Microbiology Lecture #32

Cold Pathogenicity/mechanism:

Virus (VP1) binds specific receptors (ICAM-1 protein) on throate (pharyngeal) epithilium, enter cells by direct penetration go through sense stranded virus replication inside the cell Express viral protein that makes ribosomes translate only viral mRNAs because it uses a soluble protein that attaches to the ribosome Exit: Lysis of cells that lead to inflammation

Flu (Influenza) Transmission: Incubation time: Burst time: Burst size: Dose:

airborne droplets of respiratory tract inhaled or contracted to respiratory tract 1-2 days 6 hours, 100,000 only 10-100 virions

What are the different classes of influenza virus and how are they categorized?

classified according to different classes of H and N Both H and N serve as key antigens for host immune system Considerable antigenic variation of H and N due to high mutation rate of flu virus.

Flu (Influenza) Mechanism: Signs/Symptoms:

1. H binds receptors (neuraminic acid) on epithilial cells N helps out, virus gets endocytosed 2. virus uncoated, low pH of endosome/early phagosome allows 3. Replicate (antisense RNA virus), assemble, bud and then spread to nearby cells. H and N go to the plasma membrane and the nuclear membrane to get translated. 4. Infected cells die (worked to death), sluff off Destroy mucosal escalator, fever to 104F, cough, body aches, exhaustion, mild sneezing, inflammation

Flu (Influenze) How long is someone contagious for? Why does it cause you to ache? Can a secondary infection occur? If so, what is it?

7 days Due to body's response: your own cytokines trigger headaches, body aches, and exhaustion. Pneumococcal pneumonia, usually the cause of death

What are the different types of the influenza virus?What is different between them?

A, B, and C. A: infects a wide variety of animals-humans, but wild birds are the natural hosts B and C infect humans but don't cause pandemics and they are less virulent Class C is the least virulent because they lack neurominidase.

Flu (Influenza) Treatment: Prevention:

Amantadine or rimantadine inhibit uncoating -not recommended for newer strains due to resistance Neuraminidase inhibitors -Relenza and Tamiflu stop the spread of the virus if it is given early enough The antiviral drugs reduce duration about 1-2 days and decreases severity but you will still get signs. Usually your immune system (Cell Mediated Immunity and Antibody Mediated Immunity) will get rid of it through time -NO ASPIRIN Prevent with dead agent vaccine: given yearly to produce memory B cells Newer vaccine: attenuated (Flumist)

What are the major differences for the symptoms between the cold and the flu?

Cold: runny stuffy nose, sneezing, sore throat, chest discomfort, cough, inflammation, complications: sinus and ear infections Influenza: high fever that lasts 3-4 days, headache, general aches and pains, fatigue and weakness that can last for a month, exhaustion, Complications: bronchitis, pneumonia, can be life threatening

What are the different glycoproteins in an influenza virus?

H (hemagglutinin) spike: protein (ligand) that facilitates attachment of virus to host cell receptor (neuraminic acid) N (neuraminidase) functions in entry/exit from host cell Protein found in envelope. It digests off neuraminic acid so virus can get away from the sticky plasma membrane.

What are the glycoproteins that are located on an influenza virus called? What are the other characteristics of an influenza virus?

H spike (hemagglutinin) and N spike (neuraminidase). They also contain an envelope and RNA.

_________: uses hemagglutinin protein that facilitate attachment of virus to host cell receptor (neuraminic acid). Also uses neuraminidase that digests off neuraminic aka sialic acid so virus can get away from the sticky plasma membrane

Influenza (the flu)

Cold Transmission How does it travel from person to person: Incubation time: When does the infected person become contagious? Virulent? Signs/Symptoms:

Inhalation but mainly contact to nose, eyes 1-3 day incubation time Infected person contagious for only first symptomatic 2-3 days Virus is not that virulent dry scratchy RAW throat, RED runny nose, cough-no fever usually INFLAMMATION: due to the lysis of cells, red, swollen

Flu(Infleunza) How likely is it to get long-term immunity? What are the different ways a flu virus can change? How good is your memory response to these changes?

It is very hard due to antigenic variation. 1. Antigenic variation of small scale changes (antigenic Drift) due to point mutations- since minor substitutions in viral proteins -minor gradual changes because of missense mutations Cell mediated and antibody mediated memory are partially useful since some antigens stay the same or similar. -You may get clinical flu disease but less serious symptoms since the plasma Bs and cyto Ts from memory cells work to some degree. 2. Antigenic shift: large scale antigenic variation changes -trading of genome parts between human and avian virus (new H and N) to create hybrid virus -mixing of an avian and a human form in a pig (co-infection in a pig) -Hybrid virus has potentially worst virulence genes of avian virus with human virus structural genes -give it ability to infect human cells and cause severe effects -Antigens very different so memory response is totally useless

Common Cold major agent: Where does it infect: WHAT DOES IT NOT INFECT: Sensitive to:

Rhinovirus stays in the nose and does not infect the lungs Sensitive to detergent and acid

Common Cold agent: genome: characteristics:

some adenoviruses and mainly Rhinoviruses; refers to a group of RNA viruses (100s of types + RNA strand -can be translated right away by the host cell's ribosomes have no envelope which means lysis will occur Capsid made of 4 major surface proteins VP1-VP4