Antiviral effects of blackberry extract against herpes simplex virus type 1

Abstract

Objective: The aim of this study was to evaluate antiviral properties of blackberry extract against herpes simplex virus type 1 (HSV-1) in vitro.

Study design: HSV-infected oral epithelial (OKF6) cells and cell-free virus suspensions were treated with blackberry extract (2.24-1,400 μg/mL), and virus yield and infectivity were quantified by direct plaque assay.

Results: Blackberry extract ≥56 μg/mL inhibited HSV-1 replication in oral epithelial cells by >99% (P < .005). Concentrations ≥280 μg/mL were antiviral when the extract was added after virus adsorption and entry. Exposure of cell-free virus to ≥280 μg/mL blackberry extract for 15 minutes at room temperature was virucidal (P = .0002). The virucidal effects were not due to pH changes at concentrations up to 1,500 μg/mL.

Conclusions: Blackberry extract inhibited the early stages of HSV-1 replication and had potent virucidal activity. These properties suggest that this natural fruit extract could provide advantage as a topical prophylactic/therapeutic agent for HSV infections.

Copyright © 2011 Mosby, Inc. All rights reserved.

Figures

Figure 1. Blackberry Extract has antiviral properties

Oral epithelial cells were inoculated with HSV-1 strain 17+ (MOI = 0.05) in the presence of the indicated concentration of blackberry extract. Following cell adsorption at 37°C and two rinses with PBS, fresh cell culture media containing the indicated concentration of blackberry extract was added and incubation was continued overnight at 37°C. Twenty four hours post inoculation, cells were freeze-thawed 3 times and virus yield was quantified on Vero cell monolayers by the direct plaque assay. Data represents the average +/− SD of triplicate replication assays (i.e. n = 3). *, p < 0.005.

Figure 2. Cell entry protects HSV-1 from antiviral effects of blackberry extract

HSV-1 strain 17+ was added to oral epithelial cells at an MOI = 0.05 and allowed to adsorb and enter for 1 hr at 37°C. Fresh cell culture media, containing the indicated concentration of blackberry extract, was added and incubation was continued overnight, followed by two PBS rinses. Twenty four hours post inoculation, cells were freeze-thawed 3 times and virus yield was quantified on Vero cell monolayers by the direct plaque assay. Data represents the average +/− SD of triplicate replication assays (i.e. n = 3). *, p < 0.005.

Figure 3. BBE inactivates HSV-1

Cell-free suspensions of HSV-1 (Strain 17+) were incubated at 37°C for 1 hr with the indicated concentration of BBE. Infections virus was quantified by the direct plaque assay in triplicate. Results are the average of two independent experiments (n = 2) and are presented relative to untreated controls (100%). *, p < 0.005.

Figure 4. BBE inactivates HSV-1

Cell-free suspensions of HSV-1 (Strain 17+) were incubated at room temperature for 15 minutes with the indicated concentration of BBE. Infectious virus was quantified by the direct plaque assay in triplicate. Results are the average of two independent experiments in duplicate (n = 4) and are presented relative to untreated controls (100%). *, p < 0.005.