RESUMO
OBJECTIVE: To determine the candidate genes for engineering vaccine of Ascaris lumbricoides. METHODS: pMD18-T-ALAg and plasmid expression vector pET-28a(+) were digested with BamH I and EcoR I and linked to each other. The resultant plasmid pET-28a(+)-ALAg was transferred into E. coli BL21 (DE3) and its expression was induced with IPTG, and the recombinant ALAg(rALAg) was purified. A total of 30 mice were equally divided into 3 groups, the mice in each group were injected with rALAg-FCA, FCA and PBS respectively, then they were attacked by infectious eggs of Ascaris (3 600 per mouse). The IgG levels in sera of mice in each group were detected by indirect ELASA. RESULTS: rALAg was recognized by the sera from repeatedly Ascaris lumbricoides inoculated rabbits. The numbers of larvae of Ascaris lumbricoides from liver and lung of mice were 25.30 +/- 4.55 in the rALAg-FCA group and 57.60 +/- 5.76 in the PBS group, respectively, the former being the reducing rate of 69.26%, and the difference among the 3 groups showed statistical significances (P < 0.01). The IgG levels (A450 value) of the rALAg-FCA, FCA and PBS groups were 0.858 +/- 0.003, 0.149 +/- 0.004 and 0.134 +/- 0.004, respectively, there were statistical differences among them (P < 0.01). CONCLUSION: ALAg can be used as a candidate gene of genetic engineering vaccine of Ascaris lumbricoides.