Decreased peripheral dendritic cell numbers in dengue virus infection.

Laboratory predictors of severe forms of dengue virus (DENV) infection are needed. These clinical forms seem to be associated with high viremia, stressing the importance of immune responses, which could involve dendritic cells (DC). Yet, very few studies have evaluated DC after DENV infection. We assessed peripheral blood DC subset numbers in mild and severe forms of dengue in 44 patients, older than 15 years old, infected with serotypes DENV-2, 3 or 4. Patients were divided in high, intermediate and no detectable viremia according to results of molecular biology amplification of DENV. Serological status of anti-DENV IgG or IgM determined primary or secondary infections. Plasmacytoid and myeloid DC absolute and relative numbers were reduced in infected patients when compared to an age-matched healthy control group, but no significant differences in DC numbers were observed between mild or severe forms of disease. A severe disease was more frequent in patients infected with DENV-2 serotype and with secondary infection but no significant differences in DC subset numbers were found related to these variables. Viremia levels did not correlate to disease severity yet were associated to lower DC numbers. Plasmacytoid DC numbers were significantly lower in high and intermediate viremia groups compared to non-infected controls, but not in no detectable viremia patients. Myeloid DC numbers were also significantly lower than controls, even in no detectable viremia patients. These results confirm that circulating DC subset numbers are reduced after DENV infection, although this is not a biomarker of severe forms of dengue in adults.