Antiviral Activity of Rosa damascena Mill. and Rosa alba L. Essential Oils against the Multiplication of Herpes Simplex Virus Type 1 Strains Sensitive and Resistant to Acyclovir

Simple Summary Herpes simplex virus type 1 (HSV) is a coated DNA virus of the Herpesviridae family. It causes painful infections of the mouth, throat, face, eyes, central nervous system, as well as infections of the anal-genital area. The specific drugs for chemotherapy of HSV have been based on nucleoside analogues, with acyclovir (ACV) being the most widely used. The most serious problem in the application of nucleoside analogues is the rapid formation of resistant mutants, which also often leads to treatment failure. The search for new therapeutic alternatives for the treatment of HSV is necessary for the successful control of diseases caused by herpes infection. Rose essential oils are widely used in alternative medicine due to their many proven benefits for human health. In the treatment of bacterial and viral infections, they reduce the chance of developing resistance. In this study, we investigated the effects of the Bulgarian Rosa damascena Mill. and Rosa alba L. essential oils on the viral reproduction of susceptible (Victoria strain) and acyclovir-resistant (R-100) strains individually and in combination with acyclovir. When the rose oils were added after the virus entered the cell, co-administered with ACV at a concentration four times lower than the IC50, they contributed to a significant reduction in viral yield by more than 20% of the expected inhibition of viral replication in the Victoria strain and more than 10% of the previously presumptive inhibition in the R-100 strain. Background: The specific chemotherapeutics against herpes simplex virus type 1 (HSV) are nucleoside analogues such as acyclovir (ACV), but the most important problem is the formation of resistant mutants. The search for new therapeutic alternatives leads us to the purpose of investigating the effects of Rosa damascena Mill. and Rosa alba L. essential oils on the viral reproduction of susceptible (Victoria) and acyclovir-resistant (R-100) strains of HSV-1 replication in vitro, individually and in combination with acyclovir. Methods: Cytopathic effect inhibition test was used for assessment of antiviral activity of the oils, and the three-dimensional model of Prichard and Shipman was applied to evaluate the combined effect of oils with ACV on HSV-1 replication. Results: Both oils do not affect the replication of viral strains; they are able to influence only viral adsorption and extracellular virions and protect healthy cells from subsequent infection. In combination with lower doses of acyclovir, both oils demonstrate a significant synergistic effect on the replication of HSV-1, which is more contagious than the Victoria strain. Conclusions: The nonspecific mechanism of the reduction in viral reproduction caused by rose oils and the synergistic effect of their co-administration with the lower doses of specific inhibitor ACV makes them suitable therapeutics for overcoming viral resistance to HSV-1 infections.