Smriti K. Kundu

Two Double-Blinded, Randomized, Comparative Trials of 4 Human Immunodeficiency Virus Type 1 (HIV-1) Envelope Vaccines in HIV-1—Infected Individuals across a Spectrum of Disease Severity: AIDS Clinical Trials Groups 209 and 214

The potential role of human immunodeficiency virus type 1 (HIV-1)-specific immune responses in controlling viral replication in vivo has stimulated interest in enhancing virus-specific immunity by vaccinating infected individuals with HIV-1 or its components. These studies were undertaken to define patient populations most likely to respond to vaccination, with the induction of novel HIV-1-specific cellular immune responses, and to compare the safety and immunogenicity of several candidate recombinant HIV-1 envelope vaccines and adjuvants. New lymphoproliferative responses (LPRs) developed in <30% of vaccine recipients. LPRs were elicited primarily in study participants with a CD4 cell count >350 cells/mm(3) and were usually strain restricted. Responders tended to be more likely than nonresponders to have an undetectable level of HIV-1 RNA at baseline (P=.067). Induction of new cellular immune responses by HIV-1 envelope vaccines is a function of the immunologic stage of disease and baseline plasma HIV-1 RNA level and exhibits considerable vaccine strain specificity.

A phase I, placebo-controlled trial of multi-dose recombinant human interleukin-12 in patients with HIV infection

Objectives Interleukin (IL)-12 is a cytokine that stimulates T lymphocytes and natural killer cells to generate a Type 1 T-helper lymphocyte immune response. The primary objective of this study was to determine the safety and immunologic activity of repeated recombinant human IL-12 (rhIL-12) dosing in HIV-infected patients over a broad range of the HIV disease spectrum. Design A randomized, placebo-controlled, Phase 1 trial design was chosen to control for the effects of HIV disease alone on safety and immunologic measurements. Methods HIV-infected patients on antiretroviral therapy received rhIL-12 or placebo twice weekly for 4 weeks. Subjects were monitored for safety and changes in absolute lymphocyte subset number, serum interferon (IFN)γ and neopterin levels, plasma HIV RNA level, peripheral blood mononuclear cell (PBMC)-inducible IFNγ responses to mitogen, and PBMC proliferative responses to phytohemagglutinin, tetanus, Candida, Mycobacterium avium complex, streptokinase, and HIV p24 and gp160 antigens. Results rhIL-12 was well tolerated at doses up to 100 ng/kg in subjects enrolled with CD4 cell counts < 50 × 106 cells/l and at all doses in subjects with CD4 cell counts of 300 × 106−500 × 106 cells/l. rhIL-12 resulted in dose-related increases in serum neopterin (particularly in subjects with baseline CD4 cell counts of 300–500 × 106 cells/l) but in no significant changes in other immunologic measurements or plasma HIV RNA levels. Conclusions rhIL-12 dosed twice weekly at ⩽ 100 ng/kg was well tolerated in HIV-infected patients and resulted in dose-related increases in serum neopterin (possibly reflecting the effect of some degree of IFNγ induction). However, there was no evidence of improvement in antigen-specific immune response.

Equivalent recognition of HIV proteins, Env, Gag and Pol, by CD4+ and CD8+ cytotoxic T-lymphocytes.

ObjectivesCytotoxic T-lymphocytes (CTL) appear to be an important defense mechanism against HIV infection. This study proposes to examine the major histcompatibilty complex (MHC)-restricted HIV-1 Env-, Gag-and Pol-specific CTL activities in HIV-infected asymptomatic patients. DesignD4+ and CD8+ CTL were examined to establish whether the same HIV-1 protein (Env, Gag or Pol) was recognized by both CD4+ and CD8+ CTL with MHC antigen restriction. MethodsPeripheral blood mononuclear cells, CD4+ and CD8+ T-cells from 17 HIV-infected asymptomatic patients and 10 HIV-seronegative individuals were examined for HIV-1 Env-, Gag-and Pol-specific MHC-restricted cytotoxicity using autologous and heterologous B-lymphoblastoid cell lines infected with vaccinia recombinant expressing HIV-1 Env, Gag and Pol proteins as targets. ResultsCD4+ and CD8+ CTL specific for the HIV-1 Env, Gag and Pol were demonstrated in the peripheral blood. DR4 and DQw2 were possible sites of MHC class II restriction of CD4+ CTL. Possible MHC class I restriction sites of CD8+ CTL included A2 and B8 for Env, A1 and A2 for Gag, and A2 and B8 for Pol antigen. ConclusionsThese observations should help to define more precisely the nature and elements of protective immunity and to evaluate AIDS vaccine strategies.

Generation of Primary Peptide-Specific CD8 Cytotoxic T-Lymphocytes In Vitro Using Allogeneic Dendritic Cells

Dendritic cells (DC) are potent antigen-presenting cells (APC) capable of inducing strong T-cell-mediated immunity. Infusion of lymphoma-specific antigen-loaded autologous DC has been demonstrated to result in the generation of antigen-specific immunity and reduction in tumor burden in B-cell lymphoma patients. Cellular immunotherapy employing antigen-loaded DC could have a potential therapeutic impact in tumors and viral infections, including HIV infection. However, DC in HIV-infected individuals and breast cancer patients are believed to be functionally defective. Therefore, the potential of using allogeneic DC offers significant implications for DC immunotherapy in AIDS and immunocompromised cancer patients. To explore the potential of allogeneic DC therapy in vivo, we tested the ability of allogeneic DC to generate primary peptide-specific CD8+ cytotoxic T-lymphocyte (CTL) responses in vitro. Our results indicate that DC from HLA class I-matched individuals elicit primary immune responses in vitro using viral peptides as naive antigens. A primary peptide-specific immune response could also be detected even when only one HLA allele (HLA-A*0201) was matched between the allogeneic DC and T-lymphocytes. The ability to generate primary peptide-specific responses in vitro is strongly indicative of the in vivo therapeutic potential of allogeneic DC.

In vivo persistence of donor cells following adoptive transfer of allogeneic dendritic cells in HIV-infected patients.

Peripheral blood samples from HIV-seropositive individuals enrolled in a pilot clinical trial investigating the use of allogeneic dendritic cell therapy were evaluated for mixed chimerism. In this study, dendritic cells from HLA-identical, HIV-seronegative siblings were used. Patients received an infusion of dendritic cells pulsed with HIV MN gp160 protein or with peptides from HLA-A2 restricted epitopes of env, gag, and pol proteins every month for 6–9 months. Of the five allogeneic dendritic cell recipients, two showed increases in HIV antigen-specific immune responses. Allele-specific polymorphisms were identified in three sib-pairs that allowed infused donor cells to be detected using sensitive PCR-based molecular methods. Analysis of blood samples from patients showed similar patterns of donor cell persistence after the first infusion, in that cells were detectable for at least 1 week. Also, differences were observed in the kinetics of cell survival between the first and subsequent infusion cycles in all three patients. This suggests variation in HIV-specific immune responses detected among these three patients was not due to differences in persistence of infused donor cells.

Effect of therapeutic immunization with recombinant gp160 HIV-1 vaccine on HIV-1 proviral DNA and plasma RNA : Relationship to cellular immune responses

Therapeutic vaccination has been proposed as a strategy to augment immune mechanisms to control viral replication and slow clinical progression of HIV infection to disease. Following recombinant gp160 (r-gp160) immunization in three clinical trials, plasma HIV-1 RNA and cellular proviral DNA were assessed by quantitative polymerase chain reaction (PCR) in 76 HIV-seropositive subjects with CD4+ T cell counts > or = 300/mm3. Immunization increased HIV-specific cellular immune responses (e.g., cytotoxic T lymphocyte [CTL] activities, lymphocyte proliferative responses); however, there were no significant effects of immunization or cellular immune responses on measures of plasma RNA or cellular DNA viral load.

Delayed-type hypersensitivity to recombinant HIV envelope glycoprotein (rgp160) after immunization with homologous antigen.

Delayed-type hypersensitivity (DTH) responses to intradermal recombinant HIV envelope glycoprotein (rgp160) may assess cell-mediated immune responses to HIV envelope. In three studies, DTH and lymphocyte proliferation responses to rgp160 were obtained in a total of 106 HIV-seropositive subjects with CD4+ counts >400 cells/mm3. Several subjects participated in more than one study. Before immunization, DTH responses were seen in 5 of 56 (9%) of HIV-infected study subjects. After immunization with an alum-adjuvanted experimental rgp160 vaccine, DTH responses were seen in 46 of 52 (89%). Using in vitro lymphocyte proliferation activity (LPA) to rgp160 as an indication of cellular immune response, skin testing has a sensitivity of 0.75 (95% confidence Interval [CI], 0.59-0.88) and a specificity of 0.84 (95% CI, 0.72-0.92). Biopsy samples of skin that had tested positive confirmed the presence of a DTH reaction with a predominance of CD4+ T cells in the perivascular, inflammatory infiltrate. Skin testing before and after immunization with candidate AIDS vaccines could provide a simple method in the field to assess new cell mediated immune responses.

Heterogeneity of cytokine functions in HIV infection.

Immunological responses, especially cytokines, play important roles in determining the persistence of infectious agents in chronic diseases. Th1 responses enhance cellular immunity to control infection whereas Th2 immune responses down‐regulate these effector immune responses. It has been suggested that the Th1 to Th2 switch is involved in human immunodeficiency virus (HIV) disease progression. We studied the regulatory role of interleukin‐4 (IL‐4; Th2 response) on interferon‐γ (IFN‐γ; Th1 response) in HIV infection and its role in the generation of HIV‐specific cytotoxic T lymphocytes (CTL) in an in vitro system. Forty HIV‐infected, asymptomatic individuals and 20 HIV‐seronegative individuals were included in this study. Peripheral blood mononuclear cells were stimulated with phytohaemagglutinin and tetanus toxoid in the presence or absence of IL‐4 to determine the effect of IL‐4 on IFN‐γ production and HIV‐Env‐specific CTL activity. IL‐4 showed a dual effect on IFN‐γ production in HIV patients. IL‐4 down‐regulated IFN‐γ production in HIV‐seronegative individuals and in 55% of HIV patients whereas it stimulated IFN‐γ production in 45% of HIV patients. IL‐4 increased HIV‐Env‐specific CTL activity in five of seven patients of the latter group. IL‐4 has multiple biological activities, e.g. IL‐4 inhibits IFN‐γ production as well as stimulates CTL generation which in turn produces IFN‐γ. Understanding the biological significance of these interactions is of importance for immunotherapeutic approaches against HIV infection.