Optical brighteners provide Baculovirus activity enhancement and UV radiation protection

Fluorescent brighteners increase insect viral activity and provide protection against UV inactivation. The relative amount of viral UV protection has not previously been determined due to the dual nature of these compounds. In this study, two distinct viral-host systems, a nuclear polyhedrosis virus of the gypsy moth (Lymantria dispar) infecting its homologous host and a nuclear polyhedrosis virus of the alfalfa looper (Autographa californica) infecting the cabbage looper (Trichoplusia ni), were treated with various regimes of UV light from 0.5 to 120 min and fluorescent brightener 28 and were subsequently assayed with and without fluorescent brightener 28. A comparison of LC(50)s from the various treatments produced similar viral bioassay profiles in both systems. The fluorescent brighteners protected insect viruses from UV inactivation and enhanced residual activity of active virus. For the gypsy moth virus, the enhancement was 214-fold for its homologous host and for the A. californica virus, the enhancement was 41-fold for T. ni.