Correlation of genetic variability with safety of mumps vaccine Urabe AM9 strain

The Urabe AM9 strain of mumps vaccine live is known for its genetic instabi lity and some vaccines derived from this strain were withdrawn from the mar ket due to an excessive number of vaccine-associated parotitis and meningit is cases. To identify the molecular basis of this instability, we determine d complete nucleotide sequences of several stocks of the Urabe strain used for vaccine production by different manufacturers and of two clinical Isola tes from cases of vaccine-associated meningitis. In contrast to previously published studies relating the Lys(335) --> Glu mutation in the viral HN ge ne with neurovirulence of mumps virus, we could not confirm any association of this mutation with the safety of mumps vaccine. Each of the three vacci ne stocks studied had its own characteristic profile of mutations that was identified by cDNA sequencing and quantitated by mutant analysis by PCR and restriction enzyme cleavage. Determination of the mutational profile of mu mps vaccine lots could allow vaccine manufacturers to characterize seed vir uses and monitor the consistency of vaccine production to prevent emergence of virulent revertants.