In this study, to exploit a safe and effective vaccine for the prevention against avian leukemia subgroup J, we have developed the investigation of the protective antibodies induced by prokaryotic expression of avian leukemia virus subgroup J gp85 envelope protein and its anti-ALV-J infection role in chicks.At first, the gp85 gene of the subgroup J avian leukosis virus was cloned into the expressing vector pMG36e with Emr labellings, which can shuttle and express in E.coli and Lactobacillus casei.The recombinant vector pMG36e-gp85 was subsequently transformed into the competent cells Lactobacillus casei for expressing proteins we need.Through the technique of western blotting analysis and sequencing, the recombinant protein was determined.Oral immunization of chicks was carried out with the recombinant strain Lactobacillus casei harboring pMG36e-gp85 vaccine.Specific anti-ALV IgG in the serum of chicks was detected by indirect ELISA every week after the fist immunization.Seven weeks after immunization with the recombinant Lactobacillus casei, the chicks were challenged with standard-type ALV-J (NX0101).The results show that antibody levels can rise significantly after immunization with the recombinant Lactobacillus casei (pMG36e-gp85/L.casei) in chicks (P < 0.05).The average viremia of control group was 86%,while the oral group was 40%.Thus, recombinant Lactobacillus casei vaccine has some resistance on ALV-J.Our study was the first utilizing of the Lactobacillus casei vector for expressing avian leukemia virus envelope protein gp85 gene, providing reliable scientific basis for making recombinant Lactobacillus casei oral vaccine of subgroup J avian leukemia, but also providing new methods and ideas of prevention for other enveloped virus in avian disease.