NK cells and monocytes modulate primary HTLV-1 infection

Abstract

We investigated the impact of monocytes, NK cells, and CD8+ T-cells in primary HTLV-1 infection by depleting cell subsets and exposing macaques to either HTLV-1 wild type (HTLV-1WT) or to the HTLV-1p12KO mutant unable to infect replete animals due to a single point mutation in orf-I that inhibits its expression. The orf-I encoded p8/p12 proteins counteract cytotoxic NK and CD8+ T-cells and favor viral DNA persistence in monocytes. Double NK and CD8+ T-cells or CD8 depletion alone accelerated seroconversion in all animals exposed to HTLV-1WT. In contrast, HTLV-1p12KO infectivity was fully restored only when NK cells were also depleted, demonstrating a critical role of NK cells in primary infection. Monocyte/macrophage depletion resulted in accelerated seroconversion in all animals exposed to HTLV-1WT, but antibody titers to the virus were low and not sustained. Seroconversion did not occur in most animals exposed to HTLV-1p12KO. In vitro experiments in human primary monocytes or THP-1 cells comparing HTLV-1WT and HTLV-1p12KO demonstrated that orf-I expression is associated with inhibition of inflammasome activation in primary cells, with increased CD47 “don’t-eat-me signal” surface expression in virus infected cells and decreased monocyte engulfment of infected cells. Collectively, our data demonstrate a critical role for innate NK cells in primary infection and suggest a dual role of monocytes in primary infection. On one hand, orf-I expression increases the chances of viral transmission by sparing infected cells from efferocytosis, and on the other may protect the engulfed infected cells by modulating inflammasome activation. These data also suggest that, once infection is established, the stoichiometry of orf-I expression may contribute to the chronic inflammation observed in HTLV-1 infection by modulating monocyte efferocytosis.

Transient Viral Activation in Human T Cell Leukemia Virus Type 1-Infected Macaques Treated With Pomalidomide

“…(B) Schematic diagram of Pomalidomide treatment and sample collection. Four rhesus macaques previously infected with HTLV-1 ( 31 ) were treated orally with 0.2 mg/kg/day of Pomalidomide on a schedule of 6 days of treatment (black arrows) and 1 day off over a 24 day period. Blood and urine (blue arrows), bone marrow (triangles), and bronchioalveolar lavage (squares), were collected as indicated.…”

“…Four HTLV-1-infected macaques described in a previous study ( 31 ) were treated with Pom. All 4 animals had detectable viral DNA and antibody responses by 8 weeks after exposure to wild type HTLV-1, which were sustained over 21 weeks.…”

“…This cell proliferation is consistent with what we found here for Pom in the macaque model. Moreover, we recently found that CTL and NK cells are critical for the establishment of persistent HTLV-1 infection ( 31 ). Thus, Pom or Len treatment able to activate NK cells combined with the use of monoclonal antibody treatment could potentially also enhance ADCC in ATL patients.…”

“…HTLV-1 production was determined by p19Gag antigen detection by a commercially available ELISA in the culture supernatants (Zeptometrix, Buffalo, NY, United States) according to the manufacturer’s instructions. Viral DNA load was determined for established CD4 + cell cultures as previously described ( 31 ). HTLV-1-infected cells were cultured for 3 days in medium alone, 10 μM of Pom (provided by Bristol Myers Squibb, Summit, NJ, United States), or DMSO as control.…”

“…Four HTLV-1 seropositive and PCR positive rhesus macaques ( 31 ) were administered 0.2 mg/kg/day pomalidomide (provided by Bristol Myers Squibb) orally via gavage on a schedule of 6 days on drug treatment followed by 1 day off for 24 days. Blood, bone marrow and urine samples were collected on days 5, 12, 18, 24, and 47 of the study.…”