Characterization Of Wild-type Measles Viruses Research Articles

Genetic Characterization of Wild-Type Measles Viruses Isolated in Peshawar Pakistan

Background: Measles is a highly contagious disease, caused by the Measles Virus (MV). Knowledge of genotypes prevalent in any region is important in effective measles surveillance; by mapping distribution of prevalent MV genotypes at different points of time, in a region, gives an idea about the success of measles control through vaccination programs, by documenting the interruption of transmission of the endemic viral genotype. Objectives: To detect genotypes of wild type measles virus isolated from the samples collected of measles patients in Peshawar valley of Khyber Pakhtunkhwa (KPK) province, Pakistan.Material and Methods: This was a cross-sectional descriptive study. Nasopharyngeal and/or throat swab samples were collected during a measles outbreak, from February to March 2014, from clinically diagnosed measles patients (cases who met the clinical case definition of WHO). Collection and processing were done according to the standard protocols. RNA (Ribo-Nucleic Acid) was extracted directly from samples; cDNA (Complimentary Deoxy-Ribonucleic Acid) was synthesized, amplification and sequencing of 528bp of carboxy-terminal of N gene was carried out. Sequences were analyzed and data were compared with the standard reference strains of measles virus.Results: A total of nine sequences obtained were of good quality and enough in length to meet WHO criteria for genotype assignment. It was found that all the nine strains of measles virus belonged to clade B, genotype B3 and cluster B3.1. The rest of the 13 sequences which were shorter in length for genotype assignment also showed close resemblance to Genotype B3.Conclusion: Wild type measles virus strains, isolated from the samples of measles patients, in Peshawar valley of Khyber Pakhtunkhwa province of Pakistan were found to be genotype B3. It shows that genotype B3 may be the predominate genotype prevalent in Peshawar region at the time of this study.Keywords: B3 genotype, Genotyping of measles, Measles Virus, Molecular epidemiology.

Improving molecular tools for global surveillance of measles virus

BackgroundThe 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. ObjectivesThe 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 designA 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. ResultsA 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. ConclusionsThese improved molecular tools will advance molecular characterization of circulating measles viruses globally and provide enhanced quality control measures.

Genetic characterization of wild-type measles viruses isolated in China, 2006-2007.

Molecular characterization of wild-type measles viruses in China during 1995-2004 demonstrated that genotype H1 was endemic and widely distributed throughout the country. H1-associated cases and outbreaks caused a resurgence of measles beginning in 2005. A total of 210,094 measles cases and 101 deaths were reported by National Notifiable Diseases Reporting System (NNDRS) and Chinese Measles Laboratory Network (LabNet) from 2006 to 2007, and the incidences of measles were 6.8/100,000 population and 7.2/100,000 population in 2006 and 2007, respectively. Five hundred and sixty-five wild-type measles viruses were isolated from 24 of 31 provinces in mainland China during 2006 and 2007, and all of the wild type virus isolates belonged to cluster 1 of genotype H1. These results indicated that H1-cluster 1 viruses were the predominant viruses circulating in China from 2006 to 2007. This study contributes to previous efforts to generate critical baseline data about circulating wild-type measles viruses in China that will allow molecular epidemiologic studies to help measure the progress made toward China's goal of measles elimination by 2012.

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.

Genetic variability of wild-type measles viruses, circulating in the Russian Federation during the implementation of the National Measles Elimination Program, 2003–2007

Genetic characterization of wild-type measles viruses (MVs) is an important component of laboratory surveillance of measles. In this study, a phylogenetic analysis was performed of the nucleoprotein gene sequences of 228 MVs isolated in the Russian Federation between 2003 and 2007. Five genotypes, D4, D5, D6, D8, and H1, were detected. From 1999 through the first 6 months of 2003, the most prevalent genotype in the European part of Russia was D4. All genotype D4-type viruses were closely related to each other (with overall sequence diversity of ≤0.9%), suggesting the presence of a single endemic MV strain. After 2003, viruses with closely related sequences within genotype D6 (£0.9% sequence diversity) were prevalent. During this time, there was a low level of indigenous transmission of genotype D6, and genotype D6 viruses were imported from neighbouring countries, which led to the identification of two lineages of genotype D6, i.e. D6a and D6b. Lineage D6a was closely related to viruses isolated in Turkey, Kazakhstan, and Uzbekistan, whereas lineage D6b was linked to a large outbreak in Ukraine in 2005–2006. Genotypes H1, D5 and D8 were associated with sporadic cases and clusters of transmission linked to importations. Enhanced vaccination interrupted the transmission of the previous endemic lineage D4 in 2003 and of lineage D6a in 2005, although an accumulation of susceptible individuals in the population allowed for prolonged circulation of lineage D6b. These data on MV genotype distribution, in conjunction with the epidemiological data for measles, show considerable progress in measles control and suggest that regional elimination is possible.

New Measles Genotype, Uganda

We report the first genetic characterization of wildtype measles viruses from Uganda. Thirty-six virus isolates from outbreaks in 6 districts were analyzed from 2000 to 2002. Analyses of sequences of the nucleoprotein (N) and hemagglutinin (H) genes showed that the Ugandan isolates were all closely related, and phylogenetic analysis indicated that these viruses were members of a unique group within clade D. Sequences of the Ugandan viruses were not closely related to any of the World Health Organization reference sequences representing the 22 currently recognized genotypes. The minimum nucleotide divergence between the Ugandan viruses and the most closely related reference strain, genotype D2, was 3.1% for the N gene and 2.6% for the H gene. Therefore, Ugandan viruses should be considered a new, proposed genotype (d10). This new sequence information will expand the utility of molecular epidemiologic techniques for describing measles transmission patterns in eastern Africa.

Genetic characterization of measles viruses isolated in Turkey during 2000 and 2001.

BackgroundMolecular epidemiologic studies have made significant contributions to measles surveillance activities by helping to identify source and transmission pathways of the virus. This report describes the genetic characterization of wild-type measles viruses isolated in Turkey in 2000 and 2001.ResultsWild-type measles viruses were isolated from 24 cases from five provinces in Turkey during 2001. The viruses were analyzed using the standard genotyping protocols. All isolates were classified as genotype D6, the same genotype that was identified in Turkey in previous outbreaks during 1998.ConclusionTurkey has begun implementation of a national program to eliminate measles by 2010. Therefore, this baseline genotype data will provide a means to monitor the success of the elimination program.

Genetic characterization of wild-type measles viruses in Cambodia

Cambodian authorities in collaboration with the World Health Organization (WHO) are implementing a measles control plan in this measles endemic country. Genetic characterization of Cambodian wild-type measles viruses was performed to determine the genotypes involved in outbreaks, and to measure the level of virus circulation in a geographic area just beginning to implement the measles control program. Seventy-two sequences of the C terminus of the nucleoprotein gene of measles virus were obtained from 88 patients. Samples were taken from 35 among 519 outbreaks reported to the Cambodian National Immunization Program between March 2001 and June 2002. The sequences were grouped into 10 lineages which all belonged to genotype D5. The maximum nucleotide divergence was 1.3%.

Genomic characterization of wild-type measles viruses that circulated in different states in Brazil during the 1997 measles epidemic.

Despite the marked reduction in the incidence of measles in Brazil, a measles epidemic occurred in this country in 1997. The measles cases observed during this epidemic began to reappear in large numbers in São Paulo, and spread to Rio de Janeiro and other Brazilian states. In the present study molecular biology techniques were used for the detection and genomic characterization of measles viruses from clinical samples such as urine and nasopharyngeal secretions collected in the states of Rio de Janeiro, Minas Gerais and Paraná, during the 1997 epidemic. RT-PCR and nucleotide sequence analysis of part of the carboxyl-terminal region of the nucleoprotein gene of measles viruses obtained directly from clinical samples or from infected cell cultures during this epidemic classified all as wild-type of genotype D6. As the genotype D6 was identified in different Brazilian states, this study demonstrated that this genotype was circulating in Brazil during the 1997 epidemic.