Long-lasting CCR5 internalization by antibodies in a subset of long-term nonprogressors: a possible protective effect against disease progression

Abstract

Exposure to HIV-1 does not necessarily result in infection and progression toward disease, thus suggesting that the control of viral infection may be achieved. Antibodies to CCR5 have been detected in HIV-exposed but uninfected subjects (ESNs); thus, these antibodies could be involved in HIV protection. To assess whether anti-CCR5 antibodies may also contribute to slow HIV disease progression, we searched for anti-CCR5 antibodies in 497 subjects, including 85 longterm nonprogressors (LTNPs), 70 progressors, 135 HIV ؉ patients treated with highly active antiretroviral therapy (HAART), and 207 seronegative donors. We found anti-CCR5 antibodies in a fraction of the LTNPs (23.5%) but not in the other populations studied (P < .001). These antibodies recognized a conformational epitope within the first extramembrane loop of CCR5, and they induced a stable and long-lasting downregulation of CCR5 on the surface of T lymphocytes, which inhibited HIV entry. In addition, CD4 ؉ lymphocytes from LTNPs having anti-CCR5 antibodies are resistance to R5 strains of HIV-1. Follow-up studies showed that the loss of anti-CCR5 antibodies occurred in some subjects, and this loss was significantly associated with a progression toward disease, whereas subjects who retained anti-CCR5 Abs maintained their LTNP status. Induction of anti-CCR5 Abs could be relevant to vaccine design and therapeutics.

ERK1-Based Pathway as a New Selective Mechanism To Modulate CCR5 with Natural Antibodies

“…Previous works published by our and other groups (15)(16)(17)(18) proved the existence of anti-CCR5 Abs, which induced long-lasting internalization of CCR5 in the sera of a subset of LTNP and HIV-exposed uninfected subjects (12,(18)(19)(20)(21)(22). The mechanisms underlying this unconventional and atypical long-lasting downregulation of CCR5 required further investigation.…”

“…4, and LTNP no. 22, all of which had been characterized previously (12). The pool of serum samples used as negative controls was taken from LTNP negative for anti-CCR5 Abs (CCR5 Ab neg), as previously described (12).…”

“…To obtain a complete downregulation of the receptor, the cells were incubated with CCR5 Ab pos at 37˚C for 48 h (12). CCR5 Ab neg was used as negative control (12). When indicated, the cells were pretreated for 1 h with hypertonic sucrose medium (0.45 M) or filipin (2.5 mg/ml) to inhibit CCR5 internalization, with U0126 (a specific inhibitor of ERK pathway) (5 mg/ml) and with 2.5 mg/ml cycloheximide (CHX) (Sigma-Aldrich) to inhibit protein synthesis.…”

“…As both T cells, R5-SupT1-L23 cells and human CD4 + T lymphocytes, have been used to characterize CCR5 modulation, the activation status of cells has been evaluated by flow cytometry, and the mean fluorescence intensity obtained with anti-CD38 Ab was 54.5 and 34.5 for R5-SupT1-L23 cells and activated CD4 + T lymphocytes, respectively. We used a pool of five LTNP sera, each containing CCR5 Abs as previously described and characterized in a paper by our group (12). Briefly, serum anti-CCR5 Abs recognized the cyclic ECL1 peptide (YAAAQWDFGNTMCQ, aa 89-102), which is not involved in HIV binding.…”

“…Briefly, serum anti-CCR5 Abs recognized the cyclic ECL1 peptide (YAAAQWDFGNTMCQ, aa 89-102), which is not involved in HIV binding. Purified Abs on ECL1 peptide were able to induce long-lasting CCR5 internalization, both in CD4 + T lymphocytes and in CCR5-transfected cell lines, and blocked infection from CCR5-dependent strains of HIV (12). We also used a pool of serum samples from five LTNP not containing anti-CCR5 Abs, as previously described (CCR5 Ab neg) (12).…”