Defective interfering particles

[Lemay Guy]

I refer you to the Virology Directory & Dictionary of animal, bacterial 
and plant viruses by Hull, Brown and Payne, Stockton Press 1989.  This 
is probably the best place to find short and accurate definition of 
virological topics.  The new Encyclopedia of Virology is also a good,  
although more expensive book.

Defective interfering particles (DI particles): Virus particles which 
lack part of the genome of the standard virus and which interfere with 
the replication of the standard virus (by competion between the defective 
genome and the standard one for a limited supply of viral proteins).  The 
nucleic acids in DI particles depend upon the standard virus for their 
replication.  DI particles are produced by growing virus at high 
multiplicity of infection.

NB: this is partially responsible for the fact that in most viral stocks 
the total number of viral particles observed by electron microscopy is 
much higher than the titer of infectious virus

Guy Lemay
Departement de Microbiologie et Immunologie
Universite de Montreal
EMail: lemayg at ERE.UMontreal.CA