Pythiosis is a deadly
infectious disease of humans and animals living in tropical and subtropical countries. The causative agent is the oomycete Pythium insidiosum. Treatment of
pythiosis is challenging. The use of
antimicrobial agents usually fails in the treatment of
pythiosis. Many patients undergo surgical removal of an infected organ (i.e., eye, arm, and leg). The immunotherapeutic
vaccine, prepared from the
crude extract of P. insidiosum, shows limited efficacy against
pythiosis. The fatal outcome occurs in patients with advanced disease. There are urgent needs for an effective therapeutic modality for
pythiosis. Recently, the exo-1,3-β-glucanase (Exo1) has been identified as a conserve immunoreactive
protein of P. insidiosum. Exo1 was predicted to reside at the cell membrane and hydrolyze cell wall β-
glucan during cell growth. An Exo1 ortholog is absent in the human genome, making it an appealing target for drug or
vaccine development. We attempted to clone and express the
codon-optimized exo1 gene of P. insidiosum in E. coli. To solve the inclusion body formation, expression and purification of Exo1 were achievable in the denaturing condition using SDS- and
urea-based
buffers. Exo1 lacked hydrolytic activity due to the absence of proper protein folding and post-translational modifications. ELISA and Western blot analyses demonstrated the immunoreactivity of Exo1 against
pythiosis sera. In conclusion, we successfully expressed and purified the immunoreactive Exo1
protein of P. insidiosum. The recombinant Exo1 can be produced at an unlimited amount and could serve as an extra
protein to enhance the effectiveness of the current form of the
vaccine against
pythiosis.