Isolation and characterization of H4N6 avian influenza viruses from pigs with pneumonia in Canada.

In October 1999, H4N6 influenza A viruses were isolated from pigs with pneumonia on a commercial swine farm in Canada. Phylogenetic analyses of the sequences of all eight viral RNA segments demonstrated that these are wholly avian influenza viruses of the North American lineage. To our knowledge, this is the first report of interspecies transmission of an avian H4 influenza virus to domestic pigs under natural conditions.

Genetic characterization of H3N2 influenza viruses isolated from pigs in North America, 1977-1999: evidence for wholly human and reassortant virus genotypes.

Since 1998, H3N2 viruses have caused epizootics of respiratory disease in pigs throughout the major swine production regions of the U.S. These outbreaks are remarkable because swine influenza in North America had previously been caused almost exclusively by H1N1 viruses. We sequenced the full-length protein coding regions of all eight RNA segments from four H3N2 viruses that we isolated from pigs in the Midwestern U.S. between March 1998 and March 1999, as well as from H3N2 viruses recovered from a piglet in Canada in January 1997 and from a pig in Colorado in 1977. Phylogenetic analyses demonstrated that the 1977 Colorado and 1997 Ontario isolates are wholly human influenza viruses. However, the viruses isolated since 1998 from pigs in the Midwestern U.S. are reassortant viruses containing hemagglutinin, neuraminidase and PB1 polymerase genes from human influenza viruses, matrix, non-structural and nucleoprotein genes from classical swine viruses, and PA and PB2 polymerase genes from avian viruses. The HA proteins of the Midwestern reassortant swine viruses can be differentiated from those of the 1995 lineage of human H3 viruses by 12 amino acid mutations in HA1. In contrast, the Sw/ONT/97 virus, which did not spread from pig-to-pig, lacks 11 of these changes.

Virologic and serologic surveillance for human, swine and avian influenza virus infections among pigs in the north-central United States.

Influenza virus infection in pigs is both an animal health problem and a public health concern. As such, surveillance and characterization of influenza viruses in swine is important to the veterinary community and should be a part of human pandemic preparedness planning. Studies in 1976/1977 and 1988/1989 demonstrated that pigs in the U.S. were commonly infected with classical swine H1N1 viruses, whereas human H3 and avian influenza virus infections were very rare. In contrast, human H3 and avian H1 viruses have been isolated frequently from pigs in Europe and Asia over the last two decades. From September 1997 through August 1998, we isolated 26 influenza viruses from pigs in the north central United States at the point of slaughter. All 26 isolates were H1N1 viruses, and phylogenetic analyses of the hemagglutinin and nucleoprotein genes from 11 representative viruses demonstrated that these were classical swine H1 viruses. However, monoclonal antibody analyses revealed antigenic heterogeneity among the HA proteins of the 26 viruses. Serologically, 27.7% of 2,375 pigs tested had hemagglutination-inhibiting antibodies against classical swine H1 influenza virus. Of particular significance, however, the rates of seropositivity to avian H1 (7.6%) and human H3 (8.0%) viruses were substantially higher than in previous studies.

Genetic characterization of an H1N2 influenza virus isolated from a pig in Indiana.

An H1N2 influenza virus was isolated from a pig during an outbreak of respiratory disease and abortion on an Indiana farm in November 1999. Results of phylogenetic analyses indicate that this virus is a reassortant between a recent classical H1 swine virus and the reassortant H3N2 viruses that have emerged among American pigs since 1998.

[Multiple genes of delta-endotoxins from Bacillus thuringiensis subspecies galleriae]. / Mnozhestvennye geny delta-éndotoksinov Bacillus thuringiensis podvida galleriae.

Cloning and expression in E. coli delta-endotoxin genes cryIAb7, cryIG and, cryIX from Bacillus thuringiensis ssp galleriae has been performed. Restriction mapping and partial sequencing have shown the identity of the 3'-terminal parts of cryIG and cryIX, although their 5'-terminal halves corresponding to the toxin are unique. Sequencing 5'-flanking region of cryIX revealed no translation initiation site, which indicates a nonfunctional state of the gene. The clusterized locating of the cryIG and cryIG genes has been shown. The absence of a promoter-like structure in the 5'-flanking region of cryIG suggests transcription of the gene as a bicistronic mRNA with cryIX. The extremely high homology of the cryIG and cryIX 3'-terminal parts (2 kB long) suggests a recombination act in the gene origin.

Primary structure of cryX**, the novel delta-endotoxin-related gene from Bacillus thuringiensis spp. galleriae.

A cry-related sequence, designated cryX (EMBL X75019), was localized upstream of cryIG, the delta-endotoxin gene cloned from spp. galleriae of Bacillus thuringiensis and sequenced earlier [(1991) FEBS Lett. 293, 25-28]. Analysis of the cryX complete nucleotide sequence enabled us to explain its virtual crypticity and to reveal the chimeric structure of the genes, cryX and cryIG. The amino acid sequence of 1,151 residues encoded by the continuous reading frame of cryX is similar to the other delta-endotoxins but differs essentially from them.

Nucleotide sequence of a novel delta-endotoxin gene cryIg of Bacillus thuringiensis ssp. galleriae.

A gene cryIg coding for entomocidal protein delta-endotoxin of Bacillus thuringiensis ssp. galleriae str. 11-67 named CryIG has been cloned and sequenced (EMBL accession number X58120). The deduced amino acid sequence that contains 1156 amino acid residues shows only 28% of identical residues, when compared with other delta-endotoxins of the CryI family. The extent of identity is substantially higher for some regions of the sequence ('conserved blocks'), that presumably bear important structural or functional properties. This implies that CryIG delta-endotoxin follows the same type of polypeptide chain folding as other CryI proteins, whereas peculiarities of primary structure help to explain its unique specificity.

[Cloning and comparative characteristics of genes coding two structurally distant delta-endotoxins of Bacillus thuringiensis var. galleriae and kurstaki]. / Klonirovanie i sravnitel'naia kharakteristika genov dvukh strukturno otdalennykh delta-éndotoksinov Bacillus thuringiensis podvidov galleriae i kurstaki.

Representative total DNA libraries of Bac. thuringiensis var. kurstaki (strain Dipel) and galleriae (strain 11-67) have been constructed on the basis of phasmid vector lambda pSL5. Recombinant phasmid clones, carrying delta-endotoxin-coding genes of both subspecies have been isolated by means of immunoenzyme screening. Restriction mapping and partial nucleotide sequence determination have demonstrated that phasmid lambda pOC2, isolated from var. kurstaki DNA library, contains the complete delta-endotoxin-coding gene, identical to the one, described by Schnepf H.E. et al. J. Biol. Chem. 1985. V. 260. P. 6264. Recombinant phasmids lambda pOC10 and 11 have been shown to contain the full-sized gene, coding delta-endotoxin of Bac. thuringiensis var. galleriae. The protein products of the cloned genes have been characterized by Western-blot analysis and bioassays. The absence of substantial homology of two genes, evidenced by Southern-blot hybridisation, correlates with sufficiently big differences in biological specificity of the corresponding proteins. This is in accordance with our previous data on N-terminal amino acid sequence determination of delta-endotoxins of those subspecies of Bac. thuringiensis.