Sept 13, 2012.rtf

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Molecular Genetics and Microbiology
Course Code
Richard Brown

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MGY440H - lecture 1 - September 13, 2012 4 viruses - Adenovirus, Reovirus, Poliovirus (tropism - why does poliovirus cause disease where it does?), Influenza (seasonal flu as well as more virulent strains, like the 1918 flu and H5N1 flu - what factors are associated with virulence?) - ferrets sneeze - they develop symptoms - do not need to kill and dissect - can tell from appearance if ferret is sick/infected - ferrets are model animals ideal for studying influenza CUMULATIVE FINAL EXAM Oral presentation - a week to prepare - paper assigned one week before presentation date - HOW? Projector available - understand the content, explain the content - typically use Powerpoint to project images, if available - PAPERS ARE IMPORTANT, TEST-TABLE - length = 30 minutes - TALK THROUGHALL FIGURES - give a bit of background GET PAST TESTS/EXAMS - BE PREPARED FOR COMPARISONS ------------------------------------------------------------------------------------------------ How do viruses cross barriers? Physical Barriers: skin; stomach acidity; mucous secretions; into and out of bloodstream; lung epithelium (ciliated); intestinal epithelium What viruses breach skin? - herpes simplex infects mucosal cells - human papilloma virus - causes warts Some viruses can be inactivated by pH (1-2) of stomach Intestinal epithelium - villi - tips of villi are columnar cells that are fully differentiated and covered with cilia; in valley between villi are stem cells - with increasing attitude, increasing state of differentiation of cells - like an escalator - constant sloughing off and new cells replacing dead cells - if virus kills a villus cell, less water adsorption - diarrhea - tight junctions like belt around cell - prevent fluid leakage and virus entry past intestinal integrity - picornavirus like Coxsakie-B virus go through columnar epithelial cell - trnasport to tight junction and go through - polarized cells = epithelial cells attached to each other with tight junctions - M cells (microfold cells) - in between columnar cells - transport across M cells and infect adjacent columnar cells through basal-lateral surface - like rotaviruses Apical - surface above tight junctions Lateral the sides Basal surface - below tight junctions Signalling - signal given in one place and has effect somewhere else - just binding to cell can ativate signalling pathways in cell - induce cell to endocytose virus - adenovirus, hepatitis B - need to deliver genome to nucleus of cell Progency virus enters lumen (into human waste) others leave from basal surface (into bloodstream) - some exits in one direction - depends on virus - same with airway epithelium Poliovirus - replicating initially in intestional tract, then entering bloodstream Probability - if lots of virus, increase chances of interaction/infection ONCE virus gets across physical barrier, it is on surface of susceptible cell Cell level - receptors necessary but NOT SUFFICIENT for infection - if no receptor that a virus can use, will not infect that cell - example B19 - having the receptor does not mean the infection will be productive - many host factors required for virus replication - virus needs all necessary host cell factors so cell will be host for productive infection Immune system - if virus infects a few cells but cannot spread further - not likely to get sick - interferons - a cytokine - several different kinds of interferons - first line defense against disease from microbial infection
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