Evaluation of Immune Responses Induced by Co-administrationof Recombinant NP-based Influenza H1N1 Vaccineand Hemokinin-1 Adjuvant in BALB/c Mice

The prevalence of influenza epidemics and direct transmission of the emerged avian virus strains to humans have highlighted the necessity of improving the management programs against this disease. The aim of this study was to evaluate the biological adjuvant effect of hemokinin-1 (HK-1) on enhancing the immune response induced by the recombinant influenza vaccine based on the Nucleoprotein protein (NP) of the H1N1 influenza virus.

In this experimental study, a total of 40 six-week-old female BALB/c mice were divided into two control groups (5 mice per group) and three treatment groups (10 mice per group). The control groups received normal saline and HK-1 oligonucleotide adjuvant. On the other hand, the treatment groups received NP recombinant protein (twice), NP protein with HK-1 (once), as well as NP protein with HK-1 (twice). Based on the grouping, 0.1 ml of each sample was injected into the quadriceps femoris muscle of the mice. The treatment groups received a 1:10 (v/v) ratio of the NP protein and HK-1. The serum samples were collected prior to primary and reminder vaccinations in defined intervals. The immune responses were analyzed using enzyme-linked immunosorbent and lymphocyte proliferation assays. Ethics code: RSVRI.REC.98.010

The rise of the anti-influenza antibody in immunized mice with recombinant NP-based vaccine received HK-1 adjuvant was significant, compared to that in the control group (P<0.05). The results of the vaccination reminder did not indicate any changes in the humoral immune response against influenza. In response to the viral NP protein, the lymphocytes in mice receiving NP protein with HK-1 were proliferated the same as the group received NP alone.

According to the results, HK-1 has the potential to increase specific humoral antibody response following vaccination with a recombinant NP-based influenza vaccine. The addition of this adjuvant does not have a significant effect on increasing the lymphocyte stimulation index.