In Vitro Virucidal and Virustatic Properties of the Crude Extract of Cynodon dactylon against Porcine Reproductive and Respiratory Syndrome Virus

Abstract

The in vitro virustatic and virucidal tests of the crude extract of Cynodon dactylon against infection with porcine reproductive and respiratory syndrome virus (PRRSV), a cause of major devastating pig disease, were described. Crude extract of C. dactylon was prepared for cytotoxicity on tissue-culture cells that were used to measure virustatic and virucidal activities against PRRSV. Crude extract of C. dactylon at 0.78 mg/mL showed no cytotoxicity on the cell line, and at that concentration significantly inhibited replication of PRRSV as early as 24 hours post infection (hpi). C. dactylon also inactivated PRRSV as determined by immunoperoxidase monolayer assay (IPMA) compared to the control experiments. In summary, the present study may be among the earliest studies to describe virustatic and virucidal activities of C. dactylon crude extract against PRRSV in vitro. Extracts of C. dactylon may be useful for PRRSV control and prevention on pig farms.

Figure 1

Virustatic activity of C. dactylon study reagent on replication of porcine reproductive and respiratory syndrome virus (PRRSV). MARC-145 cells were infected with PRRSV at a multiplicity of infection of 1. At various time points after infection, PRRSV in supernatants were quantified for virus titer by immunoperoxidase monolayer assay. In control group, viruses in supernatants at 24 hpi were infected and replicated in the MARC-145 cells (a), while little or no PRRSV were observed in groups of study reagent (b, c). At the concentration of 0.78 mg/mL, virus could only be observed in supernatants of 48 hpi suggesting that PRRSV growth was interrupted by C. dactylon. Representative data are mean and standard error. Asterisks indicate statistical significance (P  value ≤ 0.05). Scale bar in (a, b, and c) ≈180 μm.

Figure 2

Virucidal activity on PRRSV of C. dactylon study reagent at a concentration of 0.78 mg/mL. C. dactylon study reagent was incubated with PRRSV for one hour at room temperature before inoculated onto a monolayer of MARC-145 cells. After three days in vitro, virus titer was quantified by IPMA. C. dactylon significantly inactivated PRRSV compared to the control group, while virus alone with DMEM remained infective on MARC-145 cells. Asterisks indicate statistical significance (P  value ≤ 0.05).