Antiviral viral compound from Streptomyces ghanaensis like strain against white spot syndrome virus (WSSV) of shrimp

Actinomycetes isolates collected from different environments were screened for antiviral activity against WSSV. One isolate designated as CAHSH-2 showed antiviral activity against WSSV at the concentration of 0.2 mg per shrimp. The laboratory trial of determining antiviral activity of ethyl acetate extract (EtOAcE) of CAHSH-2 against WSSV was carried out 21 times since 2014. CAHSH-2 isolate which showed antiviral activity was characterized and identified as Streptomyces ghanaensis like strain. Among the five fractions obtained from EtOAcE of potential actinomycetes isolate, F1 was found to have strong antiviral activity. The F1A and F1B sub-fractions from F1 fraction were subjected to GC-MS, FTIR, 1 H and 13 C NMR analyses and, the compounds identified were di-n-octyl phthalate and bis (2-methylheptyl) phthalate, respectively. Among these compounds, di-n-octyl phthalate showed strong antiviral activity against WSSV. Molecular docking studies revealed that di-n-octyl phthalate was found to have high binding affinity with VP26 and VP28 proteins of WSSV, whereas the bis (2-methylheptyl) phthalate showed low binding affinity with VP26 and VP28. The antiviral activity of EtOAcE of actinomycetes against WSSV was confirmed by PCR, RT-PCR, Western blot and ELISA. The EA extract of active isolate was found to be non-toxic to Artemia, post-larvae and adult Litopenaeus vannamei.