A modified MS2 bacteriophage plaque reduction assay for the rapid screening of antiviral plant extracts

Abstract

Introduction:Traditional methods of screening plant extracts and purified components for antiviral activity require up to a week to perform, prompting the need to develop more rapid quantitative methods to measure the ability of plant based preparations to block viral replication. We describe an adaption of an MS2 plaque reduction assay for use in S. aureus.Results:MS2 bacteriophage was capable of infecting and replicating in B. cereus, S. aureus and F + E. coli but not F- E. coli. Indeed, both B. cereus and S. aureus were more sensitive to MS2 induced lysis than F+ E. coli. When MS2 bacteriophage was mixed with Camellia sinensis extract (1 mg/ml), Scaevola spinescens extract (1 mg/ml) or Aloe barbadensis juice and the mixtures inoculated into S. aureus, the formation of plaques was reduced to 8.9 ± 3.8%, 5.4 ± 2.4% and 72.7 ± 20.9% of the untreated MS2 control values respectively.Conclusions:The ability of the MS2 plaque reduction assay to detect antiviral activity in these known antiviral plant preparations indicates its suitability as an antiviral screening tool. An advantage of this assay compared with traditionally used cytopathic effect reduction assays and replicon based assays is the more rapid acquisition of results. Antiviral activity was detected within 24 h of the start of testing. The MS2 assay is also inexpensive and non-pathogenic to humans making it ideal for initial screening studies or as a simulant for pathogenic viruses.

Problems of Reproducibility and Efficacy of Bioassays Using Crude Extracts, with reference to Aloe vera

“…Amongst its noted therapeutic activities, Aloe vera has been reported to have anti-bacterial, [16,17] anti-fungal, [16] antiviral, [18,19] immune-stimulatory, [20] anti-inflammatory [21,22] and anti-diabetes [23] bioactivities. However, many studies examining the therapeutic potential of Aloe extracts report conflicting results, showing either a lack of therapeutic bioactivity for some Aloe species, [24] or even toxicity associated with some Aloe vera preparations.…”

“…[16,76,89] Anthraquinones, especially aloe emodin and aloesin, were implicated in this anti-fungal activity, [76] however, the identity of anti-fungal components and their mechanisms of action have not been extensively examined. Similarly, the anti-viral activity of Aloe vera leaf extracts has been demonstrated, [18,90] although detailed purification, identification and mechanistic studies are required.…”

Interactive Antimicrobial and Toxicity Profiles of Scaevola spinescens R.Br. Extracts with Conventional Antibiotics

“…20 Another study confirmed antiviral activity for a methanolic S. spinescens extract using an MS2 bacteriophage model system. 19,21 These studies demonstrate the inhibitory potential of S. spinescens extracts against bacterial and viral pathogens. Our study aimed to extend these earlier studies by evaluating the growth inhibitory properties of S. spinescens leaf extracts against bacterial triggers of some autoimmune inflammatory diseases.…”

Screening of Brazilian medicinal plants for antiviral activity against rotavirus

“…The limited availability of antiviral drugs could be partially attributed to the Table 4 Conventional RT-PCR analysis of material collected after incubation for 48 h of MA-104 cells with rotavirus at 10 or 20 TCID50 and crude extracts at concentrations of 50 or 500 g/mL. difficulty of finding targets for drugs that eliminate the virus without harming the host cells (Cock and Kalt, 2010). Natural products from higher plants and marine organisms represent an almost inexhaustible resource of antiviral drug leads (Palombo, 2006;Sagar et al, 2010;Yasuhara-Bell et al, 2010).…”