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Simian-human immunodeficiency virus (SHIV) infection of rhesus monkeys is an important preclinical model for human immunodeficiency virus type 1 (HIV-1) vaccines, therapeutics, and cure strategies. SHIVs have been optimized by incorporating HIV-1 Env residue 375 mutations that mimic the bulky or hydrophobic residues typically found in simian immunodeficiency virus (SIV) Env to improve rhesus CD4 binding. We applied this strategy to three SHIV challenge stocks (SHIV-SF162p3, SHIV-AE16, and SHIV-325c) and observed three distinct outcomes. We constructed six Env375 variants (M, H, W, Y, F, and S) for each SHIV, and we performed a pool competition study in rhesus monkeys to define the optimal variant for each SHIV prior to generating large-scale challenge stocks. We identified SHIV-SF162p3S/wild type, SHIV-AE16W, and SHIV-325cH as the optimal variants. SHIV-SF162p3S could not be improved, as it already contained the optimal Env375 residue. SHIV-AE16W exhibited a similar replicative capacity to the parental SHIV-AE16 stock. In contrast, SHIV-325cH demonstrated a 2.6-log higher peak and 1.6-log higher setpoint viral loads than the parental SHIV-325c stock. These data demonstrate the diversity of potential outcomes following Env375 modification in SHIVs. Moreover, the clade C SHIV-325cH challenge stock may prove useful for evaluating prophylactic or therapeutic interventions against clade C HIV-1. IMPORTANCE We sought to enhance the infectivity of three SHIV stocks by optimization of a key residue in human immunodeficiency virus type 1 (HIV-1) Env (Env375). We developed the following three new simian-human immunodeficiency virus (SHIV) stocks: SHIV-SF162p3S/wild type, SHIV-AE16W, and SHIV-325cH. SHIV-SF162p3S could not be optimized, SHIV-AE16W proved comparable to the parental virus, and SHIV-325cH demonstrated markedly enhanced replicative capacity compared with the parental virus., (Copyright © 2020 Tartaglia et al.)

Simian-human immunodeficiency virus (SHIV) challenge stocks are critical for preclinical testing of vaccines, antibodies, and other interventions aimed to prevent HIV-1. A major unmet need for the field has been the lack of a SHIV challenge stock expressing circulating recombinant form 01_AE (CRF01_AE) env sequences. We therefore sought to develop mucosally transmissible SHIV challenge stocks containing HIV-1 CRF01_AE env derived from acutely HIV-1 infected individuals from Thailand. SHIV-AE6, SHIV-AE6RM, and SHIV-AE16 contained env sequences that were >99% identical to the original HIV-1 isolate and did not require in vivo passaging. These viruses exhibited CCR5 tropism and displayed a tier 2 neutralization phenotype. These challenge stocks efficiently infected rhesus monkeys by the intrarectal route, replicated to high levels during acute infection, and established chronic viremia in a subset of animals. SHIV-AE16 was titrated for use in single, high dose as well as repetitive, low dose intrarectal challenge studies. These SHIV challenge stocks should facilitate the preclinical evaluation of vaccines, monoclonal antibodies, and other interventions targeted at preventing HIV-1 CRF01_AE infection.

Unlabelled: The development of a panel of mucosally transmissible simian-human immunodeficiency virus (SHIV) challenge stocks from multiple virus clades would facilitate preclinical evaluation of candidate HIV-1 vaccines and therapeutics. The majority of SHIV stocks that have been generated to date have been derived from clade B HIV-1 env sequences from viruses isolated during chronic infection and typically required serial animal-to-animal adaptation for establishing mucosal transmissibility and pathogenicity. To capture essential features of mucosal transmission of clade C viruses, we produced a series of SHIVs with early clade C HIV-1 env sequences from acutely HIV-1-infected individuals from South Africa. SHIV-327c and SHIV-327cRM expressed env sequences that were 99.7 to 100% identical to the original HIV-1 isolate and did not require in vivo passaging for mucosal infectivity. These challenge stocks infected rhesus monkeys efficiently by both intrarectal and intravaginal routes, replicated to high levels during acute infection, and established chronic setpoint viremia in 13 of 17 (76%) infected animals. The SHIV-327cRM challenge stock was also titrated for both single, high-dose intrarectal challenges and repetitive, low-dose intrarectal challenges in rhesus monkeys. These SHIV challenge stocks should facilitate the preclinical evaluation of vaccines and other interventions aimed at preventing clade C HIV-1 infection., Importance: We describe the development of two related clade C SHIV challenge stocks. These challenge stocks should prove useful for preclinical testing of vaccines and other interventions aimed at preventing clade C HIV-1 infection., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Simian-human immunodeficiency viruses (SHIVs) that mirror natural transmitted/founder (T/F) viruses in man are needed for evaluation of HIV-1 vaccine candidates in nonhuman primates. Currently available SHIVs contain HIV-1 env genes from chronically-infected individuals and do not reflect the characteristics of biologically relevant HIV-1 strains that mediate human transmission. We chose to develop clade C SHIVs, as clade C is the major infecting subtype of HIV-1 in the world. We constructed 10 clade C SHIVs expressing Env proteins from T/F viruses. Three of these ten clade C SHIVs (SHIV KB9 C3, SHIV KB9 C4 and SHIV KB9 C5) replicated in naïve rhesus monkeys. These three SHIVs are mucosally transmissible and are neutralized by sCD4 and several HIV-1 broadly neutralizing antibodies. However, like natural T/F viruses, they exhibit low Env reactivity and a Tier 2 neutralization sensitivity. Of note, none of the clade C T/F SHIVs elicited detectable autologous neutralizing antibodies in the infected monkeys, even though antibodies that neutralized a heterologous Tier 1 HIV-1 were generated. Challenge with these three new clade C SHIVs will provide biologically relevant tests for vaccine protection in rhesus macaques., (Copyright © 2014 Elsevier Inc. All rights reserved.)