T cell cytokine responses in persons with tuberculosis and human immunodeficiency virus infection

Tuberculosis causes more extensive and life-threatening disease in patients with HIV infection than in immunocompetent persons. To investigate the hypothesis that these severe manifestations of tuberculosis may be due to alterations in cytokine production, we evaluated cytokine patterns in HIV-infected tuberculosis patients. Upon stimulation with Mycobacterium tuberculosis in vitro, PBMC from HIV-infected tuberculosis patients had reduced proliferative and type 1 responses, compared with HIV-seronegative tuberculosis patients. The reduction in proliferative responses was independent of the CD4 cell count, but the reduced type 1 response was a direct result of CD4 cell depletion. There was no enhancement of type 2 cytokine production in HIV-infected patients, although production of IL-10 was prominent in all tuberculosis patients. In HIV-infected tuberculosis patients, M. tuberculosis-induced proliferative responses were significantly enhanced by neutralizing antibodies to IL-10 but not by antibodies to IL-4 or by recombinant IL-12. The M. tuberculosis-induced type 1 response was augmented both by antibodies to IL-10 and by recombinant IL-12. Tuberculosis in the context of HIV infection is characterized by diminished type 1 responses, probably induced by immunosuppressive cytokines produced by macrophages/monocytes, rather than by type 2 cells.     

Mechanisms associated with defective TH1 cytokine production in HIV infection

Qualitative and quantitative changes in immune functions of different T-cell subsets associated with infection by human immunodeficiency virus type 1 (HIV-1) were analyzed by flow cytometric assessment of intracytoplasmic cytokines. The T(H)1 cytokines, interleukin-2 (IL-2) and interferon-gamma (IFN-gamma), were produced by both CD4 and CD8 T-cell subsets. When normal peripheral blood mononuclear cells (PBMC) were activated in culture, both cytokines were produced predominantly by CD4 (CD4) cell and only a minor fraction of normal CD8 cells produced these cytokines. In the cultures of PBMC from HIV-1-infected individuals (HIV+PBMC), more HIV+CD8 cells produced IL-2 and IFN-gamma. Production of IFN-gamma by HIV+CD4 cells was markedly reduced, while IL-2nd tumor necrosis factor-alpha (TNF-alpha) production by HIV+CD4 remained relatively intact until the disease progressed further. Normal CD4 cells which were isolated by using a cell sorter, FACSCalibur was still able to produce IL-2 and TNF-alpha. But for full production of IFN-gamma, normal CD4 required some accessory cells, the identity of which could not yet be established.     

Alloantigen-stimulated anti-HIV activity

A number of studies have suggested that an immune response to human leukocyte antigen (HLA) alloantigens may contribute to protection against HIV infection. In the present study, we examined the effect of alloantigen-stimulated cell lines obtained from peripheral blood mononuclear cells (PBMC) of HIV-uninfected (HIV-) individuals and the soluble factors produced by these cell lines on HIV-1 replication. Multiple in vitro restimulation with irradiated allogeneic PBMC from HIV- donors resulted in the expansion of CD8(+) T-cell lines that inhibited HIV-1 replication when cocultured with either autologous or heterologous in vitro-infected phytohemagglutinin (PHA) blasts. Supernatants from the alloantigen-stimulated cell lines also inhibited HIV replication in both PHA blasts and a chronically infected cell line. The alloantigen-stimulated cell lines and the factors they produced inhibited both T-cell-tropic (T) and macrophage-tropic (M) isolates of HIV-1. Blocking experiments using anti-chemokine antibodies suggested that this inhibition of HIV replication was not due to the beta-chemokines present in cocultures of cell lines with HIV-infected blasts. These results indicate that alloantigen-stimulation of PBMC from HIV- individuals activates CD8(+) T cells that produce soluble factor(s) that inhibit HIV replication of a wide spectrum of HIV-1 isolates through a chemokine-independent mechanism. This is a US government work. There are no restrictions on its use.     

Rabbit cells expressing human CD4 and human CCR5 are highly permissive for human immunodeficiency virus type 1 infection

To evaluate the feasibility of using transgenic rabbits expressing CCR5 and CD4 as a small-animal model of human immunodeficiency virus type 1 (HIV) disease, we examined whether the expression of the human chemokine receptor (CCR5) and human CD4 would render a rabbit cell line (SIRC) permissive to HIV replication. Histologically, SIRC cells expressing CD4 and CCR5 formed multinucleated cells (syncytia) upon exposure to BaL, a macrophagetropic strain of HIV that uses CCR5 for cell entry. Intracellular viral capsid p24 staining showed abundant viral gene expression in BaL-infected SIRC cells expressing CD4 and CCR5. In contrast, neither SIRC cells expressing CD4 alone nor murine 3T3 cells expressing CCR5 and CD4 exhibited significant expression of p24. These stably transfected rabbit cells were also highly permissive for the production of virions upon infection by two other CCR5-dependent strains (JR-CSF and YU-2) but not by a CXCR4-dependent strain (NL4-3). The functional integrity of these virions was demonstrated by the successful infection of human peripheral blood mononuclear cells (PBMC) with viral stocks prepared from these transfected rabbit cells. Furthermore, primary rabbit PBMC were found to be permissive for production of infectious virions after circumventing the cellular entry step. These results suggest that a transgenic rabbit model for the study of HIV disease may be feasible.     

Role of Fas ligand and receptor in the mechanism of T-cell depletion in acquired immunodeficiency syndrome: effect on CD4+ lymphocyte depletion and human immunodeficiency virus replication

Direct killing of CD4+ lymphocytes by human immunodeficiency virus-1 (HIV-1) probably cannot account for the magnitude of the loss of these cells during the course of HIV-1 infection. Experimental evidence supports a pathophysiologic role of the apoptotic process in depletion of CD4 cells in acquired immunodeficiency syndrome (AIDS). The Fas-receptor/Fas-ligand (Fas-R/Fas-L) system mediates signals for apoptosis of susceptible lymphocytes and lympoblastoid cell lines. A number of investigators have recently reported increased expression of the Fas receptor in individuals with HIV infection, along with increased sensitivity of their lymphocytes to anti-Fas antibody mimicking Fas ligand. We attempted to determine the role of Fas-mediated apoptosis in disease progression and viral replication. Increased Fas-receptor (CD95) expression on CD4+ and CD8+ lymphocytes was found in a large group of HIV-1-infected patients compared with normal controls; individuals with a diagnosis of AIDS and a history of opportunistic infection had significantly more Fas receptor expression than did asymptomatic HIV-infected persons and normal blood donor controls (P < .01). Triggering of the Fas-R by agonistic anti-Fas monoclonal antibody, CH11, was preferentially associated with apoptosis in the CD4+ cells; this effect was more pronounced in lymphocytes derived from HIV+ individuals. Soluble and membrane-bound forms of Fas-L were produced in greater amounts in peripheral blood mononuclear cells (PBMC) cultures and in plasma obtained from HIV-1-infected persons than from normal controls. Furthermore, triggering of lymphocytes from HIV-infected persons by CH11 increased levels of interleukin-1beta converting enzyme (ICE), a protein associated with apoptosis. When PBMC were cultured in the presence of CH11, p24 production per number of viable cells was decreased as compared with the same PBMC without CH11 (P < .01). These findings suggest that multiple mechanisms, including increased production of Fas-L by infected PBMC, increased Fas-R expression, and induction of a protease of ICE family, may play roles in the apoptotic depletion of CD4+ cells in HIV infection.     

Human erythrocytes bearing electroinserted CD4 neutralize infection in vitro by primary isolates of human immunodeficiency virus type 1

Human erythrocytes bearing electroinserted full-length CD4 (RBC-CD4) can bind and fuse with a laboratory strain of human immunodeficiency virus type 1 (HIV-1) or with T cells infected by HIV-1. Here we show that RBC-CD4 neutralize primary HIV-1 strains in an assay of cocultivation of peripheral blood mononuclear cells (PBMC) from HIV-1-infected persons with uninfected PBMC. RBC-CD4 inhibited viral p24 core antigen accumulation in these cocultures up to 10,000-fold compared with RBC alone. Viral p24 accumulation was inhibited equally well when measured in culture supernatants or in call extracts. The inhibition was dose-dependent and long-lived. Two types of recombinant CD4 tested in parallel were largely ineffective. The neutralization of primary HIV-1 by RBC-CD4 in vitro was demonstrated in PBMC cultures from 21 of a total of 23 patients tested at two independent sites. RBC-CD4 may offer a route to blocking HIV-1 infection in vivo.     

Evidence that activation of human T cells by porcine endothelium involves direct recognition of porcine SLA and costimulation by porcine ligands for LFA-1 and CD2

In this study we present a comprehensive evaluation of the molecular interactions between human T cells and porcine aortic endothelial cells (PAEC) that contribute to human T cell activation. Binding assays demonstrated that porcine erythrocytes (E) and PAEC express ligand(s) for the human T cell glycoprotein CD2. Prior incubation of human T cells with a blocking monoclonal antibody directed against CD2 (alpha CD2-BL) completely inhibited T cell/E and T cell/PAEC interaction. Xenogeneic mixed lymphocyte reactions (XMLR) revealed that human PBMC, or highly purified T cells were activated by PAEC in the absence of human antigen-presenting cells (APC). Addition of alpha CD2-BL or alpha LFA-1 to these assays inhibited PAEC-mediated human T cell activation. Furthermore, we demonstrated that highly purified human CD4+ and CD8+ T cells proliferated in response to PAEC and that this response was blocked by monoclonal antibodies directed against LFA-1 and CD2. Addition of alpha SLA class I blocked the proliferation of CD8+ but not CD4+ T cells, indicating direct presentation of SLA class I antigens to human T cells. We have recently shown that expression of the human complement inhibitor (CD59) on PAEC (PAEC-LXSNCD59) rendered these cells resistant to human complement-mediated activation and lysis, suggesting that human CD59 expression on PAEC could be an effective therapy for hyperacute rejection (HAR). However, recent studies have shown that in addition to its role as a complement inhibitor, CD59 binds human T cell CD2 and contributes to T cell activation. We therefore examined whether human CD59 expression on PAEC augmented the human antiporcine T cell response. We demonstrated that human T cells do not display increased binding to or activation by PAEC-LXSNCD59 relative to PAEC controls. Taken together, our data establish that PAEC directly stimulate human T cells in vitro and that interactions between the human accessory molecules CD2, LFA-1 and their PAEC surface ligands contribute to human T cell activation. In addition, the expression of human CD59 on porcine donor organs may confer resistance to human complement-mediated HAR without exacerbating the human antiporcine cellular response.     

The theory and practice of health education applied to nursing: a bi-polar approach

Because CD1-restricted T cells lack CD4 but produce IFN-gamma in response to nonpeptide mycobacterial antigens, they could play a unique role in immunity to tuberculosis. We studied CD1-restricted T cells in the context of HIV infection by expanding CD4(-) T cell lines from 10 HIV-infected patients. Upon stimulation with Mycobacterium tuberculosis antigen or upon exposure to macrophages infected with M. tuberculosis, these T cell lines proliferated, produced IFN-gamma, and showed cytolytic T cell (CTL) activity against macrophages pulsed with mycobacterial antigen, findings consistent with a protective role against M. tuberculosis. Anti-CD1b antibodies abrogated T cell proliferation, IFN-gamma production, and CTL activity, demonstrating that these T cells are CD1 restricted. IFN-gamma production in response to M. tuberculosis was enhanced by antitransforming growth factor-beta in 8/10 lines, and by IL-15 in 2/10 lines. IFN-gamma production was augmented in a nonantigen-specific manner by IL-12 in 4/8 lines. When live HIV was cocultured with CD1-restricted T cell lines, p24 antigen and proviral DNA were not detected, indicating that the T cells were not infectable with HIV. Vaccination strategies aimed at activation and expansion of M. tuberculosis-reactive CD1-restricted T cells in HIV-infected patients may constitute a novel means to provide protection against tuberculosis, while minimizing the risk of enhancing HIV replication through stimulation of CD4(+) cells.     

Disturbed CD4+ T cell homeostasis and in vitro HIV-1 susceptibility in transgenic mice expressing T cell line-tropic HIV-1 receptors

T cell line-tropic (T-tropic) HIV type 1 strains enter cells by interacting with the cell-surface molecules CD4 and CXCR4. We have generated transgenic mice predominantly expressing human CD4 and CXCR4 on their CD4-positive T lymphocytes (CD4+ T cells). Their primary thymocytes are susceptible to T-tropic but not to macrophage-tropic HIV-1 infection in vitro, albeit with a viral antigen production less efficient than human peripheral blood mononuclear cells. Interestingly, even without HIV infection, transgenic mice display a CD4+ T cell depletion profile of peripheral blood reminiscent of that seen in AIDS patients. We demonstrate that CD4+ T cell trafficking in transgenic mice is biased toward bone marrow essentially due to CXCR4 overexpression, resulting in the severe loss of CD4+ T cells from circulating blood. Our data suggest that CXCR4 plays an important role in lymphocyte trafficking through tissues, especially between peripheral blood and bone marrow, participating in the regulation of lymphocyte homeostasis in these compartments. Based on these findings, we propose a hypothetical model in which the dual function of CXCR4 in HIV-1 infection and in lymphocyte trafficking may cooperatively induce progressive HIV-1 infection and CD4+ T cell decline in patients.     

Altered expression of host-encoded complement regulators on human cytomegalovirus-infected cells

Human cytomegalovirus (HCMV)-infected cells persist in the presence of anti-HCMV antibody, suggesting that HCMV has evolved mechanisms to evade host immune defenses. Insofar as no virus-encoded complement inhibitors have been identified for HCMV, we hypothesized that HCMV infection may alter the expression of host-encoded cell surface complement inhibitors. Herein, we report that cell surface expression of two complement regulator proteins, CD55 and CD46, which are members of the regulators of complement activation (RCA) gene cluster, increased up to eightfold following infection of fibroblasts or glioblastoma cells with HCMV, but not after infection with HSV-1 or adenovirus. However, the cell surface expression of a third complement regulator, CD59, which is not a member of the RCA gene cluster, was not altered during HCMV infection. Functional studies using purified complement components demonstrated that up-regulation of CD55 suppressed the activity of cell-associated C3 convertases on HCMV-infected cells. Furthermore, increased CD55 expression protected infected cells from complement-mediated lysis, an effect which directly correlated with the length of HCMV infection. Increased expression of host-encoded complement regulator proteins may provide protection of HCMV-infected cells from the host immune response in vivo, through increasing the resistance of infected cells to complement-mediated lysis and decreasing the deposition of C3-derived products on the cell surface.     

Progressive and persistent downregulation of surface CXCR4 in CD4(+) T cells infected with human herpesvirus 7

We have previously shown that infection of CD4(+) T lymphocytes with the T-lymphotropic human herpesvirus 7 (HHV-7) downregulates surface CD4, which represents the high-affinity receptor for HHV-7. In this study, we report that HHV-7 infection also causes a progressive loss of the surface CXC-chemokine receptor 4 (CXCR4) in CD4(+) T cells, accompanied by a reduced intracellular Ca2+ flux and chemotaxis in response to stromal cell-derived factor-1 (SDF-1), the specific CXCR4 ligand. Moreover, CXCR4 is downregulated from the surface of HHV-7-infected T cells independently of CD4. Because intracellular CXCR4 antigen and mRNA levels are unaffected in productively HHV-7-infected cells, the downregulation of CXCR4 apparently does not involve a transcritional block. Since CXCR4 functions in association with CD4 to permit entry of several human immunodeficiency virus (HIV) isolates, the potential of HHV-7 to persistently downregulate the surface expression of CXCR4 may provide novel strategies for limiting HIV infection.     

Features of humoral antibacterial immunity in patients with HIV infections and AIDS

The level of antibodies to some bacterial antigens, their affinity and relationship to the level of CD4+ T-lymphocytes in persons at different stages of HIV infection was studied. The study revealed that at early stages of the development of HIV infection a decrease in the levels of antibodies to Streptococcus pneumoniae protein somatic antigen in comparison with those in HIV-negative donors occurred. In the process of the development of HIV infection an increase in the level of Staphylococcus aureus peptidoglycan and some S.aureus antigenic determinants, as well as to S.pneumoniae protein somatic antigen, took place. Patients with HIV infection who had non-specific pulmonary diseases exhibited an increased level of antibodies to Branhamella catarrhalis complex ultrasonic antigen. In patients with HIV infection having an amount of CD4+ T-lymphocytes below 200/1 the level of antibodies to bacterial antigen was higher than in patients with an amount of CD4+ T-lymphocytes varying within 200-400/1. In addition, at all stages of HIV infection and in all kinds of its complications an increase in the titer of antibodies to N-acetylglycosoaminylmuramyl dipeptide, an antigenic determinant of peptidoglycan with immunostimulating and adjuvant activity.     

T cell responses in coinfection with Onchocerca volvulus and the human immunodeficiency virus type 1

Onchocerca volvulus and the human immunodeficiency virus (HIV) are two immunocompromising infectious agents of major public health concern in Uganda. To examine the effect of coinfection with O. volvulus and HIV on cellular immune responses, lymphocyte proliferative responses and cytokine production of peripheral blood mononuclear cells (PBMC) from persons infected with O. volvulus with and without HIV type 1 infection were compared. Proliferation of PBMC to PHA and tuberculin (PPD) in coinfection was less (P = 0.08, P < 0.01) than in O. volvulus infection. O. volvulus extract stimulated lymphocyte proliferation in microfilaria-negative and HIV-negative O. volvulus infection while only an inconspicuous response was observed in microfilaria-negative coinfection. After stimulation of PBMC with PPD, the production of interferon-gamma (IFN-gamma), interleukin (IL)-4 and IL-5-demonstrated in O. volvulus infection-were reduced in coinfection with HIV (P < 0.01). While both groups failed to produce IFN-gamma in response to O. volvulus extract, only O. volvulus infected persons generated pronounced IL-5 and low IL-4 levels (0.01 > P = 0.02). The cellular immune responses in coinfection suggested an HIV-related lack of specific reactivity to O. volvulus antigen and impairment of IL-4 and IL-5 production in addition to the lack of IFN-gamma response on antigenic stimulation.     

Microglia express CCR5, CXCR4, and CCR3, but of these, CCR5 is the principal coreceptor for human immunodeficiency virus type 1 dementia isolates

Microglia are the main human immunodeficiency virus (HIV) reservoir in the central nervous system and most likely play a major role in the development of HIV dementia (HIVD). To characterize human adult microglial chemokine receptors, we analyzed the expression and calcium signaling of CCR5, CCR3, and CXCR4 and their roles in HIV entry. Microglia expressed higher levels of CCR5 than of either CCR3 or CXCR4. Of these three chemokine receptors, only CCR5 and CXCR4 were able to transduce a signal in microglia in response to their respective ligands, MIP-1beta and SDF-1alpha, as recorded by single-cell calcium flux experiments. We also found that CCR5 is the predominant coreceptor used for infection of human adult microglia by the HIV type 1 dementia isolates HIV-1DS-br, HIV-1RC-br, and HIV-1YU-2, since the anti-CCR5 antibody 2D7 was able to dramatically inhibit microglial infection by both wild-type and single-round luciferase pseudotype reporter viruses. Anti-CCR3 (7B11) and anti-CXCR4 (12G5) antibodies had little or no effect on infection. Last, we found that virus pseudotyped with the DS-br and RC-br envelopes can infect cells transfected with CD4 in conjunction with the G-protein-coupled receptors APJ, CCR8, and GPR15, which have been previously implicated in HIV entry.     

Measles virus-induced down-regulation of CD46 is associated with enhanced sensitivity to complement-mediated lysis of infected cells

CD46, the major component of the measles virus (MV) receptor complex and a member of the regulators of complement activity (RCA) gene cluster, is down-regulated in MV-infected cells. We investigated whether the reduction of surface CD46 correlates with enhanced sensitivity of lymphoid and monocytic cells to lysis by activated complement. On human U937 cells, acutely or persistently infected with MV-Edmonston (ED) vaccine strain, infection-dependent down-regulation of CD46 confers sensitivity to activated complement, regardless of the pathway of activation and the specificity of the activating antibodies. Interestingly, down-regulation of CD46 alone is sufficient to confer susceptibility of cells to complement lysis despite the continued surface expression of other RCA proteins such as CD35 and CD55. In primary cultures, both peripheral blood lymphocytes and macrophages are efficiently lysed in the presence of complement activated via the alternative pathway after MV infection. In contrast to the MV-ED infection, infection of cells with the lymphotropic MV wild-type strain WTF does not down-regulate CD46. Cells infected with MV-WTF do not exhibit enhanced susceptibility to complement lysis. These data suggest that MV strains similar to WTF that do not down-regulate CD46 may have an enhanced potential for replication and dissemination within the human host, whereas complement-mediated elimination of cells infected with CD46-down-regulating strains of MV, such as ED, may limit the spread of MV infection, and could thus represent an attenuating factor for MV.     

Use of GPR1, GPR15, and STRL33 as coreceptors by diverse human immunodeficiency virus type 1 and simian immunodeficiency virus envelope proteins

Human and simian immunodeficiency viruses (HIV and SIV, respectively) use chemokine receptors as coreceptors along with CD4 to mediate viral entry. Several orphan receptors, including GPR1, GPR15, and STRL33, can also serve as coreceptors for a more limited number of HIV and SIV isolates. We investigated whether these orphan receptors could function as efficient coreceptors for a diverse group of HIV and SIV envelopes (Envs) in comparison with the principal coreceptors CCR5 and CXCR4. We found that a limited number of HIV-1 isolates could mediate inefficient cell-cell fusion with the orphan receptors relative to CCR5 and CXCR4; however, none of the orphan receptors tested could support pseudotype virus infection despite robust infection via CCR5 or CXCR4. All except one of the SIV Envs tested mediated some degree of cell-cell fusion and pseudotype infection, with target cells expressing at least one of these orphan receptors, although CCR5 proved to be the most efficient coreceptor for infection. Only one SIV Env protein, BK28, could mediate infection using GPR1 as a coreceptor, albeit much less efficiently than with CCR5. In addition, use of these coreceptors did not correlate with the published tropism of the SIV clones and was strictly CD4 dependent for both SIV and HIV. We also examined the expression of these molecules in cell lines and primary cells widely used for virus propagation and as targets for infection. All cells examined expressed STRL33, a more limited number expressed GPR15, and GPR1 was much more restricted in its expression pattern. Taken together, our results indicate that GPR15 and STRL33 are rarely used by HIV-1 but are more frequently used by SIV strains, although not in a manner that correlates with SIV tropism.     

Induction of lymphomonocyte activation by HIV-1 glycoprotein gp120. Possible role in AIDS pathogenesis

Dysfunction of cytokine secretion pattern has been suggested to play a central role in the immunopathogenesis of HIV infection. In fact a shift of T helper cell functions from a Th1-type to TH0- or TH2-type has been observed in HIV-1 infected subjects undergoing disease progression. The inhalance of cytokine network is accompanied by persistent activation of the immune system, impaired ability to mount a proper activation response (anergy), and priming to apoptosis. Extensive investigation during the last decade has been conducted on the influence of HIV-1 gp120 or of its precursor gp160 on several lymphocyte and monocyte functions. Gp120 is able to rise intracellular calcium concentration and to induce the formation of inositol triphosphate, can block mitogen- or antigen-driven T cell activation, can induce altered cytokine production by activated PBMC subpopulations, determines impaired cytotoxicity and chemotactic response to antigens, interferes with the activity of antigen presenting cells, enhances or induces apoptosis, stimulates polyclonal B cell activation and induces or up-modulates a number of cytokines, including IL-6. TNF, IL-1-alpha and -beta, IL-10 and IL-8. Furthermore, both IFN-alpha and -gamma, as well as several markers of IFN activity, such as beta 2-microglobulin and neopterin, are induced in gp120-stimulated PBMC. However, neither IL-4 (Th2-type) nor IL-2 (Th1-type), nor DNA synthesis are activated by gp120. On the other hand gp120-stimulated PBMC express increased IL-2 receptors, and can be induced by exogenous IL-2 to proliferate, suggesting that they are in a state of at least partial activation. According to this hypothesis, other activation markers, both early (such as CD69), and late (such as CD45RO and CD71), are induced by gp120, but this even partial activation does not lead to the ability of PBMC to support productive infection by HIV-1, unless in the presence of exogenous IL-2. The HIV-induced cytokines can influence HIV infection either directly, by up- or down-modulating virus replication, or indirectly, by modulating the expression of cellular molecules. In fact, during the budding process, the HIV envelope captures a number of cell membrane proteins, including cytokine receptors such as IL-2R, adhesion molecules such as LFA-1, ICAM-1, -2, HLA Class I and II, as well as cell lineage markers. Gp120-induced cytokines, particularly IFN-gamma, upmodulate the cellular expression of intercellular adhesion molecules, such as ICAM-1. We have shown that the IFN-gamma-driven increase of the expression of ICAM-1 by cells chronically infected with HIV-1 can be transmitted to the virus progeny, resulting in phenotypic alteration of the virus, and leading to the expansion of its host cell spectrum to CD4-negative cells expressing the appropriate ligands, i.e. LFA-1. Intercellular adhesion molecules are also involved in the cell-mediated transmission of HIV infection, and the increased ICAM-1 expression induced by IFN-gamma determines a stimulation of the transmission of HIV from abortively infected endothelial cells to permissive CD4 lymphocytes. On the whole, these data indicate that HIV, or its soluble products such as gp120, can modify several PBMC functions, by inducing a number of cytokines and a partial state of immune activation. It is possible that the gp120-driven changes of PBMC functions are not only an epiphenomenon of HIV infection, but rather, it is likely that they can participate in the immunopathological events responsible for disease progression.     

The relative prognostic value of plasma HIV RNA levels and CD4 lymphocyte counts in advanced HIV infection

OBJECTIVE: It has been suggested that the plasma HIV RNA level is a better predictor of AIDS and death than the CD4 lymphocyte count. We assessed whether the prognostic value of plasma virus levels was different according to the CD4 count. DESIGN: Prospective cohort study of HIV-infected patients followed for a median of 2.91 years (range, 0.02-4.54). SETTING: Department of Infectious Diseases at Rigshospitalet, Copenhagen, Denmark. PARTICIPANTS: A group of 255 HIV-infected individuals with an initial measurement of CD4 lymphocyte count and plasma HIV RNA. MAIN OUTCOME MEASURE: Survival time. RESULTS: The plasma HIV RNA (median 101410 copies/ml; range (range 200-7200000) and the CD4 lymphocyte count (median 250 cells x 10(6)/l; range 1-1247) were negatively correlated (Pearson r = -0.53; P < 0.00001). Of the 255 patients, 110 died during follow-up. Overall, a higher HIV RNA level was associated with increased risk of death, but the association was smaller in patients with lower CD4 lymphocyte counts (test for interaction P < 0.0001). In patients with CD4 count below 50 cells x 10(6)/l the association between HIV RNA and risk of death was not statistically significant (relative hazard per 10-fold higher HIV RNA level was 1.53; P = 0.11; adjusted for age and CD4 count) while that between the CD4 count and risk of death was highly significant (relative hazard per 50% lower CD4 count 1.38; P = 0.005; adjusted for age and HIV RNA level). CONCLUSIONS: Patients were relatively lightly treated with antiretroviral drugs both before and during this study. In this situation, it appears that the HIV RNA level has a relatively weak association with risk of death in patients with advanced HIV infection and that the CD4 lymphocyte count is probably more useful in assessing prognosis.     

Functional and molecular characterization of human monoclonal antibody reactive with the immunodominant region of HIV type 1 glycoprotein 41

The immunoreactivity, functional activity, and molecular features of a human monoclonal antibody (HMAb), F240, from an HIV-1-infected individual have been studied. Flow cytometric analysis demonstrated that F240 is reactive with cells infected with a broad range of laboratory isolates but not with uninfected cells. Reactivity of F240 is greatly enhanced by preincubation of infected cells with soluble CD4, and to a much lesser extent, with F105, an HMAb reactive with the CD4-binding site of gp120. This enhancement is temperature dependent, with maximum enhancement observed at 37 degrees C, and suggests that the F240 epitope may be more accessible after gp120 has bound to CD4 in vivo. Immunoblot analysis reveals antigen specificity of F240 for gp41 or its precursor gp160. F240 specificity is mapped to the immunodominant region of the gp41 ectodomain by Pepscan analysis. This epitope has been implicated in eliciting nonprotective antibodies that enhance infection in the presence of complement. Consistent with this, F240 failed to neutralize laboratory isolates and enhanced viral infection in a complement-dependent manner. The F240 VH demonstrates extensive somatic mutations compared with the product of its closest homologous germline gene VH3-3.11. Most amino acid substitutions occur in CDR2, characteristic of an antigen-driven response, and in FR3, a phenomenon observed in other anti-HIV-1 envelope HMAbs. Primary structure analysis of the F240 heavy chain revealed strong homology in the CDR domains to an HMAb (3D6) reactive with the same gp41 region, which suggests that these HMAbs could define a potential human antibody clonotype.