orthomyxoviridae

missing capsid! no real capsid - very segment has its own

• sperical pleomorphic particles

• sinze 80-120nm - larger than many but still smaller than pow

• envelope with surface proteins

• segmentes, ss RNA, coding capacity

• 13-16kb in total

• 6-8 nucleocapsid-complexes of : NP: Nuceloprotein; PB1, PB2; PA- polymeraseprotein - exclusivley responsible for the polymerase complex

• viral RNA wrapped around NP binds to polymerase-complex

• Na Protein (Tetramer) - HA-Protein (Trimer) - M2 Protein (Tetramer) - M1 Protein - Nucleocapsid - viral RNP

• important fish disease

• europe and north or south america

• atlantic salmon in farms

• Life cycle comparable to influenza viruses ; special feature: hemagglutinin esterase and fusion protein as surface glycoprotiens

• 8 Gene segments, encode in total for 12 proteins

• 5 membrane-/matrix-associated proteins (structural proteins)

• 1. HA - hemagglutinin: trimer, receptor binding/ fusion -> surface against receptor binding

• 2. NA - neuraminidas: tetramer, release of virions -> essentially without = no infectious particles -> releases them

• 3. M1 - matric protein: membrane interior surface, morphogenesis -> inner part of envelope

• 4. M2 - membrane: ion channel protein for uncoating -> makes pH optimal for infection promising for flu vaccine (universal - in the most influenca viruses)

• 5. NEP (NS2) - nucelar export protein bound to M1; export of ribonucleoproteins

1. NS1 (nonstrucutral protein) : first reading frame NS segment - interferonantagonist; immunevasionprotein

2. PB1-F2: 90aa Protein (+1 aORF) - interferonantagonist, virulencefactorprotein - inhibits immune repsonse

3. PB1-N40: N-term, shortened PB1 funtion not yet known

• in endosom pH has to increase so the HA changes in conformation -> releases fusion peptide

• polymerase complex & nucelease proteins are produced -> need to pack the segments

• HA bins neuraminix acid - receptor (adsorption)

• Endocytosis as entry - receptor mediated

• in endosome pH decreases (also in virus particle, function M2 ion channel), conformational change of HA, fusion peptide is exposed!

• fusion between viral envelope and endosome membrane

• Uncoating and transport of ribonucleoprotein segments into the nucleus -> release of genome segments

• rna replication in the nucleus: vRNA -> mRNA/cRNA-> vRNA

• translation in cytoplasm: NP, M1, polymerase proteins back into nucleus and from new nucleocapsid (NEP as shuttle protein); HA, NA, M2 into ER and via exoctosis to cell membrane

• assembly and budding of virus particles on cell memrbane

• NA detaches viruses from receptors on the cell membrane (release)

Haemagglutinin (HA)

• attachement and fusion frotein -> class 1

• prodoce in H0

• major AG for neutralizing ABs

• translation into ER (signalpeptide); C-terminal membrananchor

• post-translational modification in Golgi (sugar)

• -> exposed as a Trimer in lipid rafts of cellmembrane

• proteolyti cleavage in HA1 and HA2 during exocytosis . not active in the cell

• -> essential for infection

• HA binds cell surface sialic acid residues (N-acetyl neuraminic acid, NANA) in a (2,3) or a (2,6) glycosidic bond linked to galactose

• neuraminic acid residues as ubiquitous receptor molecues ( is everywhere in the cell)

• human pathogenic viruses mainly use a (2.6) bound receptors

• animal pathogenic viruses differnt patterns

• avain influenza viruses prefer a (2,3) receptors

• procine influenza viruses may use a (2,3) or a (2,6)receptors

• receptor defines if virus can enter! lower respiratory trackt = living mire severe

• avian virus bind to a 2,3-NANA prevalent in avian tissues

• binds with galactose

• huan viruses bind to a 2,6 -NANA prevalent in human tissues

• second surface glycoprotein as tetramer in membrane

• second major AG (also neutralizing ABs)

• Activity: destruction of receptor; cleavage of linkage between sialic acid receptor and galactose

differentiation of influenza A viruses based on AB recognition of HA and NA.

basis for designation of newly isolated viruses

• AG serotypes of subtypes

• 18 subtypes of HA proteins (H1- H18)

• 11 subtypes of NA Proteins (N1-N11)

• genetic relationship of diff. subtypes

Genus / (Spezies) / Place of isolation / Number of virusstrain / Year / Subtype HA and Subtyp NA

• waterbirds are reservoir for (almost) all influenza A viruses (H1-16; N1-9)

• human : H1N1, H3N2

• dog N3N8

• Horse H7N7

• Swine H1N1,H1N2, H3N2

continuous changes = AG drift - mainly induced by red mutation in the genome

Sudden changes (formation of new variants/subtypes) = AG shift - change of segemnts -> very spontanuous

Mutation in RNA (genome- segments) for HA or NA

(Pointmutations, “messy” and RNA Polymerase)

small changes in antigenicity

-> selection advantages in the new host

continuous EVOLUTION

IMMUNEVASION of new virus variants

change in antignicity!

circulation A/H3N2 viruses in humans 1968-2002

temperature sensitivity can have an impact

• segmented RNA (1 segment - 1 protein)

• Reassortment of genom-gements after mixed infections

• abrupt change in the properties of the virus.

• sudden appearance of new variants/subtypes

• Markes SPECIAL CHANGES possible

• 0.3-0.5 mio deaths worldwide (WHO data 2013)

• also younger patients

• severe pneumonia with acutely fatal course

• destruction of the lungs with necrosis in bronchial and alveolar areas

• local infection

Low Pathogenic Avian Influenza - LPAI: low risk to be transmitted. will not spread within the organism -> no severe disease in the host. apathogenic virus . enteric infection

High pathogenic avian influenza - HPAI: high risk to be transmitted -> potential to be severe in humans. many enzymes -> goes to every organ = severe disease. pathogenic infection and systemic infetion - severe bleeding of embryo

• acute general disease with high morbidity and lethality

• first described in chickens in northern italy in 1878 as a “form” of fowl cholera

• 1901 virus etiology, 1955 influenza a virus identified as causative agent

• worlwide spread and major epidemics until 1930

• re-emergence of avian influenza since 1980 in the unsa

• hongkong 1997 first detection as a zoonosis

• since 2003 again very widespread in asia, europe, afrika

• international nomenclature highly pathogenic avian influenza

virus excretion: respiratory and digestive tracts

site of entry: nasopharynx

incubation time: a few hours - 3d

highly variable clinicle picture, clinical diagnosis impossible!

severe general disease in chicken birds

peracute course

dullness, sleepiness, apathy, reluctance to eat and move

respiratory distress and diarrhea, increased losses

virus cultivation in incubated hen’s egg

typing of the pathogen by:

• HA/HAH

• determination of pathogenicity LPAI/HPAI

• sequencing of the HA-Gen

• Direct RT-PCR, RT-QPCR

no effcient huma-to-human transmission so far but adaptation of the pathogen always possible. source of new pandemic

transmission: respiratory tract

contact, droplets

during coughing

mostly canalicular spread in the respiratory tract (=usually no viremia)

incubation time: a few days!!

• high fever (~41°C)

• dry cough

• fatigue

• snooty nose and eye discharge

• high morbidity, usually low morbidity

• duration of illness 1-2w

• milder course in partially immune animals

• pathogendetection by culturing (egg, cell culture)

• RT-PCR

• indirect: serum pair with HAH

• detection of a significant increase in titer (>4fold)

• resting

• no training, little stress

• symptomatic treatment

• avoidance of secondary infections (Antibiosis)

• vaccines from inactivated pathogens

• regular update of vaccines

• basic immunization

• regular boost vaccinations

• regular boost vaccinations

• establishment of herd immunity

aim is solid protection against influenza by vaccination:

• against drift variants of an influenza a virus subtype

• across-subtypes?

• strategies:

  • immunisation with additional virusAG, T cell mediated immunity

  • improvement of immunostimulation

• methods: alternative vaccine-systems: MVA vector vaccines