Optimization of Recombinant Flavivirus Antigens for Infection Serology: Towards Syndrome-Based Multiplex Tests

Mora Cardenas, Erick Noe (2020). Optimization of Recombinant Flavivirus Antigens for Infection Serology: Towards Syndrome-Based Multiplex Tests. PhD thesis The Open University.

Abstract

Sensitive and specific pathogen detection is an essential prerequisite for the prevention and treatment of infectious diseases. The similarities of clinical symptoms and serological cross-reactivity of viral structural antigens make the diagnosis of flavivirus infection problematic. Therefore, the main aim of this thesis was the development of a non-structural protein 1 (NS1) based serological assay for the diagnosis of flaviviruses.

Recombinant NS1 (rNS1) oligomers consistent with the native secreted form of the protein were purified for TBEV, WNV, ZIKV, USUV, and DENV 1-4. The ability of rNS1 proteins to detect specific antibodies was analyzed using sera of immunized mice and well-characterized human sera samples. These antigens were used in a standard ELISA format and shown to be highly sensitive and specific compared to commercial assays.

The optimized NS1-based ELISA was used to assess the IgM/IgG responses to WNV and USUV in North-Eastern Italy. The results of the analysis confirmed the area as endemic for USUV and contributed to the characterization of the first human cases of USUV infection in blood donors. The NS1-based ELISA was also applied to 200 sera samples from patients exhibiting febrile illness who visited the University of Maiduguri Teaching Hospital in Nigeria. Only 11 of 200 serum samples were negative for all the flaviviruses tested, while all other samples were positive for at least one pathogen. Molecular analysis confirmed the circulation of flaviviruses in the region, including zika virus.

In conclusion, rNS1 represents a valuable option for the serology of flaviviruses with reduced cross-reactivity and high sensitivity.

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