Influenza B virus is a human pathogen whose origin and possible reservoir in nature are not known. An influenza B virus was isolated from a naturally infected harbor seal (Phoca vitulina) and was found to be infectious to seal kidney cells in vitro. Sequence analyses and serology indicated that influenza virus B/Seal/Netherlands/1/99 is closely related to strains that circulated in humans 4 to 5 years earlier. Retrospective analyses of sera collected from 971 seals showed a prevalence of antibodies to influenza B virus in 2% of the animals after 1995 and in none before 1995. This animal reservoir, harboring influenza B viruses that have circulated in the past, may pose a direct threat to humans.
"In fact, in addition to HPV-11, Bordetella pertussis and measles viruses have been reported to be human-specific pathogens [39,40] (Table 2). Moreover, the IBV is restricted to humans with the exception of an infection identified in seals stranded on the Dutch coast . At present, however, the repertoire of peptides bound by each allele is limited in the experimental data. "
[Show abstract][Hide abstract] ABSTRACT: Background
Diversity among human leukocyte antigen (HLA) molecules has been maintained by host-pathogen coevolution over a long period of time. Reflecting this diversity, the HLA loci are the most polymorphic in the human genome. One characteristic of HLA diversity is long-term persistence of allelic lineages, which causes trans-species polymorphisms to be shared among closely related species. Modern humans have disseminated across the world after their exodus from Africa, while chimpanzees have remained in Africa since the speciation event between humans and chimpanzees. It is thought that modern humans have recently acquired resistance to novel pathogens outside Africa. In the present study, we investigated HLA alleles that could contribute to this local adaptation in humans and also studied the contribution of natural selection to human evolution by using molecular data.
Phylogenetic analysis of HLA-DRB1 genes identified two major groups, HLA Groups A and B. Group A formed a monophyletic clade distinct from DRB1 alleles in other Catarrhini, suggesting that Group A is a human-specific allelic group. Our estimates of divergence time suggested that seven HLA-DRB1 Group A allelic lineages in humans have been maintained since before the speciation event between humans and chimpanzees, while chimpanzees possess only one DRB1 allelic lineage (Patr-DRB1*03), which is a sister group to Group A. Experimental data showed that some Group A alleles bound to peptides derived from human-specific pathogens. Of the Group A alleles, three exist at high frequencies in several local populations outside Africa.
HLA Group A alleles are likely to have been retained in human lineages for a long period of time and have not expanded since the divergence of humans and chimpanzees. On the other hand, most orthologs of HLA Group A alleles may have been lost in the chimpanzee due to differences in selective pressures. The presence of alleles with high frequency outside of Africa suggests these HLA molecules result from the local adaptations of humans. Our study helps elucidate the mechanism by which the human adaptive immune system has coevolved with pathogens over a long period of time.
"reservoir and co - circulation of different multiple lineages in single population increase the chances for reassortment and generating new viruses [ Xu et al . , 2004 ] . In addition , other epidemiological factors , such as multitype interference and accumula - tion of permissive reservoirs may control influenza B virus infection and epidemics [ Osterhaus et al . , 2000 ; Yang et al . , 2012 ] ."
"While various hosts were identified for influenza A viruses (for review see , ), influenza B viruses were until 1999 only detected in humans. In 1999, an influenza B virus was isolated from harbor seals (Phoca vitulina) which was different from influenza B viruses circulating among humans at that time . In addition, during a sero-survey of seals of the Dutch coastal waters using serum samples collected from 2002 to 2012, antibodies were detected against influenza B virus in only 9 seals in 2010 (43% of the tested serum samples of this year) and one in 2011 (0.7% of the tested serum samples of this year; both harbor seals and grey seals [Halichoerus grypus]) . "
[Show abstract][Hide abstract] ABSTRACT: Influenza A and B viruses circulate among humans causing epidemics almost annually. While various hosts for influenza A viruses exist, influenza B viruses have been detected only in humans and seals. However, recurrent infections of seals in Dutch coastal waters with influenza B viruses that are antigenetically distinct from influenza B viruses circulating among humans suggest that influenza B viruses have been introduced into this seal population by another, non-human, host. Harbour porpoises (Phocoena phocoena) are sympatric with seals in these waters and are also occasionally in close contact with humans after stranding and subsequent rehabilitation. In addition, virus attachment studies demonstrated that influenza B viruses can bind to cells of the respiratory tract of these animals. Therefore, we hypothesized that harbour porpoises might be a reservoir of influenza B viruses. In the present study, an unique set of serum samples from 79 harbour porpoises, stranded alive on the Dutch coast between 2003 and 2013, was tested for the presence of antibodies against influenza B viruses by use of the hemagglutination inhibition test and for antibodies against influenza A viruses by use of a competitive influenza A nucleoprotein ELISA. No antibodies were detected against either virus, suggesting that influenza A and B virus infections of harbour porpoises in Dutch coastal waters are not common, which was supported by statistical analysis of the dataset.
PLoS ONE 02/2014; 9(2):e89058. DOI:10.1371/journal.pone.0089058 · 3.23 Impact Factor
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