Further-attenuated measles vaccine: virus passages affect viral surface protein expression, immunogenicity and histopathology pattern in vivo.

Measles vaccine viruses Leningrad-16 (L-16) and Moscow-5 (M-5, an L-16-derived clonal variant), at passage levels used for vaccination and after ten further low-multiplicity passages on quail embryo (QE) cells, were compared for (1) immunogenicity, (2) histopathological lesions induced in vivo and (3) surface protein expression within infected cells and on the virion surface. At the 10th passage, viruses evoked a poorer neutralizing antibody response in guinea pigs, induced an earlier appearance of more pronounced pathological lesions and replicated faster in Vero cells than the original viruses. H protein expression increased 1.8-2.3-fold after 10 passages of the L-16 variant, but remained virtually unaltered for the M-5 variant. F protein expression of both 10th-passage variants was 0.5-0.8 that of the original virus variants. A similar two-fold decrease in F protein expression was noted after a single virus passage in guinea pigs. The data implicate the loss of F protein as a cause of reduced immunogenicity of further attenuated measles vaccines.

Comparative clinico-morphological investigations of the CNS of monkeys and of the eye teguments of guinea pigs infected with different measles virus strains.

Measles virus strains Edmonston and L-16 have been studied in 10 intracerebrally (i.c.) infected monkeys and in 155 guinea pigs infected into the anterior eye chamber. The strains appeared to differ in pathogenicity for monkeys and guinea pigs. The more pathogenic Edmonston strain caused encephalitis in monkeys, whereas in guinea pigs it caused iridocyclitis, keratoconjunctivitis and follicular conjunctivitis. Strain L-16 was not neurovirulent for monkeys, while in guinea pigs it caused follicular conjunctivitis. Specific pathohistological changes detected in the CNS of monkeys and in the eye teguments of guinea pigs were confirmed by virologic and serologic findings.

Clinical and morphologic studies on the guinea pig eye infected with human influenza virus strains of different virulence.

Human influenza virus serotypes H3N2 and H2N2 caused iridocyclitis and uveitis when inoculated at does of 10(6) 6.5 EID50 into the guinea pig eye anterior chamber. Virulent influenza virus strains and their attenuated variants prepared by passaging in chick embryos (CE) have been compared in this model. These studies showed that virulent viruses cause more severe damage in the eyes than the attenuated strains.