Different Tempo and Anatomic Location of Dual-Tropic and X4 Virus Emergence in a Model of R5 Simian-Human Immunodeficiency Virus Infection

Abstract

We previously reported coreceptor switch in rhesus macaques inoculated intravenously with R5 simianhuman immunodeficiency virus SF162P3N (SHIV SF162P3N ). Whether R5-to-X4 virus evolution occurs in mucosally infected animals and in which anatomic site the switch occurs, however, were not addressed. We herein report a change in coreceptor preference in macaques infected intrarectally with SHIV SF162P3N . The switch occurred in infected animals with high levels of virus replication and undetectable antiviral antibody response and required sequence changes in the V3 loop of the gp120 envelope protein. X4 virus emergence was associated with an accelerated drop in peripheral CD4؉ T-cell count but followed rather than preceded the onset of CD4 ؉ T-cell loss. The conditions, genotypic requirements, and patterns of coreceptor switch in intrarectally infected animals were thus remarkably consistent with those found in macaques infected intravenously. They also overlapped with those reported for humans, suggestive of a common mechanism for coreceptor switch in the two hosts. Furthermore, two independent R5-to-X4 evolutionary pathways were identified in one infected animal, giving rise to dual-tropic and X4 viruses which differed in switch kinetics and tissue localization. The dual-tropic switch event predominated early, and the virus established infection in multiple tissues sites. In contrast, the switch to X4 virus occurred later, initiating and expanding mainly in peripheral lymph nodes. These findings help define R5 SHIV SF162P3N infection of rhesus macaques as a model to study the mechanistic basis, dynamics, and sites of HIV-1 coreceptor switch.

Fitness Disadvantage of Transitional Intermediates Contributes to Dynamic Change in the Infecting-Virus Population during Coreceptor Switch in R5 Simian/Human Immunodeficiency Virus-Infected Macaques

“…The generation of DG08 Env expression plasmids and luciferase-reporter viruses has been described previously (43). For expression of CA28 envelope glycoproteins, fulllength gp160 coding sequence was amplified from RT products with primers SH43 (5Ј-AAGACAGAATTCATGAGAGTGAAGGGGATCAGGAAG-3Ј) and SH44 (5Ј-AGAGAGGGATCCTTATAGCAAAGCCCTTTCAAAGCCC T-3Ј) and subcloned into the pCAGGS vector.…”

“…X4 variants with HR insertions in the V3 loop were also found in the i.r.-infected macaque DG08 near end-stage disease (43). In addition to this evolutionary pathway, however, phylogenetically distinct variants that harbored four amino acid deletions in the C-terminal stem region of the V3 loop (ATGD; designated ⌬22-25) and that preferred CCR5 over CXCR4 were also found in DG08 (Table 1).…”

“…However, while the genotypic and phenotypic determinants for expansion or switch to CXCR4 use are well characterized, the mechanistic basis and obstacles for change in coreceptor preference in vivo are yet to be fully elucidated. Among several factors that have been proposed as playing important roles, fitness disadvantage of the transitional intermediates compared with the initial R5 viruses has been suggested to constitute one of the blockades to coreceptor switching (34, 42), explaining the late appearance of X4 viruses.We recently developed an R5 simian/human immunodeficiency virus (SHIV) SF162P3N infection of a rhesus macaque model to study coreceptor switch in vivo (27,28,43). The macaques infected intravenously (i.v.)…”

“…We recently developed an R5 simian/human immunodeficiency virus (SHIV) SF162P3N infection of a rhesus macaque model to study coreceptor switch in vivo (27,28,43). The macaques infected intravenously (i.v.)…”

Emergence of CD4 Independence Envelopes and Astrocyte Infection in R5 Simian-Human Immunodeficiency Virus Model of Encephalitis

“…CSF and plasma samples were available from five (ET94, DN57, DG08, DE86, and DG07) of the seven subtype B R5 SHIVE macaques at terminal disease, allowing us to examine whether there was compartmentalization of viral genomes. Sequence analysis of CSF env variants showed the absence of signature CXCR4-determining V3 sequences in ET94, DG08, and DE86 (data not shown), even though these animals had X4 viruses in the blood and in at least one peripheral lymph node (LN) at the time of necropsy (75,76). Phylogenetic analysis of the env V3-to-V5 region (660 bp) showed clustering of Envs from the CSF in a lineage that is separated from the plasma in macaques DG08 and DE86.…”