BACKGROUND: The development of reagents to identify and characterize antigen-specific B cells has been challenging.

METHODS: We recently developed Alexa Fluor-labeled dengue viruses (AF DENV) to characterize antigen-specific B cells in the peripheral blood of DENV-immune individuals.

RESULTS: In this study, we used AF DENV-1 together with AF DENV-2 on PBMC from children in Thailand undergoing acute primary or secondary DENV-1 infections to analyze the phenotypes of antigen-specific B cells that reflected their exposure or clinical diagnosis. DENV serotype-specific and cross-reactive B cells were identified in PBMC from all subjects. Frequencies of AF-DENV+ class switched memory B cells (IgD-CD27+ CD19+ cells) reached up to 8% during acute infection and early convalescence. AF DENV-labeled B cells expressed high levels of CD27 and CD38 during acute infection, characteristic of plasmablasts, and transitioned into memory B cells (CD38-CD27+) at the early convalescent time point. There was higher activation of memory B cells early during acute secondary infection suggesting reactivation from a previous DENV infection.

CONCLUSIONS: AF DENV reveal changes in the phenotype of DENV serotype-specific and cross-reactive B cells during and after natural DENV infection and could be useful in analysis of the response to DENV vaccination.