Summary
A technic for a virus neutralization test, capable of standardization both as to procedure and interpretation, has been described. Individual ampules of virus-suspension are frozen and stored at −76 C, then titrated under the exact conditions of time, temperature and serum-concentration as employed in the neutralization-test. Based on the determined range of variability of host-susceptibility to each virus, the higher dilution for the neutralization-test was selected, thus obtaining maximal sensitivity. The value of the function of this dilution to the fifty per cent end-point dilution is adopted as a “actor” for use with any other titrated suspension of the same virus. “Factors” have been determined for the viruses of St. Louis encephalitis, Western equine encephalomyelitis and the Armstrong adapted Lansing strain of poliomyelitis virus. Details are presented of a satisfactory technic to be used for each virus, and the reasons for the differences are considered.
Footnotes
Aided by a grant from the National Foundation for Infantile Paralysis, Inc.
