Aotus nancymaae model predicts human immune response to the placental malaria vaccine candidate VAR2CSA

Placental malaria vaccines (PMVs) are being developed to prevent severe sequelae of placental malaria (PM) in pregnant women and their offspring. The leading candidate vaccine antigen VAR2CSA mediates parasite binding to placental receptor chondroitin sulfate A (CSA). Despite promising results in small animal studies, recent human trials of the first two PMV candidates (PAMVAC and PRIMVAC) generated limited cross-reactivity and cross-inhibitory activity to heterologous parasites. Here we immunized Aotus nancymaae monkeys with three PMV candidates (PAMVAC, PRIMVAC and ID1-ID2a_M1010) adjuvanted with Alhydrogel, and exploited the model to investigate boosting of functional vaccine responses during PM episodes as well as with nanoparticle antigens. PMV candidates induced high levels of antigen-specific IgG with significant cross-reactivity across PMV antigens by enzyme-linked immunosorbent assay. Conversely, PMV antibodies recognized native VAR2CSA and blocked CSA adhesion of only homologous parasites and not of heterologous parasites. PM episodes did not significantly boost VAR2CSA antibody levels or serum functional activity; nanoparticle and monomer antigens alike boosted serum reactivity but not functional activities. Overall, PMV candidates induced functional antibodies with limited heterologous activity in Aotus monkeys, similar to responses reported in humans. The Aotus model appears suitable for preclinical downselection of PMV candidates and assessment of antibody boosting by PM episodes.

Therapeutic vaccination using cationic liposome-adjuvanted HIV type 1 peptides representing HLA-supertype-restricted subdominant T cell epitopes: safety, immunogenicity, and feasibility in Guinea-Bissau

We have designed a therapeutic HIV-1 vaccine concept based on peptides together with the adjuvant CAF01. Peptides represented 15 HLA-supertype-restricted subdominant and conserved CD8 T cell epitopes and three CD4 T-helper cell epitopes. In this phase I clinical trial, safety and immunogenicity were assessed in untreated HIV-1-infected individuals in Guinea-Bissau, West Africa. Twenty-three HIV-1-infected individuals were randomized to receive placebo (n=5) or vaccine (n=18). Safety was appraised by clinical follow-up combined with monitoring of biochemistry, hematology, CD4 T cell counts, and HIV-1 viral loads. T cell immunogenicity was monitored longitudinally by interferon (IFN)-γ ELISpot. New vaccine-specific T cell responses were induced in 6/14 vaccinees for whom ELISpot data were valid. CD4 T cell counts and viral loads were stable. The study shows that therapeutic immunization is feasible and safe in Guinea-Bissau and that it is possible to redirect T cell immunity with CAF01-adjuvanted HIV-1 peptide vaccine during untreated HIV-1 infection in some patients. However, relatively few preexisting and vaccine-induced HIV-1 T cell responses to CD8 T cell epitopes were detected against HIV-1 using IFN-γ ELISpot in this chronically infected African population.