Mechanisms by Which Interleukin-12 Corrects Defective NK Cell Anticryptococcal Activity in HIV-Infected Patients.

Stephen K Kyei,Anutosh Ganguly,Richard F Xiang,M John Gill,Christopher H Mody,Martina Timm-Mccann,Pina Colarusso,Shaunna M Huston,Henry Ogbomo,Shushun Li,Stuart M Levitz,Françoise Dromer

doi:10.1128/mbio.00878-16

Abstract

ABSTRACTCryptococcus neoformans is a pathogenic yeast and a leading cause of life-threatening meningitis in AIDS patients. Natural killer (NK) cells are important immune effector cells that directly recognize and kill C. neoformans via a perforin-dependent cytotoxic mechanism. We previously showed that NK cells from HIV-infected patients have aberrant anticryptococcal killing and that interleukin-12 (IL-12) restores the activity at least partially through restoration of NKp30. However, the mechanisms causing this defect or how IL-12 restores the function was unknown. By examining the sequential steps in NK cell killing of Cryptococcus, we found that NK cells from HIV-infected patients had defective binding of NK cells to C. neoformans. Moreover, those NK cells that bound to C. neoformans failed to polarize perforin-containing granules to the microbial synapse compared to healthy controls, suggesting that binding was insufficient to restore a defect in perforin polarization. We also identified lower expression of intracellular perforin and defective perforin release from NK cells of HIV-infected patients in response to C. neoformans. Importantly, treatment of NK cells from HIV-infected patients with IL-12 reversed the multiple defects in binding, granule polarization, perforin content, and perforin release and restored anticryptococcal activity. Thus, there are multiple defects in the cytolytic machinery of NK cells from HIV-infected patients, which cumulatively result in defective NK cell anticryptococcal activity, and each of these defects can be reversed with IL-12.

Highlights

Cryptococcus neoformans is a pathogenic yeast and a leading cause of life-threatening meningitis in AIDS patients
It had previously been shown that Natural killer (NK) cells from antiretroviral therapy (ART)-naive HIV-infected patients had defective anticryptococcal activity [33]
We were interested in determining whether the impaired anticryptococcal activity was similar in HIV-infected patients who were receiving ART and whether IL-12 restored the activity in both groups of patients

Summary

Introduction

Cryptococcus neoformans is a pathogenic yeast and a leading cause of life-threatening meningitis in AIDS patients. Treatment of NK cells from HIV-infected patients with IL-12 reversed the multiple defects in binding, granule polarization, perforin content, and perforin release and restored anticryptococcal activity. We demonstrated that NK cells from HIV-infected patients failed to kill Cryptococcus due to defects in perforin expression, granule polarization, and release of perforin. IL-12 restored recognition of C. neoformans through binding of the NK-activating receptor NKp30 These observations identify important mechanisms used by NK cells to kill microbes and determine that defects in NK cells from HIV-infected patients are reversible. The major cytolytic granule proteins include perforin and granulysin (membrane-disrupting proteins) and granzymes (serine proteases) [21] It is not clear whether these sequential processes are involved in NK cell-mediated microbial killing

Methods

Results

Conclusion