Postbaccalaureate Fellow National Institute of Allergy and Infectious Diseases, National Institutes of Health, United States
Disclosure(s):
Ysabelle Broderson: No financial relationships to disclose
Introduction/Rationale: Dengue virus (DENV) is a mosquito-borne flavivirus that impacts over 50% of the global population. A better understanding of DENV-specific immune responses is needed to improve vaccines. Antibody-dependent neutrophil phagocytosis has been associated with protection against hemorrhagic fever, yet excessive neutrophil activation contributes to severe dengue, and the phenotypes of protective neutrophils remain undefined. To characterize how neutrophils respond to DENV, we evaluated neutrophil phenotypes in dengue vaccine recipients and in vitro.
Methods: 10 participants, with distinct DENV exposure histories, were vaccinated with a monovalent DENV3 vaccine. Cellular neutrophil markers were measured by flow cytometry at baseline (day 0) and on days 1 and 9 post-vaccination. Neutrophils from healthy donors were stimulated in vitro with different DENV serotypes, and their phenotypes were evaluated by flow cytometry.
Results: Following DENV3 vaccination, the total neutrophil population from all recipients showed elevated SYK and decreased CD33 expression indicating activation and maturation. When compared to participants with high vaccine viremia (N = 7), those with low viremia (N = 3) had increased expressions of CD16 and CD15 and lower CD62L on day 1. Furthermore, low viremic participants had increased CD63 in SYK positive neutrophils on day 9. In-vitro, neutrophils exposed to DENV4 survived up to 96 hours post-stimulation with no evidence of viral infection at various multiplicities of infection (MOI 1-17).
Conclusion: Neutrophils from participants with low viremia show increased activation, maturation and degranulation supporting their protective role in dengue. Healthy donor neutrophils responding to dengue virus in vitro will be used to characterize how sera from participants with high or low vaccine replication alters neutrophil activity. Overall, a better understanding of neutrophil responses to DENV can inform therapeutic options.
