Scientific consultation on cell mediated immunity (CMI) in dengue and dengue vaccine development.

Dengue is a re-emerging arboviral disease of great public health importance. Limited understanding of protective immune responses against dengue has hampered advancement of dengue vaccine candidates. Demonstrating an immunological correlate of protection has been limited to associating quantitative neutralizing antibody titers with clinical outcomes following infection. There have been a number of studies investigating the role of cell mediated immunity (CMI) in natural infections and these have demonstrated roles in both virus clearance and potentiating disease. Vaccine developers have extended the exploratory study of CMI in natural infection to the study of dengue vaccine recipients. Primary infections and monovalent vaccine administration generates dengue type-specific T-cell responses. Secondary infection, vaccination of flavivirus primed individuals, or administration of multivalent vaccine candidates results in broad, cross-reactive T-cell responses, similar to the broadening of antibody patterns. However, the precise function of CMI in protection or disease pathology remains ill-defined and, at present, there is no evidence to suggest that CMI can be utilized as a correlate of protection. Nonetheless, the study of CMI in natural infection and following vaccine administration should continue in an attempt to improve the understanding of dengue immunopathology, vaccine candidate immunogenicity, and potential correlates of protection.