Atividade de três drogas antivirais sobre os herpesvírus bovino tipos 1, 2 e 5 em cultivo celular / Activity of three antiviral drugs against bovine herpesviruses 1, 2 and 5 in cell culture

ABSTRACT

The activity of three anti-herpetic drugs (Acyclovir [ACV], Gancyclovir [GCV] and Foscarnet [PFA]) was tested against bovine herpesvirus 1 (BoHV-1), 2 (BoHV-2) and 5 (BoHV-5) in vitro using the plaque reduction assay. Different drug concentrations were tested against one hundred 50 percent tissue culture infectious dose (TCID50) of the respective viruses. Drug concentrations lower than 200μg/mL resulted in viability rates of more than 80 percent for MDBK and Hep2 cells in the MTT test (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). The selectivity index (IS) of the drugs was calculated dividing the concentration of the drug that is cytotoxic for 50 percent of the cells (CC50) by the concentration of the drug that was effective in reducing by 50 percent the number of viral plaques (EC50) for the three herpesviruses. Thus, ACV was shown to be moderately active against BoHV-1 (EC50 112.9μg/mL; IS 4.5), BoHV-2 (EC50 114.2μg/mL; IS 4.5) and BoHV-5 (EC50 96.9μg/mL; IS 5.3). GCV was effective against BoHV-2 (EC50 33.5μg/mL; IS 16.6), moderately effective against BoHV-5 (EC50 123.2μg/mL; IS 4.5) and poorly active against BoHV-1 (EC50 335.8μg/mL; IS 1.7). PFA exhibited the highest antiviral activity, being the only drug that, at concentration of 100μg/mL, completely inhibited plaque formation by all three viruses. PFA was the most effective in vitro against BoHV-1 (EC50 29.5μg/mL; IS 42.2), BoHV-2 (EC50 45.2μg/mL; IS 27.6) and BoHV-5 (EC50 7.8μg/mL; IS 160.6). Thus, the results indicate that PFA is a promising candidate for experimental therapeutic testing in vivo against bovine herpesviruses.

RESUMO

A atividade de três fármacos antivirais (Aciclovir [ACV], Ganciclovir [GCV] e Foscarnet [PFA]) foi testada in vitro frente aos herpesvírus bovino tipos 1 (BoHV-1), 2 (BoHV-2) e 5 (BoHV-5). Para isso, utilizou-se o teste de reducao de placas virais em cultivo celular, testando-se diferentes concentracoes dos farmacos frente a 100 doses infectantes para 50 por cento dos cultivos celulares (DICC50) dos respectivos virus. Pelo teste de MTT (3-(4,5-Dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide), verificou-se que concentracoes inferiores a 200ƒÊg/mL dos tres antivirais resultaram em indices de viabilidade de celulas MDBK e Hep2 superiores a 80 por cento. Com base na concentracao citotoxica para 50 por cento das celulas (CC50) e na concentracao dos farmacos efetiva para inibir em 50 por cento o numero de placas virais (EC50), calculou-se o indice de seletividade (IS) dos antivirais para os tres herpesvirus. Assim, o ACV demonstrou ser moderadamente ativo frente ao BoHV-1 (EC50 112,9ƒÊg/mL e IS 4,5), ao BoHV-2 (EC50 114,2 ƒÊg/mL e IS 4,5) e BoHV-5 (EC50 96,9ƒÊg/mL e IS 5,3). O GCV apresentou atividade moderada frente ao BoHV-2 (EC50 33,5ƒÊg/mL e IS 16,6) e, em menor grau, contra o BoHV-5 (EC50 123,2ƒÊg/mL e IS 4,5), sendo ineficaz frente ao BoHV-1 (EC50 335,8ƒÊg/mL e IS 1,7). O PFA apresentou atividade antiviral mais pronunciada, sendo o unico farmaco que, na concentracao de 100ƒÊg/mL, inibiu completamente a producao de placas pelos tres virus testados. O PFA foi o mais efetivo in vitro frente ao BoHV-1 (EC50 29,5ƒÊg/mL e IS 42,2), ao BoHV-2 (EC50 45,2ƒÊg/mL e IS 27,6) e ao BoHV-5 (EC50 7,8ƒÊg/mL e IS 160,6). Portanto, os resultados obtidos indicam que o PFA pode se constituir em um candidato para terapia experimental de infeccoes pelos herpesvirus de bovinos in vivo.