Novel Strategy To Adapt Simian-Human Immunodeficiency Virus E1 Carrying env from an RV144 Volunteer to Rhesus Macaques: Coreceptor Switch and Final Recovery of a Pathogenic Virus with Exclusive R5 Tropism

Abstract

The phase III RV144 human immunodeficiency virus (HIV) vaccine trial conducted in Thailand remains the only study to show efficacy in decreasing the HIV acquisition risk. In Thailand, circulating recombinant forms of HIV clade A/E (CRF01_AE) predominate; in such viruses, originates from clade E (HIV-E). We constructed a simian-human immunodeficiency virus (SHIV) chimera carrying isolated from an RV144 placebo recipient in the SHIV-1157ipd3N4 backbone. The latter contains long terminal repeats (LTRs) with duplicated NF-κB sites, thus resembling HIV LTRs. We devised a novel strategy to adapt the parental infectious molecular clone (IMC), R5 SHIV-E1, to rhesus macaques: the simultaneous depletion of B and CD8 cells followed by the intramuscular inoculation of proviral DNA and repeated administrations of cell-free virus. High-level viremia and CD4 T-cell depletion ensued. Passage 3 virus unexpectedly caused acute, irreversible CD4 T-cell loss; the partially adapted SHIV had become dual tropic. Virus and IMCs with exclusive R5 tropism were reisolated from earlier passages, combined, and used to complete adaptation through additional macaques. The final isolate, SHIV-E1p5, remained solely R5 tropic. It had a tier 2 neutralization phenotype, was mucosally transmissible, and was pathogenic. Deep sequencing revealed 99% Env amino acid sequence conservation; X4-only and dual-tropic strains had evolved independently from an early branch of parental SHIV-E1. To conclude, our primate model data reveal that SHIV-E1p5 recapitulates important aspects of HIV transmission and pathobiology in humans. Understanding the protective principles that lead to a safe, effective vaccine against HIV in nonhuman primate (NHP) models requires test viruses that allow the evaluation of anti-HIV envelope responses. Reduced HIV acquisition risk in RV144 has been linked to nonneutralizing IgG antibodies with a range of effector activities. Definitive experiments to decipher the mechanisms of the partial protection observed in RV144 require passive-immunization studies in NHPs with a relevant test virus. We have generated such a virus by inserting from an RV144 placebo recipient into a SHIV backbone with HIV-like LTRs. The final SHIV-E1p5 isolate, grown in rhesus monkey peripheral blood mononuclear cells, was mucosally transmissible and pathogenic. Earlier SHIV-E passages showed a coreceptor switch, again mimicking HIV biology in humans. Thus, our series of SHIV-E strains mirrors HIV transmission and disease progression in humans. SHIV-E1p5 represents a biologically relevant tool to assess prevention strategies.

Adaptation of an R5 Simian-Human Immunodeficiency Virus Encoding an HIV Clade A Envelope with or without Ablation of Adaptive Host Immunity: Differential Selection of Viral Mutants

“…We conclude that the passaged biological isolate SHIV-KNH1144p4 is still exclusively R5 tropic after adaptation. Importantly, unlike what we had observed during SHIV-E adaptation (18), this isolate did not undergo expansion of its coreceptor usage during the extended, high-level replication in the immunodepleted host.…”

“…Ablation of adaptive host immunity and NK function to optimize SHIV-A adaptation. Recently, we described the adaptation of a SHIV-E to RMs by employing a strategy to allow unbridled virus replication in RMs by transiently inhibiting adaptive host immunity along with components of innate immunity (18). This same strategy was used to continue adapting SHIV-A in the next RM, RTp-9.…”

“…also been developed by inoculating RMs with cocktails of SHIV variants (17). Recently, a tier 2 SHIV carrying a clade E env was adapted to RMs (18). Three groups have reported constructing SHIVs carrying clade A envs.…”

“…Although Hatziioannou et al have used ablation of CD8 ϩ cells for viral adaptation to macaques (23), our group is the first to our knowledge to use the combination of anti-CD8 and anti-CD20 MAbs to temporarily block the generation of both adaptive T-cell and antibody-mediated antiviral immune responses to optimize the host milieu for viral replication and adaptation. This strategy was previously used to adapt SHIV-E to RMs (18). Single-agent anti-CD20 MAb has not been used by others for the purpose of SHIV adaption, although this MAb has been employed by Mao et al to assess the influence of B cells on acute SHIV infection (24).…”