Design Concepts of Virus-Like Particle-Based HIV-1 Vaccines.

Prophylactic vaccines remain the best approach for controlling the human immunodeficiency virus-1 (HIV-1) transmission. Despite the limited efficacy of the RV144 trial in Thailand, there is still no vaccine candidate that has been proven successful. Consequently, great efforts have been made to improve HIV-1 antigens design and discover delivery platforms for optimal immune elicitation. Owing to immunogenic, structural, and functional diversity, virus-like particles (VLPs) could act as efficient vaccine carriers to display HIV-1 immunogens and provide a variety of HIV-1 vaccine development strategies as well as prime-boost regimes. Here, we describe VLP-based HIV-1 vaccine candidates that have been enrolled in HIV-1 clinical trials and summarize current advances and challenges according to preclinical results obtained from five distinct strategies. This mini-review provides multiple perspectives to help in developing new generations of VLP-based HIV-1 vaccine candidates with better capacity to elicit specific anti-HIV immune responses.

p17 from HIV induces brain endothelial cell angiogenesis through EGFR-1-mediated cell signalling activation.

HIV-associated neurocognitive disorder in HIV patients substantially reduces their quality of life. We previously showed that the HIV matrix protein, p17 could stimulate lymph-angiogenesis in vitro potentially contributing to lymphoma tumour growth and in addition is associated with vascular activation in neuro-degenerating brain tissue; here, therefore, we have investigated the detailed molecular mechanisms of this action. We performed in vitro cell culture, angiogenesis experiments, phospho-protein microarrays and Western blotting to identify cellular signalling induced by p17 within human brain endothelial cells (HbMEC), and inhibitor studies to block p17-induced vascular growth. We also characterised the effects of hippocampal CA1 injection of p17 on epidermal growth factor receptor-1 (EGFR1) expression linked to our murine model of dementia. p17 strongly induced angiogenesis of HbMEC (migration, tube formation and spheroid growth). p17 concomitantly increased phosphorylation of EGFR1 as well as down-stream intermediates ERK1/2, FAK, PLC-γ and PKC-ß whilst an inhibitor peptide of EGFR, blocked cell signalling and angiogenesis. Finally, Mice that showed reduced cognitive function and behavioural deficiencies after p17 injection, demonstrated that p17 localised in cortical microvessels and also neurones many of which stained positive for p-EGFR1 by histology/IHC. This work provides strong support that p17 may be involved in initiating and/or perpetuating vascular tissue pathophysiology associated with comorbidity in HIV patients.

Effect of Several HIV Antigens Simultaneously Loaded with G2-NN16 Carbosilane Dendrimer in the Cell Uptake and Functionality of Human Dendritic Cells.

Dendrimers are highly branched, star-shaped, and nanosized polymers that have been proposed as new carriers for specific HIV-1 peptides. Dendritic cells (DCs) are the most-potent antigen-presenting cells that play a major role in the development of cell-mediated immunotherapy due to the generation and regulation of adaptive immune responses against HIV-1. This article reports on the associated behavior of two or three HIV-derived peptides simultaneously (p24/gp160 or p24/gp160/NEF) with cationic carbosilane dendrimer G2-NN16. We have found that (i) immature DCs (iDCs) and mature (mDCs) did not capture efficiently HIV peptides regarding the uptake level when cells were treated with G2-NN16-peptide complex alone; (ii) the ability of DCs to migrate was not depending on the peptides presence; and (iii) with the use of molecular dynamic simulation, a mixture of peptides decreased the cell uptake of the other peptides (in particular, NEF hinders the binding of more peptides and is especially obstructing of the binding of gp160 to G2-NN16). The results suggest that G2-NN16 cannot be considered as an alternative carrier for delivering two or more HIV-derived peptides to DCs.

The HIV matrix protein p17 promotes the activation of human hepatic stellate cells through interactions with CXCR2 and Syndecan-2.

BACKGROUND: The human immunodeficiency virus type 1 (HIV-1) p17 is a matrix protein involved in virus life's cycle. CXCR2 and Syndecan-2, the two major coreceptors for the p17 protein, are expressed in hepatic stellate cells (HSCs), a key cell type involved in matrix deposition in liver fibrotic disorders. AIM: In this report we have investigated the in vitro impact of p17 on HSCs transdifferentiation and function and underlying signaling pathways involved in these processes. METHODS: LX-2 cells, a human HSC line, and primary HSC were challenged with p17 and expressions of fibrogenic markers and of p17 receptors were assessed by qRT-PCR and Western blot. Downstream intracellular signaling pathways were evaluated with qRT-PCR and Western blot as well as after pre-treatment with specific pathway inhibitors. RESULTS: Exposure of LX2 cells to p17 increases their contractile force, reshapes the cytoskeleton fibers and upregulates the expression of transdifferentiation markers including αSMA, COL1α1 and endothelin-1 through the activation of Jak/STAT and Rho signaling pathways. These effects are lost in HSCs pre-incubated with a serum from HIV positive person who underwent a vaccination with a p17 peptide. Confocal laser microscopy studies demonstrates that CXCR2 and syndecan-2 co-associate at the plasma membrane after exposure to p17. Immunostaining of HIV/HCV liver biopsies from co-infected patients reveals that the progression of liver fibrosis correlates with a reduced expression of CXCR2. CONCLUSIONS: The HIV matrix protein p17 is pro-fibrogenic through its interactions both with CXCR2 and syndecan-2 on activated HSCs.

The HIV matrix protein p17 subverts nuclear receptors expression and induces a STAT1-dependent proinflammatory phenotype in monocytes.

BACKGROUND: Long-term remission of HIV-1 disease can be readily achieved by combinations of highly effective antiretroviral therapy (HAART). However, a residual persistent immune activation caused by circulating non infectious particles or viral proteins is observed under HAART and might contribute to an higher risk of non-AIDS pathologies and death in HIV infected persons. A sustained immune activation supports lipid dysmetabolism and increased risk for development of accelerated atehrosclerosis and ischemic complication in virologically suppressed HIV-infected persons receiving HAART. AIM: While several HIV proteins have been identified and characterized for their ability to maintain immune activation, the role of HIV-p17, a matrix protein involved in the viral replication, is still undefined. RESULTS: Here, we report that exposure of macrophages to recombinant human p17 induces the expression of proinflammatory and proatherogenic genes (MCP-1, ICAM-1, CD40, CD86 and CD36) while downregulating the expression of nuclear receptors (FXR and PPARγ) that counter-regulate the proinflammatory response and modulate lipid metabolism in these cells. Exposure of macrophage cell lines to p17 activates a signaling pathway mediated by Rack-1/Jak-1/STAT-1 and causes a promoter-dependent regulation of STAT-1 target genes. These effects are abrogated by sera obtained from HIV-infected persons vaccinated with a p17 peptide. Ligands for FXR and PPARγ counteract the effects of p17. CONCLUSIONS: The results of this study show that HIV p17 highjacks a Rack-1/Jak-1/STAT-1 pathway in macrophages, and that the activation of this pathway leads to a simultaneous dysregulation of immune and metabolic functions. The binding of STAT-1 to specific responsive elements in the promoter of PPARγ and FXR and MCP-1 shifts macrophages toward a pro-atherogenetic phenotype characterized by high levels of expression of the scavenger receptor CD36. The present work identifies p17 as a novel target in HIV therapy and grounds the development of anti-p17 small molecules or vaccines.

HIV-1 matrix protein p17 binds to the IL-8 receptor CXCR1 and shows IL-8-like chemokine activity on monocytes through Rho/ROCK activation.

Exogenous HIV-1 matrix protein p17 was found to deregulate biologic activities of many different immune cells that are directly or indirectly involved in AIDS pathogenesis after binding to unknown cellular receptor(s). In particular, p17 was found to induce a functional program in monocytes related to activation and inflammation. In the present study, we demonstrate that CXCR1 is the receptor molecule responsible for p17 chemokine-like activity on monocytes. After CXCR1 binding, p17 was capable of triggering rapid adhesion and chemotaxis of monocytes through a pathway that involved Rho/ROCK. Moreover, CXCR1-silenced primary monocytes lost responsiveness to p17 chemoattraction, whereas CXCR1-transfected Jurkat cells acquired responsiveness. Surface plasmon resonance studies confirmed the capacity of p17 to bind CXCR1 and showed that the p17/CXCR1 interaction occurred with a low affinity compared with that measured for IL-8, the physiologic CXCR1 ligand. In all of its activities, p17 mimicked IL-8, the natural high-affinity ligand of CXCR1. Recent studies have highlighted the role of IL-8 and CXCR1 in HIV-1 replication and AIDS pathogenesis. Our findings herein call for an exploration of the therapeutic potential of blocking the p17/IL-8/CXCR1 axis in HIV-1 infection.

HIV-1 matrix protein p17 induces human plasmacytoid dendritic cells to acquire a migratory immature cell phenotype.

Numerical and functional defects in plasmacytoid dendritic cells (pDCs) are an important hallmark of progressive HIV-1 infection, yet its etiology remains obscure. HIV-1 p17 matrix protein (p17) modulates a variety of cellular responses, and its biological activity depends on the expression of p17 receptors (p17Rs) on the surface of target cells. In this study, we show that peripheral blood pDCs express p17Rs on their surface and that freshly isolated pDCs are sensitive to p17 stimulation. Upon p17 treatment, pDCs undergo phenotypic differentiation with up-regulation of CCR7. A chemotaxis assay reveals that p17-treated pDCs migrate in response to CCL19, suggesting that these cells may acquire the ability to migrate to secondary lymphoid organs. In contrast, p17 does not induce release of type I IFN nor does it enhance pDC expression of CD80, CD86, CD83, or MHC class II. Microarray gene expression analysis indicated that p17-stimulated pDCs down-regulate the expression of molecules whose functions are crucial for efficient protein synthesis, protection from apoptosis, and cell proliferation induction. Based on these results, we propose a model where p17 induces immature circulating pDCs to home in lymph nodes devoid of their ability to serve as a link between innate and adaptative immune systems.

An IL-15 dependent CD8 T cell response to selected HIV epitopes is related to viral control in early-treated HIV-infected subjects.

In some early-treated HIV-positive patients, Structured Treatment Interruption (STI) is associated to spontaneous control of viral rebound. Thus, in this clinical setting, we analyzed the immunological parameters associated to viral control. Two groups of early treated patients who underwent STI were retrospectively defined, according to the ability to spontaneously control HIV replication (Controller and Non-controller). Plasma cytokine levels were analyzed by multiplex analysis. CD8 T cell differentiation was determined by polychromatic flow cytometry. Antigen-specific IFN-gamma production was analyzed by ELISpot and intracellular staining after stimulation with HIV-peptides. Long-term Elispot assays were performed in the presence or absence of IL-15. Plasma IL-15 was found decreased over a period of time in Non-Controller patients, whereas a restricted response to Gag (aa.167-202 and 265-279) and Nef (aa.86-100 and 111-138) immunodominant epitopes was more frequently observed in Controller patients. Interestingly, in two Non-Controller patients the CD8-mediated T cells response to immunodominant epitopes could be restored in vitro by IL-15, suggesting a major role of cytokine homeostasis on the generation of protective immunity. In early-treated HIV+ patients undergoing STI, HIV replication control was associated to CD8 T cell maturation and sustained IL-15 levels, leading to HIV-specific CD8 T cell responses against selected Gag and Nef epitopes.

Cross-subtype T-cell immune responses induced by a human immunodeficiency virus type 1 group m consensus env immunogen.

The genetic diversity among globally circulating human immunodeficiency virus type 1 (HIV-1) strains is a serious challenge for HIV-1 vaccine design. We have generated a synthetic group M consensus env gene (CON6) for induction of cross-subtype immune responses and report here a comparative study of T-cell responses to this and natural strain env immunogens in a murine model. Three different strains of mice were immunized with CON6 as well as subtype A, B, or C env immunogens, using a DNA prime-recombinant vaccinia virus boost strategy. T-cell epitopes were mapped by gamma interferon enzyme-linked immunospot analysis using five overlapping Env peptide sets from heterologous subtype A, B, and C viruses. The CON6-derived vaccine was immunogenic and induced a greater number of T-cell epitope responses than any single wild-type subtype A, B, and C env immunogen and similar T-cell responses to a polyvalent vaccine. The responses were comparable to within-clade responses but significantly more than between-clade responses. The magnitude of the T-cell responses induced by CON6 (measured by individual epitope peptides) was also greater than the magnitude of responses induced by individual wild-type env immunogens. Though the limited major histocompatibility complex repertoire in inbred mice does not necessarily predict responses in nonhuman primates and humans, these results suggest that synthetic centralized env immunogens represent a promising approach for HIV-1 vaccine design that merits further characterization.

Mucosal and systemic HIV-1-specific immunity in HIV-1-exposed but uninfected heterosexual men.

BACKGROUND: Despite multiple, repeated exposures to HIV-1, some individuals never seroconvert. Mucosal and systemic immune correlates of this condition have been analysed in HIV-1-exposed women but no data are available concerning mucosal immunity and HIV-1-specific immune responses in exposed but uninfected men. DESIGN: We analysed cellular and humoral immune parameters in peripheral lymphocytes, seminal fluid and urethral swabs of 14 recently HIV-1-exposed seonegative (ESN) heterosexual men, seven HIV-seropositive patients and seven healthy controls. RESULTS: HIV-1-specific IgA were detected in urethral swabs of 11 out of 14 ESN and of six out of seven HIV-seropositive patients; Env- and Gag-specific IFNgamma-producing CD4 and CD8 peripheral lymphocytes were present in ESN and HIV-seropositive patients; seminal lymphocytes, but not peripheral blood lymphocytes, of ESN were enriched in activated populations (CD8CD38RO and CD4CD25). p24-specific cytotoxic T lymphocytes were correlated with the percentage of CD4 in the HIV-seropositive partners. High urethral concentrations of HIV-1-specific IgA were seen in those ESN with the most recent unprotected sexual episode. CONCLUSIONS: This is the first report of HIV-specific mucosal immunity in ESN men. These data add to the body of knowledge of the immune correlates present in exposed, uninfected individuals and might be important in vaccine design.

HIV-1 matrix protein p17 enhances the proliferative activity of natural killer cells and increases their ability to secrete proinflammatory cytokines.

We investigated the effects of human immunodeficiency type-1 virus (HIV-1) matrix protein p17 on freshly isolated and purified human natural killer (NK) cells. HIV-1 p17 increased the cytokines interleukin (IL) 2, IL-12 and IL-15, and induced natural killer cell proliferation, but not cytotoxicity. This effect was specific because it was abrogated by anti-p17 monoclonal antibody. Moreover, HIV-1 p17 enhanced the cytokine-induced production of tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma by NK cells. IL-4 downregulated IFN-gamma and TNF-alpha secretion in IL-2- and IL-15-treated NK cells. HIV-1 p17 restored the ability of NK cells to produce both cytokines when added to the cultures simultaneously with IL-4. The property of p17 to increase the production of TNF-alpha and IFN-gamma might be a mechanism used by HIV-1 to modulate the immune system to support its replication and spreading.

[Effect of HIV antigen glycoproteins and morphine on accompanying reactions of liberating Ag+-sensitive SH-containing nonprotein compounds in the "antigen-antibody" interaction]. / Vliianie glikoproteinov antigena VICh i morfina na soputsvuiushchuiu reaktsiia vysvobozhdeniia Ag+-chuvstvitel'nykh SH-soderzhashchikh nebelkovykh soedinenii pri vzaimodeistvii "antigen-antitelo".

The interaction of blood serum immunoglobulins of M, G, and A classes of the donors with monospecific serums (MSS)-anti-IgM, anti-IgG and anti-IgG was established to be associated by Ag(+)-sensitive-SH containing non protein compounds release. This phenomenon formation should be related to a parallel running associated reaction mediated by conformational and/or some other changes of immunoglobulins macrostructure under highly specific intermolecular interaction with adequate MSS in the reactive mixtures. As a rule these processes are associated by the break and reduction of mixed disulphide bounds between thiol containing nonprotein compounds and proteins. HIV antigen glycoproteins and morphine preliminary introduced into the analogic reactive mixtures were found to block this phenomenon. If in these reactive mixtures the serums including three serotypes hepatitis B virus antigen is introduced this phenomenon is preserved. This effect of HIV antigen glycoproteins and morphine could be explained by their direct and/or mediated influence on the immunoglobulins macrostructure. As a result of the latter the immunoglobulins structure-functional status is infringed, being indirectly evidenced by absence of the associated reaction of release Ag(+)-sensitive-SH containing non protein compounds in the reactive mixtures. The processes presented are capable to play an essential role in formation of polyclonal gammapathy under HIV-infection.

HIV-1 matrix protein p17 increases the production of proinflammatory cytokines and counteracts IL-4 activity by binding to a cellular receptor.

Purified recombinant HIV-1 p17 matrix protein significantly increased HIV-1 replication in preactivated peripheral blood mononuclear cell cultures obtained from healthy donors. Because HIV-1 infection and replication is related to cell activation and differentiation status, in the present study, we investigated the role played by p17 during the process of T cell stimulation. Using freshly isolated peripheral blood mononuclear cells, we demonstrate that p17 was able to enhance levels of tumor necrosis factor alpha and IFN-gamma released from cells stimulated by IL-2. IL-4 was found to down-regulate IFN-gamma and tumor necrosis factor alpha, and p17 restored the ability of cells to produce both cytokines. The property of p17 to increase production of proinflammatory cytokines could be a mechanism exploited by the virus to create a more suitable environment for HIV-1 infection and replication. Our data show that p17 exerts its biological activity after binding to a specific cellular receptor expressed on activated T lymphocytes. The functional p17 epitope involved in receptor binding was found to be located at the NH(2)-terminal region of viral protein. Immunization of BALB/c mice with a 14-aa synthetic peptide representative of the HIV-1 p17 functional region (SGGELDRWEKIRLR) resulted in the development of p17 neutralizing antibodies capable of blocking the interaction between p17 and its cellular receptor. Our results define a role for p17 in HIV-1 pathogenesis and contribute to our understanding of the molecular mechanism of HIV-1 infection and the development of additional antiviral therapeutic strategies.

An anti-human immunodeficiency virus multiple antigen peptide encompassing the cleavage region of the env precursor interferes with membrane fusion at a post-CD4 binding step.

CLIV is a multiple antigen peptide ([PTKAKRRVVQREKR](4)-K(2)-K-betaA) that encompasses the cleavage region of the human immunodeficiency virus type 1 (HIV-1) envelope precursor. It displays an antiviral activity against HIV-1 and HIV-2 and inhibits HIV-1 Env-mediated cell-to-cell fusion. This effect has previously been attributed to interference with Env processing, resulting in the expression of a nonfusogenic envelope [Virology (1998) 247, 137]. However, we show here that CLIV does not alter the status of Env cleavage at steady state. Using various aggregation/syncytium assays that allow us to discriminate between gp120/CD4 binding and binding followed by gp41-mediated fusion, we demonstrate that CLIV inhibits a step of the cell-to-cell fusion process after CD4 binding. We demonstrate also that CLIV binds at 37 degrees C to a single class of protein present at the CD4(+) cell surface (Scatchard analysis: K(d) = 8 nM; B(max) = 10(4) sites/cell) and that the fusion inhibition activity seems to correlate with binding to this proteic component. In contrast, CLIV interacts with neither membrane-inserted nor CD4-associated Env. We therefore propose that CLIV interferes after Env/CD4 binding with a step of the membrane fusion process that may involve the C-terminal domain of gp120.

CXCR4 and CCR5 expression on CD4+ T cells in vivo and HIV-1 antigen beta-chemokine production in vitro after treatment with HIV-1 immunogen (REMUNE).

BACKGROUND: The chemokine receptors CXCR4 and CCR5 have been identified as the major coreceptors for HIV-1 on CD4+ cells and macrophages. The natural ligands for these receptors are SDF-1 and the beta-chemokines (MIP-1alpha, MIP-1beta, RANTES), respectively, and are the products of a variety of immune cells, including CD8+ T lymphocytes. STUDY DESIGN/METHODS: We hypothesized that the ability to stimulate the natural ligands for these receptors using an immune based therapy might influence in vivo chemokine receptor expression. RESULTS: In vivo CXCR4 expression remained stable after treatment with an HIV-1 Immunogen (REMUNE), whereas CCR5 expression on CD4+ T cells decreased (p < .05). Furthermore, HIV-1 antigen-specific production of beta-chemokines in vitro was also augmented (P < .05). CONCLUSIONS: These preliminary results suggest that this HIV-1-specific immune-based therapy can stimulate antigen-specific beta-chemokine production in vitro and downregulate CCR5 receptor expression on CD4 cells in vivo.

Whole-killed gp120-depleted HIV-1 antigen in a murine model for prophylactic vaccination.

In this study, the effects were examined of dose and adjuvant of whole-killed gp120-depleted HIV-1 antigen on antibody and cytokine responses in a murine model. Immunization with increasing doses of inactivated HIV-1 antigen in Incomplete Freund's Adjuvant (IFA) resulted in increased production of IL-4 and IgG1 antibody with decreased production of interferon gamma. Immunization with inactivated HIV-1 antigen in Detox PC adjuvant produced TH1 type predominant cytokine patterns along with IgG2a subclass antibody. Higher levels of interferon gamma were associated with immunization with inactivated HIV-1 antigen in Detox PC compared with inactivated HIV-1 in IFA or inactivated HIV-1 in saline. Inactivated HIV-1 antigen in Detox PC adjuvant produced a trend of lower levels of the beta-chemokine MIP-1 alpha compared with inactivated HIV-1 in IFA or saline. Dose and adjuvant play an important role in the type of immune response elicited to a whole-killed HIV vaccine. Low doses of inactivated HIV-1 antigen in Detox PC adjuvant are currently being studied in animal models in order to optimize cell-mediated immunity against HIV infection.

HIV p17 enhances lymphocyte proliferation and HIV-1 replication after binding to a human serum factor.

OBJECTIVE: To analyse the role of recombinant HIV-1 protein p17 in the modulation of cell activity. METHODS: Peripheral blood mononuclear cells (PBMC) obtained from healthy donors were cultured in the presence or absence of p17 with mitogens such as phytohaemagglutinin or interleukin-2 and their response assayed by cell proliferation. Cross-linking experiments were employed to investigate the presence of a binding between p17 and factor(s) present in human serum. An immunoenzymatic assay for p24 antigen detection was used to analyse the effect of the addition of exogenous p17 to cultures of PBMC infected with HIV-1 in vitro. RESULTS: Purified recombinant p17 protein at a concentration of 0.25 microg/ml significantly increased the proliferation of preactivated PBMC obtained from healthy donors. This effect was obtained by binding p17 to factor(s) present in human serum and observed on both CD4+ and CD8+ T cells. Recombinant p17 also induced an increased rate of HIV-1 replication, probably due to enhanced T-cell proliferation. The activity of p17 protein was inhibited by anti-p17 antibodies generated by injecting recombinant p17 in rabbits, but not by human antibodies generated during the natural course of HIV infection. CONCLUSION: Characterization of the human factor(s) and identification of the interacting p17 epitope(s) will improve our understanding of the mechanisms used by HIV to efficiently replicate in our organisms.

HIV-1 p17 and IFN-gamma both induce fructose 1,6-bisphosphatase.

The p17 matrix protein of the human immunodeficiency virus type 1 (HIV-1) plays a crucial role in AIDS pathogenesis. It orchestrates viral assembly and directs the preintegration complex to the nucleus of infected cells. Recently, the three-dimensional structure of p17 was shown to resemble that of interferon-gamma (IFN-gamma), suggesting that both proteins might share analogous functions. We demonstrate that in monocytes, p17 shares with IFN-gamma the ability to induce 1alpha-hydroxylase activity and to activate fructose 1,6-bisphosphatase gene expression in the presence of 25-hydroxyvitamin D3. However, p17 does not bind to the IFN-gamma cell membrane receptor and fails to increase expression of IFN-gamma-induced proteins, such as tryptophanyl-tRNA synthetase, Fc gammaRI, and HLA DR or B7/BB1 antigens. Altogether, our results raise the possibility that the structural resemblance between p17 and IFN-gamma causes the selective activation of a common pathway resulting in the production of 1,25-dihydroxyvitamin D3. We also found that unlike IFN-gamma, p17 increases the intracellular ATP content. Since transport of the HIV-1 preintegration complex through the nuclear membrane is an ATP-dependent process, our observation suggests that p17 plays a double role in this active transport, not only by acting as a chaperone molecule but also by recruiting the necessary energy for this process.

An interferon-gamma (IFN-gamma) based whole blood assay to detect T cell response to antigens in HIV-1 infected patients.

Recently it has been reported that cytokine production by T cells in response to antigens may be more sensitive test than lymphoproliferation. T cell reactivities to antigens is usually performed on isolated PBMCs, however whole blood is being used frequently for cytokine production studies. A whole blood assay is described to measure T cell mediated immune responses to HIV-1 and recall antigens. The cultures were performed in 96-well plates in which only 25 microliters of whole blood was required. We studied the production of IFN gamma in short term culture (24 hours) of 1/10 diluted heparinized whole blood (HWB) from 22 HIV-1 (+) patients grouped according to the 1993 classification of the CDC. IFN gamma was measured with an immunoassay in supernatants of HWB cultured in parallel experiments in the presence of supernatant of HIV-1LAI infected CD4+ T cells, p24 HIV antigen, PPD, tetanus toxoid (TET) and PHA. We found no production of IFN gamma in response to HIV-1 antigens in 15 HIV-1 (-) subjects; whereas a specific IFN gamma production in the presence of HIV-1 antigen was obtained in all of the 9 group A patients, in 7 of 8 group B patients and in 2 of 5 group C patients. In response to recall antigens (TET, PPD), we obtained IFN gamma production in 6 of 9 group A patients, 5 of 8 group B patients and in 1 of 5 group C patients, the response to PHA decreased but remained preserved until late in the disease. The HWB assay is a quick and simple potentially valuable tool for assessing cellular immune function in HIV-1+ patients.