Dengue virus infection elicits highly polarized CX3CR1⁺cytotoxic CD4⁺T cells associated with protective immunity

Abstract

Dengue virus (DENV) is a rapidly spreading pathogen with unusual pathogenesis, and correlates of protection from severe dengue disease and vaccine efficacy have not yet been established. Although DENV-specific CD8 + T-cell responses have been extensively studied, the breadth and specificity of CD4 + T-cell responses remains to be defined. Here we define HLA-restricted CD4 + T-cell epitopes resulting from natural infection with dengue virus in a hyperepidemic setting. Ex vivo flow-cytometric analysis of DENVspecific CD4+ T cells revealed that the virus-specific cells were highly polarized, with a strong bias toward a CX3CR1 A ll four of the dengue virus serotypes (DENV 1-4) have spread rapidly within countries and across regions in the past few decades, resulting in an increased frequency of epidemics and severe dengue disease. Multiple serotypes circulate simultaneously in many tropical countries, and recent outbreaks have been reported in Europe and the continental United States (1, 2). These circumstances make dengue the most prevalent and rapidly spreading mosquito-borne viral disease in humans (3). Recent reports estimate that 390 million infections occur each year, with ∼25% of cases resulting in symptomatic disease (2).All four dengue serotypes can cause a spectrum of disease, ranging from self-limiting dengue fever to potentially lethal severe dengue disease, such as states of dengue hemorrhagic fever and Dengue shock syndrome, which are associated with the plasma leakage syndromes leading to visceral organ injury (4). It is not yet fully understood why only a subset of people infected with DENV progresses to severe disease. One risk factor for severe disease is the acquisition of DENV-reactive Abs before secondary infection with a different serotype (heterologous infection). These Abs can either be acquired from a previous infection with a different serotype or, in the case of infants, acquired from an immune mother (5, 6). It has been shown that subneutralizing levels of DENV-specific Abs exacerbate disease in a phenomenon termed Ab-dependent enhancement of infection (7,8). In brief, dengue-specific crossreactive Abs produced after an initial DENV infection combine with those produced after a second viral infection to form immune complexes that perpetuate infection by increasing the number of infected cells and, therefore, viral output per cell (6).The observation that only a minority of patients develops severe disease suggests that host genetic factors may play an important role in disease severity. Relatedly, a role for T cells in control of disease has been suggested by several studies that correlate the expression of certain HLA molecules with susceptibility to or protection from DENV disease (9-15). HLA molecules are one of the most polymorphic host factors in humans, with several thousand variants thus far known (16,17). Each HLA variant is present with variable frequency, depending on ethnic lineage and geographic locality. For HLA class I MHC restricted responses, it has been recently shown tha...

Dengue vaccine–induced CD8+ T cell immunity confers protection in the context of enhancing, interfering maternal antibodies

“…Interestingly, although at low level (~0.8%), CD107a expression was also detected in CD4 + T cells. DENV-specific CD4 + CTLs were previously described and shown to lyse target cells (18,21,76) but the low frequency of such cells in the current study suggests a minor role in protection. A large fraction (~19%) of CD8 + T cells in the vaccinated-challenged group also expressed IFN-γ.…”

“…+ subset, was recently demonstrated in mice (17,18,20) and humans (19,21). To test this hypothesis, 3-wko pups born to DENV-naive or PDK53-immunized dams were vaccinated, or not, with PDK53 and subsequently challenged with D2Y98P-PP1 at 6 weeks of age (20 days after vaccination).…”

“…This has led the dengue scientific community to consider the role of T cells in protection against DENV. Recent evidence from mouse and human studies suggests indeed that T cells, particularly the CD8 + subset, may be important mediators of protection (17)(18)(19)(20)(21)(22). Greater appreciation of the importance of T cells is also evident from recent vaccine developments that focus on the assessment of T cell activity in vaccinated individuals and animals (23)(24)(25)(26).…”

Human CD4 + T Cell Responses to an Attenuated Tetravalent Dengue Vaccine Parallel Those Induced by Natural Infection in Magnitude, HLA Restriction, and Antigen Specificity

“…The interplay between low titers, cross-reactive neutralizing antibody titers, and cell-mediated immunity in subjects who are protected is currently unknown. In previous studies, we further showed that either a monovalent or tetravalent DLAV formulation elicited vigorous CD8 ϩ responses comparable to those observed in areas of hyperendemicity and associated with high frequencies of secondary infections and natural immunity (16). However, it is unknown whether tetravalent DLAV vaccination results in the induction of effective CD4 ϩ responses.…”

“…In animal models of DENV disease, depletion of CD4 ϩ T cells does not exacerbate disease, but their induction with DENV-specific T cell epitopes can protect animals from DENV challenge (15). In humans, DENV-specific CD4 ϩ T cells display unique phenotypes, and in several cases, MHC class II alleles associated with the most vigorous responses are also associated with decreased disease susceptibility (16). These CD4 ϩ T cells dominantly recognize the capsid (C) and the nonstructural 3 (NS3) and NS5 antigens, while the envelope (E) protein appears to be a minor target (17,18).…”