Abstract
Reticuloendotheliosis is an important immunosuppressive disease, associated with avian reticuloendotheliosis virus (REV) infection, and causes notable economic losses worldwide. Glycoprotein gp90 is an important structural protein of REV, and considered to be the most important immunogenic antigen, which can induce neutralizing antibodies against REV. In this study, an optimized suspension culture system was developed and applied to secretory express the immunogenic surface antigen gp90. To achieve an optimal glycosylation, the gp90 was designed to secretory expressed into the supernatant of the cell culture, which also occurs in the natural protein maturation procedure of REV. Serum-free culture medium was introduced to simplify the purification process and reduce the production costs. Based on the purified glycosylated gp90, an oil-emulsion subunit REV vaccine candidate was developed and evaluated in chickens. The subunit gp90-based vaccine induced fast immune responses, high levels of antibodies (REV-specific antibody, gp90-specific antibody, and neutralizing antibody against REV), and preferential T helper 2 (Th2) (interleukin-4 secretion) not Th1 (interferon-γ secretion) response. Furthermore, the viremia induced by REV infection was significantly reduced in chickens immunized with the glycosylated gp90. Overall, an optimized secretory expression system for glycosylated gp90 was developed, and the glycosylated gp90 obtained in this study retained good immunogenicity and could be an attractive vaccine candidate to protect chickens against REV horizonal infection.
Highlights
Reticuloendotheliosis virus (REV) is a type-C avian retrovirus [1] that causes tumors, immunosuppression, growth retardation, persistent viremia, or even deaths [2,3,4,5] in variable susceptible hosts, including chicken [6], pigeons [7], ducks [8], geese [9], quails [10], and peafowl [11]
The immunosuppression induced by REV infection can reduce the efficiency of vaccines and increase the probability of co-infection with other bacteria or viruses, such as avian influenza virus (AIV) [12], Newcastle disease virus (NDV) [13], fowl adenoviruses (FAdVs) [14], chicken anemia virus (CAV) [15], avian leucosis virus (ALV) [16], Marek’s disease virus (MDV) [17], fowlpox virus (FWPV) [18], or infectious bursa disease virus (IBDV) [19]
Glycosylated gp90 showed better immunogenicity than DNA vaccine or prokaryotic non-glycosylated gp90 expressed in E. coli, which could fully protect the animals from viremia after REV infection [25], highlighting the importance of the glycosylation for gp90 immunogenicity
Summary
Reticuloendotheliosis virus (REV) is a type-C avian retrovirus [1] that causes tumors, immunosuppression, growth retardation, persistent viremia, or even deaths [2,3,4,5] in variable susceptible hosts, including chicken [6], pigeons [7], ducks [8], geese [9], quails [10], and peafowl [11]. Interaction between the env derivative of REV and the cellular component that functions as a. Non-glycosylated gp was expressed in E. coli, and the immunogenicity of gp coupled with adjuvant CpG-ODN or Poly (I:C) was evaluated [27, 28]. Various DNA vaccines have been developed and provided variable protection to chickens against REV infection, demonstrating that the DNA prime-protein boost vaccination strategy could enhance both humoral and cellular immune responses in chickens [29, 30]. To further improve the immunogenicity, glycosylated gp was expressed in Pichia pastoris. Glycosylated gp showed better immunogenicity than DNA vaccine or prokaryotic non-glycosylated gp expressed in E. coli, which could fully protect the animals from viremia after REV infection [25], highlighting the importance of the glycosylation for gp immunogenicity. Gp expressed from Pichia pastoris is glycosylated, the degree of gp glycosylation is not enough
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