Assignment: Haemagglutination in RBC
Assignment: Haemagglutination in RBC
Haemagglutinin • HA named because it causes haemagglutination in RBC
• Binds to sialic acid on epithelial cells to initiated viral entry
• Sialic acid is linked to galactose in different configurations
• Isolates from different species vary in ability to bind to sialic acid/galactose – Human and swine isolates prefer Sia-Gal in an α2- 6 linkage
– Avian and equine isolates prefer α2-3 linkage
Haemagglutinin linkages • Isolates from different species vary in ability to bind to sialic acid/galactose – Human and swine isolates prefer Sia-Gal in an α2-6 linkage
– Avian and equine isolates prefer α2-3 linkage • Human epithelial cells (main target for flu) have the α2-6 configuration whereas goblet cells lower in the respiratory tract have α2-3
• Swine respiratory tract has both binding sites (and possibly more variation)
• Pigs act as mixing bowl
• HA binds to sialic acid on cell so prevents release of new virion after budding
• NA cleaves sialic acid from sugar allowing virion to be released
• Cleavage is not equivalent by all subtypes • Most strains have a preference for the α2-3 configuration
1. Virion is endocytosed
2. RNA released into the cytosol and then enter the nucleus 3b. Transcription occurs
6. NEP and M1 traffic newly replicated RNA to the membrane
3a-4. Transcribed RNA is transported to cytoplasm for translation or remains in nucleus
5. New viral proteins are synthesised. 5a. Other proteins returned to nucleus to form new vRNA particles 5b. NA and HA transported to membrane.
7. New virions bud off
Influenza • Occurs seasonally–generally between October and April in
the UK • Symptoms include:
– High temperature – Aches and pains in joints – Headaches – Watery eyes – Fatigue – Sore throat and watery discharge from nose – Diarrhoea
• At risk groups given flu vaccine seasonally • Nasal spray vaccine for 2, 3 and 4 year olds introduced in
Why is flu seasonal? • People are indoors leading to increase in transmission • Less ultraviolet radiation may reduce the likelihood of the virus being
damaged or killed • Cold temperatures lead to drier air, which may dehydrate mucus
membranes • Aerosol transmission of the virus is enhanced when the air is cold and
dry – Virus degraded in moist air – Infected hosts shedding the virus for a longer period of time in cold
• The virus may linger longer on exposed surfaces (doorknobs, countertops, etc.) in colder temperatures
• Influenza virus has a “butter-like coating”. The coating melts when it enters the respiratory tract – Cold – coating becomes a hardened shell – Warm – coating melts before the virus reaches the respiratory tract
Transmission of flu • Inhaling infected droplets when people sneeze, cough or speak – Indirect – Up to 1 metre
• Inhaling droplets through direct contact – Kissing
• Indirect transmission (fomite transmission) – e.g. hand to mucous
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.
Use a standard 10 to 12 point (10 to 12 characters per inch) typeface. Smaller or compressed type and papers with small margins or single-spacing are hard to read. It is better to let your essay run over the recommended number of pages than to try to compress it into fewer pages.
Likewise, large type, large margins, large indentations, triple-spacing, increased leading (space between lines), increased kerning (space between letters), and any other such attempts at “padding” to increase the length of a paper are unacceptable, wasteful of trees, and will not fool your professor.
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.