Molecular epidemiology of measles virus in Japan

A Case of Early Onset Subacute Sclerosing Panencephalitis Presented as Juvenile Myoclonic Epilepsy

A 7.5 years girl presented with myoclonic jerks with prolonged duration coming progressively at shorter intervals for last six moinths. There was declining academic performances. The dystonic, dyskinetic movements and ataxia were there for last three months. The stages were progressing too rapidly. IgG antibody titre to measles virus was found to be positive with EEG changes which confirms diagnosis. SSPE at so early age with atypical presentation is unique in this indexed case.

Simple method for differentiating measles vaccine from wild-type strains using loop-mediated isothermal amplification

Because of increasing measles vaccine coverage, the proportion of patients with modified measles has been increasing. Such patients have low-grade fever with very mild eruptions similar to vaccine-related adverse events. Differentiation between these two pathogenic conditions is required to improve the quality of laboratory-based measles surveillance. In this study, vaccine-specific and wild-type specific primer sets were designed for loop-mediated isothermal amplification in the N gene, and vaccine strains, C1, D3, D4, D5, D8, D9, G3 and H1 wild strains were examined. Three vaccine strains were efficiently amplified using a vaccine-specific primer set with an approximately 10-times higher sensitivity than wild-type primer. Modified measles was differentiated from vaccine-associated cases by this system, but limitations were encountered with the other genotypes.

Improving molecular tools for global surveillance of measles virus

BACKGROUND

The genetic characterization of wild-type measles viruses plays an important role in the description of viral transmission pathways and the verification of measles elimination. The 450 nucleotides that encode the carboxyl-terminus of the nucleoprotein (N-450) are routinely sequenced for genotype analysis.

OBJECTIVES

The objectives of this study were to develop improved primers and controls for RT-PCR reactions used for genotyping of measles samples and to develop a method to provide a convenient, safe, and inexpensive means to distribute measles RNA for RT-PCR assays and practice panels.

STUDY DESIGN

A newly designed, genetically defined synthetic RNA and RNA isolated from cells infected with currently circulating genotypes were used to compare the sensitivity of primer pairs in RT-PCR and nested PCR. FTA® cards loaded with lysates of measles infected cells were tested for their ability to preserve viral RNA and destroy virus infectivity.

RESULTS

A new primer pair, MeV216/MeV214, was able to amplify N-450 from viruses representing 10 currently circulating genotypes and a genotype A vaccine strain and demonstrated 100-fold increased sensitivity compared to the previously used primer set. A nested PCR assay further increased the sensitivity of detection from patient samples. A synthetic positive control RNA was developed that produced PCR products that are distinguishable by size from PCR products amplified from clinical samples. FTA® cards completely inactivated measles virus and stabilized RNA for at least six months.

CONCLUSIONS

These improved molecular tools will advance molecular characterization of circulating measles viruses globally and provide enhanced quality control measures.

Measles resurgence associated with continued circulation of genotype H1 viruses in China, 2005

Measles morbidity and mortality decreased significantly after measles vaccine was introduced into China in 1965. From 1995 to 2004, average annual measles incidence decreased to 5.6 cases per 100,000 population following the establishment of a national two-dose regimen. Molecular characterization of wild-type measles viruses demonstrated that genotype H1 was endemic and widely distributed throughout the country in China during 1995-2004. A total of 124,865 cases and 55 deaths were reported from the National Notifiable Diseases Reporting System (NNDRS) in 2005, which represented a 69.05% increase compared with 2004. Over 16,000 serum samples obtained from 914 measles outbreaks and the measles IgM positive rate was 81%. 213 wild-type measles viruses were isolated from 18 of 31 provinces in China during 2005, and all of the isolates belonged to genotype H1. The ranges of the nucleotide sequence and predicted amino acid sequence homologies of the 213 genotype H1 strains were 93.4%-100% and 90.0%-100%, respectively. H1-associated cases and outbreaks caused the measles resurgence in China in 2005. H1 genotype has the most inner variation within genotype, it could be divided into 2 clusters, and cluster 1 viruses were predominant in China throughout 2005.

Genotyping of recent measles virus strains from Russia and Vietnam by nucleotide-specific multiplex PCR

The nucleoprotein genes of 49 measles virus (MV) strains circulating in Russia between 2000 and 2006 and in Vietnam in 2003 were analyzed by genotype-specific PCR and the results were compared with their sequences. The sequences revealed the presence of genotypes H1 and H2 in the center (Nha Trang) and the north (Hanoi) of Vietnam, respectively. The relative diversity of the H2 strains suggested an endemic circulation of these viruses in the capital. In contrast genotype H1 strains from Nha Trang were homogenous genetically, which may indicate a recent importation. The strains obtained from 12 different regions of the Russian Federation were assigned to the genotypes H1, D4, and D6. Most strains (81.4%) were correctly genotyped by a multiplex PCR method which was sensitive to genotype-specific mutations [Kremer et al. (2004): J Clin Microbiol 42: 3017-3022]. Ambiguous or negative results for some clade H and genotype D6 strains were due to point mutations in the type-specific primer binding sites. After exchanging a single nucleotide in both the clade H- and the genotype D6-specific primers, all strains were assigned correctly to their genotype. A simplified procedure for use in Vietnam was developed to distinguish directly between genotypes H1 and H2 and any non-H genotype. These results demonstrate that our multiplex PCR method can be adapted easily to new sequence variants or specific epidemiological situations, and thus be very useful for rapid genotyping of large number of samples even in laboratories which do not have sequencing facilities.

A novel monolayer cell line derived from human umbilical cord blood cells shows high sensitivity to measles virus

Measles virus (MeV) research is largely dependent on the B95a cell line, which is derived from marmoset B lymphocytes. As this cell line is persistently infected with Epstein-Barr virus (EBV), a novel cell line, COBL-a, was established from human umbilical cord blood. COBL-a cells have a significant advantage over B95a cells because they are of human origin, are free from EBV and have higher sensitivity to wild-type MeV. Thus, COBL-a cells should prove very valuable for both epidemiological and basic studies of MeV.

Current status of measles in Japan: molecular and seroepidemiological studies

On account of the measles vaccination campaign, with vaccinations carried out on the first birthdays of children, the number of reported cases of measles was reduced to 545 in 2005, which is the lowest so far in Japan. We conducted a molecular epidemiological study of measles virus to determine the circulating measles virus genotypes in Japan since 1984. Different genotypes, C1, D3, D5, and H1, were the major strains isolated in outbreaks in 1984, 1987-1988, 1991-1993, and 2000, respectively. When measles was in the control phase, a sporadic outbreak was reported, but the causative virus was found to be of imported measles virus lineage. We also conducted a seroepidemiological study to investigate the persistence of vaccine-acquired immunity in Himeji City, Japan. Before 1990, vaccine coverage was 84.5% and it increased gradually, to 88.5% in 1991-1995, 92.7% in 1996-2000, and 94.6% after 2000. Measles outbreaks were observed annually before 1978 and in 1980, 1981, 1984, 1990, and 1996; there were no measles cases after 1997 in Himeji City. In 1994-1998, a serological study of 795 sera showed that measles neutralization test (NT) antibodies were sufficiently preserved, even 12 years after the first-dose immunization. In 1999-2003, 26 (3.7%) of 695 sera were negative for NT. The positive rate for measles NT decreased to approximately 90% as the elapsed time after the first-dose immunization increased to 6 or 7 years. The immunity obtained after receiving measles vaccine decays by 6-7 years after the first dose when the measles was controlled. A two-dose schedule of measles vaccine was implemented in Japan in 2006; we should continue molecular and serological surveillance.

Laboratory investigations are indispensable to monitor the progress of measles elimination--results of the German Measles Sentinel 1999-2003

BACKGROUND

The elimination of measles is a goal set by the World Health Organisation to be reached by 2010 in the European region.

OBJECTIVES

To enhance the measles surveillance in Germany, a country-wide laboratory supported a sentinel was established.

STUDY DESIGN

A network of >1200 representatively distributed practitioners reported detailed data on all clinically diagnosed cases and provided specimens for laboratory diagnosis.

RESULTS

A total of 3225 suspected cases were reported between October 1999 and December 2003. The incidence in Western Germany decreased from >15 cases per 100,000 population to one case in 2003, while in Eastern Germany <1 case per 100,000 population was observed during these years. Laboratory investigations were undertaken in 40% of cases in 2000/2001. This rate increased to 79% in 2003. Simultaneously, the rate of confirmed cases dropped from 60% in the former years to 23% in 2003. Measles virus (MV) detection by serology and by PCR revealed concordant results in 92%. Most suspected cases (85%) were unvaccinated with 66% being laboratory confirmed. Only 10% of suspected cases occurred in vaccinated individuals and very few (22%) could be confirmed. Analyses of confirmed measles in vaccinated patients (n = 49) revealed 24.5% primary vaccine failures, 24.5% reinfections after successful vaccination and 31% MV infection before or shortly after vaccination. The genetic characterisation of 389 MV isolates identified eight genotypes: B3, C2, D4, D5, D6, D7, G2 and H1. Only the C2, D6 and D7 MV genotypes circulated endemically in Western Germany. The newly emerged MV D7 almost completely replaced the pre-existing C2 and D6 MVs in 2001. The few measles cases detected in Eastern Germany were mostly caused by imported MVs.

CONCLUSION

The data demonstrate that laboratory investigations including molecular methods are an indispensable tool for surveillance in all countries advanced in measles elimination.