A new research paper by WHV and the University of Massachusetts Chan Medical School scientists was recently accepted in NPj Vaccines, an open access journal by Nature Publishing Group. The study, led by Dr. Shan Lu, analyzed samples from the phase 1 DP6-001 trial to further characterize the specific immune responses elicited by the first-generation HIV vaccine candidate PDPHV and found that the gp120-specific antibodies were primarily of the IgG1 isotype, a finding that is consistent with other HIV vaccine studies. Furthermore, HIV-1 envelope protein variable regions V1 and V2 were actively targeted by the antibodies as determined by specific binding to both peptide and V1V2-carrying scaffolds. The antibodies showed potent and broad ADCC responses. In addition, the B cell ELISPOT analysis demonstrated persistence of gp120-specific memory B cells for at least 6 months after the last dose. This long-lasting, high level memory response as elicited by PDPHV has so far not been reported in any other HIV-1 vaccine trial. It was found that non-persistent immune responses in RV144 trial may have contributed to low level of protection against HIV infection in study volunteers.
These new findings indicate that the polyvalent heterologous prime-boost vaccination regimen – using the first generation PDPHV candidate – was able to elicit broadly reactive binding antibodies and ADCC responses as well as durable gp120-specific memory B cells in humans. The formulation of this vaccine has since been improved by selecting the most optimal ENV variants based on the screening of a large panel of viruses (Wang, et al. 2017), forming the second generation PDPHV candidate that has since been tested in the phase 1a trial HVTN124 and is currently under investigation in the phase 1b WHV138 trial. Immunogenicity analyses of the second generation PDPHV candidate are ongoing for HVTN124 samples and results from the first batch of analyses will be published in the near future.