New SHIVs and Improved Design Strategy for Modeling HIV-1 Transmission, Immunopathogenesis, Prevention, and Cure

Abstract

Previously, we showed that substitution of HIV-1 Env residue 375-Ser by bulky aromatic residues enhances binding to rhesus CD4 and enables primary HIV-1 Envs to support efficient replication as simian-human immunodeficiency virus (SHIV) chimeras in rhesus macaques (RMs). Here, we test this design strategy more broadly by constructing SHIVs containing ten primary Envs corresponding to HIV-1 subtypes A, B, C, AE and AG. All ten SHIVs bearing wildtype Env375 residues replicated efficiently in human CD4+ T cells, but only one replicated efficiently in primary rhesus cells. This was a subtype AE SHIV that naturally contained His at Env375. Replacement of wildtype Env375 residues by Trp, Tyr, Phe or His in the other nine SHIVs led to efficient replication in rhesus CD4+ T cells in vitro and in vivo. Nine SHIVs containing optimized Env375 alleles were grown large-scale in primary rhesus CD4+ T cells to serve as challenge stocks in preclinical prevention trials. These virus stocks were genetically homogeneous, native-like in Env antigenicity and tier-2 neutralization sensitivity, and transmissible by rectal, vaginal, penile, oral or intravenous routes. To facilitate future SHIV constructions, we engineered a simplified second-generation design scheme and validated it in RMs. Overall, our findings demonstrate that SHIVs bearing primary Envs with bulky aromatic substitutions at Env375 consistently replicate in RMs, recapitulating many features of HIV-1 infection in humans. Such SHIVs are efficiently transmitted by mucosal routes common to HIV-1 infection and can be used to test vaccine efficacy in preclinical monkey trials. Importance SHIV infection of Indian rhesus macaques is an important animal model for studying HIV-1 transmission, prevention, immunopathogenesis and cure. Such research is timely, given recent progress with active and passive immunization and novel approaches to HIV-1 cure. Given the multifaceted roles of HIV-1 Env in cell tropism and virus entry, and as a target for neutralizing and non-neutralizing antibodies, Envs selected for SHIV construction are of paramount importance. Until recently, it has been impossible to strategically design SHIVs bearing clinically relevant Envs that replicate consistently in monkeys. This changed with the discovery that bulky aromatic substitutions at residue Env375 confer enhanced affinity to rhesus CD4. Here, we show that 10 new SHIVs bearing primary HIV-1 Envs with residue 375 substitutions replicated efficiently in RMs and could be transmitted efficiently across rectal, vaginal, penile and oral mucosa. These findings suggest an expanded role for SHIVs as a model of HIV-1 infection.

Detection of the HIV-1 accessory proteins Nef and Vpu by flow cytometry represents a new tool to study their functional interplay within a single infected CD4+ T cell

“…The IMCs encoding for HIV-1 reference strains AD8, JR-FL, JR-CSF, NL4-3, YU-2 were described elsewhere (141)(142)(143)(144)(145)(146). HIV-1 group O (RBF206), SIVcpz (TAN2) and chimeric SIVmac/HIV-1 IMC constructs (SHIVAD8-EO and SHIV.AE.40100) were generated as previously published (147)(148)(149)(150). CH058 IMCs defective for Vpu and/or Nef expression were previously described (58).…”

Potent anti-viral activity of a trispecific HIV neutralizing antibody in SHIV-infected monkeys

“…In brief, animals were inoculated intrarectally with one milliliter of a 1:8 dilution of challenge stock. This corresponds to an animal infectious dose of approximately 5 based on the reported AID50 titer which was 1 milliliter of 1:120 dilution of the challenge stock (Li et al, 2021). The infection was confirmed by measuring plasma viremia weekly and allowed to progress for 6 weeks.…”

Advancing HIV Broadly Neutralizing Antibodies: From Discovery to the Clinic

“…The result is a chimeric virus with most SIV proteins intact, but carrying Env from a particular HIV isolate. An additional mutation has been added to several new SHIV strains to improve binding of the Env to the macaque CD4 receptor ( 64 ) and further improvements continue to be made ( 65 , 66 ). The disease course for SIV and SHIV are similar and somewhat variable depending upon the strain, but overall pathogenesis is measured in months to a few years, which is much more rapid than that of HIV in humans ( 65 , 67 , 68 ).…”

“…An additional mutation has been added to several new SHIV strains to improve binding of the Env to the macaque CD4 receptor ( 64 ) and further improvements continue to be made ( 65 , 66 ). The disease course for SIV and SHIV are similar and somewhat variable depending upon the strain, but overall pathogenesis is measured in months to a few years, which is much more rapid than that of HIV in humans ( 65 , 67 , 68 ). Nevertheless, NHP models using SHIV infection have contributed substantially to the advancement of HIV bNAb use in both adult ( 69 , 70 ) and pediatric settings ( 71 ).…”