Poster Presentation Melbourne Immunotherapy Network Winter Symposium 2021

Pomalidomide as an immunomodulatory agent to enhance NK cell anti-HIV immunity (#119)

Rachel D Pascoe 1 , Judy J Chang 2 , Celine Gubser 2 , Alexander Barrow 1 , Wen Shi Lee 1 , James McMahon 3 , Jenny Anderson 2 , Sharon R Lewin 2 3 4 , Thomas A Rasmussen 2
  1. Department of Microbiology and Immunology, The University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
  2. Department of Infectious Diseases, The University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
  3. Department of Infectious Diseases, Alfred Hospital and Monash University, Melbourne, Victoria, Australia
  4. Victorian Infectious Diseases Service, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia

Chronic HIV infection is characterised by dysfunction of key immune effector cells including CD8+ T cells and NK cells that persist despite successful viral suppression by antiretroviral therapy (ART). Here, we investigated pomalidomide, an immunomodulatory drug licensed for the treatment of multiple myeloma and Kaposi’s Sarcoma, to augment anti-HIV immune responses through enhancing NK cell cytotoxicity. 

Pomalidomide was assessed at a therapeutically relevant concentration ex vivo in PBMC from uninfected donors and ART-suppressed people with HIV (PWH). Direct NK cytotoxicity was assessed by co-culturing pomalidomide-treated PBMC with the MHC-I devoid K562 cell line. We next established a novel assay where pomalidomide pre-treated NK cells were co-cultured with in vitro HIV-infected autologous CD4+ T cells carrying an EGFP-reporter. The effect of pomalidomide on direct NK cell killing of productively HIV-infected CD4+ T cells was quantified from the reduction in GFP+HIV-infected cells. Antibody dependent cellular cytotoxicity (ADCC) was assessed using the 8E5 cell line, with 50% of cells containing a single defective provirus and expressing p24 and envelope. Pomalidomide pre-treated NK cells and 8E5 were cultured with anti-HIV immunoglobulin or an isotype control, with HIV-specific ADCC measured as a relative reduction in p24+ 8E5 cells.

Treatment with pomalidomide in both HIV-negative donors and PWH significantly enhanced NK killing of K562 cells, in both HIV-negative donors and PWH, with 34.7% (95% CI 23.8-51.05; P=0.0002) greater cytotoxicity in PWH, relative to DMSO. Concurrently, CD56brightCD16+ NK cell subset was expanded in the presence of pomalidomide. Pomalidomide treatment significantly enhanced direct NK-mediated killing of in vitro HIV-infected autologous CD4+ T cells. In contrast, pomalidomide did not enhance anti-HIV ADCC.

These results show that pomalidomide can enhance direct NK cell cytotoxicity and augment killing of HIV-infected cells, and may be employed in therapeutic strategies to eliminate or control the persisting HIV reservoir.