Accession Number : AD0291632

Title :   ESTIMATION OF LD50 TITER OF VENEZUELAN EQUINE ENCEPHALOMYELITIS PREPARATIONS FROM A SINGLE-DILUTION ASSAY,

Corporate Author : ARMY BIOLOGICAL LABS FREDERICK MD

Personal Author(s) : RILEY, JEAN M. ; PATRICK, WILLIAM C. III ; CAMPBELL, WILLIAM E. JR.

Report Date : DEC 1962

Pagination or Media Count : 1

Abstract : When suspensions of Venezuelan equine encephalomyelitis (VEE) virus were injected intracerebrally into groups of mice, a nearly linear relationship was observed between the concentration of the virus injected and the mean reciprocal time-to-death of the mice. Ninety-one VEE preparations were assayed in duplicate, and by plotting the relationship between the reciprocal time-to-death for mice given the 10 to the minus 6 dilution of virus and the MICLD50 values for the virus preparations, a reference curve was established. Using this reference curve it was possible to estimate directly the LD50 values of virus suspensions of unknown concentration from the mean reciprocal time-todeath of a group of mice injected with a single dilution. In this work, the number of mice used was reduced by 62.5 per cent, the titrations were complete in three to five days compared with the usual ten to fourteen days, three to four times as many assays could be done in a day, and no assays had to be repeated since end-points were not missed. The precision of the singledilution assay compared favorably with that of the LD50 titration. (Author)

Descriptors :   *EQUINE ENCEPHALOMYELITIS VIRUS, *VIRUSES, DOSAGE, MEASUREMENT, MICE.

Distribution Statement : APPROVED FOR PUBLIC RELEASE