Virology, Immunology, Antibiotics and crap like that
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In Latin "virus" means
poisonous malodorous substance
Who was the first person believed to have died from a virus
Pharaoh Ramses V
When were the first plant and animal viruses discovered?
1890s
What did Pharaoh Ramses V die from (potentially)?
small pox
What is the Genome of a Virus?
either DNA or RNA
Give the 5 basic characteristics of Viruses
1. genome of either RNA or DNA 2. Obligate intracellular parasites 3. Composed of nucleic acid and proteins 4. Filterable 5. Not susceptible to antibiotics
What does filterable mean?
direct indication of size
what are the 2 generic classes of viruses?
naked viruses and enveloped viruses
Describe a nucleocapsid
nucleic acid-protein assembly packaged within the virion
What is the capsid composed of?
capsomeres
what makes up capsomeres?
protein subunits
what are the 3 types of nulceocapsid symmetry?
icosahedral, helical, complex
Describe the core
located within the nucleocapsid. Made of nucleic acid and protein.
what does icosahedral mean?
20 sided
what is the usual protein found in the core?
transcriptase
Describe an enveloped virus
nucleocapsid surrounded by an altered host cell membrane
What does the envelope of a virus contain?
viral-encoded proteins such as peplomers or spikes
what is the purpose of spikes?
essential in host cell - virus interaction
List the 7 basic steps of replication
1. Adsorption 2. Penetration 3. Uncoating. 4. Replication of proteins 5. Replication of nucleic acids 6. Maturation. 7. Release
What are the 2 types of release at the end of replication?
cytolysis and budding
where is the Eclipse phase?
Between steps 4 and 5 of replication
What is it called when an individual is infected but you cannot see s/s of disease yet?
Eclipse phase
How does adhesion work?
attachment of virus to host cell via receptors like the primary receptor and the co-receptor
How does penetration work?
receptor-mediated endocytosis
Describe plaque formation
produced viral colonies. In the middle of the plaque is the virus
How are viruses classified?
the Baltimore classification
Class 1 virus
dsDNA. Ex: herpes simplex virus, -pox viruses
Class II virus
ssDNA ex: parvovirus affects dogs
Class III virus
dsRNA ex: rotovirus
Class IV virus
+ssRNA ex: polio
Class V virus
-ssRNA ex: mumps, measles, influenza
Class VI virus
+ssRNA ex: retroviruses, HIV
Class VII virus
partially dsDNA with RNA intermediates ex: Hep B
what is the difference between class IV and class VI viruses?
Class 6 has reverse transcriptase in it
what does the + mean?
the genome of the virus can be directly used as mRNA
What does the - mean?
the genome of the virus cannot directly act as mRNA
Where does replication generally take place in DNA?
the nucleus
what are the 2 rounds of transcription in DNA viruses?
one from parental DNA and one from progeny DNA
what's in the nucleus that viruses need?
nucleotides, polymerases
what is the purpose of EVP?
help in replication
what is the purpose of LVP?
act as structural proteins
what are examples of structural proteins?
capsid, peplomeres
where is polymerase typically found?
in the nucleus
Where does replication of RNA in viruses usually take place?
cell cytoplasm
why can replication of RNA take place in the cell cytoplasm?
what change in morphology happens during transformation
flat cells change to round cells
what change in behavior happens during transformation
contact inhibition- cells touch and stop growing
what change in growth patterns happen during transformation
cells are pushed through checkpoints in cell cycle so they keep growing regardless of mutations
Who discovered oncogenes
Payton Rous
what are the 2 types of oncogenes?
v-onc and c-onc
what is another name for c-oncogenes?
proto-oncogenes
describe c-oncogenes
cellular genes that promote cell cycle regulation
describe v-oncogenes
c-onc genes picked up by viruses
oncogenes alter what?
typical cell cycle regulation
what happens in the 5 stages of the cell cycle?
G1: growth phase, RNA and Protein synthesis G0: resting stage S: DNA replication G2: RNA and Protein synthesis M: Mitosis
how is the cell cycle controlled?
through checkpoints that regulate the progression of cell from one stage to another
what are the 5 normal functions of oncogenes?
growth factors growth factor receptors signal proteins cell cycle and cell death regulators transcription factors
what are 2 tumor suppressors?
p53 and RB
what are 2 growth activators:
hormones and protoncogenes
when does virus-induced transformation occur?
tumor suppressors are inactivated enhancement of growth factors
how are growth activators enhanced?
viral oncogenes are incorporated into the host genome. viral DNA is incorporated near a proto-oncogene
what are 3 transforming viruses?
papillomavirus Human herpes Hep B
what are the 4 types of retroviruses?
HTLV-1 HTLV-2 HIV1 HIV2
what does HTLV stand for?
human T-cell lymphotrophic virus
what are HTLV 1 and 2 and HIV 1 and 2 subdivided into?
oncoviruses and lentiviruses
what is a lentivirus?
slow growing virus
is HIV 1 or 2 more common?
1
what is the structure and class of retroviruses?
enveloped +ssRNA virus. Class VI
what is essential in recognition of target cells?
envelope glycoproteins
describe the order of the retroviral gene structure?
LTR-GAG-POL-ENV-LTR
what is LTR
long terminal repeats
what is GAG made of?
nucleoid capsid, core,
what is POL made of?
RT, RNase H, Integrase
what do ENV do?
envelope proteins code for spikes
what are the 9 steps of HIV replication?
1. adsorption 2. penetration and uptake via gp41 3. Reverse transcription in cytoplasm 4. DNA replication 5. Move into nucleus for integration into host chromosomes as provirus 6. Host transcription factors bind LTR. Cytokine secretion by immune cells can enhance HIV transcription 7. Assembly 8. Budding of immature viral particle 9. Long proteins are cleaved by viral proteases now making the virus infectious
Why does HIV mutate so quickly?
lack of proofreading activity in RT
what is HAART?
highly active anti-retroviral therapy
what is the first stage of HIV?
4-8 weeks initial infection
what is the second stage of HIV?
2-10 years asymptomatic phase
what is the third stage of HIV?
2-3 years AIDS/ARC
Define AIDS
immunosuppresion caused by HIV due to drop in TH cells to levels of <200
what 4 common diseases are associated with HIV infections?
pneumocystis carinii kaposis sarcoma mycobacterium species cryptosporidium sp
what does pneumocystis carinii cause?
atypical pneumonia
what does mycobacterium sp. cause?
TB
what is cryptosporidium sp.?
parasite that causes diarrhea
where did HIV originate?
Congo region of Africa
what did HIV originate from?
SIV simian immunodeficiency virus
where was SIM found?
chimpanzees
define antibiotics
antimicrobial agent produced by a bacteria or fungus
antimicrobial agent produced in the lab
synthetics
antimicrobial agent produced by a bacteria or fungus but altered in the laboratory
semi-synthetic
an antibiotic that kills or inhibits a wide range of microbes would be:
broad spectrum
an antibiotic that kills or inhibits a limited range of microbes
narrow spectrum
what is an example of a broad spectrum antibiotic:
tetracycline
what is an example of a narrow spectrum antibiotic:
penicillin
what does -cidal mean?
to kill
what does static mean?
to inhibit
what are characteristics of an ideal antimicrobic:
selectively toxic soluble and active in dilute concentrations stable not susceptible to antimicrobial defenses complements host defenses does not compromise the host
what do beta lactams do?
bind to penicillin-binding proteins that cross link NAM
what are 3 examples of beta lactams
penicillins cephalosporins carbapenems
what is vancomycin
fairly toxic antibiotic. last resort
what is bacitracin
only given topically
what is PBP?
penicliin binding protein
what is penicillin derived from?
fungus penicillin sp
what is the natural form of penicillin?
penicillin G
what is penicillin made up of?
thiozolidine ring, beta lactam ring, variable side chain
are penicillins more effective against gram + or gram - bct?
gram +
how is resistance acquired
via production of beta-lactamase
what does beta-lactamase target?
the beta-lactam ring
what is the structure of cephalosporins similar to?
penicillin
define intrinsic resistance
due to natural anatomical or physiological barriers
define acquired resistance
due to the acquisition of antibiotic resistance
what are SUPERBUGS?
strains of pathogens that have become increasingly antibiotic resistant
what is MRSA?
methicillin resistant staphylococcus aureus
what is VRE
vancomycin-resistant enterococus
what is CRE?
carbapenem-resistant enterobacteriaceae
what is C diff and how do you get it?
clostridium difficile, get it by overuse of antibiotics. causes psudomembranous colitis
what are side effects of host/drug reactions
toxicity ( renal/hepatic) allergic responses, alteration of microflora
what is an example of an alteration of microflora?
yeast infection
what is the function of normal microbiota?
modification of pH and oxygen tension chemical excretion creating physical obstacles stimulating immune system
what is the source of most opportunistic infections?