Characterising genetic variants in the KLRK1 gene associated with severe dengue and their impact on the function of Natural Killer cells

Abstract

The global burden of dengue fever is increasing yearly due to climate change, global
travel and urbaniza8on, with over six million cases and six thousand deaths reported in 2023.
Severe disease resultsin dengue haemorrhagic fever (DHF) and may progress to dengue shock
syndrome (DSS) characterized by plasma leakage and organ failure, with a mortality rate of up
to 20%.
Natural Killer (NK) cells represent a first line of defence, directly aiding in viral
clearance by killing virus-infected cells. A major pathway through which NK cells recognise
their target is through the NKG2D receptor, which interacts with the MIC-B stress ligand. This
triggers the mobilisa8on and release of cytotoxic granules at the immunological synapse,
resul8ng in target cell death.
A 2011 genome-wide associa8on study (GWAS) iden8fied MIC-B as a suscep8bility
locus for DSS, and more recently, two single nucleo8de variants (SNVs) within the
3’untranslated region (UTR) of NK cell lec8n-like receptor K1 (KLRK1), encoding NKG2D, were
found to be significantly associated with severe disease within a pa8ent cohort. To address
the impact of KLRK1 variants on NK cell func8on, CRISPR-Cas9 edited NK-92 cells were used
as a model, with homo and heterozygous genotypes containing SNVs and/or dele8ons in the
region of interest. These cells displayed significantly and dras8cally reduced levels of surface
NKG2D. We demonstrate that down-regula8on of the NKG2D receptor has severe
consequences on cell viability, and addi8onally reduces NK cell killing capacity of K562 target
cells, including those possessing a DENV replicon, by a similar magnitude to what is observed
when fully blocking the NKG2D receptor in wild-type (WT) NK-92 cells.
These results suggest that the given SNVs associated with severe dengue outcomes
may lead to impaired NK cell responses by limi8ng an individual’s base-line levels of surface
NKG2D, exacerba8ng immune dysfunc8on and ul8mately contribu8ng to DSS.

Date of Award	1 Oct 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Laura Rivino (Supervisor) & Borko Amulic (Supervisor)