Evaluation of immunogenicity of recombinant influenza nucleoprotein (NP) for universal vaccine

Background: Influenza vaccines based on conserved proteins are being developed persistently. The conserved protein vaccines based on Nucleoprotein (NP) are highly protected vaccines against influenza viruses that can be used as a Universal vaccine. Aluminum hydroxide (Alum) is the most common adjuvant used in vaccine formulation to improve immunization by altering the epitopes’ folds. However, due to its toxic effects on the nervous system, especially in infants and young children exposed to multiple vaccine injections during brain development, it is better to use more desirable options such as carbohydrate-based adjuvants. Sucrose ester (SE) is a carbohydrate and non-ionic surfactant that is compatible with the human body and environmentally friendly. This study evaluated the immunogenicity of recombinant NP molecule prepared in a prokaryotic with the accompaniment of sucrose ester adjuvant against lethal influenza virus challenge in a Balb/c mice model. Methods: The recombinant vector of PET-28a-NP was used to produce NP molecule. The vaccines containing an NP with or without Alum or sucrose ester adjuvants were injected into the mice. The Effectiveness and immunogenicity were examined by evaluating the humeral immunity induction by Immunoglobulin G (IgG), and its subunits production, and cellular immunity induction by Interferon-Gamma (IFN-γ) and Interleukin-4 (IL-4) production by ELISA Method and also animal’s surveillance was documented. The study took part at the Influenza and other respiratory viruses department of Pasteur institute of Iran in November 2018. Results: The animals’ surveillance in the Np group was 57.1%, NP+SE was (71.4%), and NP+SE was 64.28%. Also, IgG and its subunits, IL4, and IFN-γ production in both Alum and SE combined vaccines compared to NP alone were significant. Conclusion: In combination with the carbohydrate adjuvant containing sucrose ester compared to the formulation with alum adjuvant, the NP could provide proper and considerable protection and immunity against the homologous strain (H1N1) of the Influenza A virus. It is recommended that SE usage as an adjuvant results in an adequate immune response and less toxic effect.