Viruses and infection

Question 1

What must viruses do in order to transmit?

Answer 1

Replicate inside the host

Viruses must evade or suppress host responses

Question 2

What is the host environment like?

Answer 2

Hostile

Innate and adaptive immune responses

Cells are inherently antiviral - virus sensing

Question 3

Why do symptoms of viral disease arise?

Answer 3

Virus wanting to transmit - cough and diarrhea

Host responding to virus - fever

Question 4

What is the shape of HIV?

Answer 4

Cone-shaped

Question 5

What cells does HIV infect?

Answer 5

Activated CD4 T cells

Question 6

Where on the CD4 T cells do HIV bind?

Answer 6

CCR5 co-receptors

Question 7

Course of HIV progression

Answer 7

High level of viremia at beginning of the disease

Viral set point is reached

CD4 cell death and viral replication remains high byt CONSTANT

Question 8

Does the viral set point vary from person to person?

Answer 8

Yes

Question 9

What happens to the course of HIV progression without treatment?

Answer 9

CD4 levels continue to drop

Too low levels = immunocompromised

Susceptibel to opportunistic infections

AIDS develops and eventually death

Question 10

What is a common feature of RNA viruses?

Answer 10

Vast turnover

Question 11

Why do RNA viruses have such a high turnover?

Answer 11

RNA polymerase and reverse transcriptase don’t have the proofreading and error correcting functions as DNA polymerase

Every time a virus divides, mutations or errors happen to the structure

Question 12

What is a quasispecies?

Answer 12

Accumulation of diversity of viruses

Viruses related by a single or multiple mutations

Question 13

What are the implications of the vast turnover of viruses?

Answer 13

Profound implications for

Immunity

Developing vaccines

Drug therapy

Question 14

What is a phylogenetic tree?

Answer 14

Tree showing the varying HIV sequences within a single individual

Question 15

What is the difference between the flu and HIV?

Answer 15

HIV develops mutations within a host

Flu does not develop mutations within a host

Question 16

What are the two mechanisms by which the flu changes genetically?

Answer 16

Antigenic shift

Antigenic drift

Question 17

What is the main difference between antigenic shift and antigenic drift?

Answer 17

Antigenic shift - more radical changes in the antigenic profile of the flu virus

Antigenic drift - gradual change in the genes encoding the Haemagglutinin receptor

Question 18

Antigenic shift is the cause of the flu pandemic

TRUE or FALSE

Answer 18

TRUE

Question 19

Describe effect of antigenic shift on the flu

Answer 19

Influenza is a negative sense RNA virus

Genome made up of 8 segmented RNA molecules

Each molecule codes for one protein

A consequence of this - if two virus strains infect the same cell, there is segment reassortment between 8 molecules

Question 20

Describe effect of antigenic drift on the flu

Answer 20

Gradual change in the genes encoding Haemagglutinin receptors

Antibody won’t bind to the genetically mutated Hg

Question 21

What type of virus infection is HIV?

Answer 21

Persistent

Clinical latency

Infection occurs as a result of decreasing CD4 numbers

Increase in likelihood of opportunistic infection

Evades immunity by changing faster that the body can develop antibodies

Question 22

What type of virus infection is Influenza?

Answer 22

Acute infection

Rapid onset of illness and immune clearance

Shift in strain leads to pandemic

Question 23

What types of virus infection is herpes?

Answer 23

Latent

Periodic peaks of viral load interstersed by nothing

Interplay between replication of the virus and immune system