Annapurna Vyakarnam

Presence of HIV-1 Gag-Specific IFN-γ+IL-2+ and CD28+IL-2+ CD4 T Cell Responses Is Associated with Nonprogression in HIV-1 Infection

HIV immunity is likely CD4 T cell dependent. HIV-specific CD4 T cell proliferative responses are reported to correlate inversely with virus load and directly with specific CD8 responses. However, the phenotype and cytokine profile of specific CD4 T cells that correlate with disease is unknown. We compared the number/function of Gag p24-specific CD4 T cells in 17 HIV-infected long-term nonprogressors (LTNPs) infected for a median of 14.6 years with those of 16 slow progressors (SPs), also HIV infected for a median of 14 years but whose CD4 count had declined to <500 cells/μl. Compared with SPs, LTNPs had higher numbers of specific CD4s that were double positive for IFN-γ and IL-2 as well as CD28 and IL-2. However, CD4 T cells that produced IL-2 alone (IL-2+IFN-γ−) or IFN-γ alone (IFN-γ+IL-2−) did not differ between LTNPs and SPs. The decrease in p24-specific CD28+IL-2+ cells with a concomitant increase of p24-specific CD28−IL-2+ cells occurred before those specific for a non-HIV Ag, CMV. p24-specific CD28−IL-2+ cells were evident in LTNPs and SPs, whereas the CMV-specific CD28−IL-2+ response was confined to SPs. The difference between LTNPs and SPs in the Gag p24 IFN-γ+IL-2+ response was maintained when responses to total Gag (p17 plus p24) were measured. The percentage and absolute number of Gag-specific IFN-γ+IL-2+ but not of IFN-γ+IL-2− CD4s correlated inversely with virus load. The Gag-specific IFN-γ+IL-2+ CD4 response also correlated positively with the percentage of Gag-specific IFN-γ+ CD8 T cells in these subjects. Accumulation of specific CD28−IL-2+ helpers and loss of IFN-γ+IL-2+ CD4 T cells may compromise specific CD8 responses and, in turn, immunity to HIV.

Tumour necrosis factors (α, β) induced by Hiv-1 in peripheral blood mononuclear cells potentiate virus replication

Cytokines such as tumour necrosis factor (TNF) can induce HIV-1 production in T-cell tumour lines. However, it is not known if the same occurs in freshly isolated mononuclear cells, nor is it known if the virus can itself regulate cellular cytokine production. In this paper we report that HIV-1 induces peripheral blood mononuclear cells (PBMC) and CD4+ T lymphocytes to secrete TNF alpha, TNF beta and interferon-gamma (IFN gamma), three cytokines having multifunctional activities and complex physiological roles. We also show that separate addition of exogenous recombinant (r) TNF alpha or rTNF beta or rIFN gamma increases HIV-1-induced syncytium formation in both PBMC and CD4+ cells by up to 10,000-fold, with TNF alpha being most potent in this regard. Finally, we show that syncytium formation induced by diverse HIV-1 isolates and LAV-2 is inhibited without the addition of exogenous r-cytokines by the respective anti-cytokine antibodies. Our study therefore demonstrates that efficient HIV replication in primary mononuclear cells is associated with the ability of the virus to induce TNF and IFN gamma secretion.

Novel innate immune functions of the whey acidic protein family

Studies on the interaction of HIV with host factors have recently highlighted a potential role in the pathogenesis of AIDS for three distinct members of the whey acidic protein (WAP) family, secretory leukocyte protease inhibitor, Elafin, and ps20. Identified by an evolutionarily conserved canonical four-disulphide structural domain [whey four disulphide core domain (WFDC)], WAP proteins are increasingly being shown to display functions beyond both protease inhibition and anti-infective activity, to which they were originally ascribed. We propose novel mechanisms on why this might be the case based on an analysis of the structure-function of its human members. Our analysis suggests that the interaction of HIV with WAP proteins might unravel unknown functions of the ancient WFDC and inform novel immunotherapies for the treatment of HIV and broader virus infections.

Immunization of human HIV-seronegative volunteers with recombinant p17/p24:Ty virus-like particles elicits HIV-1 p24-specific cellular and humoral immune responses.

ObjectiveTo evaluate the immune response to HIV-1 p24 generated in vivo by p17/p24:Ty virus-like particles (p17/p24:Ty-VLP) by examining the lymphoproliferative and antibody (Ab) responses to HIV-1 p24, as well as Gag-specific cytotoxic T lymphocytes (CTL), in HIV-seronegative volunteers immunized with hybrid p17/p24:Ty-VLP. Design and methodsSixteen HIV-seronegative volunteers were immunized with p17/p24:Ty-VLP at two dose levels (100 or 500

ALTERED PRODUCTION OF TUMOUR NECROSIS FACTORS ALPHA AND BETA AND INTERFERON GAMMA BY HIV-INFECTED INDIVIDUALS

mU.g) and monitored for the following 48 weeks for production of anti-p24 and anti-p17 Ab, in vitro lymphoproliferative responses to HIV-1 p24 and p17, and in vitro CTL responses to HIV-1 Gag. ResultsTwelve out of the 16 volunteers had significant p24-specific proliferative responses, with volunteers on the higher dose schedule exhibiting earlier proliferative responses than those on the lower dose schedule. Proliferative responses in both volunteer groups were similar in overall magnitude but appeared at different times during the immunization schedule. Anti-p24 Ab were detected in six out of the nine individuals in the lower dose group and in five out of the seven in the higher dose group. There was a good correlation between the presence of p24-specific Ab and the detection of lymphoproliferative responses to the p24 protein in peripheral blood mononuclear cells isolated from the same individuals. Anti-p17 Ab were detected in five volunteers. No Gag-specific CTL responses were detected. ConclusionWe conclude that hybrid HIV-1 p17/p24:Ty-VLP are capable of inducing both cellular and humoral immunity to HIV-1 Gag p17 and p24 components and are worthy of further study as a potential HIV immunotherapeutic.

Hiv infection alters the production of both type 1 and 2 cytokines but does not induce a polarized type 1 or 2 state

In vitro studies shows that recombinant tumour necrosis factor (TNF) α and β, and interferon‐gamma (IFN‐γ) can enhance HIV replication, and peripheral blood mononuclear cells (PBMC) infected with HIV in vitro secrete high levels of the same cytokines. As T cells secrete all three mediators, the capacity of T cell activation signals to trigger cytokine production in PBMC from HIV‐infected individuals was investigated as such patients may be immunocompromised. We demonstrate that asymptomatic seropositives in CDC group II/III as well as patients who have progressed to CDC group IV of the disease proliferate efficiently to anti‐CD3 antibody, recombinant interleukin‐2 (rIL‐2), phytohaemagglutinin (PHA), PHA plus phorbol 12, 13 dibutyrate (PMA) but secrete significantly (P>0.05) higher amounts of TNF‐α, TNF‐β and IFN‐γ compared with controls in response to the same stimulants. We also show a difference between group II/III and group IV patients with the latter secreting more TNF‐α and IFN‐γ. The kinetics of TNF‐α and ‐β and IFN‐γ production was stimulus dependent with overall levels varying in time for each stimulus. Furthermore, the kinetics of the response to all three stimulants were altered in seropositives; CDC group II/III and group IV patients secreted higher levels of cytokines over several time points compared to controls. The altered production of these mediators by HIV‐infected patients may contribute to disease progression and to the pathogenesis of AIDS.

Epidemiological risk factors for hypersensitivity reactions to abacavir

Objective:To test the T-helper (TH)1/TH2 cytokine paradigm in HIV infection. Design and methods:Cytokine profiles in two separate studies of HIV patients and controls are presented: (i) a longitudinal study of HIV patients with CD4 counts > 500 × 106/l tested at three timepoints compared with controls; (ii) a blinded cross-sectional study of controls and patients with high (> 500 × 10/6l) and low (< 500 × 106/l) CD4 counts. Peripheral blood mononuclear cells (PBMC) from patients and controls were tested for the production of two type 1 [interleukin (IL)-2, interferon (IFN)-γ] and two type 2 (IL-4, IL-10) cytokines by enzyme-linked immunosorbent assay. Both spontaneous and mitogen-induced cytokine production was measured. Results:HIV infection was noted to have the following effects on cytokine production: (i) it led to the in vivo activation of type 2 cytokines in a small group of individuals with high CD4 numbers characterized by the spontaneous release of IL-4 and IL-10. Longitudinal data showed high spontaneous IL-4 and IL-10 to be a consistent feature of the patient group (at each timepoint some patients were high producers) but to be variable in a given individual; (ii) HIV infection impaired the ability of PBMC to respond to stimuli (selected for their ability to optimally induce each cytokine) in terms of IL-2, IL-4 and IL-10 production in patients with both high and low CD4 cell counts; and (iii) conversely, HIV infection led to an overproduction of IFN-γ in patients with high CD4 counts; patients with low CD4 produced normal levels of IFN-γ. Conclusions:Our observations did not suggest polarization of the type 1/type 2 cytokine profile in HIV patients. Instead, the data suggested more complex changes to type 1/type 2 cytokine patterns in HIV infection than originally proposed by the TH1/TH2 dichtomy.

Comparison between HIV‐ and CMV‐specific T cell responses in long‐term HIV infected donors

We investigated risk factors for hypersensitivity reactions (HSR) to abacavir in a case–control study. In a multivariate analysis, white race [odds ratio (OR), 5.16; 95% confidence interval (CI), 1.16–22.97] and a higher CD8 cell count at initiation of abacavir (>850 vs. ≤850 cells: OR, 3.74; 95% CI, 1.19–11.77) were found to be significantly associated with the development of HSR. Age, gender, stage of disease, prior antiretroviral exposure and type of concurrent antiretroviral therapy were not associated with HSR. Differences in predisposition to HSR according to ethnicity and baseline CD8 cell count may be explained by the reported MHC genetic associations with HSR.

Innate immunity against HIV: a priority target for HIV prevention research

The mechanisms underlying non‐progression in HIV‐1 infection are not well understood; however, this state has been associated previously with strong HIV‐1‐specific CD8+ T cell responses and the preservation of proliferative CD4+ T cell responses to HIV‐1 antigens. Using a combination of interferon‐gamma (IFN‐γ) ELISpot assays and tetramer staining, the HIV‐1‐specific CD8+ T cell populations were quantified and characterized in untreated long‐term HIV‐1‐infected non‐progressors and individuals with slowly progressive disease, both in relation to CD4+ T cell responses, and in comparison with responses to cytomegalovirus (CMV) antigens. High levels of CD8+ T cell responses specific for HIV‐1 or CMV were observed, but neither their frequency nor their phenotype seemed to differ between the two patient groups. Moreover, while CMV‐specific CD4+ T cell responses were preserved in these donors, IFN‐γ release by HIV‐1‐specific CD4+ T cells was generally low. These data raise questions with regard to the role played by CD8+ T cells in the establishment and maintenance of long‐term non‐progression.

WFDC1/ps20 is a novel innate immunomodulatory signature protein of human immunodeficiency virus (HIV)-Permissive CD4(+) CD45RO(+) memory T cells that promotes infection by upregulating CD54 integrin expression and is elevated in HIV type 1 infection

This review summarizes recent advances and current gaps in understanding of innate immunity to human immunodeficiency virus (HIV) infection, and identifies key scientific priorities to enable application of this knowledge to the development of novel prevention strategies (vaccines and microbicides). It builds on productive discussion and new data arising out of a workshop on innate immunity against HIV held at the European Commission in Brussels, together with recent observations from the literature.Increasing evidence suggests that innate responses are key determinants of the outcome of HIV infection, influencing critical events in the earliest stages of infection including the efficiency of mucosal HIV transmission, establishment of initial foci of infection and local virus replication/spread as well as virus dissemination, the ensuing acute burst of viral replication, and the persisting viral load established. They also impact on the subsequent level of ongoing viral replication and rate of disease progression. Modulation of innate immunity thus has the potential to constitute a powerful effector strategy to complement traditional approaches to HIV prophylaxis and therapy. Importantly, there is increasing evidence to suggest that many arms of the innate response play both protective and pathogenic roles in HIV infection. Consequently, understanding the contributions made by components of the host innate response to HIV acquisition/spread versus control is a critical pre-requisite for the employment of innate immunity in vaccine or microbicide design, so that appropriate responses can be targeted for up- or down-modulation. There is also an important need to understand the mechanisms via which innate responses are triggered and mediate their activity, and to define the structure-function relationships of individual innate factors, so that they can be selectively exploited or inhibited. Finally, strategies for achieving modulation of innate functions need to be developed and subjected to rigorous testing to ensure that they achieve the desired level of protection without stimulation of immunopathological effects. Priority areas are identified where there are opportunities to accelerate the translation of recent gains in understanding of innate immunity into the design of improved or novel vaccine and microbicide strategies against HIV infection.