RESUMO
A high rate of post-vaccinal aseptic meningitis for Urabe AM9 mumps virus strain is well documented. This strain is composed of two virus variants differing at the nt 1081 (A/G) region in the hemagglutinin-neuraminidase (HN) gene. An association of HN-A(1081) variant with neurovirulence has been proposed. In order to test for neurotropism we isolated the HN-A(1081) and HN-G(1081) virus variants from Urabe AM9 mumps virus vaccine. Sequential passages were performed in monkey kidney Vero cells and human neuroblastoma SH-SY5Y cells. Viral replication was determined by conventional and real-time RT-PCR. The results show that clone HN-A(1081) can replicate efficiently in both cell types. However, a defective replication of clone HN-G(1081), lacking its genetic marker, was observed after the third passage in neuroblastoma cells. Kinetics assays showed that clone HN-A(1081) replicates faster than clone HN-G(1081). Viral clones were also inoculated into the brains of newborn rats. Clone HN-A(1081) replicated 14 times, while clone HN-G(1081) merely duplicated its level over the initial inoculum. These results suggest that there is a selective replication of HN-A(1081) mumps virus variants in cells of nervous origin.
Assuntos
Proteína HN/genética , Vacina contra Caxumba , Vírus da Caxumba/fisiologia , Vírus da Caxumba/patogenicidade , Neuroblastoma/virologia , Replicação Viral , Animais , Animais Recém-Nascidos , Encéfalo/virologia , Linhagem Celular , Linhagem Celular Tumoral , Chlorocebus aethiops , Clonagem Molecular , Proteína HN/química , Proteína HN/metabolismo , Humanos , Caxumba/virologia , Vírus da Caxumba/genética , Mutação Puntual , Ratos , Células VeroRESUMO
A mass immunization campaign with a Urabe-containing measles-mumps-rubella vaccine was carried out in 1997 in the city of Salvador, northeastern Brazil, with a target population of children aged 1-11 years. There was an outbreak of aseptic meningitis following the mass campaign. Cases of aseptic meningitis were ascertained through data collected from the records of children admitted to the local referral hospital for infectious diseases between March and October of 1997, using previously defined eligibility criteria. Vaccination histories were obtained through home visits or telephone calls. Eighty-seven cases fulfilled the study criteria. Of those, 58 cases were diagnosed after the vaccination campaign. An elevated risk of aseptic meningitis was observed 3 weeks after Brazil's national vaccination day compared with the risk in the prevaccination period (relative risk = 14.3; 95% confidence interval: 7.9, 25.7). This result was confirmed by a case series analysis (relative risk = 30.4; 95% confidence interval: 11.5, 80.8). The estimated risk of aseptic meningitis was 1 in 14,000 doses. This study confirms a link between measles-mumps-rubella vaccination and aseptic meningitis. The authors discuss the implications of this for the organization and planning of mass immunization campaigns.