Characterization of envelope function of transmitted viruses circulating in Mbeya, Tanzania, and its impact on disease progression

An understanding of the biological characteristics of transmitted viruses provides important insights into HIV pathogenesis and informs vaccine development. The aim of the study was to characterize env function of transmitted viruses and its role in disease progression

High prevalence of ST-elevation, early repolarization, and left ventricular hypertrophy during the eligibility assessment for an HIV vaccine trial in young, healthy Tanzanians

BACKGROUND: Vaccinia based immunizations have caused myo/pericarditis and vaccine study volunteers are monitored by ECG. We report ECG outcome obtained during the screening period for an HIV vaccine trial. METHODS: ECG was performed in healthy Tanzanian volunteers. ECG abnormalities and findings interfering with the interpretation of myo/pericarditis were subject to study ineligibility. We determined the prevalence of left ventricular hypertrophy (LVH) defined by the Sokolow-Lyon (SL) or the Cornell index, ST-elevations and early repolarization (ERP) in association with gender, age, BMI and body height by regression analysis adjusted for gender and age. RESULTS: In 257 volunteers (median age 23 years, 63% males) overall positivity for LVH defined by SL or Cornell criteria was seen in 20.6% and 3.5%, ST-elevations ≥ 0.1 mV or ≥ 0.2 mV in 77.8% and 38.1%, and ERP in 23.4%. Positive SL criteria were associated with male gender (PR 7.84, p < 0.001) and lower age (PR 0.70, p = 0.002), and associated with increased body height and lower BMI in univariate analysis. Positive Cornell criteria were only associated with lower age (PR 0.44, p = 0.010). ST-elevations ≥ 0.2 mV were associated with male gender (PR 8.05, p < 0.001) and lower age (PR 0.81, p = 0.003), and ERP with male gender (PR 2.86, p < 0.001). Vaccine study ineligibility due to ECG findings was concluded in 22.1% of the screening population. CONCLUSIONS: High prevalence of LVH according to SL in association with ST-elevation and ERP is especially found in young and male Africans. ECG variations need to be considered for eligibility criteria in studies investigating potential cardiotoxic agents in Africa

Low specificity of determine HIV1/2 RDT using whole blood in south west Tanzania

Objective: To evaluate the diagnostic performance of two rapid detection tests (RDTs) for HIV 1/2 in plasma and in whole blood samples. Methods: More than 15,000 study subjects above the age of two years participated in two rounds of a cohort study to determine the prevalence of HIV. HIV testing was performed using the Determine HIV 1/2 test (Abbott) in the first (2006/2007) and the HIV 1/2 STAT-PAK Dipstick Assay (Chembio) in the second round (2007/2008) of the survey. Positive results were classified into faint and strong bands depending on the visual appearance of the test strip and confirmed by ELISA and Western blot. Results: The sensitivity and specificity of the Determine RDT were 100% (95% confidence interval = 86.8 to 100%) and 96.8% (95.9 to 97.6%) in whole blood and 100% (99.7 to 100%) and 97.9% (97.6 to 98.1%) in plasma respectively. Specificity was highly dependent on the tested sample type: when using whole blood, 67.1% of positive results were false positive, as opposed to 17.4% in plasma. Test strips with only faint positive bands were more often false positive than strips showing strong bands and were more common in whole blood than in plasma. Evaluation of the STAT-PAK RDT in plasma during the second year resulted in a sensitivity of 99.7% (99.1 to 99.9%) and a specificity of 99.3% (99.1 to 99.4%) with 6.9% of the positive results being false. Conclusions: Our study shows that the Determine HIV 1/2 strip test with its high sensitivity is an excellent tool to screen for HIV infection, but that – at least in our setting – it can not be recommended as a confirmatory test in VCT campaigns where whole blood is used

Preferential Targeting of Conserved Gag Regions after Vaccination with a Heterologous DNA prime - Modified Vaccinia Ankara (MVA) boost HIV-1 vaccine regimen

Prime-boost vaccination strategies against HIV-1 often include multiple variants for a given immunogen for better coverage of the extensive viral diversity. To study the immunologic effects of this approach, we characterized breadth, phenotype, function and specificity of Gag-specific T cells induced by a DNA-prime Modified Vaccinia Ankara (MVA)-boost vaccination strategy, which uses mismatched Gag immunogens in the TamoVac 01 phase IIa trial. Healthy Tanzanian volunteers received three injections of the DNA-SMI vaccine encoding for a subtype B and AB-recombinant Gagp37 and two vaccinations with MVA-CMDR encoding subtype A Gagp55 Gag-specific T-cell responses were studied in 42 vaccinees using fresh peripheral blood mononuclear cells. After the first MVA-CMDR boost, vaccine-induced IFN-γ(+) Gag-specific T cell responses were dominated by CD4(+) T cells (compared to CD8(+) T cells, p<0.001) that co-expressed IL-2 (66.4%) and/or TNFα (63.7%). A median of 3 antigenic regions were targeted with a higher median response magnitude to Gagp24 regions - more conserved between prime and boost - as compared to regions within Gagp15 (not primed) and Gagp17 (less conserved, both p<0.0001). Four regions within Gagp24 were each targeted by 45% to 74% of vaccinees upon restimulation with DNA-SMI-Gag matched peptides. The response rate to individual antigenic regions correlated with the sequence homology between the MVA and DNA Gag encoded immunogens (p=0.04, r(2)=0.47). In summary, after the first MVA-CMDR boost, the sequence-mismatched DNA-prime MVA-boost vaccine strategy induced a Gag-specific T cell response that was dominated by polyfunctional CD4(+) T cells and that targeted multiple antigenic regions within the conserved Gagp24 Protein.IMPORTANCE Genetic diversity is a major challenge for the design of vaccines against variable viruses. While including multiple variants for a given immunogen in prime-boost vaccination strategies is one approach that aims to improve coverage for global virus variants, the immunologic consequences of this strategy have been poorly defined so far. It is unclear whether inclusion of multiple variants in prime-boost vaccination strategies improves recognition of variant viruses by T cells and by which mechanisms this would be achieved; either by improved cross-recogniton of multiple variants for a given antigenic region or rather through preferential targeting of antigenic regions more conserved between prime and boost. Engineering vaccines to induce adaptive immune responses that preferentially target conserved antigenic regions of viral vulnerability might facilitate better immune control after preventive and therapeutic vaccination for HIV and for other variable viruses