Characterization of Human CD8 T Cell Responses in Dengue Virus-Infected Patients from India

Abstract

Epidemiological studies suggest that India has the largest number of dengue virus infection cases worldwide. However, there is minimal information about the immunological responses in these patients. CD8 T cells are important in dengue, because they have been implicated in both protection and immunopathology. Here, we provide a detailed analysis of HLA-DR+ CD38+ and HLA-DR− CD38+ effector CD8 T cell subsets in dengue patients from India and Thailand. Both CD8 T cell subsets expanded and expressed markers indicative of antigen-driven proliferation, tissue homing, and cytotoxic effector functions, with the HLA-DR+ CD38+ subset being the most striking in these effector qualities. The breadth of the dengue-specific CD8 T cell response was diverse, with NS3-specific cells being the most dominant. Interestingly, only a small fraction of these activated effector CD8 T cells produced gamma interferon (IFN-γ) when stimulated with dengue virus peptide pools. Transcriptomics revealed downregulation of key molecules involved in T cell receptor (TCR) signaling. Consistent with this, the majority of these CD8 T cells remained IFN-γ unresponsive even after TCR-dependent polyclonal stimulation (anti-CD3 plus anti-CD28) but produced IFN-γ by TCR-independent polyclonal stimulation (phorbol 12-myristate 13-acetate [PMA] plus ionomycin). Thus, the vast majority of these proliferating, highly differentiated effector CD8 T cells probably acquire TCR refractoriness at the time the patient is experiencing febrile illness that leads to IFN-γ unresponsiveness. Our studies open novel avenues for understanding the mechanisms that fine-tune the balance between CD8 T cell-mediated protective versus pathological effects in dengue.IMPORTANCE Dengue is becoming a global public health concern. Although CD8 T cells have been implicated both in protection and in the cytokine-mediated immunopathology of dengue, how the balance is maintained between these opposing functions remains unknown. We comprehensively characterized CD8 T cell subsets in dengue patients from India and Thailand and show that these cells expand massively and express phenotypes indicative of overwhelming antigenic stimulus and tissue homing/cytotoxic-effector functions but that a vast majority of them fail to produce IFN-γ in vitro. Interestingly, the cells were fully capable of producing the cytokine when stimulated in a T cell receptor (TCR)-independent manner but failed to do so in TCR-dependent stimulation. These results, together with transcriptomics, revealed that the vast majority of these CD8 T cells from dengue patients become cytokine unresponsive due to TCR signaling insufficiencies. These observations open novel avenues for understanding the mechanisms that fine-tune the balance between CD8-mediated protective versus pathological effects.

Prior Dengue Virus Exposure Shapes T Cell Immunity to Zika Virus in Humans

“…Importantly, our data indicate that DENV preexposure also alters the quality of responses. While no difference was seen between DENV-preexposed and DENV-naive donors at the level of composition of memory subsets in the responding cells or the degree of multifunctionality, DENVspecific CD8 responses from DENV-preexposed donors significantly upregulated granzyme B and PD1, suggesting a more differentiated phenotype, similar to what was detected in secondary DENV infection (27,34).…”

Association of dengue virus‐specific polyfunctional T‐cell responses with clinical disease severity in acute dengue infection

“…7 However, we found that in acute infection only 18.1% to 23.3% of DENV-specific T cells produced two cytokines/ effectors, possibly due to the downregulation of T-cell receptor signaling pathways involved in cytokine during acute dengue. 38 Although the mean frequency of single cytokine-/effector-producing T cells was between 0.1% and 1.9% of the CD8+ T-cell population, the mean frequency of T cells producing a combination of TNF-α/ IFNγ, TNF-α/MIP-1β, or IFNγ/MIP-1β was less than 0.3% of all CD8+ T cells. However, CD107a/MIP-1β expressing CD8+ T cells in patients with DHF was between 1.2% and 1.5% of all CD8+ T cells.…”

“…37 However, it has been shown that DENV-specific T-cell responses were absent or present in very low frequencies when the patient enters the critical phase of illness, and that TNF-α production by T cells did not associate with severe disease. 20,25,38,39 Indeed it was shown that children who had a higher frequency of DENV-specific T cells producing TNF-α, IFNγ, and interleukin-2 were more likely to have the development of subclinical infection rather than symptomatic illness. 40 In human and animal influenza viral infection, TNF-α was shown to have more potent antiviral effects than IFNγ or IFNα.…”

Interleukin‐33 contributes to disease severity in Dengue virus infection in mice

“…It is noteworthy that this partial reversal was in the face of complete inhibition of the haematological alterations, cytokine production and granulocyte recruitment. The effect of the CD8 + T cells and NK cells could manifest in an even more pronounced fashion at a later phase of the infection 35,36 , a hypothesis that merits to be investigated using a less severe model of DENV2 infection. 29,30 Moreover, the IL-33-ST2 signalling axis in NK cells is important to the host response during certain viral infections.…”

“…33,34 Our analysis was carried out on days 4 and 6 after infection. The effect of the CD8 + T cells and NK cells could manifest in an even more pronounced fashion at a later phase of the infection 35,36 , a hypothesis that merits to be investigated using a less severe model of DENV2 infection. Nevertheless, the limited administration of the CXCR2 inhibitor at an early stage of infection (day 0 and 3) was markedly effective in attenuating the disease pathology by reducing organ damage, mortality and weight loss.…”