We have developed a set of reverse transcription-PCR assays for the detection and identification of known and novel paramyxoviruses in clinical specimens. Primers were designed from the conserved motifs of the polymerase pol gene sequences to detect members of the Paramyxovirinae or Pneumovirinae subfamily or groups of genera within the Paramyxovirinae subfamily. The consensus-degenerate hybrid oligonucleotide primer design and seminested or nested PCR assay design were used to enhance the breadth of reactivity and sensitivity of the respective assays. Using expressed RNA and 10-fold dilution series of virus-infected tissue culture isolates from different members of the family or genera, these assays were able to detect on average between 100 and 500 copies of template RNA. The assays were specific to the respective group of genera or subfamily viruses. This set of primers enhances our ability to look for novel viruses in outbreaks and diseases of unknown etiology.

Inbred mouse strains exhibit significant differences in their susceptibility to viruses in the genus Flavivirus, which includes human pathogens such as yellow fever, Dengue, and West Nile virus. A single gene, designated Flv, confers this differential susceptibility and was mapped previously to a region of mouse chromosome 5. A positional cloning strategy was used to identify 22 genes from the Flv gene interval including 10 members of the 2 -5 -oligoadenylate synthetase gene family. One 2 -5 -oligoadenylate synthetase gene, Oas1b, was identified as Flv by correlation between genotype and phenotype in nine mouse strains. Susceptible mouse strains produce a protein lacking 30% of the C-terminal sequence as compared with the resistant counterpart because of the presence of a premature stop codon. The Oas1b gene differs from all the other murine Oas genes by a unique four-amino acid deletion in the P-loop located within the conserved RNA binding domain. Expression of the resistant allele of Oas1b in susceptible embryo fibroblasts resulted in partial inhibition of the replication of a flavivirus but not of an alpha togavirus.I nnate resistance to flavivirus-induced morbidity and mortality was demonstrated in mice in the 1920s (1) and showed monogenic autosomal dominant inheritance (2). The alleles that determined resistance and susceptibility were designated Flv r and Flv s , respectively (3). Resistant mice are susceptible to infections with other types of viruses but are resistant to all flaviviruses (4). Resistant mice can be infected by flaviviruses, but the virus titers in their tissues are lower by 1,000-10,000 times than those in the tissues of susceptible animals, and the spread of the infection in resistant mice is slower (5, 6). Cell cultures derived from many different tissues of resistant mice also produce lower yields of virus; peak titers from resistant cultures are 100-1,000 times lower than those from susceptible cultures (7-9). Previous studies indicate that the Flv gene product acts intracellularly on flavivirus replication.The flavivirus-resistant allele was demonstrated in wild Mus musculus domesticus populations in both the U.S. and Australia, and flavivirus genetic resistance was reported in other Mus species (10-12). Most commonly used inbred laboratory mouse strains were derived from a small number of progenitors, and the majority of them have a homozygous flavivirus-susceptible genotype. Only the Det, BSVR, BRVR, CASA͞Rk, CAST͞Ei, MOLD͞Rk, and PRI inbred strains have the resistant allele (13). The characteristics of a resistant-like allele (designated Flv r -like) in CASA͞Rk and CAST͞Ei strains were similar to those of the PRI Flv r allele. The MOLD͞Rk animals carry an allele designated minor resistance, Flv mr , that can protect carriers from disease after infection with the attenuated 17D strain of yellow fever virus but not from the virulent Murray Valley encephalitis virus (10).The resistant allele from donor PRI mice was introduced onto the susceptible C3H͞He background to produce the co...

Two antigenically and genetically distinct lineages of influenza B viruses, represented by the reference strains B/Victoria/2/1987 and B/Yamagata/16/1988, have cocirculated in humans since at least 1983. Between 1992 and 2000, Victoria lineage viruses were detected only in eastern Asia. From March to September of 2001 and during the 2001-2002 influenza season, Victoria lineage viruses were detected for the first time in a decade in several countries including Canada, USA, Italy, Netherlands, Norway, Philippines, India, and Oman. Phylogenetic analysis of the hemagglutinin (HA) gene of these viruses revealed that the viruses fell into two distinct clades: one group, represented by the reference strain B/Hong Kong/330/2001, contained viruses sharing three signature amino acids, Arg116, Asn121, and Glu164, while the other group of viruses, represented by B/Oman/16296/2001, shared Thr121 compared to the previous reference strain, B/Shandong/7/97. A number of the viruses in the latter group have been found to be reassortants having a Victoria lineage HA and a Yamagata lineage NA. In the current 2001-2002 season, Victoria-like viruses have now been associated with outbreaks in Asia, Europe, and North America. The reemergence of these Victoria lineage viruses worldwide, the fact that the majority of the B/Victoria-like isolates have poor cross-reactivity to B/Sichuan/379/99-like viruses in current vaccines, and the lack of exposure of young children in many areas of the world to these viruses has resulted in a World Health Organization Northern Hemisphere recommendation for the inclusion of a B/Victoria-like strain in vaccines for the 2002-2003 influenza season.