Serological Evaluation of H9-RBD-Pichia, a Novel Recombinant Influenza Vaccine, in BALB/c Mice

Background: The H9N2 influenza virus is one of the most important subtypes of influenza that has caused irreparable damage to the poultry industry, and many efforts are underway to develop its recombinant vaccines.Objectives: This study aims to evaluate the effectiveness of H9-RBD-Pichia, a novel recombinant subunit vaccine, in stimulating the immune system and producing hemagglutinin-inhibiting antibodies in mice.Methods: A total of 24 female BALB/c mice were purchased and randomly divided into six groups: Group 1 received oral administration of lysed yeast twice, group 2 received one injection of lysed yeast, group 3 received two injections of lysed yeast, group 4 received one injection of pure recombinant protein, group 5 received two injections of pure recombinant protein and group 6 was negative control. Prime and booster immunizations were performed on days 14 and 28, respectively. Sera samples were collected on day 42. Hemagglutination (HA) and hemagglutination inhibition (HI) assays were performed on antigen and sera samples, respectively.Results: HA titers of 1:4, 1:4, and 1:32 were seen in the positive control, intact, and bead-treated yeasts, respectively, showing the functionality of the expressed H9-RBD recombinant protein. HI assay showed this vaccine could stimulate the immune system and produce anti-hemagglutinin antibodies in mice. The highest antibody titer (1:512) was observed when yeast lysate was injected twice on days 14 and 28.Conclusion: The H9-RBD-Pichia vaccine has been produced based on genetic engineering technology and could produce high titers of hemagglutinin-inhibiting antibodies in mice.

Serological Evaluation of H9-RBD-Pichia, a Novel Recombinant Influenza Vaccine, in BALB/c Mice Keywords:

H9N2 , influenza , Pichia pastoris , recombinant vaccine