Highly pathogenic avian Influenza A virus [Elektronische Ressource] : pathogenesis, vaccine and antiviral / vorgelegt von Karoline Dröbner

Karoline Dröbner

Sujets

• Naturwissenschaften

Informations

• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2010
• Nombre de lectures: 25
• Langue: Deutsch
• Poids de l'ouvrage: 13 Mo

Extrait

HIGHLY PATHOGENIC AVIAN INFLUENZA
A VIRUS: PATHOGENESIS, VACCINE AND
ANTIVIRAL









Dissertation
der Mathematisch-Naturwissenschaftlichen Fakultät
der Eberhard Karls Universität Tübingen
zur Erlangung des Grades eines
Doktors der Naturwissenschaften
(Dr. rer. nat.)






vorgelegt von
Karoline Dröbner
aus Stettin



Tübingen
2010


1




























Tag der mündlichen Qualifikation: 13.01.2011
Dekan: Prof. Dr. Wolfgang Rosenstiel
1. Berichterstatter: Prof. Dr. Oliver Planz
2. Berichterstatter: Prof. Dr. Hans-Georg Rammensee

2ZUSAMMENFASSUNG
Infektionen des Menschen mit hochpathogenen aviären Influenzaviren (HPAIV) weisen im
Vergleich zu den saisonalen Influenza-Fällen einen besonders schweren Krankheitsverlauf
auf. Die Sterberate humaner H5N1-Infektionen liegt derzeit bei etwa 60%. Im August 2010
sind nachweislich 504 Personen an vom H5N1-Virus verursachter aviären Influenza erkrankt
und 299 daran gestorben. Der Krankheitsverlauf einer HPAIV-Infektion ist durch eine
Reduktion der Lymphozyten (Lymphopenie), einer Hyperinduktion von Zytokinen und
Chemokinen (Hyperzytokinämie), sowie ein plötzliches akutes Lungen- und
Multiorganversagen gekennzeichnet. Die immunologischen und viralen Faktoren, die zu
einem solch kritischen Verlauf der H5N1-Infektion führen, sind bislang nicht ausreichend
bekannt. Ein weiteres Problem für die Behandlung der HPAIV-Infektion stellt die
zunehmende Resistenz der humanpathogenen H5N1-Isolate gegenüber den gängigen
antiviralen Medikamenten dar. Auch wenn eine Adaptation des Virus, die eine
Weiterverbreitung von Mensch zu Mensch in großen Dimensionen ermöglichen würde, bisher
nicht erfolgt ist, lässt sich diese für die Zukunft nicht ausschließen. Die begrenzten
Möglichkeiten zur Bekämpfung von HPAIV-Infektionen verdeutlichen den dringenden
Bedarf an neuen, effektiven Maßnahmen gegen diese Krankheit. Für die Entwicklung neuer
antiviraler Medikamente und Impfungen gegen das Influenza A Virus müssen die Vorgänge,
die den kritischen Verlauf der HPAIV-Infektion beeinflussen besser verstanden werden.
Das Ziel dieser Dissertation war es, einen besseren Einblick in genau diese Vorgänge zu
bekommen und nach alternativen Möglichkeiten zur Behandlung der HPAIV-Infektion zu
suchen. Im Rahmen der hier zusammengefassten wissenschaftlichen Publikationen wurde die
Rolle des NF- ĸB-Signalweges bei der Bekämpfung viraler Infektionen untersucht. Es folgte
eine Studie zur Beteiligung der Hyperzytokinämie an der H5N1-vermittelten Pathogenese.
Des Weiteren konnte ein möglicher Mechanismus der die virusvermittelte Lymphopenie
verursacht aufgezeigt werden. Weiterhin erfolgte die Charakterisierung immunologischer
Mechanismen, die maßgeblich am Schutz gegen HPAIV-Infektionen nach Vakzinierung
beteiligt sind. Schließlich, konnte die antivirale Wirkung von Polyphenolen als Alternative zu
den gängigen antiviralen Medikamenten in vitro, sowie im Mausmodell gezeigt werden.
3HIGHLY PATHOGENIC AVIAN INFLUENZA A VIRUS:
PATHOGENESIS, VACCINE AND ANTIVIRAL
K. Droebner

Influenza virus leads to acute respiratory infection in humans with severity ranging from
morbidity to mortality. Seasonal epidemic outbreaks of human influenza viruses occur
annually during autumn and winter and cause estimated 250.000 – 500.000 deaths worldwide
each year (World Health Organisation; WHO 2009a). In addition to the epidemic form of the
disease, pandemic outbreaks occur regularly. Beside the current swine origin influenza virus
(SOIV) H1N1v outbreak, three of these pandemics occurred in the last century, in 1918, 1957,
and 1968 resulting in millions of deaths within the human population (Oxford 2000; Palese
2004; Hsieh et al. 2006).
Influenza A viruses are enveloped viruses with a single-stranded RNA genome of negative
polarity that is divided into eight RNA segments. Influenza virions have two major surface
glycoproteins: hemagglutinin (HA) and neuraminidase (NA). They are distinguished in
several subtypes according to those surface proteins. Until today, 16 different HA and 9
different NA proteins are known. All combinations of HA and NA can be found in wild
waterfowl, but only combinations of H1, H2, H3, and N1 and N2 circulate within the human
population (Whittaker 2001; Julkunen et al. 2001). Some strains of avian influenza viruses
lead to lethal infection in birds. Such outbreaks of highly pathogenic avian influenza are
caused by H5 and H7 subtypes.
Although, avian viruses were previously thought to be incapable of infecting humans, in 1997
a direct avian to human transmission occurred. Highly pathogenic avian influenza viruses
(HPAIV) of the subtype H5N1 were transmitted from domestic poultry to humans in Hong
Kong (de Jong et al. 1997; Claas et al. 1998). Infections of humans with the HPAIV are much
more fatal, in contrast to seasonal influenza infections and the current pandemic outbreak. The
mortality rate of human HPAIV H5N1 infections is around 60%. In August 2010, 504
confirmed cases of avian H5N1 infections in humans have been reported, while 299 of them
were lethal (WHO 2010a). HPAIV-mediated disease is characterized by lymphopenia,
cytokine dysregulation, acute respiratory distress syndrome and multiorgan failure (Beigel et
al. 2005).
Virus-host interactions are not only crucial for the defence against influenza virus infections,
moreover these sometimes can negatively impact H5N1 mediated disease severity. However,
both viral and immunological factors leading to H5N1 mediated severe influenza are only
poorly understood. In addition, many of the human H5N1 virus isolates are already resistant
4to the two main classes of anti-influenza drugs, namely inhibitors of the viral M2 ion channel
protein or viral neuraminidase inhibitors (Hayden & Hay 1992; de Jong et al. 2005;
McKimm-Breschkin et al. 2007). Therefore, options for control and treatment of H5N1
infections are limited, demonstrating the urgent need for new effective countermeasures
against this important disease. Fortunately, the spread of the virus is limited by a rare human-
to-human transmission. Although, HPAIV H5N1 has not evolved to a form that allows to
spread easily between humans, it is still considered by WHO (WHO 2010b) as a potential
pandemic strain. Moreover, the possibility of a reassortment between the pandemic SOIV
H1N1v and H5N1 influenza virus strain is indeed a frightening but feasible association. A
mixed strain capable of efficient human-to-human transmission may cause a serious pandemic
with fatal mortality rates. A basic requirement for the development of new antiviral agents
and vaccines against the influenza A virus is the understanding of how and why influenza
viruses cause disease in humans and what influences disease severity.
The aim of this Ph.D thesis was to provide a better understanding of the immunological
mechanisms that influence the critical outcome of HPAIV infection. The second goal of this
work was to identify a new promising anti-influenza agent which can be used against
infections with HPAIV. In the range of the scientific publications presented here I
investigated the role of the NF- κB signalling pathway in viral infections. I determined the
impact of two major hallmarks of HPAIV infection, hypercytokinemia and lymphopenia on
the critical H5N1-mediated disease outcome. Furthermore, I characterized immune
mechanisms that provide cross-protection against lethal influenza A H5N1 virus infection.
Finally, as an alternative approach to the common anti-viral drugs I studied the antiviral
activity of polyphenols against influenza virus.

Studies on the pathogenesis
Infections with H5N1 differ from the common influenza virus infections. While seasonal
influenza epidemics affect the very young, the elderly and persons with an impaired immune
system, infections with most avian influenza subtypes cause either mild infections or no
disease at all, in humans (Beare & Webster 1991; Koopmans et al. 2004; Butt et al. 2005). In
contrast, the HPAIV H5N1 is much more virulent than other avian influenza A viruses and
targets mostly young and middle-aged people. Human infections with H5N1 result in severe
disease leading to death. The role of virological and host-specific factors responsible for the
establishment of such critical disease outcomes and for the altered host specificity still needs
to be determined. The pathogenesis of fatal HPAIV infection involves a number of viral
5factors that have been suggested to be involved in increased virulence of H5N1 viruses (Hatta
et al. 2001; Salomon et al. 2006; Mansfield 2007; Neumann et al. 2007; Kortweg & Gu 2008;
Gabriel et al. 2005 and 2009). The dysfunction of the immune system including a
dysregulation of cytokines and chemokines, an up-regulation of tumour necrosis factor-
+relate