Immunopathogenesis of HIV infection

HIV-Nef enhances interleukin-2 production and phosphatidylinositol 3-kinase activity in a human T cell line

OBJECTIVE

The Nef protein has a major influence on disease pathogenesis in HIV-infected individuals. The objective of the present study was to examine the effects of Nef on T lymphocyte activation and associated signalling events.

DESIGN

A recombinant vaccinia expression system was used to express Nef in a human T cell line. Stimulation of these cells with anti-CD28 antibody, and either phorbol 12-myristate 13-acetate (PMA) or anti-CD3, activates signal transduction pathways and results in IL-2 production and IL-2 receptor alpha-chain (CD25) expression. Cellular responses were examined in cells expressing either Nef or an irrelevant control protein.

METHODS

Activation of signalling was assessed by immunoblot analysis, or by in-vitro phosphatidylinositol 3-kinase (PI3K) assays. IL-2 production was measured by enzyme-linked immunosorbent assay, and CD25 cell surface expression was examined using flow cytometry.

RESULTS

Infection of cells with recombinant vaccinia expressing HIV-nef resulted in a marked increase in the production of IL-2 when cells were activated. The enhanced IL-2 response was accompanied by an increase in the level of PI3K activity. IL-2 production remained sensitive to inhibition with the PI3K competitive inhibitor Ly294002, and to the fungal macrolide, rapamycin. In contrast, CD25 expression was not affected, and there were no measurable changes to nuclear factor kappaB (NFkappaB) activation pathways.

CONCLUSION

Enhanced IL-2 production in stimulated T cells expressing HIV-Nef is associated with increased activation of PI3K-dependent signalling pathways. The results support a model in which Nef affects HIV disease progression by distorting T cell responses.

Analysis of virologic and immunologic events in HIV infection

A number of pathogenic events occurring immediately after the transmission of HIV lead to the establishment of chronic infection. In fact, despite the detection of vigorous virus-specific immune responses during primary infection, HIV is able to establish chronic infection in most of the cases. This is the result of several virologic and immunologic mechanisms that HIV has evolved to escape and/or to weaken virus-specific immune responses. Lymphoid organs represent the primary anatomic site for the establishment of chronic infection, and if highly active antiretroviral therapy is not initiated in early stage disease, there is a progressive destruction of lymphoid tissue that ultimately leads to the profound immunosuppression typical of AIDS. Therefore, analysis of lymphoid organs is crucial for the correct evaluation of the effectiveness of antiretroviral therapy in HIV infection.

Competitive coexistence in antiviral immunity

Adaptive immunity to viruses in vertebrates is mediated by two distinct but complementary branches of the immune system: the cellular response, which eliminates infected cells, and the humoral response, which eliminates infectious virus. This leads to an interesting contest, since the two responses compete, albeit indirectly, for proliferative stimuli. How can a host mount a coordinated antiviral campaign? Here we show that competition may lead to a state of "competitive coexistence" in which, counterintuitively, each branch complements the other, with clinical benefit to the host. The principle is similar to free-market economics, in which firms compete, but the consumer benefits. Experimental evidence suggests this is a useful paradigm in antiviral immunity.

Immunological evaluation of human immunodeficiency virus infected individuals by flow cytometry

Human immunodeficiency virus (HIV) infection heavily compromises the immune system. The decrease of the T cell CD4+ subset along the evolution to acquired immunodeficiency syndrome has been considered as a hallmark of HIV infection. In this paper we review some aspects of the immunopathology of HIV infection and discuss the importance of the flow cytometry for the evaluation of the T lymphocyte subsets in the follow-up of HIV infected children and adults, and for the monitoring of the immune reconstitution upon antiretroviral therapy.

Role of the p38 and MEK-1/2/p42/44 MAP kinase pathways in the differential activation of human immunodeficiency virus gene expression by ultraviolet and ionizing radiation

Ultraviolet (UV) radiation is a potent activator of human immunodeficiency virus (HIV) gene expression in a HeLa cell clone having stably integrated copies of an HIV cat (cat gene under control of the HIV promoter) reporter construct, whereas ionizing radiation is ineffective. UV-activated HIV gene expression is completely blocked by the specific p38 mitogen-activated protein (MAP) kinase inhibitor SB203580 and by expression of a kinase-inactive p38 mutant that interferes with normal p38 function, suggesting that this stress-activated protein kinase plays an important role in UV-mediated transcriptional activation of HIV. In support of these findings, we show here that Western blot analysis demonstrated rapid and significant activation of p38 MAP kinase by UV. On the other hand, gamma-radiation activated p38 MAP kinase very poorly in HeLa cells at both low and high doses at times (5-30 min) when UV radiation was effective. UV radiation also activated HIV gene expression (< or = 9-fold) in 1G5 Jurkat T-cells stably transfected with a luciferase reporter gene under control of the HIV promoter. In these cells, gamma-radiation stimulated HIV gene expression but to a lesser extent (< or = 3-fold) and with different kinetics than after UV radiation, and this response was obliterated by the incubation of cells with the mitogen-activated protein kinase/Erk kinase (MEK)-1/2 inhibitor PD98059. This result suggests that in these cells signaling in response to gamma-radiation is transduced through the MEK-1/2/p42/44 MAP kinase pathway to increase HIV gene expression. All combined, these results suggest that activation of p38 MAP kinase is necessary for efficient HIV gene expression triggered by DNA damaging agents, and, in a cell type-specific manner, activation of the MEK-1/2/p42/44 MAP kinase pathway is important for triggering a response to gamma-radiation. Thus, it appears as if UV signaling leading to HIV gene expression requires the p38 MAP kinase pathway whereas activation by gamma-radiation requires the MEK-1/2/p42/44 MAP kinase pathway.

Management of HIV-infected children in the home and institutional settings. Care of children and infections control in schools, day care, hospital settings, home, foster care, and adoption

The likelihood of high-risk pediatric exposure to HIV infection, other than perinatal exposure, has been shown to be low in most cases, and HIV PEP should be considered on a case-by-case basis. Generic considerations in the management of children who have become HIV infected emphasizes the principles of inclusion, maintaining confidentiality of a child's HIV status, and notifying those who need to know about the HIV status to care properly for the child or adolescent. Although appropriate infection-control precautions are applicable for all children and for many pathogens, children especially HIV-infected children, exposed to such pathogens, must be managed in a timely fashion. In many cases, recommendations that are applicable in one setting are applicable in others. Some exceptions apply, including infection-control precautions in hospitals versus other settings. A few additional considerations have been made for special settings and activities, including adoption, foster care, athletics, summer camp, and other recreational activities.

Virus phenotype switching and disease progression in HIV-1 infection

One of the phenotypic distinctions between different strains of human immunodeficiency virus type 1 (HIV-1) has to do with the ability to cause target cells to form large multinucleate bodies known as syncytia. There are two phenotypes according to this characterization: syncytium-inducing (SI) and non-syncytium-inducing (NSI). NSI strains are usually present throughout infection, while SI strains are typically seen at the beginning of the infection and near the onset of AIDS. The late emergence of SI strains is referred to as phenotype switching. In this paper we analyse the factors that lead to phenotype switching and contribute to the dynamics of disease progression. We show that a strong immune system selects for NSI strains while a weak immune system favours SI strains. The model explicitly accounts for the fact that CD4+ cells are both targets of HIV infection and crucial for activating immune responses against HIV In such a model, SI strains can emerge after a long and variable period of NSI dominated infection. Furthermore, versions of the model which do not explicitly account for HIV-specific, activated CD4+ cells do not exhibit phenotype switching, emphasizing the critical importance of this pool of cells.

Telomere loss in peripheral blood mononuclear cells may be moderately accelerated during highly active antiretroviral therapy (HAART)

It has been speculated that infection with HIV-1 may lead to a significant increase in turnover, and subsequent exhaustion, of immune repopulation. Given that telomeric DNA is lost on mitotic replication, telomere lengths can be used as an indirect gauge of this rate. We have analyzed the mean telomere restriction fragment lengths in peripheral blood mononuclear cells (PBMC) from 31 patients with established, though mainly untreated, HIV infection and found them to be no different than those among healthy controls. Our results are in line with several findings in CD4+ cell fractions but contradict a previous report suggesting that telomere shortening contributes to immune failure. Interestingly, after approximately 2 years of subsequent aggressive antiretroviral treatment we found a telomere reduction corresponding to a loss of about 250 base pairs per year; this is roughly tenfold above that predicted from healthy individuals. This could partly result from nucleoside analogue inhibition of the natural telomere replacement enzyme, telomerase-a reverse transcriptase inducible in certain hematopoietic cells. However, this may also indicate accelerated cell replacement on initiation of optimal therapeutic regimes or result from changes in the composition of the PBMC pool. These results suggest careful monitoring of telomere lengths during long-term HAART.

Serial analysis of gene expression in HIV-1-infected T cell lines

The gene expression profile of the HIV-1 infection state was analyzed in the human T cell line MOLT-4. Using the serial analysis of gene expression (SAGE) method, a total of 142¿ omitted¿603 SAGE tags were sequenced and identified, representing 43¿ omitted¿581 unique mRNA species. Comparison of expression patterns revealed that 53 cellular genes were differentially expressed upon HIV-1 infection. Northern blot and RT-PCR analyses confirmed the altered expression of the genes in both MOLT-4 and MT-4 cells. Up-regulated genes were mainly composed of transcription factors and genes related to T cell activation, whereas down-regulated genes were comprised of mitochondrial proteins, actin-related factors and translational factors. These findings indicate that persistent T cell activation, which may accelerate HIV-1 replication, and the disruption of cellular housekeeping genes including those involved in anti-apoptotic systems, may play an important role in HIV-1-induced pathogenesis.

Fatal immunopathogenesis by SIV/HIV-1 (SHIV) containing a variant form of the HIV-1SF33 env gene in juvenile and newborn rhesus macaques

SIV/HIV-1 (SHIV) chimeric clones, constructed by substituting portions of the pathogenic molecular clone SIVmac239 with counterpart portions from HIV-1 clones, provide a means to analyze functions of selected HIV-1 genes in vivo in nonhuman primates. Our studies focused on SHIVSF33, which contains the vpu, tat, rev, and env genes of the cytopathic, T-cell line tropic clone HIV-1sf33 (subtype-B); this clone has a premature stop codon in the vpu gene. In three juvenile macaques inoculated intravenously with SHIVSF33, low-level persistent infection was established; no disease was observed for a period of >2 years. However, at approximately 16 months p.i., one of four SHIVSF33-infected juvenile macaques exhibited an increase in virus load, depletion of CD4(+) T cells in peripheral blood and lymph nodes, and other symptoms of simian AIDS (SAIDS). Virus recovered from this animal in the symptomatic stage was designated SHIVSF33a (A, adapted); this virus displayed multiple amino acid sequence changes throughout the HIV-1 env gene compared with the input SHIVSF33 clone. Additionally, a mutation in all clones from SHIVSF33a restored the open reading frame for the vpu gene. In vitro evaluations in tissue-culture systems revealed that SHIVSF33a replicated to higher levels and exhibited greater cytopathicity than SHIVSF33. Furthermore cloned env genes for SHIVSF33a were more fusogenic in a cell-fusion assay compared with the env gene of the SHIVSF33. Intravenous inoculation of SHIVsf33a into juvenile and newborn macaques resulted in a rapid decline in CD4(+) T cells to very low levels and development of a fatal AIDS-like disease. A cell-free preparation of this pathogenic chimeric virus also established persistent infection when applied to oral mucosal membranes of juvenile macaques and produced a fatal AIDS-like disease. These studies on pathogenic SHIVSF33a establish the basis for further investigations on the role of the HIV-1 env gene in virus adaptation and in mechanism(s) of immunodeficiency in primates; moreover, the chimeric virus SHIVSF33a can play a role in elucidating mucosal membrane transmission and development of antiviral vaccines in newborns as well as juvenile and adult macaques.

The moving target: mechanisms of HIV persistence during primary infection

The vigorous host immune responses detected during primary HIV infection fail to prevent the establishment of chronic infection because HIV has evolved multiple strategies to make these responses ineffective. Here, Hugo Soudeyns and Giuseppe Pantaleo discuss the mechanisms that allow HIV to persist in the host.

Inactivation of human immunodeficiency virus type 1 by nonoxynol-9, C31G, or an alkyl sulfate, sodium dodecyl sulfate

A highly desirable approach to prevention of human immunodeficiency virus type 1 (HIV-1) transmission during sexual intercourse is the development of nontoxic, topical, broad spectrum microbicides effective against transmission of cell-associated and cell-free virus. Toward this end, the HIV-1 inactivation potential of surface active agents C31G and an alkyl sulfate, sodium dodecyl sulfate (SDS) was assessed. Because of its extensive use as a microbicidal agent, nonoxynol-9 (N-9) was used as a reference against which C31G and SDS were compared. Viral inactivation was measured using HIV-1 LTR-beta-galactosidase indicator cells (expressing CD4 or CD4/CCR5) derived from HeLa cells, a cell line of human cervical adenocarcinoma origin. In experiments which examined inactivation of cell-free HIV-1, C31G was generally more effective than N-9. Viral inactivation by SDS occurred at twice the concentration necessary to achieve similar levels of inactivation using either N-9 or C31G. Using HeLa and HeLa-derived cells in cytotoxicity studies, it was demonstrated that SDS is as much as 11 and five times less cytotoxic than N-9 or C31G, respectively, during 48 h of continuous exposure. SDS (unlike C31G and N-9) can inactivate non-enveloped viruses such as human papillomavirus (HPV) [Howett, M.K., Neely, E.B., Christensen, N.D., Wigdahl, B., Krebs, F.C., Malamud, D., Patrick, S.D., Pickel, M.D., Welsh, P.A., Reed, C.A., Ward, M.G., Budgeon, L.R., Kreider, J.W., 1999. A broad-spectrum microbicide with virucidal activity against sexually transmitted viruses. Antimicrob. Agents Chemother. 43(2), 314-321]. Since addition of SDS to C31G or N-9 may make the resulting microbicidal mixtures broadly effective against both enveloped and non-enveloped viruses, several surface active agent combinations were evaluated for their abilities to inactivate HIV-1. Addition of SDS to either C31G or N-9 resulted in mixtures that were only slightly less effective than equivalent concentrations of C31G or N-9 alone. To investigate inactivation of cell-associated infectivity, HIV-1 IIIB-infected SupT1 cells were treated with N-9, C31G, or SDS. Inactivation of cell-associated infectivity required higher microbicide concentrations than were needed for inactivation of cell-free virus. However, the relative activities of N-9, C31G, or SDS were similar to those seen in assays of inactivation using cell-free virus. These studies suggest that C31G and SDS may be attractive candidates for human trials as topical microbicides effective against HIV-1 transmission since both function at concentrations that provide effective viral inactivation with low levels of cytotoxicity. SDS microbicides (used alone or with other microbicides) may provide the added advantage of protection from HPV infection.

A simple relationship between viral load and survival time in HIV-1 infection

Despite important recent insights into the short-term dynamics of HIV-1 infection, our understanding of the long-term pathogenesis of AIDS remains unclear. Using an approach that places rapid progressors, typical progressors, and nonprogressors on a single clinical spectrum of disease progression, we quantitate the previously reported relationship between viral load and survival time. We introduce the concept of viral constant, present evidence that this quantity is conserved across patients, and explore the immunopathological implications of this finding. We conclude with a quantitative approach for assessing the benefits of a given regime of antiviral therapy.

Purification of RBF-2, a transcription factor with specificity for the most conserved cis-element of naturally occurring HIV-1 LTRs

The combination of high turnover and error-prone reverse transcription results in naturally occurring human immunodeficiency virus-1 long terminal repeats that differ considerably from the prototype sequence. Although no transcription-factor-binding site escapes mutation, the only mutated site that appears to be invariably compensated by co-occurrence of its duplication is the RBE III site, a target for the transcription factor RBF-2. In this work, we characterize RBF-2 further by biochemical purification. RBF-2 was purified by chromatography on heparin agarose and Mono-Q ion exchange chromatography, followed by affinity chromatography on mutant and wild-type RBE III oligonucleotide columns. The purified RBF-2 preparation contained 4 major and 1 minor polypeptides of 50, 100, 110, 120 and 125 kD, as detected by silver staining in SDS-PAGE gels. UV cross-linking revealed a specific 100-kD species, indicating that this protein likely represents the DNA-binding component of a complex. A second factor with DNA-binding specificity similar to that of RBF-2, called RBF-B, was also identified by heparin-agarose fractionation, which suggests that effects of the RBE III cis-element may be mediated by a combination of factors in vivo.

Lack of viral escape and defective in vivo activation of human immunodeficiency virus type 1-specific cytotoxic T lymphocytes in rapidly progressive infection

Human immunodeficiency virus type 1 (HIV-1)-specific immune responses over the course of rapidly progressive infection are not well defined. Detailed longitudinal analyses of neutralizing antibodies, lymphocyte proliferation, in vivo-activated and memory cytotoxic T-lymphocyte (CTL) responses, and viral sequence variation were performed on a patient who presented with acute HIV-1 infection, developed an AIDS-defining illness 13 months later, and died 45 months after presentation. Neutralizing-antibody responses remained weak throughout, and no HIV-1-specific lymphocyte proliferative responses were seen even early in the disease course. Strong in vivo-activated CTL directed against Env and Pol epitopes were present at the time of the initial drop in viremia but were quickly lost. Memory CTL against Env and Pol epitopes were detected throughout the course of infection; however, these CTL were not activated in vivo. Despite an initially narrow CTL response, new epitopes were not targeted as the disease progressed. Viral sequencing showed the emergence of variants within the two targeted CTL epitopes; however, viral variants within the immunodominant Env epitope were well recognized by CTL, and there was no evidence of viral escape from immune system detection within this epitope. These data demonstrate a narrowly directed, static CTL response in a patient with rapidly progressive disease. We also show that disease progression can occur in the presence of persistent memory CTL recognition of autologous epitopes and in the absence of detectable escape from CTL responses, consistent with an in vivo defect in activation of CTL.

Downregulation of Bcl-2, but not of Bax or Bcl-x, is associated with T lymphocyte apoptosis in HIV infection and restored by antiretroviral therapy or by interleukin 2

The role of Bcl-2, Bax, and Bcl-x in the apoptosis of T lymphocytes in HIV-infected individuals was investigated. A strong correlation between Bcl-2 downregulation and spontaneous apoptosis has been reported by various groups in short-term cultures of CD8+ but not of CD4+ T lymphocytes. We describe a similar correlation in CD4+ T cells and provide an explanation why Bcl-2 downregulation in these cells has not been detected so far. In apoptotic cells not only Bcl-2, but also the CD4 surface receptors, are downregulated, preventing the detection of these cells in flow cytometric analysis. In contrast to Bcl-2, no correlation is detectable between Bax or Bcl-x expression and apoptosis. T lymphocytes of HIV-infected, but not of control, individuals display ex vivo a heterogeneous Bcl-2 expression pattern with a low and a high Bcl-2-expressing lymphocyte fraction. The proportion of low Bcl-2-expressing T cells correlates with a higher viral load in these individuals. Antiretroviral therapy significantly reduces the proportion of low Bcl-2-expressing lymphocytes, which is associated with a decrease in apoptosis. Bcl-2 downregulation and spontaneous apoptosis of T lymphocytes from HIV-infected individuals can be partially prevented by the exogeneous addition of IL-2, but not of IL-12, IL-4, or antibodies that prevent the CD95/CD95 ligand pathway of apoptosis.

Longitudinal study of antibody reactivity against HIV-1 envelope and a peptide representing a conserved site on Gp41 in HIV-1-infected patients

This study was designed to distinguish between antibodies in HIV-1-infected patients directed against epitopes accessible on the native HIV-1 envelope (Env) complex and non-native Env epitopes. Peptide p#13 (Env. aa642-673) containing the neutralising 2F5 epitope and recombinant soluble glycoprotein 160 (rsgp160) were used in ELISA to determine the antibody (Ab) reactivity in sera of 116 HIV-1-infected individuals and 18 HIV negative controls. The reactivity of sera classified CDC stage C against p#13 was significantly decreased in comparison to stage A sera, while staying constant against rsgp160. Accordingly, in 6 out of 8 individual patients tested over time the response against p#13 was declining at later time points of infection. The reactivity of patients' sera against p#13 corresponded directly to the recognition of infected T cells and largely also to the CD4 cell count. The causal relationships of these phenomena are not clear. It is conceivable that antibodies against epitopes on HIV are lost or escape mutants arise and consequently control of HIV is lost and virus load increases as it is known for CDC stage C. Alternatively, increasing virus load may affect B cells recognising native Env epitopes and turn antibody production down by some mechanism. In this latter scenario helper T cells might have a critical role.

The implication of the chemokine receptor CXCR4 in HIV-1 envelope protein-induced apoptosis is independent of the G protein-mediated signalling

OBJECTIVE

The envelope glycoprotein complex (gp120/gp41)n of HIV-1 is one of the viral products responsible for increased apoptosis in HIV infection. Here the role of the chemokine receptor CXCR4 in HIV-1 envelope protein-induced apoptosis was investigated.

METHODS

Apoptosis occurring in cocultures of chronically HIV-1 IIIB-infected cells with CD4 target cells expressing the CXCR4 receptor was quantified by terminal deoxinucleotidyl transferase dUTP nick end labeling (TUNEL) or propidium iodide staining followed by fluorescent antibody cell sorting, which allows the evaluation of single-cell killing. Moreover global (single cell- and syncytium-associated) apoptosis was quantified by a new radioactive TUNEL-derived assay.

RESULTS

By using these different techniques it was shown that single and syncytium-forming CD4 T cells die by apoptosis upon contact with envelope protein expressing cells independently of viral replication. Moreover, both the CXCR4 agonist SDF-1alpha, and the antagonist AMD3100, showed inhibitory effects on HIV-1 envelope protein-induced apoptosis in the CD4 T-cell subset of peripheral blood mononuclear cells and CD4 cell lines. CXCR4 signalling-induced by HIV-1 envelope proteins in CD4 T cells was not detected. Furthermore, it was shown that envelope protein-induced apoptosis can occur after treating target cells with the Gi-protein inhibitor pertussis toxin.

CONCLUSIONS

Evidence is provided for a role of CXCR4 in the mechanisms of HIV envelope protein-induced pathogenesis, contributing to selective CD4 cell killing. The results suggest that CXCR4 is involved in HIV-1-induced apoptosis; however, this role does not appear to involve G-protein-mediated CXCR4 signalling.

Recognition of defined epitopes by affinity-purified anti-immunoglobulin fab autoantibodies isolated from HIV-infected humans

Infection of humans with HIV-1 has previously been independently shown to result in the generation of autoantibodies (AAbs) reactive with immunoglobulin Fab fragments (Heidelberg), and with autoantibodies to T-cell receptors (TCRs) (Tucson). Here, we carry out epitope mapping studies of affinity-purified AAbs to Fab fragments prepared from individual HIV-positive patients for their capacity to bind recombinant constructs and peptide-defined epitopes modeling TCR and Ig light chains. Some affinity-purified autoantibodies reacted strongly with TCRs expressed by intact T-cells, and recombinant Valpha/Vbeta constructs as well as with certain synthetic peptide epitopes. The binding reactions of affinity-purified AAbs of individual patients were distinct, and the AAb preparations consisted of populations of polyclonal lgs as reflected in specificity and isotype. AAb pools from individual patients all bound particular regions of TCR and Ig chains defined by comprehensive peptide synthesis including the CDR1 and Fr3 segments of the variable domains and the joining segment/switch peptide. In addition, other reactivities to restricted regions of alpha, beta and lambda light chains were documented. These results substantiate the cross-reactivity of TCR and Ig-Fab determinants, and are consistent with the hypothesis that autoantibodies arising as a consequence of HIV infection can have an immunomodulatory role.

CD4(+) T cell-mediated control of a gamma-herpesvirus in B cell-deficient mice is mediated by IFN-gamma

The lack of B cells and antibody does not prevent mice from dealing effectively with a pathogenic gamma-herpesvirus. Both CD4(+) and CD8(+) T cells contribute to the control of virus replication in the respiratory tract, with the depletion of either lymphocyte subset leading to increased titers in the lung. However, the further neutralization of IFN-gamma diminishes the effectiveness of the CD4(+) T cell response and causes substantially increased mortality. Experiments with bone marrow radiation chimeras indicate that the immune CD4(+) effectors operate optimally when there is the potential for direct interaction with virus-infected targets expressing MHC class II glycoproteins, suggesting that the IFN-gamma produced by these lymphocytes is functioning at short range. The numbers of latently infected cells in the spleens of carrier mice are also significantly increased by the concurrent depletion of both the CD4(+) population and IFN-gamma. These experiments raise the possibility that the defective control of intercurrent gamma-herpesvirus infections in patients with AIDS not only is due solely to the absence of helper T cells but also reflects the loss of an important set of CD4(+) effectors.

Association between exercise and HIV disease progression in a cohort of homosexual men

PURPOSE

To study the relationship between exercise and human immunodeficiency virus (HIV) disease progression.

METHODS

415 individuals (156 HIV positive, 259 HIV negative), from a cohort study of 851 homosexual men from New York City, 1985-1991. By 1991, 68 of the 156 persons developed Acquired Immune Deficiency Syndrome (AIDS) and 49 died with AIDS. Exercise was defined as self-report of exercising 3-4 times/week or daily at entry; less was considered nonexercise. CD4 lymphocyte decline was constructed for each subject by modeling log CD4 count against time in days. The association between exercise and progression to AIDS and death with AIDS, adjusting for baseline CD4 count, was determined using Cox model. Linear regression was used to model CD4 decline with exercise for HIV positive and HIV negative groups separately, adjusting for initial CD4 count.

RESULTS

Having exercised was associated with slower progression to AIDS at 1 year (HR = 0.68, 90% confidence interval (CI): 0.4-1.17); hazard ratios (HR) at 2, 3, and 4 years were 0.96, 1.18, and 1.36, respectively. Having exercised was also associated with slower progression to death with AIDS at 1 year (HR = 0.37, 90% CI: 0.14-0.94) with hazard ratios at 2, 3, and 4 years of 0.68, 0.98, and 1.27, respectively, suggesting a protective effect close to the time exercise was assessed, but an increased risk after 2 years. Exercising 3-4 times/week had a more protective effect than daily exercise. Exercisers in the HIV positive group showed an increase in CD4 count during a year by a factor of 1.07.

CONCLUSION

Moderate physical activity may slow HIV disease progression.

Angiocentric CD3(+) T-cell infiltrates in human immunodeficiency virus type 1-associated central nervous system disease in children

A significant proportion of brain tissue specimens from children with AIDS show evidence of vascular inflammation in the form of transmural and/or perivascular mononuclear-cell infiltrates at autopsy. Previous studies have shown that in contrast to inflammatory lesions observed in human immunodeficiency virus type 1 (HIV-1) encephalitis, in which monocytes/macrophages are the prevailing mononuclear cells, these infiltrates consist mostly of lymphocytes. Perivascular mononuclear-cell infiltrates were found in brain tissue specimens collected at autopsy from five of six children with AIDS and consisted of CD3(+) T cells and equal or greater proportions of CD68(+) monocytes/macrophages. Transmural (including endothelial) mononuclear-cell infiltrates were evident in one patient and comprised predominantly CD3(+) T cells and small or, in certain vessels, approximately equal proportions of CD68(+) monocytes/macrophages. There was a clear preponderance of CD3(+) CD8(+) T cells on the endothelial side of transmural infiltrates. In active lesions of transmural vasculitis, CD3(+) T-cell infiltrates exhibited a distinctive zonal distribution. The majority of CD3(+) cells were also CD8(+) and CD45RO+. Scattered perivascular monocytes/macrophages in foci of florid vasculitis were immunoreactive for the p24 core protein. In contrast to the perivascular space, the intervening brain neuropil was dominated by monocytes/macrophages, microglia, and reactive astrocytes, containing only scant CD3(+) CD8(+) cells. Five of six patients showed evidence of calcific vasculopathy, but only two exhibited HIV-1 encephalitis. One patient had multiple subacute cerebral and brainstem infarcts associated with a widespread, fulminant mononuclear-cell vasculitis. A second patient had an old brain infarct associated with fibrointimal thickening of large leptomeningeal vessels. These infiltrating CD3(+) T cells may be responsible for HIV-1-associated CNS vasculitis and vasculopathy and for endothelial-cell injury and the opening of the blood-brain barrier in children with AIDS.

LTR and tat variability of HIV-1 isolates from patients with divergent rates of disease progression

The genetic heterogeneity and transcription activity of the human immunodeficiency virus type 1 (HIV-1) LTR region and tat gene have been examined. Comparison involved the relevant genomic regions of viruses isolated from twenty long-term survivors and from ten typical progressors. No significant differences were observed in mutation frequencies among the two groups, although there was a significant higher proportion of synonymous substitutions in the tat gene of viruses from typical progressors. Four LTR sequences showed an insertion of 20-31 residues at the junction between the LTR Nef-coding and the LTR noncoding region. Neither these insertions nor other genetic changes found in these sequences affected the LTR transcription function, as measured in transient expression assays using transfection of both established cell lines and peripheral blood lymphocytes with plasmid DNA. The results did not allow the association of structural or functional alterations in LTR or tat with a degree of disease progression. The results reinforce the concepts of complexity of HIV-1 evolution in infected individuals, and the multifactorial nature of progression to AIDS.

Interactions between HIV1 Nef and vacuolar ATPase facilitate the internalization of CD4

CD4 is the primary receptor for the human immunodeficiency virus (HIV). Nef is an accessory protein of HIV that decreases the expression of CD4 on the surface of infected cells. In this study, we identified the Nef binding protein 1 (NBP1), which interacts specifically with Nef in vitro and in vivo. Since it shares sequence similarity with the catalytic subunit of the vacuolar ATPase (V-ATPase) and complements the loss of this VMA13 gene in yeast, NBP1 is the human homolog of Vma13p. Direct interactions between Nef and NBP1 were correlated with the ability of Nef to internalize CD4. The expression of the antisense NBP1 abrogated these effects. We conclude that NBP1 helps to connect Nef with the endocytic pathway.

A simplified vaccinologists' vaccinology and the pursuit of a vaccine against AIDS

Vaccinology is the science and engineering of developing vaccines to prevent infectious diseases. Guidelines come from knowledge of pathogenesis and from successful past vaccines. The vaccine enterprise relies on the evolution of appropriate science and technology. Governmental support and industrial participation are key to successful development of new vaccines. A large challenge for vaccinology is a vaccine which protects against AIDS. Though misguided in its first decade, current vaccine research is directed to use of any and all viral antigens and to elicit both cell-mediated and humoral immune responses that are resident, with memory, at the mucosal sites of viral entry. Recent seminal discoveries guiding the future include selective elicitation of both Type 1 and Type 2 immune responses, and prime-boosting using recombinant viral or DNA vectors and expressed antigens. Success in vaccinology depends on simplification of the complex and on iterative processes in a well-defined pathway. The present and future of vaccinology are discussed in depth.

Uncertainty in illness across the HIV/AIDS trajectory

Uncertainty is a chronic and pervasive source of psychological distress for persons living with HIV. Numerous sources of heightened uncertainty, including complex changing treatments, ambiguous symptom patterns, and fears of ostracizing social response, play a critical role in the experience of HIV-positive persons and are linked with negative perceptions of quality of life and poor psychological adjustment. Currently, research on uncertainty in HIV fails to explicate the uncertainty experience over time. Because the uncertainty of HIV varies over the course of the illness, an explicit consideration of the sources of uncertainty over the HIV illness trajectory is needed to forecast the informational and stress management needs of persons facing uncertainty about HIV illness. A biopsychosocial model developed to characterize the HIV stigma trajectory provides a useful framework modified to depict uncertainty across the HIV illness experience. Uncertainty in four phases of the HIV illness trajectory are differentiated: (a) at risk, (b) diagnosis, (c) latent, and (d) manifest.

Effector CD4+ and CD8+ T-cell mechanisms in the control of respiratory virus infections

The rules for T-cell-mediated control of viruses that infect via the respiratory mucosae show both common themes and differences, depending on the nature of the pathogen. Virus-specific CD8+ cytotoxic T lymphocytes (CTLs) are the key effectors of virus clearance in mice infected with both negative strand RNA viruses (influenza and Sendai) and a DNA virus, the murine gamma-herpesvirus-68 (MHV-68). Recently completed experiments establish that these activated CD8+ T cells indeed operate primarily via contact-dependent lysis. Perforin-mediated cytotoxicity seems to be the preferred mode, though a Fas-based mechanism can apparently serve as an alternative mechanism. Immune CD4+ T cells functioning in the absence of the CD8+ subset cannot eliminate MHV-68 from lung epithelial cells, are somewhat less efficient than the CD8+ CTLs at clearing the RNA viruses, and are generally ineffectual in mice that lack B lymphocytes. Though cytokine secretion by CD4+ and CD8+ T cells in the virus-infected lung may promote both T-cell extravasation and macrophage activation, such processes are not alone sufficient to deal consistently with any of these infections. However, CD4+ T help is mandatory for an effective B-cell response, and can operate to promote the clonal expansion of virus-specific CD8+ T cells in the lymph nodes and spleen. Furthermore, a concurrent CD4+ T-cell response seems to be essential for maintaining continued CD8+ T-cell surveillance and effector capacity through the persistent, latent phase of MHV-68 infection in B cells. Thus, the evidence to date supports a very traditional view; CD8+ T cells function mainly as killers and the CD4+ T cells as helpers in these respiratory virus infections.

The CXC chemokine stromal cell-derived factor 1 is not responsible for CD8+ T cell suppression of syncytia-inducing strains of HIV-1

Primary CD8+ T cells from HIV+ asymptomatics can suppress virus production from CD4(+) T cells acutely infected with either non-syncytia-inducing (NSI) or syncytia-inducing (SI) HIV-1 isolates. NSI strains of HIV-1 predominantly use the CCR5 chemokine receptor as a fusion cofactor, whereas fusion of T cell line-adapted SI isolates is mediated by another chemokine receptor, CXCR4. The CCR5 ligands RANTES (regulated on activation, normal T cell expressed and secreted), macrophage inflammatory protein 1alpha (MIP-1alpha), and MIP-1beta are HIV-1 suppressive factors secreted by CD8+ cells that inhibit NSI viruses. Recently, the CXC chemokine stromal cell-derived factor 1 (SDF-1) was identified as a ligand for CXCR4 and shown to inhibit SI strains. We speculated that SDF-1 might be an effector molecule for CD8+ suppression of SI isolates and assessed several SDF-1 preparations for inhibition of HIV-1LAI-mediated cell-cell fusion, and examined levels of SDF-1 transcripts in CD8(+) T cells. SDF-1 fusion inhibitory activity correlated with the N terminus, and the alpha and beta forms of SDF-1 exhibited equivalent fusion blocking activity. SDF-1 preparations having the N terminus described by Bleul et al. (Bleul, C.C., Fuhlbrigge, R.C., Casasnovas, J.M., Aiuti, A. & Springer, T.A. (1996) J. Exp. Med. 184, 1101-1109) readily blocked HIV-1LAI-mediated fusion, whereas forms containing two or three additional N-terminal amino acids lacked this activity despite their ability to bind and/or signal through CXCR4. Though SDF-1 is constitutively expressed in most tissues, CD8 T cells contained extremely low levels of SDF-1 mRNA transcripts (<1 transcript/5,000 cells), and these levels did not correlate with virus suppressive activity. We conclude that suppression of SI strains of HIV-1 by CD8+ T cells is unlikely to involve SDF-1.

Cellular proteins in HIV virions

Human immunodeficiency virus type-1 (HIV-1) virions contain both virus-encoded and cellular proteins. Recent advances in the detection, isolation, and functional characterisation of host proteins incorporated in the virion have begun to provide for new perspectives on the interactions between virus and cell. The acquisition of host proteins by HIV-1 may also influence viral pathology in vivo. This article reviews detection and analysis of host proteins found in HIV-1 particles and presents some potential roles that these proteins might play in the biology of this important virus. Copyright 1997 John Wiley & Sons, Ltd.

Quantification of HIV-1 viral RNA and proviral DNA by isotopic competitive PCR

A quantitative isotopic competitive PCR (icPCR) assay was established using 32P-labeled primers targeting the HIV-1 gag gene followed by quantification using a phosphoimager. The detection limit varied from 3 to 10 molecules of DNA and 10 to 100 molecules of RNA per reaction. The icPCR quantification of HIV-1 DNA copies correlated well with the cell number of 8E5/LAV cells bearing a single provirus (r2 = 0.95). Provirus quantification was applied to overnight infected donor PBMCs, thereby determining infectious virus titres in culture supernatants as a rapid alternative to limiting dilution culture. Parallel quantification of the HIV-1 RNA indicated the infectious virus fraction to be 0.3%. In 39 HIV-1-infected patients with clinical stages A (n = 17), B (n = 15), and C (n = 7), the HIV-1 RNA in the plasma was determined ranging from 100 to 90600 RNA copies/ml. The results of icPCR and a commercial assay (ROCHE Amplicor HIV-1 Monitor) correlated well (r = 0.97). In 13 additional patients, the plasma viral load per ml was compared with the proviral load per 10(6) PBMC showing a viral excess of 10-1000-fold (mean of 85, r = 0.7, P < 0.01). It is concluded that icPCR is suitable for the measurement of proviral and viral load in experimental and clinical settings.