HIV-2 infection is characterized by a low pathogenicity and a low virus production. We tested the hypothesis of a limited distribution of the HIV-2 reservoir among central-memory CD4 T cells (TCM), similarly to models of HIV-1 functional cure or of non pathogenic SIV infection.
14 ARV-naïve patients with non-progressive infection included in the ANRS CO5 HIV-2 Cohort were assessed; their median CD4 cells/mm3 was 966 [IQR: 820-1216]. Subpopulations were sorted into CD3-CD4+ monocytes, CD25+CD69+HLADR+ activated, CD25-CD69-HLADR- resting CD4+ T cells and among those into naïve (TN), TCM, transitional-memory (TTM) and effector-memory (TEM) cells. Cell-associated HIV-2-DNA was isolated from sorted subsets with QIAamp DNA Mini or Micro kit® (Qiagen) according to cell numbers. HIV-2 DNA was quantified using a real-time PCR assay with a limit of detection (LOD) 95% of 3 c/PCR and a limit of quantification (LOQ) of 6 c/PCR. HIV-2 reactivation assays were performed by CD8- T cells culture with anti-CD3+CD28+IL-2+IL-7 for 30 days.
Plasma viral load (pVL) was <40 c/mL in 12 patients, among them 4 had a positive ultra-sensitive pVL above 1 c/mL (IQR=1-12). Median total HIV-2 DNA in PBMC was above the LOQ in 13 patients with a median of 1.94 log10 c/106 PBMC (IQR=1.53-2.13). After sorting, HIV-2 DNA was undetectable among monocytes, and above the LOQ only in TTM from 4 patients (median=2.25 [IQR: 1.99-2.94] log10 c/106 cells) and in TCM from 1 patient (1.75 log10 c/106 cells). HIV-2 DNA levels were above the LOD in 3, 12, 9 and 10 patients in TN, TCM, TTM and TEM, respectively. When integrating subsets proportions, the median contribution of TN, TCM, TTM and TEM to the HIV-2 reservoirs was 0%, 33%, 46% and 8%, respectively. The HIV-2 DNA levels in TTM were positively correlated to those in PBMC (p=0.008; r=0.67). After CD8- T cells reactivation, HIV-2 RNA was detected in 3 of the 11 tested samples with the highest HIV-2 DNA values that were quantified in TTM (n=2) or TCM (n=1).
Overall, these HIV-2-infected patients had low circulating HIV-2 reservoirs that were quantifiable in only 5 of the 14 patients tested, mainly distributed in TTM and reactivable in vitro in only 3 of these 5 patients. These results confirm the hypothesis of a limited reservoir in TCM, thus supporting the concept of the relative protection of central-memory T cells as an attribute of low pathogenicity models of HIV/SIV infection.