Generation and Evaluation of Clade C Simian-Human Immunodeficiency Virus Challenge Stocks

Abstract

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, highdose 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. IMPORTANCEWe 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.

Envelope residue 375 substitutions in simian–human immunodeficiency viruses enhance CD4 binding and replication in rhesus macaques

“…1, we have created seven consecutive SHIVs from primary or T/F subtype A, B, C, and D HIV-1 viruses that infect and replicate efficiently and persistently in RMs, in some cases leading to AIDS pathology and death. This finding contrasts with four recent reports (35)(36)(37)(38) that used a conventional KB9 SHIV design strategy (20), where the vast majority of 91 SHIVs constructed from primary HIV-1 Envs failed to replicate efficiently or persistently in vivo. Not only is the success rate of the strategy described in the present report far higher, but it has the advantage of allowing for strategic, prospective targeting of desirable HIV-1 Envs for SHIV construction and analysis, which was highlighted in the present study by SHIVs containing T/F Envs corresponding to HIV-1 CH505 (53,55,75), CH848, and BG505 (54,(57)(58)(59)(60), all of which evolved in their human hosts to elicit bNAbs.…”

“…They, along with other authors (35)(36)(37)(38), concluded that a paramount objective continues to be the development of pathogenic SHIVs that encode env sequences from circulating T/F HIV-1 variants and establish persistent infection without passage or adaptation in macaques. The present report goes a long way toward reaching this goal.…”

“…By necessity, then, SHIVs developed thus far contain HIV-1 Envs derived from one of four sources: (i) laboratory-adapted CXCR4-tropic HIV-1 strains (28); (ii) viruses passaged in vitro so as to acquire Env adaptations necessary for efficient infection of rhCD4 T cells, but at the cost of reduced conformational masking and protection from antibody neutralization (29)(30)(31); (iii) in vivo passaged and adapted virus swarms or clones (14,15,(17)(18)(19)(20)(21)(32)(33)(34); or (iv) random screens of primary HIV-1 strains for rare viruses that encode Envs that fortuitously bind rhCD4 and allow for rhesus cell entry and replication (35)(36)(37)(38).…”

“…SHIV-HXBc2 was further modified by substitution of the env gene from the dual CCR5/CXCR4 tropic HIV-1 89.6 strain, followed by additional passages in RMs, resulting in a highly pathogenic CXCR4 tropic phenotype (14,15,20). Henceforth, a molecular clone (SHIV-KB9) of this strain served as a preferred backbone for SHIV constructions, including four recent reports (35)(36)(37)(38). Other SHIV constructions have been similarly complicated (9,18,21,29,30,32,33).…”

Protection against a mixed SHIV challenge by a broadly neutralizing antibody cocktail

“…with 500 TCID 50 of SHIV-SF162P3 + 500 TCID 50 of SHIV-325C. Generation of these SHIV stocks has been previously described (21, 22, 32). …”