Virus-Host Cell Interactions

Question 1

Non-productive infection

Answer 1

viral infection that doe snot lead to the production of infectious virions

Question 2

Abortive infection

Answer 2

non-productive infection because the virus lacks virus synthesis post-adsorption

Question 3

interference non-productive infection

Answer 3

virus interferes with the growth of other viruses in the same cell

Question 4

Productive infections

Answer 4

successful replication of virus post-adsorption

Question 5

Productive infections may result in

Answer 5

non-lethal alteration to cell/cell function, cell damage/death, or persistent infection without cell death

Question 6

Latent-persistent infection

Answer 6

intermittent acute episodes of disease b/w which there is an absence of infectious particles (Herpes simplex)

Question 7

Chronic-persistent infection

Answer 7

continued presence of virus, disease maybe absent or associated with late immunopathological disease (hepatitis B)

Question 8

Slow-persistent infection

Answer 8

long incubation, slow progression, lethal disease

Question 9

Sterilizing immunity

Answer 9

infection is resolved and immunity has been strengthen

Question 10

Most common outcome of a viral infection is

Answer 10

an asymptomatic infection with a seroconversion

Question 11

Following an infection damage or death may occur due to

Answer 11

immunopathology or autoimmune induction

Question 12

Lytic infection

Answer 12

causes cell modification and death; inhibits host macromolecule synthesis, cytopathic effect (toxic to cells), inclusion bodies and cell fusion, apoptosis, chromosomal alterations –>malignancy

Question 13

Tumor

Answer 13

mass of new tissue which persists and grow independently of its surrounding

Question 14

Transformation

Answer 14

conversion of cell from restricted growth to unrestricted growth

Question 15

Transformed cell characteristics

Answer 15

loss of contact inhibition, unrestricted growth, loss of senescence, appearance of new antigens, metabolic and genetic changes

Question 16

RNA tumor viruses

Answer 16

human T cell leukemia virus (HTLV) target t helper cell

Question 17

DNA tumor viruses

Answer 17

HPV (cervical cancer), EBV (Burkitt’s lymphoma), HBV (liver cancer)

Question 18

Benign neoplasm due to viral infections examples

Answer 18

human wart virus, poxvirus

Question 19

Stages of the virus replication cycle

Answer 19

Attachment, Penetration, Uncoating, Macromolecular Synthesis,

Question 20

Attachment step of viral replication cycle

Answer 20

virus binds specific receptor (MAJOR determinant of infectivity)

Question 21

Specific attachment of virus to receptor determines

Answer 21

host range, tissue tropism (where in the body it can survive), target of antiviral therapy

Question 22

Fusion inhibitors for HIV

Answer 22

target specific HIV receptor on cells and prevent fusion of virion and human cell preventing infection

Question 23

Penetration step of viral replication cycle (3 ways)

Answer 23

Methods of penetration: Direct penetration, surface eclipse pH dependent, receptor-mediated endocytosis

Question 24

Direct penetration

Answer 24

NON-enveloped viruses, nucleocapsid attaches to cell surface releasing viral NA genome

Question 25

Surface eclipse

Answer 25

pH independent cell entry; ENVELOPED viruses fuse with the CM releasing viral NA

Question 26

Receptor-mediated endocytosis

Answer 26

ENVELOPED virus binds specific receptor, endocytosis occurs, virus envelope fuses with endosome membrane to release viral genome

Question 27

Uncoating step of viral replication cycle

Answer 27

removal of protective coats with release of NA; infectivity is lost at this point

Question 28

What two antivirals inhibit the uncoating step of Influenza A.

Answer 28

Rimantidine and Amantidine

Question 29

Macromolecular Synthesis step of viral replication cycle

Answer 29

synthesis of viral encoded proteins and viral genome

Question 30

DNA viruses replicate in the

Answer 30

nucleus

Question 31

RNA viruses replicate in the

Answer 31

cytoplasm

Question 32

Pox virus (DNA) replicates in the

Answer 32

cytoplasm

Question 33

Influenze virus (RNA) replicates in the

Answer 33

nucleus

Question 34

(+)ssRNA, (-)ssRNA, dsRNA all

Answer 34

encode for RNA-dependent RNA polymerase

Question 35

The exception to all RNA viruses needing to encode for RNApol is:

Answer 35

retroviruses (HIV) they encode for reverse transcriptase which transcribes DNA from RNA, then to mRNA

Question 36

azidothymidine AZT, ddI, ddC, 3TC, D4T

Answer 36

nucleoside analogue reverse transcriptase inhibitor (NRTI) - target for HIV

Question 37

(-)ssRNA and dsRNA must carry

Answer 37

gene for RNApol and RNApol protein to transcribe the mRNA

Question 38

(+)ssRNA must carry

Answer 38

ONLY the gene for RNApol

Question 39

RNApol is capable of

Answer 39

transcribing the mirror image of the strand (complimentary strand)

Question 40

DNA viruses replicate

Answer 40

using host cell DNA replication machinery

Question 41

RNA viruses replicate

Answer 41

using encoded RNApol, and some require RNA pol proteins

Question 42

The exception is HIV retrovirus which replicates

Answer 42

using reverse transcriptase (ssRNA --> dsDNA (inserted into genome)-->mRNA)

Question 43

Integrase inhibitor

Answer 43

prevents the insertion of HIV DNA into the genome for replication

Question 44

Cidofovir

Answer 44

inhibitor of nucleic acid synthesis - nucleotide analog (smallpox treatment)

Question 45

Acyclovir, Valacyclovir, Famciclovir, Penciclovir, Ganciclovir

Answer 45

inhibitor of nucleic acid synthesis - nucleotide analog (human herpes viruses 1-8)

Question 46

Foscarnet

Answer 46

inhibitor of nucleic acid synthesis - nucleotide analog (CMV and HSV)

Question 47

Viruses may be released from cells in 3 ways

Answer 47

lysis of cells, slow release without lysis, or budding

Question 48

Budding

Answer 48

Viral proteins cluster and replace all host proteins in that segment of the CM, nucleocapsid bind to viral proteins and an enveloped virus is released

Question 49

Neuraminidase inhibitors (oseltamivir, sanamivir)

Answer 49

selectively inhibit neuraminidase of Influenza A and B

Question 50

HIV protease inhibitors prevents the viral protease that initially cleaves the proteins to functional proteins , these are:

Answer 50

Saquinavir, indinavir, amprenavir, nelfinavir, ritonavir

Question 51

Primary replication site

Answer 51

site where 1st replication takes place, if near port of entry = short incubation period

Question 52

Secondary replication site

Answer 52

site where 2nd replication takes place

Question 53

Local spread ___________ occurs, spread within host _________ occurs

Answer 53

always ; may

Question 54

Spread within a host may occur through

Answer 54

cell-to-cell, bloodstream, lymphatics, nerves, transplacentally