Induction of tier-2 neutralizing antibodies in mice with a DNA-encoded HIV envelope native like trimer

Abstract

HIV Envelope (Env) is the main vaccine target for induction of neutralizing antibodies. Stabilizing Env into native-like trimer (NLT) conformations is required for recombinant protein immunogens to induce autologous neutralizing antibodies(nAbs) against difficult to neutralize HIV strains (tier-2) in rabbits and non-human primates. Immunizations of mice with NLTs have generally failed to induce tier-2 nAbs. Here, we show that DNA-encoded NLTs fold properly in vivo and induce autologous tier-2 nAbs in mice. DNA-encoded NLTs also uniquely induce both CD4 + and CD8 + T-cell responses as compared to corresponding protein immunizations. Murine neutralizing antibodies are identified with an advanced sequencing technology. The structure of an Env-Ab (C05) complex, as determined by cryo-EM, identifies a previously undescribed neutralizing Env C3/V5 epitope. Beyond potential functional immunity gains, DNA vaccines permit in vivo folding of structured antigens and provide significant cost and speed advantages for enabling rapid evaluation of new HIV vaccines.

Single-component multilayered self-assembling protein nanoparticles presenting glycan-trimmed uncleaved prefusion optimized envelope trimers as HIV-1 vaccine candidates

“…While BG505 SOSIP and HR1 N -redesigned trimers were ineffective in NAb induction in mice ( 27, 55 ), a reengineered I3-01 NP displaying the HR1 N -redesigned trimer elicited potent tier 2 murine NAbs to the C3/V4 epitope ( 27, 71 ). Recently, an autologous tier 2 NAb response was induced in mice by iron oxide NP (IO-NP)-attached SOSIP trimers ( 96 ) and a DNA trimer vaccine ( 70 ), both using long-boost intervals. In contrast to the challenges encountered in mice, native-like trimers can readily elicit tier 2 NAbs in rabbits but mostly to specific holes in the glycan shield ( 56 ).…”

“…Although rabbits can readily generate autologous tier 2 NAb responses, they mainly target strain-specific holes in the glycan shield (56) or neoepitopes at the trimer base (73). The tier 2 NAb responses in wildtype mice and NHPs are sporadic and often target glycan-rich regions on the Env that are immunodominant in human infection (67,70,71). Although bNAb responses were occasionally reported (52,58,(139)(140)(141), it is unclear whether these are reproducible outcomes of a general vaccine solution or coincidence.…”

“…4 ). For in vivo evaluation, we used the mouse model as a primary indicator because it is inexpensive, difficult, and known to generate tier 2 NAbs to epitopes that are found in human infection ( 70, 71 ). Rabbits were tested to provide another immunogenicity readout and probe glycan holes.…”

“…Our results revealed the importance of glycan trimming in improving the immunogenicity of HIV-1 Env vaccines in both trimer and NP forms. The 50-86% FVR noted for glycan-trimmed trimer groups was rather surprising, given the past failures in tier 2 NAb elicitation by stabilized BG505 trimers (27,55) and difficulties in improving it (70,96). Glycan trimming not only enabled antibody access to a broad range of epitopes that would otherwise be occluded by the glycan shield but also minimized glycan-related immunodominance (e.g., glycan holes and clusters).…”

“…The former (small, exposed protein surfaces within the glycan shield) are the primary target of autologous tier-2 NAbs in rabbits (56)(57)(58)(59)(60)(61)(62)(63)(64)(65), whereas the latter elicits non-neutralizing antibodies (nNAbs) in multiple species (63,66,67) and causes trimer disassembly during immunization (68). In rodents, glycan epitopes at C3/V4 and C3/V5 accounted for the autologous NAb response induced by BG505 Env (69)(70)(71). In nonhuman primates (NHPs), the BG505 SOSIP trimer elicited an autologous NAb response to C3/465 (60,72).…”