Dengue is a mosquito-borne viral disease caused by dengue virus (DENV). The disease is endemic to more than 100 countries with 390 million dengue infections per year. Humoral immune responses during primary and secondary DENV infections are well investigated. However, the impact of DENV infection on B cell subsets and their antibody-independent functions are not well documented. Through this study, we aimed to define the distribution of B cell subsets in the acute phase of DENV infection and characterise the effect of DENV infection on B cell functions such as differentiation into memory and plasma cells and cytokine production. In our cohort of Cambodian children, we observed decreased percentages of CD24hiCD38hi B cells and CD27- naïve B cells within the CD19 population and increased percentages of CD27+CD38hiCD138+ plasma cells as early as 4 days post appearance of fever in patients with severe dengue compared to patients with mild disease. Lower percentages of CD19+CD24hiCD38hi B cells in DENV-infected patients were associated with decreased concentrations of soluble CD40L in patient plasma and decreased platelet counts in these patients. In addition, CD19+CD24hiCD38hi and CD19+CD27- B cells from DENV-infected patients did not produce IL-10 or TNF-α upon stimulation in vitro suggesting their contribution to an altered immune response during DENV infection. In addition, CD19+CD27- naïve B cells isolated from dengue patients were refractory to TLR/anti-IgM stimulation in vitro, which correlated to the increased expression of inhibitory Fcγ receptors (FcγR) CD32 and LILRB1 on CD19+CD27- naïve B cells from DENV-infected patients. Collectively, our results indicate that a defective B cell response in dengue patients may contribute to the pathogenesis of dengue during the early phase of infection.
Dengue is the most prevalent arthropod-borne viral disease. Clinical symptoms of dengue virus (DENV) infection range from classical mild dengue fever to severe, life-threatening dengue shock syndrome. However, most DENV infections cause few or no symptoms. Asymptomatic DENV-infected patients provide a unique opportunity to decipher the host immune responses leading to virus elimination without negative impact on t v 'health. We used an integrated approach of transcriptional profiling and immunological analysis comparing a Cambodian population of strictly asymptomatic viremic individuals with clinical dengue patients. Whereas inflammatory pathways and innate immune responses were similar between asymptomatic individuals and clinical dengue patients, expression of proteins related to antigen presentation and subsequent T and B cell activation pathways were differentially regulated, independent of viral load or previous DENV infection. Feedback mechanisms controlled the immune response in asymptomatic viremic individuals as demonstrated by increased activation of T cell apoptosis-related pathways and Fc$\gamma$RIIB signaling associated with decreased anti-DENV specific antibody concentrations. Taken together, our data illustrate that symptom-free DENV infection in children is determined by increased activation of the adaptive immune compartment and proper control mechanisms leading to elimination of viral infection without excessive immune activation, having implications for novel vaccine development strategies.