Antibody‐Dependent Cellular Cytotoxicity Mediated by Plasma Obtained before Secondary Dengue Virus Infections: Potential Involvement in Early Control of Viral Replication

Neutralizing and non-neutralizing monoclonal antibodies against dengue virus E protein derived from a naturally infected patient

Background

Antibodies produced in response to infection with any of the four serotypes of dengue virus generally provide homotypic immunity. However, prior infection or circulating maternal antibodies can also mediate a non-protective antibody response that can enhance the course of disease in a subsequent heterotypic infection. Naturally occurring human monoclonal antibodies can help us understand the protective and pathogenic roles of the humoral immune system in dengue virus infection.

Results

Epstein-Barr Virus (EBV) transformation of B cells isolated from the peripheral blood of a human subject with previous dengue infection was performed. B cell cultures were screened by ELISA for antibodies to dengue (DENV) envelope (E) protein. ELISA positive cultures were cloned by limiting dilution. Three IgG1 human monoclonal antibodies (HMAbs) were purified and their binding specificity to E protein was verified by ELISA and biolayer interferometry. Neutralization and enhancement assays were conducted in epithelial and macrophage-like cell lines, respectively. All three HMAbs bound to E from at least two of the four DENV serotypes, one of the HMAbs was neutralizing, and all were able to enhance DENV infection.

Conclusions

HMAbs against DENV can be successfully generated by EBV transformation of B cells from patients at least two years after naturally acquired DENV infections. These antibodies show different patterns of cross-reactivity, neutralizing, and enhancement activity.

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.