Micro viral infections

Question 2

Define virus

Answer 2

Obligate intracellular pathogen; no metabolic pathways; cannot reproduce independently; acellular; no cytoplasm (often take some with them when they leave cell - covered)

Question 3

Extracellular state of virus

Answer 3

aka virion; protein coat (capsid) surrounds nucleic acid; nucleic acid plus capsid = nucleocapsid; outer layer is membrane from budding off host cell with viral proteins - protects and recognizes host cells

Question 4

Intracellular state of virus

Answer 4

capsid removed or membrane left behind; virus exists and nucleic acid

Question 5

Distinguishing viruses

Answer 5

Type of genetic material they contain (most important); Kinds of cells they attack; Size of virus; Nature of capsid coat; Shape of virus; Presence or absence of envelope

Question 6

Viral Envelope

Answer 6

From host cell membrane, gained during replication or release; sometimes insert viral glycoproteins (before they leave) - needed to target next cell

Question 7

Entry methods

Answer 7

Direct penetration: capsid recognizes receptors, inject DNA into cell, rare; Membrane fusion: envelope glycoproteins recognize cell, fuse, nucleic acid unleashed (HIV); phagocytosis: virus phagocytized, avoids phagosome, release nucleic acid (influenza)

Question 8

Genetic material of viruses. 2 important points about this

Answer 8

dsDNA, ssDNA, dsRNA, ssRNA; MUST regenerate itself, and MUST form mRNA to be effective

Question 9

Describe the types of genome in viruses**

Answer 9

dsDNA: replicated in nucleus; ssDNA; dsRNA:, ssRNA: + for sense strand (can be read right away), - for antisense;

Question 10

Where can assembly happen?

Answer 10

Cytosol or nucleus, depending on method of replication

Question 11

Culturing viruses

Answer 11

Hard, need a living cell; Tissue culture:

Question 12

Influenza

Answer 12

• ve sense NRA; exoenzymes (neuraminidase) help break down mucous, hemagglutinin is needed to enter

Question 13

Hemagglutinin action

Answer 13

binds to membrane, influenza gets internalized into phagosome, pH begins to drop in phagosome, conformation of hemag. changes and inserts into membrane and folds the membranes together

Question 14

Antigenic drift

Answer 14

Influenza enters host, mutations occur in replication in host, virus has slightly different epitopes; antigenic variation due to continual mutation

Question 15

Antigenic shift

Answer 15

2 influenza viruses enter host, genes and antigens from both are incorporated into new virions, very different strain released

Question 16

AIDS definition

Answer 16

presence of opportunistic or rare infections associated with the presence of human immunodeficiency virus (HIV)

Question 17

Explain the mechanism of HIV

Answer 17

see video/text***

Question 18

Pathogenesis of AIDS

Answer 18

text*** -CD4 cell count decreases, HIV antibodies increase for a time and remove HIV from blood; HIV integrated into genome; CD4s decline, not able to replenish antibodies

Question 19

Why can’t we generate more antibodies at the end, even tho we have memory cells?

Answer 19

HIV mutates gradually, but we cannot generate a new response because the CD4s are getting depleted .