Quantitative aspects of nuclear polyhedrosis virus infections in lepidopterous larvae: The dose-survival time relationship

Abstract

Dose-survival time relationships are presented for neonate larvae of Heliothis zea inoculated with H. zea singly embedded nuclear polyhedrosis virus (HzSNPV) and Trichoplusia ni inoculated with the 1A clone of Autographa californica multiply embedded NPV, the HOB-mutant of this clone, or T. ni SNPV. For each of these virus-host combinations, plots of median survival time (ST) against logarithm of the inoculum concentration have the shape of an inverted sigmoid curve. The plateau of ST 50 values at low doses is interpreted as resulting from the dose received by responding larvae remaining constant while the proportion of treated larvae receiving this dose decreases; evidence is presented that the plateau values at high doses are not produced by saturation of virus receptor sites on the midgut epithelium. A close similarity was noted between the dose-survival time relation of baculoviruses and their hosts on the one hand, and that of vertebrate pathogens and their hosts on the other; for the latter, mathematical modelswith predictive power have been developed.