RE: Virology Digest, Vol 29, Issue 1
Dunowska, Magda
If you have a pure virus prep, maybe you could titrate it (to get PFU/mL value), and then extract viral DNA and estimate the number of viral particles based on the amount of viral DNA present, knowing that parvoviruses have a single-stranded DNA genome about 5.2 kbp in size? Just a thought...
Magda
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Subject: Virology Digest, Vol 29, Issue 1
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Today's Topics:
1. particle to pfu ratios (Bowers, Doria)
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Message: 1
Date: Wed, 7 May 2008 12:26:10 -0400
From: "Bowers, Doria" <dbo...@unf.edu>
Subject: [Virology] particle to pfu ratios
To: <viro...@magpie.bio.indiana.edu>
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<783CE756031AB141B532...@DIAMOND.unfcsd.unf.edu>
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We are wondering what the particle:PFU ratio is for porcine parvovirus.
Any ideas how to acquire this statistic?
Doria Bowers
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Dunowska, Magda
If you have a pure virus prep, maybe you could titrate it (to get PFU/mL value), and then extract viral DNA and estimate the number of viral particles based on the amount of viral DNA present, knowing that parvoviruses have a single-stranded DNA genome about 5.2 kbp in size? Just a thought...
Magda
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Randhawa, Parmjeet
particles could also be quantitated by electron microscopy but that will
not distinguish viable from non-viable virions.
Parmjeet Randhawa, M.D.
Professor of Pathology,
Division of Transplant Pathology,
University of Pittsburgh, Department of Pathology,
E737 UPMC-Montefiore Hospital,
3459 Fifth Ave, Pittsburgh, PA 15213.
Phone: 412 647 7646
Fax: 412 647 5237
Dunowska, Magda
Hi everybody,
With respect to Parmjeet's email below: I got the 5.2 from a description in a veterinary virology book, but after your email I did check that info. So, parvovirus genomes are 5 kbp long according to the latest report on virus taxonomy (http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.050.1.01.htm) and the available full genome sequences of porcine parvovirus on GenBank are about this length (a link to a recent submission of a whole sequence of 5075 bp: http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=9628826).
Also, I am not sure how accurate the EM would be for quantifying viral particles, as it is a pretty insensitive tool and one needs at least 10*6 particles/mL to be even able to see them under EM, but I would be very interested to know whether or not anybody out there have used it for this purpose?
Magda Dunowska, LW (vet), PhD
Senior Lecturer in Veterinary Infectious Diseases (Virology)
Institute of Veterinary, Animal and Biomedical Sciences
Te Kura Mātauranga Kararehe
Massey University
Palmerston North
New Zealand
Phone : (06) 356-9099 ext 7571
Website : http://ivabs.massey.ac.nz
Randhawa, Parmjeet
Thanks for the correction. I was confusing genome size with virion diameter. Parvovirus is much smaller (approximately 20 nm versus 50 nm).
The low sensitivity of electron microscopy is an issue for clinical diagnosis but should not be for virus grown in culture. I do not have personal experience in quantitation or the accuracy thereof.
I will be interested in data on the accuracy of PFU measurements too. Since it involves serial dilution of a stock the accuracy would depend on how many dilution steps are used before actual plating.
Parmjeet