NO ASSOCIATION BETWEEN VIRAL CYTOPATHIC EFFECT IN MCCOY CELLS AND MTT COLORIMETRIC ASSAY FOR THE IN VITRO ANTI-RABIES EVALUATION.

Rabies is an important viral disease with a great impact on public health due to its extensively fatal outcome. In endemic areas, rabies may be responsible for over 50,000 human fatalities per year, which is a high number, since a well-established prophylaxis by immunization is available. Despite experimental protocols, no antiviral drugs are currently effective against rabies virus infection. For this reason, antivirals directed to treat human rabies need to be developed. In order to standardize in vitro antiviral screening for rabies virus, we evaluated two methods: the inhibition of cytopathic effect (CPE) and the MTT assay. Anti-rabies activity was only measurable by CPE, while the MTT assay failed to detect antiviral activity in rabies infected McCoy cells. In addition, no significant correlation was observed when comparing both assays. The correlation between the inhibition of CPE and MTT assay was shown when Vero cells were infected with herpes simplex virus type 1 and Hep-2 cells were infected with adenovirus type 5, reinforcing that despite the reliable CPE, McCoy cells infected with rabies cannot be assessed by MTT. In conclusion, these results have shown that the inhibition of CPE should be used for anti-rabies screening in McCoy cells, while the MTT assay was unsuitable in this in vitro system. DOI:  http://dx.doi.org/10.17525/vrr.v17i1-2.57