Yellow fever virus. I. Development and evaluation of a plaque neutralization test.

Heretofore, the most reliable way of measuring yellow fever virus antibody was to use the mouse neutralization (MN) test employing either suckling or weanling mice. Certain disadvantages (e.g., expense both of animals and of maintaining a mouse colony, allergic reactions of many laboratory workers, and the relatively long time, 21 days, before end points are reached) are inherent in any program with mice or other laboratory animal species and have discouraged the use of the MN test by many laboratories. A previously reported plaque neutralization (PN) test with primary chick embryo cell cultures could not be consistently reproduced by later investigators. We have developed a convenient and reproducible PN test employing the MA-104 embryonic rhesus monkey kidney cell culture and a single agar-overlay procedure. When compared with MN tests with newborn (1 to 3 days old) and weanling (16 to 20 g, 24 to 28 days old) mice inoculated by the intracranial route, the PN test was the most sensitive for measuring neutralizing antibody; it was also less variable, less costly, and it achieved results in the shortest period of time. End points could be determined in 5 to 6 days for the PN test as compared to 21 days for the MN test.