Up-regulation of extracellular copper/zinc superoxide dismutase mRNA after transmission of the filarial parasite Acanthocheilonema viteae in the vertebrate host Meriones unguiculatus

The gene encoding the cytoplasmic copper/zinc superoxide dismutase (AVSOD1) from the filarial parasite Acanthocheilonema viteae was isolated from a genomic DNA library using a degenerate oligonucleotide probe. Additionally, cDNAs of the AVSOD1 and the secreted extracellular SOD (AVSOD2) were both cloned by RT-PCR, and the AVSOD2 was expressed at high levels in E. coli. The amino acid sequence of the AVSOD1 is 89.5 and 87.5% identical to that of the corresponding enzymes of Brugia pahangi and Onchocerca volvulus, respectively. In contrast, the AVSOD2 shows a lower degree of identity to the other filarial SODs and is extensively glycosylated. RT-PCR studies demonstrate the expression of both SOD subtypes in all developmental stages of A. viteae and indicate up-regulation of the AVSOD2 expression after transmission from the vector to the definitive host. This suggests an enhanced requirement for SOD activity in post-infective larval stages and adults of A. viteae. ELISAs performed with purified recombinant AVSOD2 show that the AVSOD2 is not a major target for the immune system in naturally infected jirds.