W12 Essentials of Virology II

Question 1

The structure of viral genomes

Answer 1

Configuration of viral genomes;

Single-stranded RNA (ssRNA)

Double-stranded RNA (dsRNA)

Single-stranded DNA (ssDNA)

Double-stranded RNA (dsDNA)

Double-stranded genomes have complementary base pairing

RNA genomes can be linear and segmented i.e. more than one RNA per capsid

DNA genomes can be linear or circular.

Genomes can be encode information (genes) in
positive or negative sense; 5’-3’ or 3’-5’ respectively.

Question 2

Virus proteins - polymerase

Answer 2

Polymerase proteins are enzymes that are involved in the catalysis of nucleotides to nucleic acids

Viruses with DNA genomes produce DNA polymerases

Viruses with RNA genomes produce RNA polymerases

Polymerase proteins interact with nucleic acid in protein-nucleic acid interactions

Question 3

Virus proteins - structural proteins

Answer 3

Proteins that form the capsid into which nucleic acid is packaged.

Proteins interact with one another in protein-protein interactions.

Question 4

Virus proteins – Pathogenesis

Answer 4

As “obligate cellular parasites” viral and cellular proteins shape the intracellular environment to facilitate virus replication or evasion of an immune response.

Commonly, changes to intracellular environment that facilitate virus replication or evasion of an immune response lead to disease; pathogensis.

Question 5

Virus pathogenesis - Cancer

Answer 5

As cells divide, they go through the “cell cycle”. During the cell cycle the cell produces factors that a virus might need. An example of this is the production of nucleotides that can be used by viral polymerases to make new viral genomes.

Some viruses produce proteins that ensure the cell continually goes through the cell cycle.

Cancer can be defined as uncontrolled cell division. Thus, viruses can cause cancer by causing uncontrolled cell division that benefits their replication.

Question 6

Human papilloma viruses (HPVs)

Answer 6

– Papilloma virus, circular dsDNA genome, skin cancer

Question 7

Epstein-Barr virus (EBV)

Answer 7

Herpes virus, linear dsDNA genome, lymphoma

Question 8

Hepatitis B virus (HBV)

Answer 8

Hepadnavirus, circular dsDNA genome, carcinoma

Question 9

Hepatitis C virus (HCV)

Answer 9

Flavivirus, ssRNA genome, carcinoma

Question 10

Human herpes virus 8 (HHV-8)

Answer 10

Herpes virus, linear dsDNA genome, lymphoma

Question 11

Human T-lymphotrophic virus-1 (HTLV-1)

Answer 11

Retrovirus, RNA-DNA genome, leukemia/ lymphoma

Question 12

Merkel cell polyomavirus (MCV)

Answer 12

Polyomavirus, dsDNA genome, carcinoma

Question 13

Human Papillomavirus (HPV) proteins E6 and E7

Answer 13

Human Papillomavirus (HPV) proteins E6 and E7 “remove the brakes” of the cell cycle

Question 14

Virus pathogenesis - Immunodeficiency

Answer 14

Viruses must evade immune responses. Some immune responses are mediated by specific cells of the immune system. These immune cells recognize and kill cells infected by virus.

To evade this type of immune response, some viruses replicate in the immune cells whose function is to recognize and kill infected cells.

Replication in immune cells hides the virus from immune cells and inhibits immune cell function.

Inhibition of immune cell function allows other pathogens to replicate in virus infected hosts and, thus, disease occurs.

Question 15

HIV associated pathogens

Answer 15

Virus
Kaposi’s sarcoma herpesvirus (KSHV)
Herpes simplex virus (HSV)

Bacteria
Mycobacterium tuberculosis
Salmonella

Fungus
Candida
Cryptococcus neoformans

Parasite
Cryptosporidium
Toxoplasma gondii