Pharmacological Targeting of Sphingosine Kinases Impedes HIV-1 Infection of CD4 T Cells through SAMHD1 Modulation

Sphingosine-1-phosphate (S1P) is a sphingolipid modulator of a myriad of cellular processes, and therapeutic targeting of S1P signaling is utilized clinically to treat multiple sclerosis. We have previously shown that functional antagonism of S1P receptors reduces cell-free, cell-to-cell, and latent HIV-1 infection in primary CD4 T cells. In this work, we examined whether targeting sphingosine kinase 1 or 2 (SPHK1/2) to inhibit S1P production would prevent infection using multiple HIV-1 primary isolates and infectious molecular clones. SPHK inhibition reduced HIV transmission between primary CD4 T cells in both cell-to-cell transmission and pretreatment coculture models. Mechanistically, pharmacological inhibition of SPHK reduced susceptibility to infection primarily by downregulating phosphorylated SAMHD1 (pSAMHD1), enhancing the activity of this innate HIV-1 restriction factor. Furthermore, genetic disruption of either SPHK1 or SPHK2 by CRISPR/Cas9 reduced phosphorylation of SAMHD1, demonstrating the role of these kinases in modulation of SAMHD1 activity. The effect of SPHK inhibition on limiting HIV-1 infection in CD4 T cells was observed irrespective of the biological sex or age of the donor, with neither variable significantly influencing the effectiveness of SPHK inhibition. Our results demonstrate that targeting SPHK inhibits transmission of HIV-1 via modulation of SAMHD1 phosphorylation to decrease permissiveness to infection in CD4 T cells and suggests that therapeutic targeting of this pathway early in infection enables development of strategies to prevent establishment of infection and hinder cell-to-cell transmission of HIV-1. IMPORTANCE HIV-1 infection, once established, requires lifelong treatment due to the ability of the virus to maintain latent infection in its host and become reactivated during an interruption in antiretroviral treatment (ART). Although preventing transmission and acquisition of HIV is an important goal, no ART thus far have exploited harnessing a component of the host immune system to combat transmission of the virus. We have previously shown that inhibition of sphingosine-1-phosphate (S1P) receptors, a component of S1P signaling, reduces HIV-1 infection in human CD4 T cells. We therefore investigated inhibition of sphingosine kinases, another element of this signaling system, in this work. We found that inhibition of sphingosine kinases 1 and 2 (SPHK1/2) could reduce HIV-1 transmission, both among CD4 T cells and between macrophages and CD4 T cells. Our research therefore suggests that therapeutic targeting of SPHK or S1P receptors may aid in the development of strategies to prevent establishment and transmission of HIV-1 infection among immune cells.