Human immunodeficiency virus type 2 (HIV-2) is generally considered capable of using a broad range of coreceptors. Since HIV-2 variants from individuals with nonprogressive infection were not studied previously, the possibility that broad coreceptor usage is a property of variants associated with progressive infection could not be excluded. To test this, we determined the coreceptor usage of 43 HIV-2 variants isolated from six long-term-infected individuals with undetectable plasma viremia. Using GHOST indicator cells, we showed for the first time that the only coreceptors efficiently used by low-pathogenic HIV-2 variants are CCR5, GPR15 (BOB), and CXCR6 (BONZO). Surprisingly, control HIV-2 variants (n ‫؍‬ 45) isolated from seven viremic individuals also mainly used these three coreceptors, whereas use of CCR1, CCR2b, or CCR3 was rare. Nearly a quarter of all HIV-2 variants tested could infect the parental GHOST cells, which could be partially explained by CXCR4 usage. Use of CXCR4 was observed only for HIV-2 variants from viremic individuals. Thirty-eight variants from aviremic and viremic HIV-2-infected individuals were additionally tested in U87 cells. All except one were capable of infecting the parental U87 cells, often with high efficiency. When virus production in parental cells was regarded as background in the coreceptor-transduced cell lines, the results in U87 cells were largely in agreement with the findings in GHOST cells. HIV-2 isolates from aviremic individuals commonly use as coreceptors CCR5, GPR15, and CXCR6, as well as an unidentified receptor expressed by U87 cells. Broad coreceptor usage, therefore, does not appear to be associated with pathogenicity of HIV-2.

Recent studies indicate that the time required for virus‐infected cells to become vulnerable for the activity of CTL is of significance for the capacity of CTL to control ongoing viral reproduction. To investigate whether this applies to the effectiveness of HIV‐1‐specific CTL, we measured virus production in cultures containing CD4+ T cells inoculated with HIV at low multiplicity of infection, and CTL directed against an early protein, Rev, or a late protein, RT. The Rev‐specific CTL prevented at least 2 log10 more HIV‐1 production, in 10 days, than similar numbers of RT‐specific CTL. To study how CTL effectiveness depends on variations in the potency of effector functions and kinetics of HIV protein expression, we developed a mathematical model describing CTL‐target cell interactions during successive infection cycles. The results show that substantially higher CTL‐mediated target cell elimination rates are required to achieve control as there is less time for CTL to act before infected cells release progeny virions. Furthermore, in vitro experiments with HIV recombinant viruses showed that the RT‐specific CTL were at least as effective as the Rev‐specific CTL, but only if the RT epitope was expressed as part of the early protein Nef. Together these results indicate that CTL control ongoing HIV reproduction more effectively if they are able to recognize infected cells earlier during individual viral replication cycles. This provides rationale for immunization strategies that aim at inducing, boosting or skewing CTL responses to early regulatory proteins in AIDS vaccine development.

NCT02401828.