The Sensitivity of Adenovirus and Herpes simplex virus to Honey

Abstract

Honey has been used for centuries as a medicine to treat various ailments and infections. A large amount of research has established that honey has potent antibacterial activity. However, the sensitivity to honey of viral species that cause infections has been studied in only a small number of cases. The aim of this study was to obtain data to clarify and extend knowledge obtained from these previous studies of honey's antiviral activity, and especially study those viruses that cause localised infections which have limited or no therapy available, which are suitable to treatment with topically applied honey.

The susceptible A549 cell line and viral isolates of Adenovirus serotypes 1, 3, and 8, and Herpes simplex virus serotypes 1 and 2, were provided by the Waikato Hospital Virology Laboratory. A number of types of honey were investigated from a range of sources: Manuka honey with high concentrations of methylglyoxal, unique manuka factor activity, and phenolics, Honeydew and Rewarewa honeys which have high antioxidant activity, and Ling Heather honey which is high in phenolic compounds. These honeys were selected due to their range of characteristic activities in order to make comparisons with antiviral activity. A variety of tests using cell culture were developed to evaluate the sensitivity of the viruses to whole honey. Each test scored and monitored the development of morphological changes to the cells, to observe whether the honey treatment can prevent the development of these changes known as viral cytopathic effect. These included tests for: protection, in which the cells were pre-treated with, and incubated either with or without honey; prevention, where honey was used to treat infected cells, and in plaque reduction assays, to examine whether it can reduce the resultant number of plaques; and neutralisation, in which the virus was directly exposed to the honey for a defined period. It was found with each type of test using cell culture that many of the honeys studied can lower the severity of viral cytopathic effect or delay its onset compared with the development observed with virus that was not treated with honey. This can suggest that the antiviral activity may be a feature of more than one type of honey. In general the antiviral effect increased with the concentration of honey and time the virus was exposed to it. Manuka honey M116 at a concentration of 10% was effective in preventing the development of viral cytopathic effect of each of virus, after the viruses at concentrations in excess of the tissue culture infectious dose had been exposed to the honey for 8 hours. Enzyme-linked immunosorbant assays were used to measure the effect the successful treatments found in the extended neutralisation experiments had on viral surface proteins necessary for viral entry into the cells. The results using this technique suggested that there was very little virus present in the samples that had been treated with honey and with the untreated virus. Therefore it could not be shown whether the honey was acting via this mechanism. It is concluded from the findings in this study that honey is likely to be an effective antiviral treatment for the therapy of localised viral infections, this needs to be verified by clinical trials.