A Kazal type serine proteinase SPI Pm2 from the black tiger shrimp Penaeus monodon is capable of neutralization and protection of hemocytes from the white spot syndrome virus

Abstract

A Kazal type serine proteinase SPI Pm2 is abundantly expressed in the hemocytes and shown to be involved in innate immune response against white spot syndrome virus (WSSV) in Penaeus monodon. The SPI Pm2 is expressed and stored in the granules in the cytoplasm of semigranular and granular but not the hyaline hemocytes. Upon WSSV challenge and progression of infection, the SPI Pm2 was secreted readily from the semigranular and granular hemocytes. The more they secreted the SPI Pm2, the less they were distinguishable from the hyaline cells. The WSSV-infected cells were either semigranular or granular hemocytes or both and depleted of SPI Pm2. The rSPI Pm2 was able to temporarily and dose-dependently neutralize the WSSV and protect the hemocytes from viral infection judging from the substantially less expression of WSSV late gene VP28. The antiviral activity was very likely due to the binding of SPI Pm2 to the components of viral particle and hemocyte cell membrane.