Neuraminidase in Viral Pathogenicity
Neuraminidase in Viral Pathogenicity
Aims of the lecture
To provide an introduction to the influenza virus and how it causes disease in humans.
• Describe the basic structure of the influenza virus
• Explain how the virus infects and replicates • Explain the importance of Haemagglutinin and Neuraminidase in viral pathogenicity
• Compare and contrast the different diagnostic techniques used to identify flu
What is influenza? • An infectious disease commonly called flu • Caused by a family of influenza viruses; A, B and C • Can infect birds and mammals including humans • Symptoms of the disease include chills, fever, runny nose, sore throat, muscle pains, fatigue, and headache
• Spread in humans by direct contact with infected individual or contaminated object and by inhalation of virus particles
• Distinct from the “common” cold, parainfluenza and stomach flu. Also different from haemophilus influenzae which is a bacterial form of respiratory disease
Influenza virus • Negative sense single stranded RNA virus – i.e cannot be directly translated to protein, must first be transcribed to sense RNA
• Influenza virus A, B and C distinguished by the nucleoprotein and the matrix protein
• All infect humans and – A infects other mammals and birds (pandemic) – B infects seals – C infects pigs and dogs
• Influenza C tends to cause mild disease
Influenza proteins (and nucleic acids)
Protein/Nucleic acid Function
Neuraminidase (NA) Membrane glycoprotein, cleaves sialic acid groups from host glycoproteins. Required for release from host cell
Haemagglutinin (HA) Membrane glycoprotein, major viral antigen. Required for entry and release from host cell
Matrix protein (M1) Provides strength and rigidity
M2 Ion channel required for pH maintenance
B1, PB2, PA RNA polymerases required for transcription of viral RNA
8 RNA segments Code 12 viral proteins
Influenza A • Generally thought to be the most pathogenic • Causes epidemics and pandemics (4 in the last 100 years)
• Classified according to their HA and NA subtypes – H1 – H18 (H18 found in 2013 in a Peruvian bat) – N1 – N10
• All subtypes can infect birds except H17N10 found only in bats
• Only H1N1 and H3N2 currently in circulation among humans
• Poor proof reading rates in viral polymerases leads to point mutation in viral HA (genetic drift)
• Occasionally mutated HA has an advantage and new HA strains emerge and infect
• Reassortment of HA in animals infected with more than one strain of influenza A also lead to new HA often novel to the human host
You must proofread your paper. But do not strictly rely on your computer’s spell-checker and grammar-checker; failure to do so indicates a lack of effort on your part and you can expect your grade to suffer accordingly. Papers with numerous misspelled words and grammatical mistakes will be penalized. Read over your paper – in silence and then aloud – before handing it in and make corrections as necessary. Often it is advantageous to have a friend proofread your paper for obvious errors. Handwritten corrections are preferable to uncorrected mistakes.
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The paper must be neatly formatted, double-spaced with a one-inch margin on the top, bottom, and sides of each page. When submitting hard copy, be sure to use white paper and print out using dark ink. If it is hard to read your essay, it will also be hard to follow your argument.