Induction of Homosubtypic and Heterosubtypic Immunity to Influenza Viruses Using a Conserved Internal and External Proteins.

The immunogenicity and protective properties of the designed recombinant fusion peptide of 3M2e and truncated nucleoprotein (trNP), originating from Influenza A virus, were investigated in the BALB/c mice model in comparison with the Mix protein (3M2e + trNP). The results were evaluated by antibody response, cytokine production, lymphocyte proliferation assay, and mortality rate after challenge with homologous (H1N1) and heterologous (H3N2) influenza viruses in BALB/c mice. The animals that received the chimer protein with or without adjuvant had more specific antibody responses and elicited memory CD4 T cells, and cytokines of Th1 and Th2 cells compared to the Mix protein. Moreover, the Mix protein, like the recombinant chimer protein, provided equal and effective protection against both homologous and heterologous challenges in mice. Nevertheless, the chimer protein demonstrated superior immune protection compared to the Mix protein. The percentage of survived animals in the adjuvanted protein group (78.4%) was less than the non-adjuvanted one (85.7%). However, the Mix protein plus Alum could induce protective immunity in only 57.1% and 42.8% of homologous and heterologous virus-challenged mice, respectively. Regarding the sufficient immunogenicity and protectivity of the chimer protein construct against influenza viruses, the findings of the study suggest that the chimer protein without a requirement of adjuvant can be used as an adequate vaccine formulation to protect against a broad spectrum of influenza viruses.