Polyvalent HIV-1 Env vaccine formulations delivered by the DNA priming plus protein boosting approach are effective in generating neutralizing antibodies against primary human immunodeficiency virus type 1 isolates from subtypes A, B, C, D and E

Abstract

A major challenge in developing an HIV-1 vaccine is to identify immunogens and their delivery methods that can elicit broad neutralizing antibodies against primary isolates of different genetic subtypes. Recently, we demonstrated that priming with DNA vaccines expressing primary HIV-1 envelope glycoprotein (Env) followed by recombinant Env protein boosting was successful in generating positive neutralizing antibody responses against a clade B primary HIV-1 isolate, JR-FL, that was not easily neutralized. In the current study, we examined whether the DNA priming plus recombinant protein boosting approach delivering a polyvalent primary Env formulation was able to generate neutralizing antibodies against primary HIV-1 viral isolates from various genetic subtypes. New Zealand White rabbits were first immunized with DNA vaccines expressing one, three or eight primary HIV-1 gp120 antigens delivered by a gene gun followed by recombinant gp120 protein boosting. Neutralizing antibody responses were examined by two independently executed neutralization assays: the first one was a single round infection neutralization assay against a panel of 10 primary HIV-1 isolates of subtypes A, B, C and E and the second one used the PhenoSense assay against a panel of 12 pseudovirues expressing primary HIV-1 Env antigens from subtypes A, B, C, D and E as well as 2 pseudoviruses expressing the Env antigens from MN and NL4-3 viruses. Rabbit sera immunized with the DNA priming plus protein boosting approach, but not DNA vaccine alone or Env protein alone, were capable of neutralizing 7 of 10 viruses in the first assay and 12 of 14 viruses in the second assay. More importantly, sera immunized with the polyvalent Env antigens were able to neutralize a significantly higher percentage of viruses than the sera immunized with the monovalent antigens. Our results suggest that DNA priming followed by recombinant Env protein boosting can be used to deliver polyvalent Env-antigen-based HIV-1 vaccines to elicit neutralizing antibody responses against viruses with diverse genetic sequence variations.

Cross-subtype antibody and cellular immune responses induced by a polyvalent DNA prime–protein boost HIV-1 vaccine in healthy human volunteers

“…Our preclinical study results also indicated that this combination vaccination approach, but not recombinant protein alone, was effective in eliciting NAbs against primary HIV isolates [19], a finding that has been confirmed subsequently by other independent studies [20][21][22][23][24][25][26]. Furthermore, when polyvalent primary Env antigen formulations were used, the DNA primeprotein boost approach was more effective than the monovalent primary Env antigen in eliciting rabbit NAbs against a wide range of selected primary viral isolates across subtypes A, B, C, D and E [27]. In the current study, a multi-gene, polyvalent DNA prime-protein boost HIV-1 vaccine was formulated based on the above preclinical study findings, and its immunogenicity was tested in healthy adults in a Phase I clinical trial.…”

“…Individual gp120 antigens (100ng/lane) were subjected to SDS-PAGE and blotted onto PVDF membrane, as previous described [27]. Blocking of PVDF membrane was done with 0.1% I-Block (Tropix, Bedford, MA).…”

DNA prime-protein boost using subtype consensus Env was effective in eliciting neutralizing antibody responses against subtype BC HIV-1 viruses circulating in China

“…A stable Chinese Hamster Ovary (CHO) cell line was constructed to express the recombinant gp120-BC protein as previously described. 8 Secreted gp120-BC protein from a stably transfected CHO cell line was harvested and purified by FPLC using Lentil lectin sepharose 4B column (GE Healthcare, Waukesha, WI).…”

“…Previously, we demonstrated that priming immunizations with DNA vaccines expressing Env antigens can significantly enhance the quality, especially the neutralizing activities, of antibody responses elicited by subunit Env protein vaccines [7][8][9][10][11] ReseaRcH papeR ReseaRcH papeR of the same subtype and whether the DNA priming step is helpful for further improving the quality of antibody responses.…”

Polyvalent vaccine approaches to combat HIV‐1 diversity

“…Unfortunately, the results of the human efficacy phase 2b trial HVTN 505, which tested a combination of three envelope (Env) immunogens from different clades as a vaccine, were disappointing 25. The HVTN 505 vaccine included a multivalent (six plasmid) DNA prime, each plasmid expressing either a clade B gag , pol or nef or a clade A, B or C env gene, followed by a boost with four recombinant adenovirus (rAd5) vectors expressing either a clade B Gag/Pol fusion protein, or clade A, B or C Envs.…”