In vitro evaluation of inhibitory effect of Lactobacillus reuteri supernatant on the replication of herpes simplex virus type 1 and expression of UL54, UL52 and UL27 genes

Human herpes virus type 1 (HSV-1) is a neurotropic pathogen that is infected more than 70% of the world population. The increasing of viral resistance to antiviral drugs and the emergence of side effects has motivated researchers to study the use of probiotics as new antiviral agents. The aim of the present study was to study for the first time the potential antiviral activity of Lactobacillus reuteri (L. reuteri) supernatant against HSV-1.

After measuring the cytotoxicity of L. reuteri supernatant by MTT assay, 1:16 dilution of it was added to HeLa cells before and after HSV-1 infection, after 1.5 hours incubation with HSV-1, and simultaneously with HSV- 1 infection. After 48 hours of incubation at 37°C, the viral titer and expression levels of UL54, UL52 and UL27 genes were measured by tissue culture infectious dose 50 (TCID ) and Real-Time PCR methods, respectively.

HSV-1 titer in the treatment conditions before infection, incubation with HSV-1, simultaneously with infection and after infection was reduced by 0.42, 3.42, 1.83, and 0.83 log 10 TCID /ml, respectively. When the bacterial supernatant was first incubated with the virus and then added to the cell, or when it was added simultaneously with the virus, the expression of the UL27, UL52, and UL54 genes decreased significantly (p<0.05). When the bacterial supernatant is added to the cell before or after virus infection, the expression of UL52 and UL54 genes does not change significantly (P>0.05).

The study findings indicated that the supernatant of L. reuteri has a potent anti-HSV-1 effect especially if it is incubated with the virus before inoculation into the cell. Its possible antiviral mechanism is to inhibit the virus by binding to it or changing the surface structure of the virus. Metabolites of L. reuteri can be considered as a novel inhibitor of HSV-1in- fection.