Long-term HIV-specific responses and delayed resumption of antiretroviral therapy after peptide immunization targeting dendritic cells.

Long-term HIV-specific immune responses and clinical outcomes were evaluated in HIV-infected patients previously immunized with p24-like peptides (Vacc-4x) targeting dendritic cells (DC). Vacc-4x-induced cellular immune responses were unchanged 1.5 years after completing immunization, and 62% were still off combined antiretroviral treatment (CART). The magnitude of early Vacc-4x responses determined whether the resumption of CART was clinically indicated 2 years after enrollment. These observations encourage further exploration of both Vacc-4x and other HIV peptide-based immunization regimens targeting DC.

Multiple antigen concentrations in delayed-type hypersensitivity (DTH) and response diversity during and after immunization with a peptide-based HIV-1 immunotherapy candidate (Vacc-4x).

Delayed-type hypersensitivity (DTH) testing represents a simple in vivo method for monitoring cellular immune responses. In a phase II clinical trial on HIV-infected patients (n = 38) of the peptide-based HIV-1 immunotherapy candidate Vacc-4x, we monitored DTH responses to three antigen concentrations of Vacc-4x. We have shown that DTH can be used quantitatively to measure immune reactions to Vacc-4x and its individual peptide components. Our data stress the qualities and differences of induration and erythema, both in discriminating individual antigens and in monitoring immunizations over time. The data also indicate that DTH baseline-status might have important impact on immunization kinetics.

Reduced viral burden amongst high responder patients following HIV-1 p24 peptide-based therapeutic immunization.

We have previously shown that HIV p24-like peptides (Vacc-4x) via activation of skin dendritic cells induced immune responses in 90% of HIV patients on highly active antiretroviral treatment (HAART). These patients (n=38) were here subjected to a final 14-week interruption of HAART. Patients with the highest delayed type hypersensitivity (DTH) responses to Vacc-4x-peptides before treatment interruption tended to achieve lower actual HIV RNA levels at the end of the study compared to Vacc-4x DTH low-responders (p=0.08) and significantly so in terms of viral loads relative to their individual pre-HAART HIV RNA set-points (p=0.04). CD4+ lymphocyte counts were maintained only among DTH high responders but decreased in the other patients during recurrent viremia (p

Divergent in vitro and in vivo correlates of HIV-specific T-cell responses during onset of HIV viraemia.

BACKGROUND: Cellular immune responses to HIV-1 have been examined mainly in peripheral blood mononuclear cells (PBMC). During onset of HIV replication and antigenaemia after discontinuation of highly active antiretroviral therapy (HAART), PBMC may theoretically contain HIV-specific T cells that are qualitatively and quantitatively different from specific T cells dominating in the tissues. PBMC responses throughout HIV immunotherapy trials may therefore be skewed during recurrent viraemia. OBJECTIVE: To compare cellular HIV-specific in vitro responses in PBMC during onset of HIV viraemia with corresponding in vivo responses, represented by classical delayed-type hypersensitivity tests (DTH). METHODS: HIV patients (n = 38), pre-immunized with four HIV-1 p24-like consensus peptides (Vacc-4x) during HAART, were subjected to a 14-week treatment interruption with recurrent HIV viraemia. Proliferative T-cell responses to Vacc-4x p24 peptides, HIV p24 protein, and cytomegalovirus (CMV) proteins were measured in PBMC. Corresponding Vacc-4x peptide DTH were expressed as skin infiltrate areas after 48 h. RESULTS: After 14 weeks without HAART, HIV-1 RNA increased to 72,500 copies/ml (median). The Vacc-4x p24 peptide- and HIV-1 p24 protein-induced T-cell proliferation concurrently decreased by 81 and 93% in PBMC during viraemia (medians, P < or = 0.03), whereas proliferative responses to CMV antigens were stable. In contrast, the Vacc-4x DTH areas, rather tended to increase by 36% (P = 0.08) and contained infiltrates dominated by proliferating T cells and macrophages. CONCLUSIONS: Divergent in vitro and in vivo HIV-specific cellular immune responses were found during recurrent HIV viraemia. The clinical relevance of both surrogate markers for HIV-related immune responses should be compared in future studies.

HLA- and dose-dependent immunogenicity of a peptide-based HIV-1 immunotherapy candidate (Vacc-4x).

OBJECTIVE: The Vacc-4x immunotherapy candidate is composed of four modified peptides corresponding to conserved domains of the HIV-1 protein p24 that preferentially include HLA-A2 restricted elements. Dose-dependent safety and immunogenicity of Vacc-4x and the significance of a HLA-A2 haplotype were examined. DESIGN: Non-AIDS, HIV-1 infected healthy patients (n = 40) stable on HAART with CD4 counts > 300 x 10 cells/l were randomized to receive either low-dose or high-dose Vacc-4x over 26 weeks in an open, prospective phase II clinical trial. METHODS: Patients received a total of 10 intradermal injections, using recombinant granulocyte-macrophage colony stimulating factor as a local adjuvant. Vacc-4x-specific cellular responses were monitored in vivo by delayed-type hypersensitivity (DTH) skin test infiltrates and in vitro by both T-cell proliferation, and induction /secretion of cytokines. RESULTS: Most patients developed Vacc-4x-specific DTHs (90%) and proliferative T-cell responses (80%) that were inter-related in magnitude. High-dose Vacc-4x generally induced stronger specific immune responses than low dose in terms of DTH areas and CD4 and CD8 T-cell proliferation. Only HLA-A2 negative patients had a definite dose advantage, and this subgroup had in fact the best overall DTH and proliferative responses. In contrast, no significant dose difference was observed for HLA-A2 positive patients. No serious adverse events were reported. CONCLUSIONS: HIV-associated specific responses were safely induced in most patients by Vacc-4x in a dose-dependent manner and were also influenced by the HLA haplotype.

Novel peptide-based HIV-1 immunotherapy.

Therapeutic immunisation of human immunodeficiency virus type 1-infected individuals should be actively pursued in the first instance to augment highly active antiretroviral therapy regimens. Peptide-based immunotherapeutic strategies offer considerable advantages over conventional approaches, particularly regarding safety. Peptide design itself is becoming increasingly sophisticated, with the rapid evolution of bioinformatics tools that can analyse not only T cell epitopes, but also their potential for successful presentation on diverse human leukocyte antigen (HLA) class I or II following intracellular processing by antigen-presenting cells (APCs). By targeting conserved viral domains, peptides acquire improved reactivity to diverse viral strains. Dendritic cells represent a powerful route of administration, as they are the most potent APCs and can present exogenous peptides on both HLA class I and II through the process of cross-presentation. In this way, soluble peptides can thereby stimulate both CD4+ and CD8+ T cells.

Phase I trial of a therapeutic HIV type 1 vaccine, Vacc-4x, in HIV type 1-infected individuals with or without antiretroviral therapy.

Highly active antiretroviral therapy (HAART) can effectively suppress HIV-1 replication but, as soon as the drugs are withdrawn, there is a rapid rebound of replicating virus. Severe metabolic toxicities and therapy failures due to the appearance of resistant virus are becoming an increasing problem that precludes long-term continuous medication. Therapeutic immunizations represent a feasible and attractive means of supplementing or, alternatively, replacing current therapies, thereby reducing the potential for emergence of drug-resistant HIV-1 strains. We have performed an open, single-center, phase I safety study of a candidate therapeutic HIV-1 vaccine, Vacc-4x, given to 11 HIV-1-infected individuals with or without antiretroviral therapy. The immunogen consists of four synthetic peptides based on the major core protein p24. To ensure optimal exposure of the immunogen to the antigen-presenting cells (APCs), the vaccine was given intradermally together with granulocyte-macrophage colony-stimulating factor (GM-CSF). Responses to the immunization protocol were determined by delayed-type hypersensitivity (DTH) reaction, interferon gamma-secreting cells in the enzyme-linked immunospot (ELISpot) assay, and antibody production to the p24 protein and the peptides. The vaccine was safe and in general well tolerated. Plasma HIV RNA levels and CD4(+) cell counts did not change appreciably during the study. All patients showed a positive DTH response. For two of the patients, the immunization protocol induced responses to one or two of the tested peptides whereas a third patient showed reactivity to one of the peptides before immunization. A weak antibody response in the peptide-specific enzyme-linked immunosorbent assay could be seen in seven patients.