Abstract:

Objective To determine the expression levels of Schistosoma-resistant genes HSP90α (heat shock protein-90α) and KPNA2 (Karyopherin α2) in different tissues of rodent Microtus fortis and their effects on the resistance against S. japonicum infection in recipient mice. Methods RT-PCR was used to determine the levels of mRNA expression of HSP90α and KPNA2 in different tissues (heart, liver, spleen, lung, kidney, brain, muscle, skin and bone marrow) of normal M. fortis. To determine the effect of HSP90α and KPNA2 on their resistance against S. japonicum infection, the recombinant retroviral vectors containing target genes, pLXSN-HSP90α and pLXSN-KPNA2, were used to make recombinant viruses. The viruses containing the target HSP90α and KPNA2 were used to transfect naive Kunming mice on day 1, 3, 7 by tail vein injection of 4×10⁵ cfu viruses to make them expressed in the recipient mice. The mice were then infected with (30 ± 2) cercaria of S. japonicum 2 days after the final injection of viruses. The mice received empty vector or PBS were used as negative controls. All mice were euthanized 42 days after cercaria challenge and adult worms were collected by portal vein drainage and livers collected to measure the egg count and the egg granuloma by HE staining. The HSP90α and KPNA2-induced resistance against S. japonicum infection was measured by the adult worm reduction, egg count reduction and the reduced liver egg-granuloma compared to mice received empty vector or PBS only. Results RT-PCR results showed that HSP90α gene was highly expressed in the brain and bone marrow of M. fortis, while KPNA2 gene highly expressed in heart, kidney and muscle. The cercaria challenge study showed that mice transfected with pLXSN-HSP90α and pLXSN-KPNA2 viruses produced 40.80% and 39.42% adult worm reduction, and 57.90% and 76.50% egg reduction, respectively, with statistical significance compared with mice received pLXSN vector only (P < 0.01). However, there was no significant difference in adult worm reduction between mice received pLXSN-HSP90α and pLXSN-KPNA2, but with significant difference for egg count reduction (57.9% for pLXSN-HSP90α group and 76.5% for pLXSN-KPNA2 group, P < 0.05). The liver sections showed that mice received pLXSN-HSP90α and pLXSN-KPNA2 had significantly less number of eggs and egg granuloma compared to mice received empty vector only. Conclusion HSP90α and KPNA2 genes are expressed differently in brain, bone marrow, heart, kidney and muscle tissues of M. fortis. Mice received viruses containing M. fortis HSP90α and KPNA2 genes acquired significant resistance against S. japonicum infection characterized by the reduced adult worms and reduced egg count and granuloma in livers of infected mice.

Key words: Microtus fortis, HSP90α, KPNA2, Schistosoma japonicum, Gene expression