The evolution of dengue virus-reactive circulating antibody repertoire

ABSTRACT The four dengue virus serotypes (DENV1-4) cause the most important mosquito-borne viral disease of humans, with ~50 million dengue cases annually and over 3 billion people worldwide at risk of infection. Yet, no treatment is currently approved for use, and the only registered vaccine is not safe and effective in all populations. The overall approach of this study is to take advantage of unique longitudinal sample sets from our long-standing cohort study in Nicaragua to address complex questions about DENV antibody and B cell immunology in a relevant epidemiological context. While antibodies generated in primary DENV infection confer protection against the same serotype, they can either protect against or enhance a subsequent infection with a different DENV serotype; however, after a secondary DENV infection, individuals acquire broader protection against multiple DENV serotypes, and the risk of severe disease is lowered. There is a critical gap in understanding the generation and maintenance of broadly neutralizing circulating antibodies and B cell immunity stemming from secondary DENV infection. Our preliminary results show that expansion of B cell recall contributes to acute secondary DENV immunity and that post-secondary memory B cells (MBCs) display broader cross- serotype neutralization as compared to post-primary MBCs. We hypothesize that the recruitment of B cell memory from a primary DENV infection into acute secondary circulating IgG, and then substantial addition of new lineages from the secondary DENV infection into long-lasting serological and B cell repertoires, together shape the distinct broadly protective profile of durable post-secondary dengue immunity. In this study, we will investigate how pre-existing MBCs generated during primary DENV infection and newly elicited lineages in secondary DENV infection contribute to broad neutralization. In particular, we will identify whether broadly neutralizing antibodies originate from the pre-existing B cell compartment or are newly elicited in secondary infection (Aim 1), and how they are maintained in serological or B cell repertoires for future protection (Aim 2). We will use innovative viral antigens for isolation of DENV-specific antibodies and B cells coupled with state-of- the-art IgG antibody proteomics (Ig-Seq) and B cell receptor sequencing (BCR-Seq) platforms, with robust bioinformatics pipelines. Selected representative monoclonal antibodies will be expressed and functionally evaluated using established, standardized neutralization assays. We have assembled a team with complementary expertise in B cell biology, flavivirus virology, immunology, and epidemiology, coupled with cutting-edge 'antibodyomic' serological and genomic sequencing technologies and analytic systems. Overall, the proposed research will begin to define at the cellular and serological level the evolution of antibody- mediated immunity that generates broad neutralization against DENV upon secondary infection in order to guide improved vaccine design strategies.