Abstract
BackgroundPorcine circovirus type 2 (PCV2) is the main causative agent of porcine circovirus diseases (PCVDs) which causes huge yearly economic losses in the swine industry. Capsid protein (Cap) is the major structural protein of PCV2 that can induce a protective immune response. Therefore, developing a novel and safe subunit vaccine against PCV2 infection is needed.ResultsIn this study, the Cap gene was bound to the truncated calreticulin (CRT) (120–250 aa/120–308 aa) at the N/C terminal, and then the CRT-Cap fusion genes were expressed in Escherichia coli (E.coli). The size-exclusion chromatography and dynamic light scattering (DLS) data showed that the purified recombinant CRT-Cap fusion protein (rP5F) existed in the form of polymers. Immunization with rP5F stimulated high levels of PCV2 specific antibody and neutralization antibody in mice, which were almost identical to those induced by the commercial subunit and inactivated vaccines. The lymphocyte proliferation and cytokine secretion were also detected in rP5F immunized mice. According to the results of PCV2-challenge experiment, the virus loads significantly decreased in mice immunized with rP5F. The data obtained in the current study revealed that rP5F had the potential to be a subunit vaccine candidate against PCV2 in the future.ConclusionsWe have successfully expressed Cap-CRT fusion proteins in E.coli and optimized rP5F could form into immunogenic polymers. Mice immunized with rP5F efficiently induced humoral and part of cellular immune responses and decreased the virus content against PCV2-challenge, which suggested that rF5P could be a potential subunit vaccine candidate.
Highlights
Porcine circovirus type 2 (PCV2) is the main causative agent of porcine circovirus diseases (PCVDs) which causes huge yearly economic losses in the swine industry
PCV1 is nonpathogenic [2], and PCV2 is associated with several diseases, collectively named as porcine circovirus associated disease (PCVAD), which causes reproductive failure and huge economic losses all over the world [3]
The BALB/c mouse is one of the animal models, as it has a clear background and frees from external interference, it is the most extensively used in PCV2 inactivated or subunit vaccine researches [9, 10]
Summary
Porcine circovirus type 2 (PCV2) is the main causative agent of porcine circovirus diseases (PCVDs) which causes huge yearly economic losses in the swine industry. Capsid protein (Cap) is the major structural protein of PCV2 that can induce a protective immune response. Developing a novel and safe subunit vaccine against PCV2 infection is needed. PCV1 is nonpathogenic [2], and PCV2 is associated with several diseases, collectively named as porcine circovirus associated disease (PCVAD), which causes reproductive failure and huge economic losses all over the world [3]. It has been reported that all the commercial vaccines were able to reduce clinical symptoms and improve reproduction to some extent in PCV2 positive farms, while they failed to eradicate this virus from farms [6, 7]. As PCV2 infection may initiate immunosuppression and cause subsequent failure of the immune response in pigs [8], a more effective vaccine should be developed to prevent PCV2 infections in swine herds. The BALB/c mouse is one of the animal models, as it has a clear background and frees from external interference, it is the most extensively used in PCV2 inactivated or subunit vaccine researches [9, 10]
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