SINGLE-DOSE ASSAY TECHNIQUE FOR VARIOLA VIRUS
Abstract
The standard measurement for assay of the pox viruses is titration of pock-infectious units (PIU) on the chorioallantoic membrane (CAM) of embryonated eggs. Pock counts are not only time consuming and imprecise but also do not always reflect the degree of animal infectivity. Thus a biological assay is needed that would (1) require a minimum of time and (2) have acceptable precision. Preliminary titrations made in 11 day-old embryonated eggs and in suckling mice (6 to 24 hours of age) demonstrated a linear relationship between the concentration of variola virus injected and the mean time to death (MTD) of the hosts. This linear response indicated the injection of a single dose of virus suspension and the measurement of the MTD should result in an acceptable assay method. Seven replicate samples of liquid preparations (20 per cent CAM in heart infusion broth) and the freeze dried material obtained with these suspensions were assayed in triplicate and the MTD values (in hours) with estimated 95 per cent confidence limits were: Preparation Eggs Suckling Mice Liquid 76 = 18 181 = 14 Dry 42 = 6 107 = 13 The use of the MTD assay resulted in a saving of time, a saving in the number of hosts necessary per assay, and increased precision.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1963
- Accession Number
- AD0407086
Entities
People
- Jean M. Riley
- Michael D. Orlando
Organizations
- United States Army Biological Warfare Laboratories