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Characterizations of antigenic and receptor binding properties of avian H5N1 and 2009 pandemic H1N1 virusesLau, Siu-ying., 劉韶瑩. January 2011 (has links)
Avian H5N1 viruses have perpetuated in poultry and caused sporadic human transmission since 1997. Vaccine candidates for the potential pandemic caused by H5N1 viruses have been continuously updated by World Health Organization. Multiple genetic lineages of H5N1 viruses which co-circulate and rapidly evolve in different regions, together with periodic population replacement of newly emerged genetic and antigenic variants in the field, pose great challenge for H5N1 vaccine candidate selection. The complexity of avian H5N1 viruses evolution raises an important issue for studying antigenic properties and also for projecting antigenic trend of this virus since the model established for the seasonal influenza viruses may not apply to H5N1 viruses which they are still in the animal phase. In contrast, the 2009 pandemic H1N1 viruses have established as another seasonal influenza viruses in humans. How will this swine originated viruses evolve genetically and antigenically in humans? For the first in human history, we are able to track the changes of pandemic viruses from the very beginning when they transmitted to human.
This study focuses on antigenic and receptor binding properties of avian
H5N1 viruses from 1997 to 2010 and 2009 pandemic H1N1 viruses from 2009 to 2011. It is found that avian H5N1 viruses continue to display highly diverse antigenic profile. The newly emerged H5N1 virus variants of clade 2.3.4 in 2008 and clade 2.3.2 in 2010 exhibit distinct antigenic properties as compared to the genetically similar viruses that were characterized previously. Receptor binding analysis showed H5N1 viruses still exhibit binding preference for avian type receptor. However, analysis of escape mutants selected from H5N1 viruses exposed to H5 monoclonal antibodies in cell based assay indicates that mutations in the conserved sites may cause switch of receptor binding specificity to human type or dual specificity for both human and avian.
Based on antigenic and receptor binding analyses, it is found that the 2009 pandemic H1N1 viruses isolated from 2009 to 2011 are relatively stable. Most of the antigenic variants to monoclonal antibodies are transient and not able to become prevalent. It remains to be investigated if more significant antigenic variants may emerge in the coming seasons when population immunity prevails this virus.
In conclusion, this study showed that clade 2.3 avian H5N1 viruses become increasingly antigenic distinct as compared to clade 2.1 and 2.2 viruses. Antigenic variation in antigenic sites may change receptor binding specificity in avian H5N1 viruses. The 2009 pandemic H1N1 viruses remain stable up to date but continue monitoring in coming seasons is necessary. / published_or_final_version / Microbiology / Master / Master of Philosophy
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Genetic adaptation of an avian influenza A virus to swine cellsBourret, Vincent Jacques Richard January 2014 (has links)
No description available.
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Genome packaging in influenza A virusKudryavtseva, Katerine January 2014 (has links)
No description available.
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The role of the non-structural protein of human influenza A viruses (NS1A protein) during infection of human cellsKim, Mee-jung. January 2002 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.
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Genesis and prevalence of H1N2 swine influenza virus in pigs from southern ChinaMa, Siu-kit., 馬少傑. January 2005 (has links)
published_or_final_version / Medical Sciences / Master / Master of Medical Sciences
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Development of recombinant adeno-associated virus delivering short-hairpin RNAs to inhibit the replication of influenza A virusesZhang, Gui, 张桂 January 2011 (has links)
published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy
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A mutation in avian influenza H5 hemagglutinin with efficient packaging into lentiviral backbone and its implications on receptorbindingLam, Yuen-man, 林婉雯 January 2011 (has links)
Because diagnostic tests for highly pathogenic avian influenza (HPAI) viruses require
the use of replication-competent viruses in a biosafety level 3 containment, numerous
studies have looked at ways to develop alternative tests. Lentiviral particles
pseudotyped with H5 hemagglutinin (HA), the surface glycoprotein of influenza virus,
have been described as useful and safe tools for research and serological surveillance
on the HPAI viruses. However, not all H5 HA give rise to efficient H5 pseudotyped
lentiviral particles (H5pp) production. HA from A/Cambodia/408008/05 H5N1
(H5Cam) and HA from A/Anhui/1/05 H5N1 (H5Anh) exhibit a dramatic difference in
their ability to pseudotype lentiviral particles. H5Cam gives the highest H5pp
production among all HAs tested, whereas the lowest has been observed with H5Anh.
The objective of this study was to investigate the molecular determinants that govern
efficient H5pp production.
Based on the amino acid differences between H5Cam and H5Anh, H5Anh mutants
were generated by site-directed mutagenesis. Strikingly, a single amino acid change,
A134V, in the 130-loop receptor-binding domain of HA, significantly increased H5pp
production with H5Anh. The finding that valine 134 is crucial for H5pp production was
confirmed by reciprocal H5Cam and H5Anh mutants, which displayed either a
dramatic decrease or increase in H5pp production, respectively.
Influenza virus and H5pp bud at the plasma membrane, therefore changes in HA cell
surface expression could affect the production of H5pp. Thus, cell surface expressions
of H5Cam and H5Anh were compared by flow cytometry. Intriguingly, H5Cam
displayed a higher plasma membrane expression than H5Anh, suggesting that transport
is important for H5pp production. Introduction of V134A mutation in H5Cam reduced
its surface expression to that of H5Anh; by contrast, H5Anh mutant harboring A134V
mutation largely restored its expression.
Next the effect of A134V mutation on the binding of HA to sialic acid receptors was
investigated. A cell-based Enzyme-linked Immunosorbent Assay was developed to
measure binding of wild-type and mutated HA. Soluble recombinant proteins were
produced by mammalian cells stably transfected with HA gene ectodomain and were
mostly trimeric as indicated by discontinuous native gel electrophoresis. Interestingly,
H5Anh proteins exhibited a stronger binding to MDCK cells than H5Cam proteins, and
introduction of A134V mutation in H5Anh proteins reduced the binding. By contrast,
as predicted, the reciprocal V134A mutation induced a major increase in binding to
cellular receptors. It is likely that stronger binding of H5Anh to sialic acids could
hinder the release of H5pp. Consistent with this notion, the ability of H5Anh to
generate H5pp was significantly increased in a sialylation deficient Lec2 cell, a CHO
mutant cell line.
In conclusion, H5Cam allows efficient H5pp production whereas H5Anh does not.
With several lines of evidence, it is likely that the behavior of H5Anh can be explained
by a stronger binding to sialic acid receptors that is dependent on a single amino acid
residue at position 134. Since A134V is a naturally occurring mutation observed
occasionally in human host, these results may have implications for the understanding
of human host adaptations of H5N1 viruses. / published_or_final_version / Biochemistry / Master / Master of Philosophy
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The genesis and development of H5N1 influenza virus in poultry in ChinaDuan, Lian, 段炼 January 2011 (has links)
published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy
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Ecology, epidemiology and immunology of avian influenza virusLeung, Yin-hung, Connie., 梁彥虹. January 2011 (has links)
published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy
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Continuing evolution of H9N2 avian influenza A viruses in poultry in southern ChinaChu, Ying-cheung., 朱盈彰. January 2011 (has links)
Our systematic influenza surveillance in southern China revealed that two lineages
of H9N2 influenza viruses, represented by Chicken/Beijing/1/94 and Quail/Hong
Kong/G1/97, became endemic in the poultry in southern China since 1990’s. These
established H9N2 lineages continually evolved to generate many different
reassortants (or genotypes) and caused sporadic human infection cases. As
co-circulating with H5N1 influenza viruses, the increasing genetic diversity and the
capability to cause sporadic human infection make the H9N2 viruses become one of
the major candidates with pandemic potential.
Even though highly pathogenic H5N1 influenza viruses were seldom detected at
the live-poultry markets of Hong Kong since 2002, H9N2 viruses were still
commonly isolated in our surveillance program. The accumulated H9N2 isolates
provided an opportunity to get insights into the continual evolution of this subtype
virus in the region. In present study, we have systematically analyzed the H9N2
influenza viruses isolated from 2005 to 2010. Antigenic and phylogenetic analyses of
60 representative H9N2 viruses showed that the Ck/Bei-like H9N2 virus lineage
continued endemic in the terrestrial poultry during the survey period in southern
China. Genotyping analyses revealed four prevalent genotypes or reassortant variants
in the field. Fifty-three of the viruses analyzed belonged to genotype B14 and B15,
which were also the major reassortant variants prevailing in southern China from
2000 to 2005. The remaining seven viruses belonged to novel genotypes that have not
been identified before. Our findings suggested that the Ck/Bei-like lineage continually
maintained high genetic diversity in this region.
The epidemiological findings showed that the isolation rate of H9N2 virus at the
marketing poultry in Hong Kong was dramatically dropped down since 2009, which
was different from what have observed in other provinces in southern China, but was
closely correlated with the hygiene measures implemented in live-poultry markets in
Hong Kong, e.g. not keeping live chicken overnight. These findings suggest the
proper market policy would directly impact the prevalence of influenza virus in the
field. / published_or_final_version / Microbiology / Master / Master of Philosophy
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