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Virology, Immunology, Antibiotics and crap like that

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?


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?


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?


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?

The RNA viruses carry their own polymerases

what factors determine viral pathogenesis?

cell susceptibility, tissue tropism, immune resistance factors

What do receptors determine?

the presence of receptors determine whether a virus will infect your lungs or kidneys or liver etc.

what are immune resistance factors?

interferons, acquired immunity

what are the two different types of acquired immunity?

humoral immunity, cell-mediated immunity

what cells are in charge of humoral and cell-mediated immunity?

B cells- humoral
T cells- cell-mediated

Define Interferons

Inducible cellular proteins

what are the 3 common types of interferons

alpha, beta, and gamma

which interferons function in viral immunity?

alpha and beta

which interferon/s function in the inflammatory response?


what do alpha and beta interferons do?

induce synthesis of antiviral proteins

is anti-viral activity specific or non-specific?


what happens in a person is interferon deficient?

they will develop a lot of viral infections

what happens when a cell become virally infected?

the cell then expresses viral antigens and is considered "foreign".

what are examples of cytotoxic cells?

cytotoxic T cells, Natural Killer cells

What do cytoxic cells do?

release perforine and granzyme B

what do perforines and granzyme B do?

leads to target cell death through apoptosis

What is the major part of Humoral Immunity?


what do antibodies do?

bind to free virions and "neutralize them"

example of acute viral infection:

common cold

example of persistent infection with shedding


example of latent viral infection:


example of persistent slow following acute infection:


example of persistent slow infection:

prion diseases

what are the 3 types of antigenic variation?

mutation, recombination, gene switching

what is another name for mutation?

antigenic drift

what is another name for recombination?

antigenic shift

what causes mutation?

change in nucleic acid sequence

what does mutation lead to?

subtle changes in antigen expression

give examples of antigenic drifts:

influenza virus, HIV

why are RNA viruses more susceptible to mutation?

they lack proofreading

what happens when a virus changes?

antigen changes, surface proteins change, change in susceptibility to drugs

how common is antigenic drift?

very common

what causes recombination?

dual infection by multiple strains of virus

what is the result of recombination

substantial variation in antigen expression

how common is antigenic shift?

not very

how many types of influenza are there?

3. A, B, C,

how are strains of influenza determined?

by their H and N spikes

what are pandemics of influenza associated with?

zoonotic transmission

what does H stand for?


what does N stand for?


what does hemagglutinin do?

attaches to host cells

what does neuraminidase do?

involved in viral budding from host cells

what is unique about influenza?

it has the amazing ability to shift from antigenic drift to shift

what does an antigen drift of influenza cause?

epidemics, that's why there must be a new vaccine every year

what does an antigen shift of influenza cause?

pandemics, usually prolonged

how are influenza strains named? ex: A/Fujian/411/2002 (H3N2)

virus type, geographic origin, strain number, year of isolation, virus subtype

T/F Influenza is the leading cause of U.S. vaccine preventable deaths?


what is zoonotic mean?

animal acquired?

when was the Spanish flu outbreak?


describe gene swithching

causes relapsing fever, genes from different infections are switched over

what is an organism that exhibits gene switching?

borrelia recurrentis

list the 6 cytopathic effects of gene switching?

1. inclusion bodies
2. cell lysis
3. cell rounding
4. syncytia formation
5. apoptosis
6. transformation

what are inclusion bodies?

remnants of viral proteins within host cells

what is syncytia formation?

multinucleated giant cell that comes when cells fuse together

what is apoptosis

programmed cell death

what is caused by apoptosis?

DNA fragmentation, formation of cellular "blebs", no inflammation

define transformation

the change of normal cells to cells exhibiting the properties typical of tumor cells

approximately ___% of all cancers are due to viruses


what 4 changes happen in transformation

morphology, behavior, biochemistry, growth patters.

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?


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?

Human herpes
Hep B

what are the 4 types of retroviruses?


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?


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?


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

Where does HIV reside?

lymph nodes

what are the 3 causes of immunodeficiency by HIV?

impaired lymphopoisis
altered cytokine/chemokine secretion

CD4 cells susceptible to HIV are found in what 5 places:

bowel epithelium
renal epithelium
brain microglia
follicular dendritic cells
fetal astrocytes

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?


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

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