Abstract
Rabbit hemorrhagic disease virus (RHDV) is the causative agent of rabbit hemorrhagic disease (RHD). RHD, characterized by hemorrhaging, liver necrosis, and high morbidity and mortality in rabbits and hares, causes severe economic losses in the rabbit industry worldwide. Due to the lack of an efficient in-vitro propagation system for RHDV, the current vaccine is produced via chemical inactivation of crude RHDV preparation derived from the livers of infected rabbits. Inactivated vaccines are effective for controlling RHD, but the potential problems of biosafety and animal welfare have negative effects on the application of inactivated vaccines. In this study, an oral Lactobacillus casei (L. casei) vaccine was used as an antigen delivery system to express RHDV capsid protein VP60(VP1)-eGFP fusion protein. The expression of the recombinant protein was confirmed via western blotting and immunofluorescence (IFA). Our results indicate that oral administration of this probiotic vaccine can stimulate secretory immunoglobulin A (SIgA)-based mucosal and IgG-based humoral immune responses in rabbits. The immunized rabbits were completely protected against challenge with RHDV. Our findings indicate that the L. casei expression system is a new strategy for the development of a safe and efficient vaccine against RHDV.
Highlights
Rabbit hemorrhagic disease (RHD), characterized by severe necrotizing hepatitis and disseminated intravascular coagulation in the liver, spleen, kidney and other solid organs, is a highly contagious and lethal infection in rabbits [1,2]
The recombinant plasmid pPG-T7g10-eGFP-VP60 was generated (Figure 1) and transformed by electroporation into competent Lactobacillus casei ATCC 393 (LC393) cells. eGFP-positive recombinant L. casei cells were collected by flow cytometry and designated as pPG-eGFP-VP60/LC393
Our results indicate that recombinant L. casei pPG-eGFP-VP60/LC393 grew normally on MRS medium without chloramphenicol, but did not grow on MRS medium containing chloramphenicol
Summary
Rabbit hemorrhagic disease (RHD), characterized by severe necrotizing hepatitis and disseminated intravascular coagulation in the liver, spleen, kidney and other solid organs, is a highly contagious and lethal infection in rabbits [1,2]. RHD is peracute and often lethal hepatitis caused by the rabbit caliciviruses Lagovirus europaeus GI. (previously called rabbit hemorrhagic disease virus—RHDV). Lagovirus europaeus GI. (previously called RHDV2 or RHDVb) [1,3,4]. This disease was first reported in China in 1984, and has, since, spread rapidly around the world in less than 10 years, causing considerable economic losses in the rabbit industry and impacting the ecology of wild rabbit populations [1,2,5,6]. GI. is endemic in Europe and Australia, and appears to be replacing GI. strains in these regions [8,9,10]
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