Longitudinal Analysis of Dengue Virus-Specific Memory T Cell Responses and Their Association With Clinical Outcome in Subsequent DENV Infection.

Luis Alberto Sanchez-Vargas,Kathryn B Anderson,Alan L Rothman,Anuja Mathew,Jeffrey R Currier,Timothy P Endy,Heather Friberg,Anon Srikiatkhachorn,Stefan Fernandez

doi:10.3389/fimmu.2021.710300

Abstract

Memory T cells resulting from primary dengue virus (DENV) infection are hypothesized to influence the clinical outcome of subsequent DENV infection. However, the few studies involving prospectively collected blood samples have found weak and inconsistent associations with outcome and variable temporal trends in DENV-specific memory T cell responses between subjects. This study used both ex-vivo and cultured ELISPOT assays to further evaluate the associations between DENV serotype-cross-reactive memory T cells and severity of secondary infection. Using ex-vivo ELISPOT assays, frequencies of memory T cells secreting IFN-γ in response to DENV structural and non-structural peptide pools were low in PBMC from multiple time points prior to symptomatic secondary DENV infection and showed a variable response to infection. There were no differences in responses between subjects who were not hospitalized (NH, n=6) and those who were hospitalized with dengue hemorrhagic fever (hDHF, n=4). In contrast, responses in cultured ELISPOT assays were more reliably detectable prior to secondary infection and showed more consistent increases after infection. Responses in cultured ELISPOT assays were higher in individuals with hDHF (n=8) compared to NH (n=9) individuals before the secondary infection, with no difference between these groups after infection. These data demonstrate an association of pre-existing DENV-specific memory responses with the severity of illness in subsequent DENV infection, and suggest that frequencies of DENV-reactive T cells measured after short-term culture may be of particular importance for assessing the risk for more severe dengue disease.

Highlights

Dengue is one of the most important arboviral disease of humans, with half of the population at risk of infection [1]
Frequencies of memory T cells secreting IFN-g in response to dengue virus (DENV) peptide pools were low in most subjects before secondary DENV2 infection with no significant increases after infection in nonhospitalized DF (NH) or hospitalized DHF (hDHF) subjects (Figures 1A, B)
PBMC from most subjects had a higher frequency of memory T cells secreting IFN-g compared to TNF-a (Figure S5). These results suggest that cultured ELISPOT was more sensitive to detect DENV-specific memory T cells compared to ex-vivo ELISPOT and different T cell populations are detected between the assays

Summary

Introduction

Dengue is one of the most important arboviral disease of humans, with half of the population at risk of infection [1]. Over 90% of severe cases occur during a secondary infection and it is well recognized that prior immunity constitutes one of the strongest risk factors for severe disease. Memory T cells from a primary DENV infection can be reactivated during secondary infection with peptides different from the prior DENV serotype and induced to express an altered profile of effector functions [7, 8]. 1-3 years post-infection, T cell responses to DENV have been low and in many cases undetectable. We found low and fluctuating T cell responses in PBMC from children prior to infection in response to overlapping peptide pools that encompassed both structural and non-structural proteins using an ex-vivo ELISPOT assay [15]

Methods

Results

Conclusion