Neutralizing (54K) and Non-neutralizing (54K and 48K) Monoclonal Antibodies against Structural and Non-structural Yellow Fever Virus Proteins Confer Immunity in Mice

The capacity of monoclonal antibodies to protect mice passively against yellow fever (YF) virus infection was investigated. Both neutralizing (54K-specific) and non-neutralizing (54K- and 48K-specific) antibodies protected mice against challenge with the RMP substrain of YF virus. Average survival times of mice inoculated intracerebrally with a standard lethal dose of YF virus differed according to the strain used: thus mice inoculated with the most neurovirulent viruses, FNV and Asibi, survived for 6 X 50 and 7 X 65 days respectively, and those with RMP virus survived for 15 X 75 days. The capacity of antibodies to protect mice passively against virus challenge was directly related to virus neurovirulence. Possible mechanisms and the significance of protection by antibodies against non-structural proteins that do not mediate neutralization, are discussed.