Measurement of trace element levels in noctuid larvae in response to baculovirus infections

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] While a number of studies have examined the effects of viral infections on the trace element status of mammals, very little is known about the roles of trace elements in insect development, plant host interaction, and response to viral infection. Inductively coupled plasma-mass spectrometry (ICP-MS) and radioactive tracers were used to investigate changes in multiple trace element (Mg, Mn, Fe, Cu, Zn and Mo) levels in the plasma/hemolymph and organs of larvae of Heliothis virescens and Helicoverpa zea (Lepidoptera: Noctuidae) during normal development and in response to baculovirus infection in their 4th and 5th instars. In ICP-MS analysis, all of the trace elements measured in the plasma of H. virescens and H. zea changed during normal development of 4th and 5th larvae. Most of the measured trace element levels in the midgut and fatbody of 4th instar H. virescens changed during larval development. Both Helicoverpa zea single nucleopolyhedrosis virus (HzSNPV) and Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infections altered the measured trace element levels in the plasma of 4th instar H. virescens. The tracer studies with 59Fe and 65Zn demonstrated a rapid uptake, rapid clearance from the midgut lumen and epithelium, and redistribution into hemolymph and other tissues after initial uptake of dietary Fe and Zn. Late in the course of baculoviral infection high amounts of 59Fe radiotracer are released into the hemolymph bound to proteins which have greater than 10,000 molecular weight. The zinc radiotracer was found significantly lower in the hemolymph in the late course of baculovirus infection. This study demonstrates that trace element levels in the tissues of 4th and 5th instar H. virescens and H. zea changed during development and in response to baculovirus infections.