In Vitro Evaluation of Antiviral Activity Effect of Selenium, Bacillus clausii Supernatant, and Their Combination on the Replication of Herpes Simplex Virus 1

About 70% of individuals worldwide suffer from herpes simplex virus 1 (HSV-1). Several studies have reported that selenium and supernatant of probiotic bacteria are antiviral; nevertheless, their effect alone or synergistically on HSV-1 is unknown.

The present study aimed to evaluate the antiviral effects of Bacillus clausii supernatant, selenium (Se), and their combination on HSV-1.

After determining cytotoxicity by the MTT assay, selenium and B. clausii supernatants were added to HeLa cells 24 hours before (pre-infection treatment) and after (post-infection treatment) HSV-1 inoculation. After 47 hours of incubation at 37°C, the viral titer and expression levels of the unique long 47 (UL47) gene were determined by the 50% tissue culture infectious dose (TCID50) and real-time polymerase chain reaction methods, respectively.

The bacterial supernatant in dilutions of 1:4 and 1:8, selenium in concentrations of 0.5 and 1 μM, and a combination of them had a cytotoxicity level lower than 80% in HeLa cells. The HSV-1 titers in pre-infection and post-infection assays with a dilution of 1:4 supernatant decreased by about 2.16 and 1 log10 TCID50/mL, respectively. Moreover, 1 μM Se could reduce the virus titer by 2.33 log10 TCID50/mL. The virus titer showed a greater decrease when Se and the bacterial supernatants were combined than when only one of the two was used. The highest selectivity index (SI) was obtained when selenium and bacterial supernatant were combined (SI = 29.2). The combined use of 1 μM Se and a 1:4 dilution of B. clausii supernatant caused the greatest drop in virus titer (3.3 log10 TCID50/mL) in comparison to other treatment conditions. The UL47 gene expression was reduced by Se at concentrations of 0.5 and 1 μM by about 1.6- and 2-fold, respectively. The UL47 expression showed a higher decline when selenium and bacterial supernatant were combined than when only one of the two was employed, which is similar to viral titer data.

Selenium and the supernatant of B. clausii have potent antiviral activity against HSV-1. The combination of selenium and the bacterial supernatant has a synergistic effect in reducing HSV-1 replication. However, further research is required to fully understand how they inhibit viruses.