Observations on the nature of the carbonate dissolution process on inclusion bodies of a nuclear polyhedrosis virus of Pseudaletia unipuncta

Abstract

Evidence is cited for the existence of a polyhedral envelope surrounding polyhedral inclusion bodies (PIB's) of a nuclear polyhedrosis virus of Pseudaletia unipuncta. Similar envelopes have been referred to as membranes by many investigators working on other types of nuclear polyhedrosis viruses. Under certain alkaline conditions, the PIB's swell, they become less refractive to light, the polyhedral matrix protein dissolves, and the occluded virions exhibit Brownian movement within the envelope. An in vitro technique is described for studying the effects of pH and molarity of the carbonates on air-dried PIB's. A curvilinear relationship exists between the molarity of the carbonate solution employed and the lowest pH at which the swollen enveloped PIB's occurred. As carbonate molarity increased from 0.025 m to 0.100 m, swollen, enveloped PIB's were observed at correspondingly lower pH values. Besides the molarity- pH relationship, metallic cations were shown to be necessary in basic solutions to produce the swollen enveloped type of PIB's. A 29% NH 4OH solution at pH 12.9 did not produce swollen enveloped PIB's. However, the addition of Na + ion to 29% NH 4OH at pH 12.9 produced swollen, enveloped PIB's. It was also determined that swollen, enveloped PIB's could be transformed into intact PIB's by neutralizing the surrounding medium and that these intact PIB's could be enveloped again below the isoelectric point of the polyhedral matrix protein by treating the PIB's with dilute CH 3COOH at pH 4.0. A theory for the mode of action of metallic cations in these reactions is proposed.