Chapter IX 



Biochemistry of Insect Viruses* 



G. H. Bergold 

 Laboratory of Insect Pathology, Sault Ste. Marie, Ontario, Canada 



I. The Chemical Changes in the Insect Host during Virus Infection 505 



II. Physicochemical Properties and Chemical Composition of Inclusion Bodies 507 



A. Physicochemical Properties 507 



B. Chemical Composition of Inclusion Body Proteins 510 



III. Chemical Composition of Virus Particles 513 



References 521 



Considerable information is available on the morphology and physico- 

 chemical properties of insect viruses and their inclusion body proteins 

 (Bergold, 1957, and Sections II and III following). Although to date few 

 concrete results have been obtained on biochemical changes in infected host 

 insects it is hoped that the following summary of data will stimulate further 

 investigations using recently developed biochemical techniques. 



I. The Chemical Changes in the Insect Host dueing Virus 



Infection 



Komarek and Breindl (1924) and Breindl (1938) investigated the meta- 

 bolism of Lymantria monacha (L.) larvae that were suffering from nuclear 

 polyhedrosis. They found a decrease of the Feulgenpositive chromatin m 

 infected nuclei during the formation of polyhedra, which suggests that 

 chromatin material is perhaps converted into polyhedra. Similar results were 

 obtained by Gratia et al. (1945), who observed, two days after infection, an 

 increase of deoxyribonucleic acid (DNA) in the chromatin and of ribonucleic 

 acid (UNA) in the cytoplasm and nucleoli in cells of Bomhyx mori (L.). The 

 increase continues until the fourth day, when DNA appears in the "ring 

 zone," but the nucleoli disappear during the formation of polyhedra. An 

 increase of DNA and RNA in diseased B. mori larvae was also found with 

 histochemical methods by Semenova (1951). Extraction experiments have 

 shown an mcrease of DNA and a decrease of UNA in diseased B. mori 



* Contribution No. 438 Division of Forest Biology, Science Service, Department of 

 Agriculture, Ottawa, Canada. 



Author's note: This subject was last reviewed in my contribution on Insect Viruses pub- 

 lished in Volume IV of the Handbuch der Virusforschung, Springer Verlag, Vienna, 1957. 



505 



