FIG. 3.

Activation of PLA₂ in response to DEN-2 virus infection and induction of apoptosis by AA. (A) Activation of PLA₂ demonstrated by increased generation of AA. DEN-2 PL046 virus was incubated with MAb 8-1 specific to DEN-2 viral NS-1 protein or incubated with neutralizing MAb 56-3.1 specific to DEN-2 viral E protein for 1 h at 37°C. [³H]AA-prelabeled SK-N-SH cells were then infected with these virus-antibody mixtures. At the indicated times, the culture supernatants containing the mixtures were collected for radioactivity measurement. (B) Exogenous AA induced apoptosis of SK-N-SH cells in a dose-dependent manner. The percentages of apoptotic cells were determined at 48 h posttreatment. (C) DNA laddering induced by exogenous AA. SK-N-SH cells were mock infected or infected with DEN-2 PL046 virus at an MOI of 5. At 48 h p.i., cellular genomic DNA was extracted and subjected to a 2% agarose gel electrophoresis, stained with ethidium bromide, and visualized on a UV light box. The values represent the means ± SD of triplicate measurements from one of three similar experiments.