E. Sandström

Amplified antigen-specific immune responses in HIV-1 infected individuals in a double blind DNA immunization and therapy interruption trial☆

Immunotherapy in patients with HIV-1 infection aims to restore and broaden immunological competence, reduce viral load and thereby permit longer periods without combined antiretroviral treatment (cART). Twelve HIV-1-infected patients on cART were immunized on the skin with DNA plasmids containing genes of several HIV-1 subtypes with or without the addition of hydroxyurea (HU), or with placebo. The mean net gain of HIV-specific CD8+ T cell responses were higher and broader in the HIV DNA vaccine groups compared to non-vaccinated individuals (p<0.05). The vaccine-induced immune responses per se had no direct effect on viral replication. In all patients combined, including placebo, the viral set point after a final structured therapy interruption (STI) was lower than prior to initiation of cART (p=0.003). Nadir CD4 levels appeared to strongly influence the post-STI viral titers. After the sixth immunization or placebo, patients could stay off cART for a median time of 15 months. The study shows that HIV DNA immunization induces broader and higher magnitudes of HIV-specific immune responses compared to structured therapy interruptions alone. Although compromised by small numbers of patients, the study also demonstrates that well-monitored STI may safely function as an immunological read out of HIV vaccine efficacy.

Clinical and immunological benefits from highly active antiretroviral therapy in spite of limited viral load reduction in HIV type 1 infection.

Both naive and memory T lymphocyte responses are lost during advanced HIV infection. Treatment with highly active antiretroviral therapy (HAART) is associated with an increase in T lymphocytes and a reduction in viral load. However, the viral response to HAART in patients with low levels of helper T lymphocytes and a high viral load is often not satisfactory. We investigated the capacity of long-term HAART to reconstitute the immune system in severely ill patients. A nonselected longitudinal patient population with high baseline viral levels and CD4(+) cells below 100 x 10(6)/liter were monitored for 2 years during HAART. Markers to estimate the therapeutic effects included viral levels and cell surface markers representing naive and memory T lymphocytes as well as activation markers, B cells, NK cells, and clinical events. After 2 years of treatment, viral load was reduced to undetectable levels in 55% (viral responders, vRs) and less than 1 log (median value) from baseline in 45% (viral low responders, vLRs). Elevated numbers of memory and naive CD4(+) and CD8(+) cells as well as a decrease in activation markers were seen in both vRs and vLRs. However, the magnitude was greater in vRs. No differences in the clinical outcome were observed between vRs and vLRs. We conclude that most patients, even in advanced stages of HIV disease, benefited from HAART. The magnitude of the response was related to good viral reduction, but even patients with poor viral reduction had a recovery of naive and memory CD4(+) and CD8(+) cells. Even a small reduction in viral load is thus of importance for health and potentially also for years of survival.

Cross-clade immune responses to Gag p24 in patients infected with different HIV-1 subtypes and correlation with HLA class I and II alleles

Individuals infected with different subtypes of HIV-1 (A, B, C, D, CRF01_AE and CRF02_AG) were analyzed for their antigen-specific immune response with respect to their HLA genetics. The p24 Gag protein was selected for analysis, since previous studies of the same cohort of patients had shown that almost 80% of these individuals responded to Gag peptides of subtypes A, B and/or C. A large number of Gag antigen-specific responses were recorded. Both previously recognized as well as new epitopes were identified, assumed to bind HLA classes I and/or II. Fifteen individuals showed class I cellular responses to T cell epitopes irrespective of the infecting virus subtype. For five individuals infected with subtypes A, B, D and CRF02_AG, new T cell epitopes are described. Responses related to the patients class I alleles are frequent, and several new putative class II responses were found.

P14-14 LB. A low dose of multigene, multiclade HIV DNA given intradermally induces strong and broad immune responses after boosting with heterologous HIV MVA

Open Access Poster presentation P14-14 LB. A low dose of multigene, multiclade HIV DNA given intradermally induces strong and broad immune responses after boosting with heterologous HIV MVA M Bakari*1, S Aboud1, C Nilsson2, J Francis1, D Buma3, C Moshiro1, EA Aris3, E Lyamuya1, M Janabi3, J Mbwana1, L Mwanyika4, R Stout5, B Hejdeman6, A Brave2, M Robb7, M Marovich7, N Michael7, P Earl8, B Moss8, B Wahren2, G Biberfeld2, K Pallangyo1, F Mhalu1 and E Sandstrom6

Long-term increase of CD4+ central memory cells in HIV-1-infected individuals by therapeutic HIV-1 rgp160 immunization☆

OBJECTIVE To evaluate functional potential and phenotypic markers in HIV-1-infected patients immunized with HIV-1 rgp160. METHODS We assessed changes in T-cell phenotype and immune function in 12 HIV-1-infected individuals that were part of a therapeutic vaccine study from 1992 to 1995 [Sandstrom E, Wahren B. Therapeutic immunisation with recombinant gp160 in HIV-1 infection: a randomised double-blind placebo-controlled trial. Nordic VAC-04 Study Group. Lancet 1999;353(9166):1735-42]. The patients received 160 microg HIV-1 rgp160 or placebo i.m. at baseline (day 0), and months 1, 2, 3, 4, 6, and thereafter every 3 months. Frozen peripheral blood mononuclear cells (PBMC) were retrieved from time points 0, 9, 12 and 24 months for phenotypic analysis utilizing flow cytometry. RESULTS Up-regulation of immune activation markers HLA-DR and CD38 was observed at baseline and throughout the monitoring period on both CD4+ and CD8+ T cells in all patients, reflecting immune activation due to persistent high viral load. Further enhanced expression of activation markers was observed over time in the vaccine group, but not the placebo group. We also observed a consistent long-term increase of the CD4+ central memory population (CD3+CD4+CD45RA-CCR7+) in the vaccinated group. CONCLUSIONS Administration of eight doses of rgp160 in a year appeared to partially reverse some of the defects exerted by HIV-1 on the immune system. A combination of vaccination with effective antiretroviral therapy (ART) may thus represent an immunotherapeutic intervention for treatment of chronic HIV-1 infection. The improvement of a HIV-1-specific central memory population and HIV-1 antigen-specific CD4+ lymphoproliferative responses may have contributed to the short-term improved survival reported in the vaccinated group.

Experiences on recruitment and retention of volunteers in the first HIV vaccine trial in Dar es Salam, Tanzania - the phase I/II HIVIS 03 trial

BackgroundEventual control of HIV/AIDS is believed to be ultimately dependent on a safe, effective and affordable vaccine. Participation of sub-Saharan Africa in the conduct of HIV trials is crucial as this region still experiences high HIV incidences. We describe the experience of recruiting and retaining volunteers in the first HIV vaccine trial (HIVIS03) in Tanzania.MethodsIn this trial enrolled volunteers from amongst Police Officers (POs) in Dar es Salaam were primed with HIV-1 DNA vaccine at months 0, 1 and 3; and boosted with HIV-1 MVA vaccine at months 9 and 21. A stepwise education provision/sensitization approach was employed to eventual recruitment. Having identified a “core” group of POs keen on HIV prevention activities, those interested to participate in the vaccine trial were invited for a first screening session that comprised of provision of detailed study information and medical evaluation. In the second screening session results of the initial assessment were provided and those eligible were assessed for willingness to participate (WTP). Those willing were consented and eventually randomized into the trial having met the eligibility criteria. Voluntary participation was emphasized throughout.ResultsOut of 408 POs who formed the core group, 364 (89.0%) attended the educational sessions. 263 out of 364 (72.2%) indicated willingness to participate in the HIV vaccine trial. 98% of those indicating WTP attended the pre-screening workshops. 220 (85.0%) indicated willingness to undergo first screening and 177 POs attended for initial screenings, of whom 162 (91.5%) underwent both clinical and laboratory screenings. 119 volunteers (73.5%) were eligible for the study. 79 were randomized into the trial, while 19 did not turn up, the major reason being partner/family advice. 60 volunteers including 15 females were recruited during a one-year period. All participated in the planned progress updates workshops. Retention into the schedule was: 98% for the 3 DNA/placebo vaccinations, while it was 83% and 73% for the first and second MVA/placebo vaccinations respectively.ConclusionIn this first HIV vaccine trial in Tanzania, we successfully recruited the volunteers and there was no significant loss to follow up. Close contact and updates on study progress facilitated the observed retention rates.Trial registration numbersISRCTN90053831 ISRNCT01132976 and ATMR2009040001075080

Potent cellular and humoral immunity against HIV-1 elicited in mice by a DNA-prime/MVA-boost vaccine regimen intended for human use

In an experimental vaccine model, mice were primed three times with plasmids encoding multiple subtypes (A, B and C) of gag, envelope (env) and reverse transcriptase (RT) and adjuvant rGM-CSF followed by modified vaccinica Ankara (MVA) with the recombinant form A_E, in theory providing protection against HIV subtypes A-E. The cellular responses, as measured by IFN-gamma secretion gave up to 2000 gag-specific SFC/million PBMC. The humoral and cellular responses were further increased by the MVA-boosts with env and gag specific ELISpot responses above 3500 secreting/106 cells. Intracellular cytokine staining showed remarkably high numbers (~15%) of gag and env specific CD8+ T cells. This paved the way for our clinical trial with the multigene/multisubtype DNA plasmids boosted with the MVA construct. Conclusions: This preclinical study clearly shows the potential of combining these particular DNA and MVAs in a prime/boost regimen and that it is possible to induce a strong and broad humoral and cellular response directed against several parts of HIV as well as to several subtypes of the virus.

P14-03. HIV-specific T-lymphocyte proliferative responses induced by a multigene multiclade HIV-1 DNA/MVA heterologous vaccine in Tanzanian volunteers

Address: 1Department of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania, 2SAIC Frederick, Inc., National Cancer Institute at Frederick, Frederick, USA, 3US Military HIV Research Program, Rockville, MD, USA, 4Venhalsan, Karolinska University Hospital, Stockholm, Sweden, 5Swedish Institute for Infectious Disease Control and Karolinska Institute, Stockholm, Sweden and 6Swedish Institute for Infectious Disease Control (SMI), Stockholm, Sweden * Corresponding author

Do circulating HIV vaccine plasmids contribute to immunogenicity in humans

Results Two months after the third immunization, an HIV RNA quantitative PCR was performed to confirm the noninfected status of the participants. In half of the vaccines, in total receiving 3–12 mg plasmid DNA, we noted reactions of plasmid DNA or values corresponding to 20– 1200 HIV RNA copies in the Roche Amplicor assay. Env and/or gag encoding plasmids were detected in the plasma or serum of the vaccines, but no HIV. A PCR for HIV protease (the protease gene is not included in the vaccine) was negative in all cases. Antigen and antibody assays have confirmed that the individuals were not infected. The study is still blinded, but a total of over 90% have responded very well by T-cell assays. Conclusion HIV vaccine plasmids given id or im were identified as late as two months after immunization. A relation between immunogenicity and circulating vaccine plasmids will be sought. DNA plasmids may give positive signals in a standard HIV RNA quantative assay. from 2006 International Meeting of The Institute of Human Virology Baltimore, USA. 17–21 November, 2006