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Adaptation of subtype a human immunodeficiency virus type 1 envelope to pig-tailed macaque cells
1Program in Molecular and Cellular Biology, University of Washington, Seattle, Washington, USA.
Abstract:
The relevance of simian/human immunodeficiency virus (SHIV) infection of macaques to HIV-1 infection in humans depends on how closely SHIVs mimic HIV-1 transmission, pathogenesis, and diversity. Circulating HIV-1 strains are predominantly subtypes C and A and overwhelmingly require CCR5 for entry, yet most SHIVs incorporate CXCR4-using subtype B envelopes (Envs). While pathogenic subtype C-based SHIVs have been constructed, the subtype A-based SHIVs (SHIV-As) constructed to date have been unable to replicate in macaque cells. To understand the barriers to SHIV-A replication in macaque cells, HIVA(Q23)/SIV(vif) was constructed by engineering a CCR5-tropic subtype A provirus to express SIV vif, which counters the macaque APOBEC3G restriction. HIVA(Q23)/SIV(vif) replicated poorly in pig-tailed macaque (Ptm) lymphocytes, but viruses were adapted to Ptm lymphocytes. Two independent mutations in gp120, G312V (V3 loop) and A204E (C2 region), were identified that increased peak virus levels by >100-fold. Introduction of G312V and A204E to multiple subtype A Envs and substitution of G312 and A204 with other residues increased entry into Ptm cells by 10- to 100-fold. G312V and A204E Env variants continued to require CCR5 for entry but were up to 50- and 200-fold more sensitive to neutralization by IgG1b12 and soluble CD4 and had a 5- to 50-fold increase in their ability to utilize Ptm CD4 compared to their wild-type counterparts. These findings identify the inefficient use of Ptm CD4 as an unappreciated restriction to subtype A HIV-1 replication in Ptm cells and reveal amino acid changes to gp120 that can overcome this barrier.
Insights
Researchers engineered a simian/human immunodeficiency virus (SHIV) subtype A to replicate in macaque cells by identifying key mutations in the gp120 protein. These findings help overcome barriers in developing better SHIV models for HIV-1 research.
Area of Science:
- Virology
- Immunodeficiency Viruses
- Primate Models
Background:
- Simian/human immunodeficiency virus (SHIV) models are crucial for studying human immunodeficiency virus type 1 (HIV-1) infection.
- Most existing SHIVs use CXCR4-using subtype B envelopes, not the predominant CCR5-using subtypes A and C found in circulating HIV-1 strains.
- Subtype A-based SHIVs (SHIV-As) have historically failed to replicate in macaque cells, limiting their utility.
Purpose of the Study:
- To investigate the barriers preventing subtype A HIV-1 replication in macaque cells.
- To engineer a functional SHIV-A model that accurately mimics HIV-1 transmission and pathogenesis.
- To identify specific viral adaptations necessary for replication in macaque hosts.
Main Methods:
- Constructed a novel SHIV-A variant, HIVA(Q23)/SIV(vif), by incorporating SIV vif to counteract macaque APOBEC3G restriction.
- Adapted the virus to replicate in pig-tailed macaque (Ptm) lymphocytes.
- Utilized next-generation sequencing and functional assays to identify key mutations in the gp120 envelope protein.
Main Results:
- Two specific mutations in gp120, G312V (V3 loop) and A204E (C2 region), significantly enhanced viral replication (>100-fold increase).
- These mutations increased viral entry into Ptm cells (10- to 100-fold) and improved utilization of Ptm CD4 (5- to 50-fold).
- The adapted viruses maintained CCR5 tropism but showed altered sensitivity to neutralization by antibodies and soluble CD4.
Conclusions:
- Inefficient utilization of pig-tailed macaque CD4 is a major restriction to subtype A HIV-1 replication in these cells.
- Specific amino acid substitutions in gp120 can overcome this restriction, enabling the development of more relevant SHIV-A models.
- These advancements are critical for creating improved SHIV models for studying HIV-1 pathogenesis and evaluating potential therapies.
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