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PubMed1993

Sequential administration of two human-rhesus rotavirus reassortant strains of VP7 serotype 1 and 2 specificity to infants and young children.

Rotavirus vaccine strains representing serotypes 1 and 2 have been derived by reassortment between genes of a rhesus rotavirus master strain, MMU18006, and the gene from human viruses coding for VP7, a surface protein with neutralizing determinants. As simultaneous administration of these two human rotavirus reassortants had resulted in disappointing strain-specific immunity, these two vaccines were administered sequentially to infants and young children to assess whether immunity to both serotypes could be achieved with two monovalent doses. Following initial immunization with RRVxDS-1, a serotype 2 vaccine, 12 of 13 shed virus and showed serologic responses to multiple rotavirus proteins. However, with subsequent administration of RRVxD, serotype 1, only 2 of 12 shed virus, and an enhancement or broadening of the immune response was not uniformly seen. Although rhesus rotavirus vaccines are immunogenic with primary administration of monovalent vaccine in seronegative children, and supplemental seroresponses are seen with a second dose, other strategies or new vaccine candidates must be sought to induce immunity against the multiple serotypes of human rotavirus.

Administration, Oral↗

PubMed1996

Frequent occurrence of genetic reassortment between influenza C virus strains in nature.

Previous studies of the haemagglutinin-esterase (HE) genes of various influenza C isolates suggested the existence of three distinct virus lineages (C/Yamagata/26/81-, C/Aichi/1/81- and C/Mississippi/80-related lineages) in Japan in the 1980s. Here we analysed the genetic properties of three strains (C/Yamagata/5/92, C/Miyagi/3/93 and C/Miyagi/4/93) isolated in Yamagata and Sendai Cities, Japan, in 1992/1993. Comparison of total or partial nucleotide sequences of the seven RNA segments of C/Yamagata/5/92 with those of 11 previous isolates suggested that the 1992 strain is a reassortant which inherited HE, P3, NP and M genes from a C/Mississippi/80-like virus and PB2, PB1 and NS genes from a C/pig/Beijing/115/81-like virus. Furthermore, it became evident that at least two (C/England/83 and C/Yamagata/9/88) of the 11 reference strains are also reassortants.

Animals↗

PubMed1996

Large outbreak of swine influenza in southern Japan caused by reassortant (H1N2) influenza viruses: its epizootic background and characterization of the causative viruses.

In the winter of 1989 and the spring of 1990, there were large outbreaks of respiratory disease in two swine herds in Nagasaki Prefecture, southern Japan. Serological surveillance indicated that the majority of swine possessed antibodies to swine influenza virus H1 haemagglutinin and neuraminidase of early H3N2 influenza virus strains. Eight viruses were isolated from swine that showed typical clinical symptoms of influenza. The haemagglutinin and neuraminidase of these isolates were closely related to those of swine H1N1 and early human H3N2 viruses, respectively. At least two types of haemagglutinin antigens, distinguished by two monoclonal antibodies, were involved in the outbreaks. Evolutionary analyses indicated that the haemagglutinin gene of the H1N2 reassortants was closely related to those of a recent swine lineage (A/sw/HK/1/74 and A/sw/Ehime/1/80 viruses). However, the neuraminidase genes of the H1N2 reassortants were similar to those of swine N2 viruses which in turn are related to early human H3N2 viruses. A comparison of partial nucleotide sequences revealed that the six other genes of A/sw/Nagasaki/1/89 were derived from those of swine H1N1 virus.

Animals↗

PubMed2004

Evidence of segment reassortment in Crimean-Congo haemorrhagic fever virus.

The complete nucleotide sequences of the small (S) and medium (M) segments of three independent strains of Crimean-Congo haemorrhagic fever (CCHF) virus isolated in Uzbekistan, Iraq and Pakistan have been determined. Partial S and M segment sequences from two additional strains and partial large segment sequences from five strains of CCHF virus have also been obtained. These data have been compiled and compared with published full-length and partial sequences of other CCHF virus strains. Analysis of virus strains for which complete and partial S and M segment sequences are available reveals that the phylogenetic grouping of some strains differ between these two segments. Data provided in this report suggest that this discrepancy is not the result of recombination, but rather the consequence of reassortment events that have occurred in some virus lineages. Although described in other genera of the Bunyaviridae family, this is the first report of segment reassortment occurring in the Nairovirus genus.

Base Sequence↗

PubMed2006

Very virulent infectious bursal disease virus: reduced pathogenicity in a rare natural segment-B-reassorted isolate.

The purpose of this study was to compare the molecular epidemiology of infectious bursal disease virus (IBDV) segments A and B of 50 natural or vaccine IBDV strains that were isolated or produced between 1972 and 2002 in 17 countries from four continents, with phenotypes ranging from attenuated to very virulent (vv). These strains were subjected to sequence and phylogenetic analysis based on partial sequences of genome segments A and B. Although there is co-evolution of the two genome segments (70 % of strains kept the same genetic relatives in the segment A- and B-defined consensus trees), several strains (26 %) were identified with the incongruence length difference test as exhibiting a significantly different phylogenetic relationship depending on which segment was analysed. This suggested that natural reassortment could have occurred. One of the possible naturally occurring reassortant strains, which exhibited a segment A related to the vvIBDV cluster whereas its segment B was not, was thoroughly sequenced (coding sequence of both segments) and submitted to a standardized experimental characterization of its acute pathogenicity. This strain induced significantly less mortality than typical vvIBDVs; however, the mechanisms for this reduced pathogenicity remain unknown, as no significant difference in the bursal lesions, post-infectious antibody response or virus production in the bursa was observed in challenged chickens.

Animals↗

PubMed2006

Phylogenetic analysis reveals a correlation between the expansion of very virulent infectious bursal disease virus and reassortment of its genome segment B.

Infectious bursal disease virus (IBDV) is a birnavirus causing immunosuppressive disease in chickens. Emergence of the very virulent form of IBDV (vvIBDV) in the late 1980s dramatically changed the epidemiology of the disease. In this study, we investigated the phylogenetic origins of its genome segments and estimated the time of emergence of their most recent common ancestors. Moreover, with recently developed coalescence techniques, we reconstructed the past population dynamics of vvIBDV and timed the onset of its expansion to the late 1980s. Our analysis suggests that genome segment A of vvIBDV emerged at least 20 years before its expansion, which argues against the hypothesis that mutation of genome segment A is the major contributing factor in the emergence and expansion of vvIBDV. Alternatively, the phylogeny of genome segment B suggests a possible reassortment event estimated to have taken place around the mid-1980s, which seems to coincide with its expansion within approximately 5 years. We therefore hypothesize that the reassortment of genome segment B initiated vvIBDV expansion in the late 1980s, possibly by enhancing the virulence of the virus synergistically with its existing genome segment A. This report reveals the possible mechanisms leading to the emergence and expansion of vvIBDV, which would certainly provide insights into the scope of surveillance and prevention efforts regarding the disease.

Animals↗

PubMed2006

Batai and Ngari viruses: M segment reassortment and association with severe febrile disease outbreaks in East Africa.

Ngari virus is an orthobunyavirus recently recognized as a reassortant between Bunyamwera virus and an as yet unidentified M segment donor. Analysis of M segment sequences of Batai and Ilesha viruses revealed 95% deduced amino acid identity between Batai virus and Ngari virus. These findings suggest Batai virus as the donor of Ngari virus M segment sequence. Analysis of Batai virus-related African isolates identified UgMP-6830, isolated from mosquitoes in Uganda, as an isolate of Batai virus. KV-141, isolated during a febrile disease outbreak in Sudan, was identified as another isolate of Ngari virus, emphasizing a role of this reassortant virus in severe human illness throughout East Africa.

Africa, Eastern↗

PubMed1999

Genetic reassortment of avian, swine, and human influenza A viruses in American pigs.

In late summer through early winter of 1998, there were several outbreaks of respiratory disease in the swine herds of North Carolina, Texas, Minnesota, and Iowa. Four viral isolates from outbreaks in different states were analyzed genetically. Genotyping and phylogenetic analyses demonstrated that the four swine viruses had emerged through two different pathways. The North Carolina isolate is the product of genetic reassortment between H3N2 human and classic swine H1N1 influenza viruses, while the others arose from reassortment of human H3N2, classic swine H1N1, and avian viral genes. The hemagglutinin genes of the four isolates were all derived from the human H3N2 virus circulating in 1995. It remains to be determined if either of these recently emerged viruses will become established in the pigs in North America and whether they will become an economic burden.

Amino Acid Sequence↗

PubMed2001

Reassortment in vivo: driving force for diversity of human rotavirus strains isolated in the United Kingdom between 1995 and 1999.

The G and P genotypes of 3,601 rotavirus strains collected in the United Kingdom between 1995 and 1999 were determined (M. Iturriza-Gómara et al., J. Clin. Microbiol. 38:4394-4401, 2000). In 95.4% of the strains the most common G and P combinations, G1P[8], G2P[4], G3P[8], and G4P[8], were found. A small but significant number (2%) of isolates from the remaining strains were reassortants of the most common cocirculating strains, e.g., G1P[4] and G2P[8]. Rotavirus G9P[6] and G9P[8] strains, which constituted 2.7% of all viruses, were genetically closely related in their G components, but the P components of the G9P[8] strains were very closely related to those of cocirculating strains of the more common G types (G1, G3, and G4). In conclusion, genetic interaction by reassortment among cocirculating rotaviruses is not a rare event and contributes significantly to their overall diversity.

DNA, Viral↗

PubMed2003

Frequent reassortment among influenza C viruses.

In a 9-year survey from December 1990 to December 1999 in Sendai City, Japan, we succeeded in isolating a total of 45 strains of influenza C virus. These 45 strains were isolated in clusters within 4 months in a year, especially from winter to early summer. Previous studies of the hemagglutinin-esterase genes of various influenza C virus isolates revealed the existence of five distinct virus lineages (Aichi/1/81-, Yamagata/26/81-, Mississippi/80-, Sao Paulo/82-, and Kanagawa/1/76-related lineage) in Japan between 1970 and the early 1990s (Y. Matsuzaki, K. Mizuta, H. Kimura, K. Sugawara, E. Tsuchiya, H. Suzuki, S. Hongo, and K. Nakamura, J. Gen. Virol. 81:1447-1452, 2000). Antigenic and genetic analyses of the 45 strains showed that they could be divided into these five virus lineages and a few antigenic groups were cocirculating in Sendai City. In 1990 and 1991 the dominant antigenic group was the Aichi/1/81 virus group, and in 1992 it was Yamagata/26/81 virus group. The Mississippi/80 virus group was isolated from 1993 to 1996, and the Yamagata/26/81 virus group reemerged in 1996 and continued to circulate until 1999. This finding led us to a speculation that the replacement of the dominant antigenic groups had occurred by immune selection within the human population in the restricted area. Phylogenetic analysis of seven RNA segments showed that 44 viruses among the 45 strains isolated in our surveillance work were reassortant viruses that have various genome compositions distinguishable from those of the reference strains of the each lineage. This observation suggests that the reassortment between two different influenza C virus strains occurs frequently in nature and the genome composition of influenza C viruses may influence their ability to spread in humans.

Antigens, Viral↗

PubMed2004

Ngari virus is a Bunyamwera virus reassortant that can be associated with large outbreaks of hemorrhagic fever in Africa.

Two isolates of a virus of the genus Orthobunyavirus (family Bunyaviridae) were obtained from hemorrhagic fever cases during a large disease outbreak in East Africa in 1997 and 1998. Sequence analysis of regions of the three genomic RNA segments of the virus (provisionally referred to as Garissa virus) suggested that it was a genetic reassortant virus with S and L segments derived from Bunyamwera virus but an M segment from an unidentified virus of the genus Orthobunyavirus. While high genetic diversity (52%) was revealed by analysis of virus M segment nucleotide sequences obtained from 21 members of the genus Orthobunyavirus, the Garissa and Ngari virus M segments were almost identical. Surprisingly, the Ngari virus L and S segments showed high sequence identity with those of Bunyamwera virus, showing that Garissa virus is an isolate of Ngari virus, which in turn is a Bunyamwera virus reassortant. Ngari virus should be considered when investigating hemorrhagic fever outbreaks throughout sub-Saharan Africa.

Africa South of the Sahara↗

PubMed2026

Reassortment of Highly Pathogenic Avian Influenza as a Driver for Zoonotic Spillover, Asia.

Highly pathogenic avian influenza H5Nx viruses remain a major zoonotic threat, yet global attention has focused largely on clade 2.3.4.4b, potentially overlooking major changes within long-endemic H5N1 lineages in Asia. Recent reports from South and Southeast Asia describe the emergence of reassortant clade 2.3.2.1 viruses alongside renewed human infections after apparent prolonged epidemiologic stability. Collectively, those events suggest a regional pattern rather than isolated anomalies. In this article, we argue that reassortment, rather than point mutation alone, might be an underrecognized driver of zoonotic risk in endemic H5N1 lineages and is reshaping those lineages. We examine why such events might be underrecognized in settings with entrenched poultry influenza, identify limitations of current surveillance systems, and call for integrated, real-time approaches linking genomic detection with phenotypic assessment across animal and human health sectors to enable timely risk assessment and coordinated public health action.

Asia↗

PubMedDate not supplied

[Reduction of the functional match of influenza virus hemagglutinin and neuraminidase after reassortation of genes].

Influenza virus A (FluA) reassortants with low-functional neuraminidase (NA) of subtype N1 and hemagglutinin (HA) of subtypes H2, H3, H4, and H13 display virion aggregation and accumulate to a lower titer because sialyl residues are not completely removed from virion components. Nonaggregating variants of FluA (H13N1) were shown to result from a mutation that reduces the HA affinity for sialyl substrates. Amino acid substitution K156E, which increases a negative charge at the edge of the receptor-binding pocket of HA large subunit (HA1), was revealed in two independent variants. This substitution was the only difference between HA1 of the original reassortant and one of its variants and, therefore, accounted for restoration of the functional match between HA and NA.

Hemagglutinin Glycoproteins, Influenza Virus↗

PubMedDate not supplied

[Live cold-adapted reassortant influenza vaccines].

The author reviews studies of live cold-adapted reassortant influenza vaccines developed in Russia and USA. These vaccines are safe and weakly reactogenic for all age groups. The vaccines (two immunizations) are highly effective in children of preschool and school age and far less effective in adults. For elderly subjects simultaneous vaccination with live and inactivated vaccines is recommended. The probability of influenza prevention by a single injection of cold-adapted vaccines is to be further investigated. Modern data indicate that cold-adapted reassortant influenza vaccines can be used for influenza prevention only in children of preschool and school age.

Adaptation, Biological↗

PubMedDate not supplied

[The determination of the genotype of natural reassortant influenza A viruses according to the core protein genes by the methods of competitive dot hybridization and sequencing].

Simultaneous circulation of different subtypes of influenza A viruses provides conditions for reassortant strains formation. A comparative investigation of genome of 47 influenza A virus strains (H1N1, H2N2, and H3N2) was carried out by competitive dot hybridization technique and sequence analysis of some of cDNA-copies of the virus genes. All the genes of 43 strains encoding nonglycolysed proteins corresponded to the serum subtype of surface glycoproteins. The reassortant pattern of genome for some genes of core proteins was revealed in 4 viruses. All the dot hybridization data were completely confirmed by sequence analysis of the genes.

Antigens, Viral↗

PubMedDate not supplied

[Development of a live culture of cold-adapted reassortant influenza vaccines].

Optimal conditions for the cultivation of the MDCK cell lines in the laboratory spinner or by using the Eagle-MEM with or without fetal serum were worked out. The cold-adapted reassortant vaccine strains of virus influenza A/H1N1, A/H3N2 and B are well replicated in the MDCK cells both in a monolayer and in the spinner by using the serum-free medium. A maximum virus titer depends on a multiplicity of infection used in a fetal medium and on the addition of trypsin. Under the optimal conditions, the titer of the studied cold-adapted reassortants, while using a serum-free medium, reaches as much as 10(9.0)-10(9.5) EID50/ml.

Adaptation, Physiological↗

PubMedDate not supplied

[Genetic and phenotypic analysis of heterogeneous population of a cold-adapted donor of the A/Leningrad/134/17/57 (H2N2) attenuation and of the donor-based reassortant influenza vaccine strains].

Cold-adapted (CA) temperature sensitive and attenuated virus A/Leningrad/134/17/57 (H2N2) (Len/17) has been recently used in Russia as a donor of internal genes in the preparation of reassortant vaccine strains of CA live influenza vaccine (LIV) for all age groups. The Len/17 population was found to be heterogeneous and to be made up of clones, which differ by combinations of mutations in internal genes. Around 50% of the Len/17 population had clones with all 8 coding mutations in internal genes. The others were made up of clones with mutation combinations, which were different from the original Len/17. The PCR restriction method was used to analyze 5 clones of Len/17 and 8 LIV vaccine strains. There were no Ala-86-Thr mutation in the M2 protein in 4 clones and 3 vaccine strains. The PB-1 gene of 4 clones and 3 vaccine strains had a mutation encoding Met-317-IIe more typical of a more attenuated virus A/Leningrad/134/47/57 (H2N2) (Len/47). The NP protein of a clone had a mutation Leu-341-IIe also typical of Len/47. However, neither the absence of mutation in the M2 gene nor an extra mutation in the PB1 gene affected the attenuation extent of reassortant CALIV.

Adolescent↗

PubMedDate not supplied

[The determination of the genotype of laboratory reassortants of the influenza A virus by competitive dot hybridization].

The genotype of laboratory reassortants produced by co-cultivation of virulent A/USSR/2/85 (H3N2) virus and multi-passaged attenuation donor A/Leningrad/9/46 virus (H1N1) was determined by two different methods: a method of competitive dot hybridization (CDH) and polyacrylamide gel electrophoresis (PAGE) with virion RNAs urea. The results of the two methods were shown to be completely identical which confirmed the potential of using CDH method for genetic typing of influenza A virus reassortant strains.

Electrophoresis, Polyacrylamide Gel↗