Immunization with cytomegalovirus gB protein produced by the Baculovirus Expression Vector System to elicit humoral immune response in BALB/c mice

Introduction: Due to the role of neutralizing antibodies which can prevent human cytomegalovirus (HCMV) infection, most of the efforts have been focused on  designing vaccines capable of eliciting protective humoral immunity. The aim of this study was to evaluate the antibody response of BALB/c mice to a truncated HCMV glycoprotein B produced in insect cells using Baculovirus Expression Vector System (BEVS). Methods: The ectodomain of HCMV gB coding sequence was synthesized and the recombinant protein was expressed in Spodoptera frugipedra (Sf9) insect cell line using BEVS. The expression of the recombinant HCMV gB was verified using an HRP-conjugated polyclonal antibody, specific for HCMV gB. The levels of antibody responses and characterization of the subclasses of IgG antibodies were evaluated after vaccination of the mice. Results: The expression of truncated HCMV gB protein (~ 70 kDa) in the infected insect cells was verified by Western blot analysis. Measurement of IgG subclasses showed the dominance of IgG1 subclass response among all of the IgG subclasses (P < 0.05) while the titers of IgG2a and IgG2b were approximately the same. Conclusion: This study demonstrated that BEVS could be used as an efficient approach for the expression of this truncated protein. The results also showed the use of this recombinant protein as a subunit vaccine could induce a significant antibody response, tilted toward IgG1.