Gareth Hardy

A Balanced Type 1/Type 2 Response Is Associated with Long-Term Nonprogressive Human Immunodeficiency Virus Type 1 Infection

ABSTRACT Previous reports have emphasized the requirements for strong type 1 cell-mediated responses in the control of human immunodeficiency virus type 1 (HIV-1). HIV-1 Gag p24-specific CD4 helper T-lymphocyte (HTL) responses have been shown to inversely correlate with viral burden in HIV-1-infected individuals. In this study, peripheral blood mononuclear cells from 70 individuals with chronic progressive HIV-1 infection (clinical progressors), 10 clinical nonprogressors, and 3 immunologically discordant progressors were assessed for HTL proliferation and type 1/type 2 cytokine production. Clinical progressors lacked functional HIV-1-specific HTLs with proliferative and cytokine-producing capacity. Clinical nonprogressors were found to respond to a wide range of HIV-1 antigens from different clades, producing both type 1 and type 2 cytokines. Immunologically discordant progressors responded strongly to clade B Gag p24 with a type 1 cytokine profile but not to other antigens. Thus, in contrast to clinical nonprogressors, neither progressors nor immunologically discordant progressors secreted interleukin-4 (IL-4) in response to HIV-1 antigens. Both clinical nonprogressors and immunologically discordant progressors responded broadly to B clade Gag p24-overlapping peptides. However, IL-4 production in the nonprogressors was restricted to a limited number of p24 peptides. No HIV-1-specific T-cell responses were seen in 20 seronegative controls. Additionally, we observed a rapid type 1 to type 2 shift in the response of one immunologically discordant progressor upon onset of clinical symptoms. These results suggest that a balanced type 1/type 2 profile correlates with successful long-term control of HIV-1.

Assessment of type 1 and type 2 cytokines in HIV type 1-infected individuals : Impact of highly active antiretroviral therapy

Although the effect of highly active antiretroviral therapy (HAART) on HIV-1 replication has been established, the mechanisms involved in restoration of immune responses and reconstitution remain unknown. This study provides evidence of changes in expression of type 1 and type 2 cytokine-specific mRNA occurring during HIV-1 infection, before and after initiation of HAART. Unstimulated PBMCs from nine HIV-1-infected individuals obtained at different time intervals before and after the initiation of HAART were assessed for specific IFN-gamma, IL-2, IL-4, and IL-10 mRNA expression, using RT-PCR. Correlation with CD4+ T cell counts and viral load was also carried out. Before initiation of HAART, in all patients, little expression of specific IFN-gamma and IL-2 (type 1 cytokine) mRNA was noted. In contrast, expression of specific IL-4 and/or IL-10 (type 2) mRNA was readily detectable in the majority of patients. After initiation of HAART there was a continuous increase in IFN-gamma and IL-2 mRNA expression, although the latter occurred in lower amounts. This paralleled a dramatic reduction in viral load and increase in CD4+ T cell counts. Type 2 cytokine-specific mRNA expression fell to undetectable levels and in some cases reappeared later in the course of HAART. Predominant expression of type 2 cytokine mRNA, before initiation of HAART, concurs with previous findings of a dominant antiproliferative, type 2 cytokine profile during HIV-1 infection. Reversion of the cytokine profile, after HAART, to a strong type 1 profile suggests that in addition to suppressing virus replication directly the immune system may be given a chance to recover.

Induction of HIV-1-specific T cell responses by administration of cytokines in late-stage patients receiving highly active anti-retroviral therapy

Highly active anti‐retroviral therapy (HAART) is associated with reduction in the morbidity and mortality of patients with advanced HIV‐1 disease. The ability of such treatment to improve immune responses against HIV‐1 and opportunistic pathogens is variable and limited. Addition of cytokine immunotherapy to this treatment may improve immune responses. IL‐2 with or without granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) was administered to HIV‐1+ individuals receiving HAART with undetectable viral loads, and CD4 counts < 100 cells/μl. In one patient presenting with Mycobacterium avium complex (MAC) infection, we evaluated the effect of cytokine immunotherapy on lymphocyte phenotype; plasma viral load; proliferative responses to mitogens, recall and HIV‐1 antigens; cytokine production and message in response to non‐specific and specific stimuli; and natural killer (NK) cell activity. Proliferation assays were performed in two similar patients. Before cytokine immunotherapy the predominant CD8+ population was mainly CD28−. No proliferation or IL‐2 production was seen in response to mitogens, recall or HIV‐1 antigens; and no HIV‐1 peptide‐specific interferon‐gamma (IFN‐γ)‐secreting cells were present. Low levels of IL‐4 were detected in response to antigens to which patients had been exposed, associated with up‐regulated expression of costimulatory molecules influenced by IL‐4. Following IL‐2 administration, loss of IL‐4 was associated with increased NK cell activity and HIV‐1 peptide‐specific and non‐specific IFN‐γ‐producing cells. Proliferative responses associated with IL‐2 production and responsiveness were only seen after subsequent concomitant administration of GM‐CSF with IL‐2. These changes mirrored clinical improvement. An imbalance of lymphocyte subsets may account for immune unresponsiveness when receiving HAART. Restoration of responses following immunotherapy suggests a shift towards a lymphocyte profile with anti‐pathogen activity.

Reconstitution of CD4+ T cell responses in HIV-1 infected individuals initiating highly active antiretroviral therapy (HAART) is associated with renewed interleukin-2 production and responsiveness

Reconstitution of functional CD4+ T cell responsiveness to in vitro stimuli is associated with continuous highly active antiretroviral therapy (HAART). Thirty‐six antiretroviral naive patients received HAART over 16 weeks. Antigen‐specific, mitogen and interleukin (IL)‐2 induced lymphocyte proliferative responses and specific IL‐2 and IL‐4 production were assessed at each time‐point, together with quantification of HIV‐1 RNA load and lymphocyte populations. Reconstitution of recall responses was limited largely to persistent antigens such as Herpes simplex virus and Candida, rather than to HIV‐1 or neo‐antigens. Recall antigens, mitogens and IL‐2‐induced renewed responses were associated with in‐vitro production of IL‐2, but not IL‐4. Differential responsiveness to low versus high concentration IL‐2 stimulus increases in a stepwise manner, suggesting normalization of IL‐2 receptor expression and improved functionality. These increases in in‐vitro proliferative responses thus probably reflect short lived effector clones, driven by ongoing antigenic stimulus associated with persisting long‐term organisms. In this context non‐responsiveness to HIV‐1 antigens suggests ongoing HIV‐1 specific clonal T cell anergy.

Immune responses and reconstitution in HIV-1 infected individuals: impact of anti-retroviral therapy, cytokines and therapeutic vaccination

Most patients with chronic HIV-1 infection lack functional CD4(+) and CD8(+) HIV-1-specific T cells with proliferative and cytolytic capacity, respectively. This is despite being able to produce intracellular cytokines in response to viral antigens. Protease inhibitor (PI)-based highly active anti-retroviral therapy (HAART) is unable to completely eradicate virus and fails to enable total restoration of immunity including induction of anti-HIV-1 responses. We have taken novel approaches towards the treatment of chronic HIV-1 disease with the aim of instigating long-term non-progressor status and depletion of virus reservoirs. HIV-1-specific CD4(+) and CD8(+) T cell responses were measured following the administration of cytokines, during therapeutic vaccination, and following treatment interruption (TI) or drug therapy change. Administration of cytokines, with or without therapeutic vaccination, in HAART treated patients, improved both CD4(+) and CD8(+) HIV-1-specific T cell responses even in late-stage disease. Virus-specific T cell responses were also seen during TI or when transient viraemia was apparent, and following therapy change from a PI- to a non-nucleoside-based HAART regimen. Reconstitution of HIV-1-specific immune responses was found to be transient and reversal to the previous anergic state was rapid. Viral reservoirs in the latently infected resting CD4(+) T cells, on follicular dendritic cells of germinal centers or even in infected thymic epithelium may be involved in clonal suppression and anergy. These may present major obstacles to the maintenance of HIV-1-specific responses and the eventual eradication of HIV-1.

Evidence of thymic reconstitution after highly active antiretroviral therapy in HIV-1 infection

We aimed to provide evidence of thymic reconstitution after highly active antiretroviral therapy (HAART) in HIV‐1 infected patients and to correlate this with the restoration of peripheral naïve T cells.

Initiation of antiretroviral therapy during recent HIV-1 infection results in lower residual viral reservoirs

Summary: To measure proviral HIV-1 DNA in patients treated with effective antiretroviral therapy (ART) during recent and chronic HIV-1 infection, and in long-term non-progressors (LTNP). We quantified HIV-1 DNA in peripheral blood samples from 39 HIV-1-infected subjects; 26 patients initiated non-nucleoside reverse transcriptase inhibitor (NNRTI) based ART at two different stages of infection: 16 during recent infection (RI) (HIV-1 exposure >60 days <1 year), and 10 during chronic infection (CI) (infected >2 years). The results were compared with those seen in 13 LTNP (infected >8 years, therapy naïve, and controlled viremia). Thirty-six weeks after initiation of ART, HIV-1-proviral DNA levels decreased from baseline in the RI group (P < 0.005) to levels comparable to LTNP. HIV-1 DNA also declined in the CI group (P = 0.053) but it remained significantly higher than in RI (P < 0.002) and LTNP (P < 0.02). However, plasma HIV-1 RNA levels become undetectable in 80% of CI patients 12 weeks post initiation of ART, compared to 41.2% in the RI group. All patients reached undetectable viremia by week 36 of therapy. These data indicate that initiation of NNRTI based ART during recent HIV-1 infection reduces HIV-1 DNA to levels comparable to those seen in LTNP, which is not apparent if therapy is started during chronic infection, and suggests an association between timing of initiation of ART and decay of the HIV-1 reservoir.

A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

BackgroundFully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.DesignChronically infected patients with low CD4 counts T-cell counts who commenced antiretroviral therapy (ART) were subsequently treated with combined interleukin-2 and therapeutic vaccination.MethodsThirty six anti-retroviral naive patients were recruited and initiated on combination ART for 17 weeks before randomization to: A) ongoing ART alone; B) ART with IL-2 twice daily for 5 days every four weeks starting at week 17 for 3 cycles; C) ART with IL-2 as in group B and Remune HIV-1 vaccine administered once every 3 months, starting at week 17; and D) ART with Remune vaccine as in group C. Patients were studied for 65 weeks following commencement of ART, with an additional prior 6 week lead-in observation period. CD4 and CD8 T-cell counts, evaluations of HIV-1 RNA levels and proliferative responses to recall and HIV-1 antigens were complemented with assessment of IL-4-secretion alongside quantification of anti-HIV-1 CD8 T-cell responses and neutralizing antibody titres.ResultsNeither IL-2 nor Remune™ vaccination induced sustained HIV-1-specific T-cell responses. However, we report an inverse relationship between HIV-1-specific proliferative responses and IL-4 production which continuously increased in patients receiving immunotherapy, but not patients receiving ART alone.ConclusionInduction of HIV-1-specific cell-mediated responses is a major challenge in chronically HIV-1-infected patients even when combining immunisation with IL-2 therapy. An antigen-specific IL-4-associated suppressive response may play a role in attenuating HIV-specific responses.

Therapeutic vaccines in HIV. 1 infection

Summary: In this review we address questions which must be considered if better attempts arc to be made to treat all persons presently infected with human immunodeficiency virus (HIV). There are thirty million people in the world presently living with HIV, only 10% of whom are likely to be able to access currently available drug therapy. Even when available, such therapy causes considerable inconvenience and undesirable clinical side effects, and fails to eradicate virus from a small reservoir of latently infected cells. Thus, we must ask what forms of alternative therapy might be used. One strategy that may he considered is to reduce virus levels as low as possible using highly active antiretroviral therapy (HAART), followed by modulation of host immunity with immunotherapy in order to effect an appropriate and efficient response mimicking that found in long‐term asymptomatic patients, with the aim of indefinitely maintaining the asymptomatic period following discontinuation of chemotherapy, or even of eradicating the virus from the latent reservoirs. In 1987, long before the advent of highly active antiretroviral therapy, J. Salk proposed the use of a ‘suitable potent non‐infectious (HIV) immunogen’ to delay or prevent the development of AIDS in infected individuals (1), The objective of administering such an agent was to ‘enhance and prolong the presetice of (immunologically) protective factors”. The stated aim at that time was ‘to destroy virus and viral antigen producing cells by the induction of the immune systems cytotoxic mechanisms known to rid the host of virus and virus producing cells”. Twelve years later, and after a quarter of a century living with HIV, and with the advent of HAART, is it time to use our knowledge of the hosts own immune system to fight this seemingly intractable invader?

Development of immunotherapeutic strategies for HIV-1

In the majority of untreated patients, HIV-1 infection presents as a progressive disease of the immune system. Recent studies indicate that immune responses can be induced in HIV-1 infected individuals, leading to some immune control of virus replication. Such immune responses are also observed in small numbers of untreated HIV-1 infected long-term non-progressor (LTNP) patients, as well as in other viral infections (including those with human herpesviruses). Emerging novel technologies, animal studies and detailed immunological studies have proven invaluable in defining the immune responses that are associated with a favourable clinical outcome. Central effector and regulatory cells are HIV-1-specific CD8+ cytotoxic T-lymphocytes (CTL) and CD4+ helper T-lymphocytes respectively. Fully functional antigen-presenting cells (APC) are also essential in all stages of HIV-1 infection and possibly some (but not all) antibody responses contribute to beneficial immunity. The availability of combination anti-retroviral drug therapy, which successfully controls viraemia, has enabled a beneficial outcome in many HIV-1 infected individuals. Since no chronically HIV-1 infected patient has been shown to eradicate virus, novel approaches utilising therapeutic immunisation and various cytokines to manipulate immune responses and to induce and steer immunity towards a desired phenotype are required. There is a clear rationale for immunotherapeutic intervention in chronic progressive HIV-1 infection, which forms the foundation for novel approaches aimed at inducing and maintaining immune control. Here we review the immunopathogenesis of HIV-1 infection and discuss the promises of therapeutic immunisation and immunotherapy in general and their potential in the treatment of chronic HIV-1 disease.