Related Experiment Video
Updated: Mar 11, 2026
Expression and Purification of Virus-like Particles for Vaccination
Published on: June 2, 2016
(In)validating experimentally derived knowledge about influenza A defective interfering particles
Laura E Liao1, Shingo Iwami2,3, Catherine A A Beauchemin4,5
1Department of Physics, Ryerson University, Toronto, Canada.
Abstract:
A defective interfering particle (DIP) in the context of influenza A virus is a virion with a significantly shortened RNA segment substituting one of eight full-length parent RNA segments, such that it is preferentially amplified. Hence, a cell co-infected with DIPs will produce mainly DIPs, suppressing infectious virus yields and affecting infection kinetics. Unfortunately, the quantification of DIPs contained in a sample is difficult because they are indistinguishable from standard virus (STV). Using a mathematical model, we investigated the standard experimental method for counting DIPs based on the reduction in STV yield (Bellett & Cooper, 1959, Journal of General Microbiology 21, 498-509 (doi:10.1099/00221287-21-3-498)). We found the method is valid for counting DIPs provided that: (i) an STV-infected cell's co-infection window is approximately half its eclipse phase (it blocks infection by other virions before it begins producing progeny virions), (ii) a cell co-infected by STV and DIP produces less than 1 STV per 1000 DIPs and (iii) a high MOI of STV stock (more than 4 PFU per cell) is added to perform the assay. Prior work makes no mention of these criteria such that the method has been applied incorrectly in several publications discussed herein. We determined influenza A virus meets these criteria, making the method suitable for counting influenza A DIPs.
Insights
Quantifying defective interfering particles (DIPs) in influenza A virus is challenging. This study validates a standard method for counting DIPs by establishing crucial criteria for its accurate application.
Area of Science:
- Virology
- Molecular Biology
- Mathematical Modeling
Background:
- Defective interfering particles (DIPs) are shortened viral RNA segments that interfere with standard virus (STV) replication.
- Quantifying DIPs is difficult due to their indistinguishability from STV.
- Previous methods for DIP quantification have lacked clear validation criteria.
Purpose of the Study:
- To investigate and validate the standard experimental method for counting DIPs based on STV yield reduction.
- To establish the specific criteria required for the accurate application of this DIP quantification method.
Main Methods:
- Utilized a mathematical model to analyze the standard DIP quantification method.
- Evaluated the impact of co-infection dynamics, STV/DIP production ratios, and multiplicity of infection (MOI) on assay validity.
- Assessed the applicability of the validated method to influenza A virus.
Main Results:
- The standard method for counting DIPs is valid under specific conditions.
- Key criteria include: STV co-infection window relative to eclipse phase, low STV production per DIP, and high STV MOI.
- Influenza A virus meets these criteria, confirming method suitability.
Conclusions:
- The standard method for DIP quantification is reliable for influenza A virus when specific criteria are met.
- Identified and clarified critical parameters previously overlooked in DIP quantification studies.
- Provides a validated approach for accurate DIP measurement in influenza A research.
