Viral Immunology and Viral Vaccines

Question 1

______ defenses are not specific to the pathogen but the general class of pathogen

Answer 1

Innate

Question 2

Describe what happens on initial exposure to a pathogen

Answer 2

On initial exposure, innate defenses are first. Innate defenses slow or stop the pathogen

Question 3

What happens upon secondary exposure to a pathogen?

Answer 3

The neutralizing antibodies and CTLs from the adaptive response can act fast to prevent disease

Question 4

Describe the barriers to infection

Answer 4

-The physical barriers can stop a microbe from infecting a person: skin, coughing, sneezing, mucus, and stomach acidity

-Antimicrobial compounds can also act on viruses to prevent infection

Question 5

When is type I interferon triggered?

Answer 5

If a virus can circumvent the physical barriers and infect a cell, type I interferon is triggered, telling the body than an infection is occurring

Question 6

What do pattern recognition receptors recognize?

Answer 6

Recognize viral RNA and DNA in an infected cell and stimulate type I interferon

Question 7

What do interferons induce?

Answer 7

Can induce a wide variety of genes in the infected cells and help guide the immune response. It is most well-known for activating a large number of proteins that have antiviral properties

Question 8

Many viruses have devised ways to reduce the ___________ response

Answer 8

type I interferon

Question 9

Describe NK cells and their function

Answer 9

1) NK cells are important cells in viral infections
2) They can kill infected cells stopping viral spread
3) They are most well-known for recognizing cells that have down-regulated their MHCI. Many viruses can down-regulate MHCI. They do this to escape CTL killing

Question 10

Describe macrophages and dendritic cells and their function

Answer 10

-They are essential in bridging the innate and adaptive immune responses

-A type of dendritic cell called a plasmacytoid DC can make large amounts of type I interferon in a viral infection. This is because they can sense a viral infection without being actively infected. No active infection means most of the ways the virus has to stop interferon production will not work in plasmacytoid DC.

Question 11

A critical part of the adaptive immune response to viral infections is the _________

Answer 11

neutralizing antibody response

Neutralizing antibodies will bind to the surface of a virus preventing the virus from infecting a cell

Question 12

Viral antigens encountered in the mucosa primarily produce dimeric _____

Answer 12

IgA

These antibodies are produced in large quantities in the mucosal surfaces, gut, and upper and lower respiratory tract

Question 13

Viruses that a viremic stage (virus in the blood) primarily produce _____

Answer 13

IgG

Question 14

Another critical adaptive response in viral infection is the activation of ________

Answer 14

cytotoxic T lymphocytes (CTLs)

CTLs are critical for viral infections because they kill infected cells. They are also crucial in keeping chronic viral infections in check

Question 15

List the 4 ways viruses subvert the immune system

Answer 15

1) Escape neutralizing antibodies by antigenic drift
2) Blocking the type I interferon response
3) Down-regulating MHC I which prevents killing CTLs
4) Killing immune cells - like HIV killing CD4 cells

Question 16

What happens if you encounter the same strain of virus?

Answer 16

1) If you encounter the same strain of virus, you are generally protected from reinfection due to the long-lived plasma cells and secreted antibodies
2) These neutralizing antibodies are present in your mucosa and blood before re-encountering the virus
3) The neutralizing antibodies present bind to the virus, prevent infection and induce sterilizing immunity. In fact, you may go through another round of affinity maturation and end up with even better antibodies and higher levels

Question 17

Describe cross-protection

Answer 17

The new strain is recognized with good affinity by antibodies from a previous strain, resulting in no infection or sickness

Question 18

Describe partial cross-protection

Answer 18

Antibodies bind with lower affinity. As a result, the antibodies cannot prevent some cells from being infected. The infection will generally clear faster, and there might be fewer symptoms because you will get helpful neutralizing antibodies quicker than in a primary infection. This will result in less spread of the virus. Also, the memory CTLs from the previous infection might be able to recognize and clear the infected cells, reducing the infections severity.

Question 19

Describe no cross-protection

Answer 19

It is like a new infection

Question 20

What do you need to get an effective vaccine?

Answer 20

1) Need to induce a protective neutralizing antibody response to the virus. The vaccine needs to include viral proteins that produce neutralizing antibodies, i.e., proteins on the surface of the virion

2) Stimulate an immune response
-Have an attenuated virus or whole killed/inactivated virus. These have viral-specific signals that will activate pattern recognition receptors in immune cells turning on the immune response
-Or include an adjuvant. An adjuvant is a substance that activates the immune system.

Question 21

Describe attenuated virus vaccine

Answer 21

Attenuated viruses replicate just a little, and the immune system sees it as a regular viral infection and mounts an immune response. The immune response can clear the virus before you get sick. These tend to be excellent vaccines

Question 22

List the 9 infections that have an attenuated vaccine

Answer 22

1) Measles, mumps, rubella (MMR)
2) Varicella Zoster (chickenpox)
3) Rotavirus
4) Nasal Influenza Vaccine
5) Yellow fever vaccine
6) Smallpox/Mpox (vaccinia)(not for the general public)
7) Oral polio (not used in the US)
8) Military only - Adeno type 4 and 7
9) Adenovirus modified vaccines for Coronavirus

Question 23

Describe Whole killed virus/Inactivated virus

Answer 23

Here the virus does not replicate at all. It can still start an immune response because it has viral proteins and nucleic acid that trigger it. Although, adding an adjuvant will usually result in a better immune response. Many more virus particles are needed in an inactivated vaccine than in an attenuated vaccine. Also, in general, more booster shots are required for complete immunity.

Question 24

List the 4 viruses than need a whole killed virus/inactivated virus vaccine

Answer 24

1) Inactivated polio vaccine (use in the US)
2) Hepatitis A vaccine
3) Rabies vaccine
4) Influenza vaccine

Question 25

Describe subunit vaccines

Answer 25

Here you just have a part of a virus; there is no chance of infection. You have to make sure you use the correct protein to get a neutralizing antibody response. An adjuvant is very helpful in subunit vaccines.

Question 26

List the 5 viruses that use subunit vaccines

Answer 26

1) HA only influenza vaccine
2) Hepatitis B vaccine
3) Human Papilloma vaccine
4) New Shingles vaccine
5) mRNA vaccines producing one or two viral proteins

Question 27

Why are some immunizations not done until the baby is one year of age?

Answer 27

Because of naturally occurring maternal antibodies.

-This is most important with the measles/mumps/rubella vaccine
-The maternal antibodies will bind the attenuated virus preventing replication of the virus. This will inhibit the attenuated strain from infecting cells and prevent an immune response in the infant. Then when the maternal antibodies leave the baby, the baby has no protection

Question 28

Natural in babies, ____ is transferred to the baby in the third trimester, and ______ in colostrum and breast milk

Answer 28

IgG; IgA

Question 29

Sometimes antibodies are given post-exposure to help prevent infection. List the illness associated with Immunoglobulin from healthy blood donors

Answer 29

Hepatitis A
Measles

Question 30

Sometimes antibodies are given post-exposure to help prevent infection. List the illnesses associated with Hyperimmune IG is from people with a high titer to a specific infection.

Answer 30

Hepatiti B
Rabies
Chickenpox
CMV
Vaccinia

Question 31

Sometimes antibodies are given post-exposure to help prevent infection. List the illnesses associated with Monoclonal antibodies to specific viruses

Answer 31

RSV-Given pre-exposure
SARS-CoV-2

Question 32

In some cases, it is possible to prevent infection after exposure by vaccination if done quickly. What illnesses is this the case for?

Answer 32

-Rabies/with Rabies Immune Globulin
-Hepatitis A
-Hepatitis B/with Hepatitis B immune globulin
-Smallpox

Question 33

Describe herd immunity

Answer 33

Herd immunity refers to the fact that the spread of infectious disease requires contact between a non-immune person (susceptible) and an infected person. The lower the number of non-immune people, the less chance the
infection has of spreading. Herd immunity will ultimately benefit non-immune people

Question 34

What percentage of the population does a vaccination to reach to protect the community

Answer 34

depends on the virus but usually spans 75-95%

Question 35

Who is protected by herd immunity?

Answer 35

-Babies
-People allergic to vaccine components
-Immunocompromised people
-People unresponsive to vaccine
-People with waning immunity to vaccine