor marker of progression of the disease.

Phenotypic and functional changes in peripheral blood monocytes during progression of human immunodeficiency virus infection. Effects of soluble immune complexes, cytokines, subcellular particulates from apoptotic cells, and HIV-1-encoded proteins on monocytes phagocytic function, oxidative burst, transendothelial migration, and cell surface phenotype

We postulated that changes in the cell surface display of molecules that facilitate cell-cell and cell-matrix adhesions may reflect the changing immunosurveillance capacity of blood monocytes during progression of human immunodeficiency virus (HIV) infections. In Centers for Disease Control (CDC) stage A patients, whose monocytes' ability to phagocytose bacteria and generate reactive oxygen intermediates is often increased, the frequency of monocytes expressing CD49d, HLA-DP, HLA-DQ, and an activation epitope of CD11a/CD18 was increased and monocyte transendothelial migration was unimpaired. In CDC stage B/C patients, whose monocytes' ability to phagocytose bacteria and migrate across confluent endothelial monolayers was diminished, surface expression of CD49e and CD62L and the percentage of monocytes expressing CD18, CD11a, CD29, CD49e, CD54, CD58, CD31, and HLA-I were significantly decreased. Incubating normal donor monocytes with immune complexes in vitro reproduced the phenotypic and functional abnormalities seen in stage B/C patients. By contrast, in vitro stimulation with subcellular particulates released by apoptotic lymphocytes reproduced changes seen in stage A patients' monocytes. Although circulating monocytes appear to be activated at all stages, these data suggest that the high levels of circulating immune complexes, found predominantly in the later stages of HIV infection, may be particularly instrumental in reducing the monocyte's capacity to maintain surveillance against infection.

Developmental and tissue-specific expression of human CD4 in transgenic rabbits

A major obstacle to understanding AIDS is the lack of a suitable small animal model for studying HIV-1 infection and the subsequent development of AIDS, and for testing diagnostic, therapeutic, and preventive modalities. Our goal is to produce a rabbit model for the study of AIDS. Here we report on the generation of transgenic rabbits that express the human CD4 (hCD4) gene. The transgene, which contains the coding region for hCD4 and approximately 23 kb of sequence upstream of the translation start site, was used previously to direct hcD4 expression on the surface of CD4+ T cells of transgenic mice (Gillespie et al., 1993: Mol Cell Biol 13:2952-2958). The hCD4 transgene was detected in five males and two females derived from the microinjection in five males and two females derived from the microinjection of 271 rabbit embryos. Both hCD4 RNA and protein were expressed in peripheral blood lymphocytes (PBLs) from all five males but neither of the females. Human CD4 was expressed on PBLs from F1 offspring of all founder males. T-cell subset analysis revealed that hCD4 expression was restricted to rabbit CD4 (rCD4) expressing lymphocytes; mature rCD4- rCD8+ lymphocytes did not express hCD4. In preliminary studies, PBLs from hCD4 transgenic rabbits produced greater amounts of HIV-1 p24 core protein following HIV-1 infection in vitro than HIV-1 p24 antigen in nontransgenic rabbit infected cultures. These results extend to rabbits our previous observation that this transgene contains the sequence elements required for high-level expression in the appropriate cells of transgenic mice. Furthermore, these and previous studies demonstrating that expression of hCD4 protein enhances HIV-1 infection of rabbit T cells in vitro, coupled with reports that normal, nontransgenic rabbits are susceptible to HIV-1 infection, suggests that the hCD4 transgenic rabbits described herein will have an increased susceptibility to HIV-1 infection. In vivo HIV-1 infection studies with these rabbits are under way.

Inhibition of apoptosis in human immunodeficiency virus-infected cells enhances virus production and facilitates persistent infection

Apoptosis is one of several mechanisms by which human immunodeficiency virus type 1 (HIV-1) exerts its cytopathic effects. CD4+ Jurkat T-cell lines overexpressing the adenovirus E1B 19K protein, a potent inhibitor of apoptosis, were used to examine the consequences of inhibition of apoptosis during acute and chronic HIV-1 infections. E1B 19K protein expression inhibited HIV-induced apoptosis, enhanced virus production, and established high levels of persistent viral infection. One E1B 19K-expressing line appeared to undergo HIV-induced death via a nonapoptotic mechanism, illustrating that HIV infection results in lymphocyte depletion through multiple pathways. Increased virus production associated with sustained cell viability suggests that therapeutic approaches involving inhibition of HIV-induced programmed cell death may be problematic.

Gouty arthritis in the acquired immunodeficiency syndrome. An unusual but aggressive case

Patients with the acquired immunodeficiency syndrome (AIDS) are characteristically hypouricemic. Therefore, the occurrence of gouty arthritis in association with AIDS would be expected to be a rare phenomenon. We describe a patient with AIDS in whom gouty arthritis developed. Features of both diseases in relation to their coexistence in this patient are discussed.

Kinetics of Gag-specific cytotoxic T lymphocyte responses during the clinical course of HIV-1 infection: a longitudinal analysis of rapid progressors and long-term asymptomatics

To gain more insight into the role of HIV-1-specific cytotoxic T lymphocytes (CTL) in the pathogenesis of AIDS, we investigated temporal relations between HIV-1 Gag-specific precursor CTL (CTLp), HIV-1 viral load, CD4+ T cell counts, and T cell function. Six HIV-1-infected subjects, who were asymptomatic for more than 8 yr with CD4+ counts > 500 cells/mm3, were compared with six subjects who progressed to AIDS within 5 yr after HIV-1 seroconversion. In the long-term asymptomatics, persistent HIV-1 Gag-specific CTL responses and very low numbers of HIV-1-infected CD4+ T cells coincided with normal and stable CD4+ counts and preserved CD3 mAb-induced T cell reactivity for more than 8 yr. In five out of six rapid progressors Gag-specific CTLp were also detected. However, early in infection the number of circulating HIV-1-infected CD4+ T cells increased despite strong and mounting Gag-specific CTL responses. During subsequent clinical progression to AIDS, loss of Gag-specific CTLp coincided with precipitating CD4+ counts and severe deterioration of T cell function. The possible relationships of HIV-1 Gag-specific CTLp to disease progression are discussed.

Changes in the viral mRNA expression pattern correlate with a rapid rate of CD4+ T-cell number decline in human immunodeficiency virus type 1-infected individuals

The rate of disease progression varies considerably among human immunodeficiency virus type 1 (HIV-1)-infected individuals. Several cross-sectional studies have shown an association between the stage of HIV-1 disease and the viral burden or the relative levels of viral gene expression. To study the extent of HIV-1 transcription and replication and its correlations with disease progression, we quantified serial, longitudinal samples of blood cells from 10 HIV-1-infected individuals with markedly different rates of CD4+ T-cell number decline following seroconversion. After normalization for the input nucleic acid content, multiply spliced viral mRNA and unspliced viral RNA were quantified by competitive reverse transcription-PCR using oligonucleotide primers which flank the major tat/rev/nef splice junction and span an internal region of the gag open reading frame, respectively. Coamplification of internal cRNA template controls was used to normalize for variation in the efficiency of reverse transcription and in vitro enzymatic amplification. Similarly, proviral DNA was also quantified by competitive PCR performed within the linear range of amplification. Viral RNA was detected in the blood cells of each individual from all time points regardless of the rate of CD4+ T-cell decline. Unspliced genomic viral RNA rapidly increased in the blood cells from HIV-1-infected individuals who had a precipitously declining CD4+ T-cell number. In contrast, both unspliced and multiply spliced viral mRNAs remained relatively stable in the blood cells from HIV-1-infected individuals who have had a relatively benign clinical course. These data demonstrate that the extent of viral transcription and replication correlates with the rate of CD4+ T-cell number decline and that quantifying intracellular viral RNA is of potential prognostic value.

Virus receptors: implications for pathogenesis and the design of antiviral agents

A virus initiates infection by attaching to its specific receptor on the surface of a susceptible host cell. This prepares the way for the virus to enter the cell. Consequently, the expression of the receptor on specific cells and tissues of the host is a major determinant of the route of entry of the virus into the host and of the patterns of virus spread and pathogenesis in the host. This review emphasizes the virus-receptor interactions of human immunodeficiency virus, the rhinoviruses, the herpesviruses, and the coronaviruses. These interactions are often found to be complex and dynamic, involving multiple sites or factors on both the virus and the host cell. Also, the receptor may play an important role in virus entry per se in addition to its role in virus binding. In the cases of human immunodeficiency virus and the rhinoviruses, ingenious approaches to therapeutic strategies based on inhibiting virus attachment and entry are under development and in clinical trials.

HIV-mediated B-lymphocyte activation and lymphomagenesis

Non-Hodgkin's (1ii)lymphoma is an AIDS-defining event in a significant percent of U.S. patients infected with the human immunodeficiency virus (HIV). Advances in anti-retroviral treatment and management of opportunistic infection have been accompanied by an increase in the incidence of these lymphomas. In the immunocompromised state of patients late in the course of HIV infection, these lymphomas represent a complication of HIV infection that is associated with an extremely poor prognosis. Currently, there is little understanding of the pathogenesis of HIV-associated lymphomas, which are nearly exclusively of B-cell origin. Experimental data do not support HIV infection in these lymphomas. While some lymphomas show evidence of EBV infection, the majority do not. Polyclonal B-cell hyperactivity during the early phases of HIV infection argues that chronic B-cell stimulation may be the major process predisposing B-cells in the HIV-infected individual to malignant transformation. The mechanism of this stimulation of normal B cells and its relationship to AIDS-associated lymphomas remain poorly understood. In this review, we will summarize current information on HIV-associated B lymphoma and then discuss our views on the association and regulation of HIV-related hyperactivity on the pathogenesis of this lymphoma.

Detection of HIV-1 RNA in plasma by isothermal amplification (NASBA) irrespective of the stage of HIV-1 infection

Using an experimental assay for isothermal amplification of HIV RNA in plasma (NASBA, Organon Teknika, Boxtel, The Netherlands), 70 samples from 59 HIV-1-infected persons and 29 samples from 28 uninfected volunteer blood donors were tested for the presence of HIV-1 RNA. The HIV-1-positive plasma samples were drawn from patients at various stages of infection: two samples from persons with signs of acute HIV infection (CDC stage I); 29 samples from 25 symptom-free persons (CDC stage II) and 39 samples from 32 persons with AIDS-related symptoms (CDC stage IV). All samples from HIV-1-infected persons had HIV-1 RNA, irrespective of the stage of infection (100% sensitivity). Testing the donor samples in duplicate, initially 54/58 samples (93%) tested negative for HIV-1 RNA. Repeated testing of the 4 samples with inconsistent test results showed all samples to be negative (specificity 100%). Detection of HIV-1 RNA in plasma by isothermal amplification (NASBA) promises to be a valuable alternative to the detection of HIV-1 RNA or DNA by the polymerase chain reaction.

A critical analysis of the HIV-T4-cell-AIDS hypothesis

The data generally accepted as proving the HIV theory of AIDS, HIV cytopathy, destruction of T4 lymphocytes, and the relationship between T4 cells, HIV and the acquired immune deficiency clinical syndrome are critically evaluated. It is concluded these data do not prove that HIV preferentially destroys T4 cells or has any cytopathic effects, nor do they demonstrate that T4 cells are preferentially destroyed in AIDS patients, or that T4 cell destruction and HIV are either necessary or sufficient prerequisites for the development of the clinical syndrome.

The role of human cytomegalovirus in haematological diseases

Infection with HCMV in healthy individuals generally results in mild or subclinical illness. Pathogenic infections occur predominantly in immunodeficient patients, such as transplant recipients, neonates and patients with AIDS. Primary infection is frequently latent or chronic and PBLs represent sites for virus latency and persistence. HCMV can be recovered from PMNL, monocytes and T-lymphocytes. Although virus-related cases of haematopoietic dysfunction are seen infrequently in infected normal persons, the importance of HCMV as a pathogenic agent in haematopoiesis is dramatically illustrated in the case of patients receiving BMT. Primary or reactivated HCMV infections are a common feature in BMT recipients, enhancing failure of marrow engraftment, GVHD, and many opportunistic infections. HCMV can infect both haematopoietic progenitor cells and stromal elements, identifying the entire haematopoietic system as a target for HCMV dissemination and latency. As a result, lympho- and myelosuppression can be due to both direct inhibition of progenitor cell growth as well as the failure of stem cell self-renewal due to stromal cell dysfunction. HCMV can also exert suppressive effects on immune cell function by direct and indirect mechanisms. These effects can have dire consequences, particularly when a state of immunosuppression already exists, as in the HIV infection. The diverse effects of CMV on the lymphohaematopoietic system are summarized in Figure 1.

Programmed cell death induced by HIV type 1 antigen stimulation is associated with a decrease in cytotoxic T lymphocyte activity in advanced HIV type 1 infection

The immune competence of peripheral blood mononuclear cells (PBMCs) from human immunodeficiency virus-seropositive (HIV+) patients was studied by assessing cytotoxic T lymphocyte (CTL) activity following recall HIV antigen stimulation. Target cells were HLA-A-matched EBV-transformed B cells expressing HIV-1 antigen. In the presence of recombinant IL-2 (rIL-2, 2 or 10 U/ml), about 50% of PBMCs from HIV+ asymptomatic patients responded to HIV-1 antigen stimulation in vitro with increased cytotoxic activity. In contrast, PBMCs from patients with overt AIDS, cultured in medium containing rIL-2 (2 U/ml) and HIV-1 antigen, showed no increase in cytotoxic activity; in the presence of rIL-2 (10 U/ml) and HIV-1 antigen, an inhibitory effect on CTL activity was observed. This inhibitory effect was associated with programmed cell death (apoptosis) of CD8+ lymphocytes and cells of both gamma/delta TcR-positive and -negative phenotypes. However, prior to the apoptosis, different TcR phenotypes of T lymphocyte reacted differently to HIV-1 antigen stimulation. The HIV-1 antigen initially appeared to cause gamma/delta TcR-positive T lymphocytes to proliferate and/or differentiate and later induced cell death. Whereas, prior to the apoptosis, no proliferation of gamma/delta TcR-negative T lymphocytes induced by HIV-1 antigen was observed.

HIV population dynamics in vivo: implications for genetic variation, pathogenesis, and therapy

Several recent reports indicate that the long, clinically latent phase that characterizes human immunodeficiency virus (HIV) infection of humans is not a period of viral inactivity, but an active process in which cells are being infected and dying at a high rate and in large numbers. These results lead to a simple steady-state model in which infection, cell death, and cell replacement are in balance, and imply that the unique feature of HIV is the extraordinarily large number of replication cycles that occur during infection of a single individual. This turnover drives both the pathogenic process and (even more than mutation rate) the development of genetic variation. This variation includes the inevitable and, in principle, predictable accumulation of mutations such as those conferring resistance to antiviral drugs whose presence before therapy must be considered in the design of therapeutic strategies.

Studies in subjects with long-term nonprogressive human immunodeficiency virus infection

BACKGROUND

In a small percentage of persons infected with human immunodeficiency virus type 1 (HIV-1), there is no progression of disease and CD4+ T-cell counts remain stable for many years. Studies of the histopathological, virologic, and immunologic characteristics of these persons may provide insight into the pathogenic mechanisms that lead to HIV disease and the protective mechanisms that prevent progression to overt disease.

METHODS AND RESULTS

We studied 15 subjects with long-term nonprogressive HIV infection and 18 subjects with progressive HIV disease. Nonprogressive infection was defined as seven or more years of documented HIV infection, with more than 600 CD4+ T cells per cubic millimeter, no antiretroviral therapy, and no HIV-related disease. Lymph nodes from the subjects with nonprogressive infection had significantly fewer of the hyperplastic features, and none of the involuted features, characteristic of nodes from subjects with progressive disease. Plasma levels of HIV-1 RNA and the viral burden in peripheral-blood mononuclear cells were both significantly lower in the subjects with nonprogressive infection than in those with progressive disease (P = 0.003 and P = 0.015, respectively). HIV could not be isolated from the plasma of the former, who also had significantly higher titers of neutralizing antibodies than the latter. There was viral replication, however, in the subjects with nonprogressive infection, and virus was consistently cultured from mononuclear cells from the lymph nodes. In the lymph nodes virus "trapping" varied with the degree of formation of germinal centers, and few cells expressing virus were found by in situ hybridization. HIV-specific cytotoxic activity was detected in all seven subjects with nonprogressive infection who were tested.

CONCLUSIONS

In persons who remain free of disease for many years despite HIV infection the viral load is low, but viral replication persists. Lymph-node architecture and immune function appear to remain intact.

Virologic and immunologic characterization of long-term survivors of human immunodeficiency virus type 1 infection

BACKGROUND

In most subjects infected with human immunodeficiency virus type 1 (HIV-1), clinical or laboratory evidence of immunodeficiency develops within 10 years of seroconversion, but a few infected people remain healthy and immunologically normal for more than a decade. Studies of these subjects, termed long-term survivors, may yield important clues for the development of prophylactic and therapeutic interventions against the acquired immunodeficiency syndrome.

METHODS AND RESULTS

We studied 10 seropositive subjects who remained asymptomatic with normal and stable CD4+ lymphocyte counts despite 12 to 15 years of HIV-1 infection. Plasma cultures were uniformly negative for infectious virus. However, particle-associated HIV-1 RNA was detected in four subjects with a sensitive branched-DNA signal-amplification assay, whereas in five others the levels of HIV-1 RNA were too low to detect. Infectious HIV-1 was detected in peripheral-blood mononuclear cells (PBMC) of three subjects by standard limiting-dilution cultures, and infectious virus was recovered from another subject with use of a CD8-depleted culture. The other six subjects had no detectable infectious virus in their PBMC. A quantitative polymerase-chain-reaction assay revealed that all subjects had detectable but low titers of viral DNA in PBMC. Overall, the viral burden in the plasma and PBMC of long-term survivors was orders of magnitude lower than that typically found in subjects with progressive disease. There was no in vitro evidence of resistance by host CD4+ lymphocytes to HIV-1 infection. However, long-term survivors had a vigorous, virus-inhibitory CD8+ lymphocyte response and a strong neutralizing-antibody response. In two subjects the kinetics of viral replication were consistent with the presence of a substantially attenuated strain of HIV-1.

CONCLUSIONS

Subjects who remain asymptomatic for many years despite HIV-1 infection have low levels of HIV-1 and a combination of strong virus-specific immune responses with some degree of attenuation of the virus.

Single cell transcript analysis of human immunodeficiency virus gene expression in the transition from latent to productive infection

In the lymph nodes of individuals infected with human immunodeficiency virus (HIV), there is evidence that points to three kinds of virus-cell relationships. Virions may be associated with CD4+ lymphocytes that are actively producing virus or may be bound at the surfaces of follicular dendritic cells like other antigens. HIV is also harbored in CD4+ lymphocytes and monocytes/macrophages in a latent form as transcriptionally silenced provirus. To ultimately investigate in vivo these and other HIV-cell interactions that play such critical roles in the persistence of virus, immune dysregulation, and depletion, we have developed an in situ hybridization method that discriminates multiply spliced from singly or unspliced viral transcripts. In this report we describe the method and the results obtained with it in an analysis of the switch from latent to productive infection of chronically infected T lymphocytes in culture. We found with this single-cell technique that there are two subpopulations in the culture, a minor one of productively infected cells and a major one of latently infected cells in which only low levels of viral transcripts terminated close to the 5' end of the viral genome were detected. Shortly after activation of viral gene expression with phorbol ester, transcripts encoding Tat and Rev increase in abundancy in individual latently infected cells and this is followed by increases in and cytoplasmic export of singly or unspliced mRNAs encoding structural proteins. These studies provide insights into the regulation of HIV gene expression from a single-cell perspective and, from that perspective, transcript profiles of productively infected cells as a frame of reference for defining HIV-cell relationships in individual cells in tissue sections.

Survey of HIV/AIDS-Related Curricula in Programs of Occupational Therapy

AIDS has affected or will affect virtually every provider of health care. The purpose of this study was to determine the quantity of HIV/AIDS-related curricula in programs of occupational therapy across the United States. A survey was distributed to the program directors of all accredited technical, undergraduate, and graduate programs in the United States. Of the 137 surveys mailed, 95 were returned, yielding a 69%% response rate. Results of the survey indicated that graduate and undergraduate professional programs devoted an average of six classroom hours to this topic while technical programs averaged three classroom hours, with the majority of program directors indicating there is no need for further HIV/AIDS related curricula in their respective programs.

Role of immune activation and cytokine expression in HIV-1-associated neurologic diseases

Central nervous system (CNS) involvement is common during human immunodeficiency virus type-1 (HIV-1) infection. The neurologic disease of the CNS most frequently observed during acquired immunodeficiency syndrome (AIDS) is HIV-1-associated cognitive/motor complex or AIDS dementia complex (ADC), which is most likely a direct consequence of HIV-1 infection of the CNS. The peripheral nervous system (PNS) is also affected in HIV-1-infected individuals and there are several features of immune- and cytokine-related pathogenesis in both the CNS and PNS that are reviewed. Several lines of evidence demonstrate aspects of immune activation in the CNS and peripheral nervous system (PNS) of HIV-1-infected individuals. The relative paucity of HIV-1 expression in contrast to widespread functional and pathologic changes in the CNS and PNS of AIDS patients, and the lack of evidence of productive infection of HIV-1 in neuronal cells in vivo lead to the possibility of indirect or immunopathogenic mechanisms for HIV-1-related neurologic diseases. Proposed mechanisms of neuronal and glial cell damage are injury of oligodendrocytes by tumor necrosis factor-alpha (TNF-alpha) released from activated macrophage/microglia, calcium-dependent excitoneurotoxicity induced by gp120 HIV-1 envelope protein, N-methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity by quinolinic acid (a product of activated macrophages), cell injury by HIV-1-specific cytotoxic T cells, and apoptosis of oligodendrocytes or neurons triggered by interaction between cell surface receptors and HIV-1 gp120 protein. Common to those mechanisms is the dependence on cellular activation with expression of proinflammatory cytokines (TNF-alpha, interleukin-1). Amplification of activation signals through the cytokine network by macrophage/astrocyte/endothelial cell interactions, and cell-to-cell contact between activated macrophages and neural cells by upregulation of adhesion molecules dramatically enhances the toxic effect of macrophage products. Expression of immunosuppressive cytokines such as interleukin-4, interleukin-6, and transforming growth factor-beta is also increased in the CNS and PNS of HIV-1-infected patients. This may serve as neuroprotective and regenerative mechanism against insults to nervous system tissue.

Early versus delayed treatment of HIV infection. Zidovudine should be given before symptoms develop

An understanding of the virology and pathogenesis of HIV infection provides a rationale for initiating early intervention with antiretroviral drugs. Even at the earliest stages of infection when HIV-infected patients are asymptomatic, viral replication is ongoing, particularly in lymphoid tissues. Initiation of antiretroviral therapy can reduce viral replication and delay disease progression. A possible objection to early intervention therapy with zidovudine is the risk of selecting out resistant isolates of HIV, which would be difficult to treat. In practice, zidovudine-resistant isolates occur significantly less frequently in patients with early-stage disease compared with those with late-stage HIV infection, thus supporting the early use of zidovudine; in addition, alternative therapies, active against zidovudine-resistant isolates, are available. Clinical trials with zidovudine in asymptomatic patients have differed in terms of length of follow-up, patient inclusion criteria, dosages and end-points. However, a number of conclusions are possible based on the results obtained: early intervention delays the progression of AIDS, delays the onset of symptomatic disease, has a favourable effect on surrogate markers of HIV infection and is well tolerated; it does not, however, seem to produce any benefit in terms of survival. It is this last point that has given rise to much of the controversy regarding early intervention with zidovudine in asymptomatic patients. Since the disease is progressive in nature with persistent and high levels of viral replication and as prolonging the period of relative health and quality of life when the patient is asymptomatic is desirable, the choice to treat before symptoms develop would appear to be the optimal therapeutic strategy.

Effect of anti-V3 antibodies on cell-free and cell-to-cell human immunodeficiency virus transmission

The present study was undertaken to compare the effects of a type-specific (HIV-1 MN) anti-V3 antibody on in vitro human immunodeficiency virus (HIV) infection of peripheral blood mononuclear cells in systems of cell-free versus cell-to-cell transmission of virus. Anti-V3 antibody completely prevented HIV-1 infection when cell-free virus was the sole mechanism of infection. A significant reduction of the neutralizing activity of the anti-V3 antibody was observed when infectivity was dependent on both cell-free and cell-to-cell mechanisms of infection. Furthermore, when cell-to-cell transfer of virions was the primary mechanism of HIV-1 infection, inhibition of HIV-1 infection was not observed. Therefore, a potent neutralizing antibody with a single epitope specificity failed to effectively control dissemination of a persistent HIV-1 infection in a system characterized predominantly by cell-to-cell transfer of virus.

Mother-to-infant HIV transmission: timing, risk factors and prevention

Identifying when--during pregnancy, delivery or the postnatal period--transmission of human immunodeficiency virus (HIV) from mother to infant usually takes place is critical to the development of methods to prevent maternal-infant transmission. Evidence is reviewed in this paper as to whether transmission occurs prepartum (early or late in gestation), intrapartum, or postpartum with breast feeding. Evidence in support of the notion of prepartum transmission has come from isolation of HIV from aborted fetal organs, comparison of maternal-child viral genotypes and study of neonatal cell-mediated immune responses. Evidence against prepartum transmission is that fewer than half of the children later known to be HIV-infected can be identified by virological tests carried out close to birth. A reduced rate of transmission in infants delivered by Caesarean section, and a reduced risk of transmission to second-born twins delivered vaginally, offers support to the view that intrapartum factors influence the risk of HIV transmission. Transmission through breast feeding can occur if a mother is infected postpartum and seems to pose some additional risk if she is already infected at parturition. The risk of infection increases with the stage of maternal HIV disease, but specific immunological, clinical and viral characteristics need to be investigated further. A clinical trial of zidovudine, used during late pregnancy and delivery and given to the infant at birth, has reported a significant reduction in transmission. Primary prevention of HIV infection in women remains a principal priority.

Lentiviral infection, immune response peptides and sleep

The aberrant sleep documented in subjects with human immunodeficiency virus (HIV) infection is uniquely important because of the contribution this poor quality sleep makes to the fatigue, disability, and eventual unemployment that befalls these patients. Especially given this importance in clinical care, the research on the prominent sleep changes described in HIV infection remains modest in quantity. The chronic asymptomatic stage of HIV infection is associated with the most intriguing and singular sleep structure changes. Especially robust is the increase in slow wave sleep, particularly in latter portions of the sleep period. This finding is rare in other primary or secondary sleep disorders. The sleep structure alterations are among the most replicable of several pathophysiological sequelae in the brain associated with early HIV infection. It is unlikely that these sleep architecture changes are psychosocial in etiology, and they occur before medical pathology is evident. They are not associated with stress, anxiety, or depression. Evidence is accumulating to support a role for the somnogenic immune peptides tumor necrosis factor (TNF)alpha and interleukin (IL-1 beta) in the sleep changes and fatigue commonly seen in HIV infection. These peptides are elevated in the blood of HIV-infected individuals, and are somnogenic in clinical use and animal models. The peripheral production of these peptides may also have a role in the regulation of normal sleep physiology. The lentivirus family contains both HIV and the feline immunodeficiency virus (FIV). The use of the FIV model of HIV infection may provide a way to further investigate the mechanism of a neurotropic, neurotoxic virus initiating the immune acute phase response and affecting sleep. Neurotropic lentivirus infection is a microbiological probe facilitating neuroimmune investigation.

Infection of circulating and liver infiltrating T cells by hepatitis C virus of different subtypes

Hepatitis C virus (HCV) infection display a very high rate of progression to chronicity and, like many other viruses causing persistent infections, it displays a tropism for the cells of the immune system. Peripheral blood mononuclear cells (PBMCs) from 21 HCV chronic carriers and long-term T cell clones derived from circulating or liver infiltrating T lymphocytes were tested by cDNA "nested" PCR for positive and negative strand HCV-RNA. The presence of HCV genomes in PBMCs is a frequent, although not constant, finding and can be accompanied by active viral replication, as suggested by the coexistence of negative strand HCV-RNA. Infected T cells are more represented in livers than in periphery, as indicated by comparing HCV-RNA detection in T cell clones isolated from both the compartments. Sequencing of viral genomes present in PBMCs and liver infiltrating lymphocytes showed that all the three major HCV genotypes present in our population of chronic carriers can infect lymphoid cells. Although each clonal population of T cells is infected by a single strain of HCV, in the same patient lymphoid cells can harbor different viral populations, different from those circulating at that moment in the serum.

Molecular detection of hepatitis C virus: impact of detection methodology on clinical and laboratory correlations

The clinical manifestations of hepatitis C virus (HCV) infection are generally indistinguishable from other causes of viral hepatitis. HCV infections are usually anicteric, asymptomatic, and rarely cause acute fulminant liver failure. Serological testing for HCV in conjunction with epidemiological studies have verified that HCV was the major cause of parenterally transmitted non-A, non-B hepatitis (NANBH). With the widespread introduction of serological screening of blood products for HCV antibody, the risk of transfusion-associated HCV infection has been dramatically reduced (to < 3 cases per 10,000 units transfused). Despite the virtual elimination of transfusion-associated infections, the diagnosis of HCV remains important because > 50% of infections are sporadic in origin, 50 to 70% of infected individuals develop chronic hepatitis, and these individuals are at risk of developing cirrhosis (> 20%) as well as hepatocellular carcinoma. Although currently available anti-HCV immunoassays function well as blood-donor screening assays, they are poor at detecting acute infection because of the prolonged lag time between infection and detection of seroconversion (approximately 10 to 26 weeks for second-generation immunoassays). In contrast, polymerase chain reaction (PCR)-based detection of HCV RNA in serum can detect infection in as little as 1 to 2 weeks after exposure. This review focuses on the impact of modern serologic and nucleic acid-based HCV detection methodology on the clinical understanding of HCV infection, its associated illnesses, and its transmissability. Quantitative and reproducible nucleic acid-based detection assays will be required to provide additional insights into the clinical spectrum of HCV infections as well as to assess the efficacy of antiviral agents.

Human immunodeficiency virus Tat induces functional unresponsiveness in T cells

Soluble proteins of the human immunodeficiency virus (HIV) might play a significant role in the pathogenesis of HIV infection. The addition of synthetic Tat peptides, but not that of the recombinant Nef or Vif protein, inhibited proliferative responses of CD4+ tetanus antigen-specific, exogenous interleukin-2 (IL-2)-independent T-cell clones in a dose-dependent manner. In addition, Tat peptides inhibited the anti-CD3 monoclonal antibody-induced proliferative responses of both purified CD4+ and CD8+ T cells. Tat did not affect proliferative responses induced by phorbol myristate acetate plus ionomycin. The Tat peptides at the concentrations used (0.1 to 3 micrograms/ml) did not affect the viability of the cells as determined by trypan blue exclusion. Treatment of Tat peptides with polyclonal Tat antibodies abrogated the inhibitory effect of Tat. Soluble Tat proteins secreted by HeLa cells transfected with the tat gene also inhibited antigen-induced proliferation of the T-cell clones. Tat inhibited the anti-CD3 monoclonal antibody-induced IL-2 mRNA expression and IL-2 secretion but did not affect IL-2 receptor alpha-chain mRNA or protein expression on peripheral blood T cells. Finally, treatment of T-cell clones with the Tat peptide did not affect the antigen-induced increase in intracellular calcium, hydrolysis of phosphatidyl inositol to inositol trisphosphate, or translocation of protein kinase C from the cytosol to the membrane. These studies demonstrate that the mechanism of the Tat-mediated inhibition of T-cell functions involves a phospholipase C gamma 1-independent pathway.

The Viral Model for AIDS: Paradigmatic Dominance, Politics, or Best Approximation of Reality?

In 1981, a non-infectious disease hypothesis was offered by the Centers for Disease Control to explain the cluster of atypical pneumonias which had appeared among gay men in the United States. Although quickly supplanted by the now widely held viral hypothesis and largely ignored by professional and media sources, that view has persisted. This article raises the question of why one explanation for the epidemic of immune system suppression has dominated the discourse on AIDS, despite the anomalies attributed to it by the proponents of other viewpoints. Alternative responses to the question are set forth drawing upon literatures in the philosophy of science and public policy formulation. Some discussion is provided of what the consequences may be if one of the contrarian hypotheses proves to be the closer approximation to the truth about AIDS etiology.

Oltipraz, a novel inhibitor of human immunodeficiency virus type 1 (HIV-1) replication

Glutathione (GSH) levels are markedly depleted in patients infected with human immunodeficiency virus type 1 (HIV-1) and supplementation of media with high concentrations (5-20 mM) of low-molecular weight thiols prevents HIV-1 replication in cultured cells. We were intrigued whether chemopreventive enzyme inducers might represent a more pharmacologically feasible method to inhibit HIV-1 replication since these compounds elevate intracellular concentrations of GSH at nontoxic doses in vivo. After establishing that all inducers surveyed were able to elevate GSH levels in human T-cell and monocytoid cell lines, we were surprised to find that oltipraz (5-pyrazinyl-4-methyl-1,2-dithiole-3-thione) was uniquely able to inhibit HIV-1 replication (IC50 = 5-15 microM). Oltipraz and other antiviral 1,2-dithiole-3-thiones (DTTs) appear to inhibit acute HIV-1 replication by inactivating reverse transcriptase (RT). However, among DTTs that inhibit HIV-1 replication in acutely infected cells, only oltipraz was able to inhibit HIV-1 replication in a chronic infection model. Thus, in addition to inactivating RT, oltipraz appears to have an additional antiviral mechanism distal to viral integration. Our laboratories are attempting to determine the mechanism by which oltipraz inhibits HIV-1 replication in chronically infected cells; we are also attempting to determine the bioorganic mechanism for the inactivation of RT. Since the covalent modification of schistosomal proteins and transcription factor(s) are thought to be responsible for the antiparasitic and chemopreventive activities of DTTs, respectively, our studies should be relevant to understanding the diverse medicinal properties of DTTs. Oltipraz, an antischistosomal drug undergoing clinical evaluation as an anticarcinogen, inhibits HIV-1 replication at concentrations achievable in human serum. It is intriguing to consider oltipraz as a therapeutic agent not only for its antiretroviral activity, but also for the prevention of HIV-1 associated neoplasms.

Disparity in the percentage of CD4+ T lymphocytes and prognosis of HIV-infected intravenous drug users in Malaysia

The CD4+ T-lymphocyte absolute count (CD4ac), CD4+ T-lymphocyte percentage (CD4%) and total lymphocyte count (Løac) were assessed in HIV-seropositive intravenous drug users (IVDU) with reference to their correlation with the clinical categories A, B, and C as stipulated by the Centre of Disease Control and Prevention, USA (CDC) and with each other. It was found that while the CD4ac and Løac correlated with the clinical categories, CD4% did not. This may suggest that in our local setting, the CD4% may not necessarily be a suitable alternative marker to CD4ac as proposed by CDC. Furthermore, the CD4% of the normal subjects in this study was found to be relatively lower than the reported Caucasian levels. This may indicate that the use of the cut-off level of less than 14% as an AIDS-defining criteria may not be applicable for our HIV-seropositive IVDU. In addition, unlike the CD4ac which correlated directly with CD4% and Løac, the CD4% did not correlate with Løac. Therefore, due to the observed disparity with clinical status of patients and its possibly lower levels in our normal population, CD4% as a marker for staging HIV disease should be used with caution in our setting. Such findings may also have an impact on the use of established markers for the monitoring and classification of HIV-infected individuals in this region.

Psychosocial counseling to improve quality of life in HIV infection

Psychosocial interventions such as cognitive behavioral stress management (CBSM), may enhance coping and social support which contribute to an improvement of quality of life factors such as emotional functioning, social functioning, and sense of well-being, for HIV-infected men during several phases of HIV spectrum disease. These phases include the acutely stressful period immediately following notification of HIV+ status, the adjustment period following this news, and the process of dealing with chronic symptomatic HIV infection. Normalization of some aspects of immunological status were found to accompany some of these psychosocial changes in the short-run. Longer-term follow-up indicated relationships between psychosocial factors and improved immunological status and physical functioning up to 2 years later. Factors such as an increased use of active coping strategies, including relaxation exercises, use of more functional appraisals and elicitation of social support, and decreased use of denial/avoidance coping strategies, may be key predictors of longer-term emotional well-being, social functioning, and physical functioning in HIV-infected populations. Special issues need to be addressed in emerging models of quality of life assessment in HIV populations. For example, the way resurgence of stigmatization and self-doubt affects sense of identity and well-being need to be addressed in quality of life research as well as in psychosocial interventions. Loss of employment and its financial and existential consequences are also factors which impact sense of self and well-being, and need to be addressed both in research as well as in interventions. The effect of repeated HIV-related bereavements upon an individual's social network and the emotional, social, and physical sequelae of bereavement have implications for HIV quality of life research as well. Quality of survival time has become a paramount issue in the context of HIV spectrum disease. Examining the relationships among coping strategies, social support, emotional well-being, realistic appraisals of one's functioning in comparison to their aspirations, and the influence of psychosocial functioning on disease course are central missions of our research program.

Influence of host cell type and V3 loop of the surface glycoprotein on susceptibility of human immunodeficiency virus type 1 to polyanion compounds

Dextran sulfate is a potent inhibitor of human immunodeficiency virus (HIV) binding and replication in lymphocytic cell lines. In this study, we demonstrate that the effect of dextran sulfate and heparin depends on the host cell type and on the V3 loop, the principal neutralizing determinant of HIV gp120. In particular, when dextran sulfate was tested on primary human macrophages infected with macrophage-tropic viruses, enhancement of infection was observed in 6 of 11 independent macrophage preparations and with 5 of 13 primary HIV isolates. Our in vitro observations might explain why enhanced HIV replication was observed in HIV-infected patients treated with dextran sulfate.

Effects of psoralen plus UVA radiation (PUVA) on HIV-1 in human beings: a pilot study

BACKGROUND

Laboratory data document the activation of the HIV-1 genome on exposure to UV radiation, including PUVA. The overall effects of UV radiation exposure on HIV-1 infection in human beings are unknown.

OBJECTIVE

Our purpose was to observe CD4 cell counts and quantitative markers of HIV-1 load in late-stage HIV-1-infected human beings receiving PUVA for various cutaneous diseases.

METHODS

Samples of peripheral blood were obtained on days 0, 14, 30, and 60 of PUVA administered in therapeutic doses. Number of CD4+ T lymphocytes was determined by flow cytometry, and HIV-1 load was measured by semiquantitative polymerase chain reaction for viral genome in peripheral blood mononuclear cells, semiquantitative RNA-polymerase chain reaction for HIV-1 RNA in serum, and determination of p24 in serum.

RESULTS

No significant changes in the measurements were observed.

CONCLUSION

This study did not detect a deleterious effect on CD4 cell count or HIV-1 load during 2 months of PUVA treatment for patients in late stages of infection, with low CD4 cell counts and high HIV-1 loads.

Serum concentrations of soluble intercellular adhesion molecule-1 and progress towards disease in patients infected with HIV

Intercellular adhesion molecule-1 (ICAM-1) is a membrane-bound molecule that is primarily involved in cell to cell adhesive interactions of the immune system. Concentrations of soluble ICAM-1 (s-ICAM-1) shed into the circulation were measured by a quantitative ELISA in HIV-infected persons without AIDS, patients with AIDS with or without evidence of acute opportunistic infection at the time of sampling, and HIV-seronegative patients with toxoplasmosis, community-acquired pneumonia, leishmaniasis and rickettsial infections. Patients were classified on the basis of clinical condition and CD4+ T-cell counts according to the 1993 revised HIV classification of the USA Centers for Disease Control. Concentrations of s-ICAM-1 in the serum of HIV-infected persons without AIDS-indicator conditions (categories A1, A2, B1 and B2) as well as in the serum of patients with AIDS (categories A3, B3, C1, C2 and C3) were significantly higher than normal (mean +/- S.E.M. 469 +/- 23, n = 60 and 780 +/- 73, n = 56, respectively, versus 329 +/- 15 ng/ml, P < 0.0001 and < 0.0001 respectively) and differed also significantly from each other (P < 0.0001). Raised concentrations of s-ICAM-1 in the serum of afebrile patients with AIDS but without acute opportunistic infection at the time of sampling (mean +/- S.E.M. 672 +/- 76, n = 29) did not differ from those of the remaining patients with AIDS or from those of HIV-seronegative patients with the infections studied. A steady and significant increase of serum concentrations of s-ICAM-1 with progress of disease according to clinical category (categories A-->B-->C, p = 0.0007) as well as with the loss of circulating CD4+ T-cells (categories 1-->2-->3, p = 0.009) was observed. Individual serum concentrations of s-ICAM-1 showed negative correlations with individual total lymphocyte (P = 0.004), CD4+ T-cell (P = 0.05), CD8+ T-cell counts (P = 0.03) as well as positive correlation with serum concentrations of soluble interleukin-2 receptors (P < 0.0001), an indirect marker of progress of HIV-related disease. Serum concentrations of s-ICAM-1 did not differ between patients with AIDS who were receiving or not receiving zidovudine at the time of sampling. A longitudinal survey is needed in order to determine whether measuring serum concentrations of s-ICAM-1, although not specific, has any predictive or prognostic value in these patients as well as whether this bioactive molecule has any pathogenetic role in the progress of disease in HIV infection.

An experimental study of primary feline immunodeficiency virus infection in cats and a historical comparison to acute simian and human immunodeficiency virus diseases

Sixteen adolescent specific pathogen free cats were inoculated with the Petaluma strain of feline immunodeficiency virus (FIV) and two cats were then necropsied at each of 5, 10, 21, 28, 42, 56, 70, and 84 day time points following infection. Lymphadenopathy gradually increased starting at Day 10 and persisted for the duration. Gross clinical signs of fever, mild to severe malaise, anorexia, diarrhea, dehydration, and generalized soreness appeared around Day 42, peaked at Day 56, and disappeared by Days 70-84 post-infection. Leukopenia, associated initially with a mild lymphopenia and later by both a mild lymphopenia and a severe neutropenia, appeared 14-28 days following infection, troughed at Day 56, and persisted thereafter. The CD4+:CD8+ T cell ratio started to decrease around Day 28, reaching a nadir at Days 56-70. This decrease was due to a decline in the absolute numbers and percentage of CD4+ T cells and an increase in the percentage of CD8+ T cells. Significant histopathologic lesions included myeloid hyperplasia between Days 56-70 post-infection; thymitis with cortical involution and follicular hyperplasia starting at Day 42; lymphoid hyperplasia of peripheral and mesenteric nodes, spleen and tonsils beginning around Day 42; typhlitis most evident from Day 56 onward, and an interstitial nephritis and pneumonitis that was most intense after Day 42. Virus was isolated from peripheral blood mononuclear cells (PBMC) beginning 2 weeks post-infection, and plasma viremia appeared 1 week later. Plasma and PBMC-associated viremia peaked at 42-56 days following infection and decreased abruptly thereafter. Proviral DNA was detectable as early as 5 days after infection in blood leukocytes and after 10 days in other organs. The central nervous system, lungs, thymus, tonsils and mesenteric lymph nodes were the earliest sites of virus localization. Antibodies to the FIV capsid protein appeared 14 days following infection and reached peak levels by Days 42-56. Abnormalities occurring during the primary stage of FIV infection were consistent with those described for acute simian and human immunodeficiency virus-induced disease.

Viral superantigen-induced hyporesponsiveness of T cells and polyclonal B cell activation in HIV-1 infection

The mechanisms of CD4 depletion and hyporesponsiveness during human immunodeficiency virus (HIV) infection are still unknown. Given the ability of superantigens to stimulate a higher number of lymphocytes than conventional antigens, they may play a major role in this process. Recently, a novel superantigen, the rabies virus nucleocapsid (NC), was described in humans. In the present work, we tested the responses of peripheral blood lymphocytes from asymptomatic HIV-infected patients to this superantigen. In contrast to its effect in normal controls, NC failed to expand T cells from HIV-infected individuals expressing the V beta 8 family, and induced a strong decrease in the response to CD3 activation. This absence of response was not the consequence of programmed cell death, and was explained by an anergic state induced by the superantigen. NC superantigen was also able to induce polyclonal activation of B cells, as measured by the secretion of anti-HIV antibodies and autoantibodies. Moreover, V beta 8 depletion experiments showed that induction of autoantibody secretion was V beta 8 dependent, whereas secretion of HIV-1 antibody was not. Interleukin secretion studies showed that NC was able to induce high levels of interleukin-4 and interleukin-10. Taken together, our results suggest a role for exogenous viral superantigens such as NC in the induction of T cell hyporesponsiveness and polyclonal B cell activation during HIV infection. The induction of a Th2 response and the role of these superantigens in the immunopathogenesis of acquired immunodeficiency syndrome are discussed.