Different mutational pathways to CXCR4 coreceptor switch of CCR5-using simian-human immunodeficiency virus.

We report here a second case of coreceptor switch in R5 simian-human immunodeficiency virus SF162P3N (SHIV(SF162P3N))-infected macaque CA28, supporting the use of this experimental system to examine factors that drive the change in coreceptor preference in vivo. Virus recovered from CA28 plasma (SHIV(CA28NP)) used both CCR5 and CXCR4 for entry, but the virus recovered from lymph node (SHIV(CA28NL)) used CXCR4 almost exclusively. Sequence and functional analyses showed that mutations in the V3 loop that conferred CXCR4 usage in macaque CA28 differed from those described in the previously reported case, demonstrating divergent mutational pathways for change in the coreceptor preference of the R5 SHIV(SF162P3N) isolate in vivo.