Enhancing insecticidal efficacy of baculovirus by early expressing an insect neurotoxin, LqhIT2, in infected Trichoplusia ni larvae.

LqhIT(2), an insect specific neurotoxin from the venom of Leiurus quinquestriatus hebraeus, has been demonstrated to improve insecticidal efficacy of Autographa californica nuclear polyhedrosis virus (AcMNPV). A polyhedrin-positive recombinant AcMNPVvAcP(hsp70)EGFP/P(pag90)IT(2) was engineered for larvae to express the enhanced green fluorescence protein (EGFP) and LqhIT(2) under the control of P(hsp70) and P(pag90) promoters, respectively. This would allow a visual observation of the viral infection and an improvement of the insecticidal efficacy. The insecticidal activity of this recombinant baculovirus, a wild type AcMNPV and four other recombinant baculoviruses, was evaluated and compared in terms of mortality, body weight, median lethal time (LT(50)), and median lethal concentration (LC(50)). Insecticidal efficacy was unaltered when treated with vAcP(hsp70)EGFP, moderately improved when infected by vAcP(10)IT(2) (a P(10)-promoted LqhIT ( 2 ) gene), and significantly elevated when treated with vAcP(pag90)IT(2) or vAcP(hsp70)EGFP/P(pag90)IT(2). No apparent difference was observed in insecticidal efficacy when additional EGFP was expressed as a visible marker. These results suggest that recombinant AcMNPV vAcP(hsp70)EGFP/P(pag90)IT(2) may be used as an effective insecticide against Trichoplusia ni and other lepidopterous insect pests.