The dynamics of influenza isolates in Uganda: Their implications and way forward

Abstract

Background:Patientswith severe dengue infectionhave shown to have impaired dengue virus (DV) specific T cell responses and higher viral loads. Our previous data have shown that DV-specific T cell responses are suppressed by IL-10. Therefore, we set out to investigate the possible mechanisms of inhibition of DV-specific T cell responses in patients with acute dengue infection. Methods & Materials: 18 adult patients with acute confirmed dengue infection were recruited following informed written consent. The first blood sample was collected during day 3-5 of illness and the second sample was collected 2 days later. Clinical disease severity was classified according to the WHO 2011 dengue guidelines. Flow-cytometry was done on freshly extracted peripheral blood mononucleocytes (PBMCs). Intracellular cytokine staining was done by stimulating PBMCs with DVNS3 overlapping peptides. Expression of CTLA-4, TIM-3, PD-1, CD27 and CD28 were determined in T cells in general and DV-specific T cells. IL-10 quantitative ELISA was done in the patients and in 10 healthy DV seropositive individuals. Results: Expression of IL-10R was significantly higher in both CD4+ T cells (p =0.007) and CD8+ T cells (p =0.005) in patients with acute dengue when compared to healthy individuals. Expression of CTLA-4 was also significantly higher (p <0.0001) among T cells in patients with acute dengue (mean 411.3, SD±100.2 MFI) whencompared tohealthy individuals (mean256.4, SD±84.4MFI). Expression of CTLA-4 was also significantly higher (p =0.009) in DV-NS3 specific T cells (mean 419.5; SD±69.5) when compared to CD3+ T cells in general (mean 386.6; SD±86.81 MFI) in the same patient. Althoughnot significant (p =0.11) serum IL-10 levels correlatedwithCTLA-4expression inTcells (spearman’s r = 0.48). CTLA-4 expression also significantly (p =0.04) correlated with serum alanine transaminase levels (spearman’s r = 0.59). PD-1 expression was higher in T cells in patients with acute dengue (mean 106.8, SD±65.43 MFI) when compared to healthy individuals (mean 88.71, SD±22.77MFI), although not significant (p =0.85). Conclusion: CTLA-4 expression appears to be higher in T cells in patients with acute dengue and significantly higher in DV-specific T cells, suggesting a role in inhibition of DV-specific immune responses.