Induction of apoptosis by dengue 2 (New Guinea C strain) virus infection in vitro

The effect of dengue 2 (New Guinea C strain; NGC) virus infection on the host cell genome was investigated. Vero cells exposed to dengue 2 NGC virus inoculum showed oligonucleosomal DNA ladders by agarose gel electrophoresis after approximately 8 days post-exposure (PE). Using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL), the presence of apoptotic cells in the dengue 2 NGC inoculum-treated Vero cell cultures was demonstrated. Approximately 31% of the infected cells were apoptotic by day 11 PE. The presence of apoptotic cells was correlated strongly (r > 0.75, Pearson) with the presence of dengue virus antigens. When purified dengue 2 virus was used a significant (P < 0.001, ANOVA) multiplicity of infection (MOI)-dependent increase in the number of apoptotic cells was observed. Furthermore, inactivation of the virus with heat and ultraviolet irradiation abrogated the ability of the virus to induce apoptosis. Thus, suggesting that infectious dengue 2 NGC virus could affect the host cells by inducing apoptotic responses.