Exam 4: Body Defenses Viruses

Question 1

When and where did the practice of variolation originate?

Answer 1

12 century China.

Question 2

How was variolation performed? Was it effective?

Answer 2

Deliberately infecting children with smallpox scabs from children surviving mild cases. Yes, greatly reduced morbidity and mortality.

Question 3

When did the practice of variolation reach Europe?

Answer 3

1700s

Question 4

Why was the practice of variolation eventually outlawed in Europe?

Answer 4

Due to the death of patients, it occurred in 1-2% of patients.

Question 5

During which century did Edward Jenner demonstrate that infection with the cowpox virus protected one from smallpox?

Answer 5

1796

Question 6

When did Louis Pasteur produce the first vaccines? Against what infectious diseases did he make vaccines?

Answer 6

1872, vaccine against fowl cholera, anthrax, and rabies. Used microbes that were intentionally weakened. Old bacterial cultures lost their virulence. Viruses grown in atypical hosts lose their virulence.

Question 7

Attenuated

Answer 7

microorganisms that have lost the ability to cause serious illness but retain the ability to stimulate immunity

Question 8

List the 5 types of vaccines:

Answer 8

1) Attenuated vaccine
2) Inactivated vaccine
3) Toxoid Vaccine
4) Combination Vaccine
5) Recombinant Vaccine

Question 9

Attenuated vaccines, what are they? How are they created? Risks and benefits?

Answer 9

Contains microbes with reduced virulence. Modified live vaccines. Viruses are typically attenuated by growing them for numerous generations in cells in which they normally don’t replicate well. Bacteria commonly attenuated by growing them under atypical conditions.Attenuation results from the cumulative effects of multiple mutations.

Causes mild infections but no serious disease. Their replication produces a large number of antigens. Vaccinated individuals can infect others, providing contact immunity, reaching a larger number of people and non-compliance becomes less of an issue. Helpful in achieving herd immunity.

Risks include vaccines containing enough virulence to cause disease in immunosuppressed individuals. They can cross the placenta and potentially harm the fetus. Reversion mutations can sometimes (rarely) restore virulence.

Question 10

Inactivated vaccines, two types? How do they work? Benefits and risks?

Answer 10

Two types whole agent vaccines and subunit vaccine. Whole agent vaccines, produced with whole microbes that have been killed. Subunit vaccines are produced with antigenic fragments of microbes. Safer than live vaccines but they have limitations. Fewer antigen molecules produced since they don’t replicate. Booster dose is often required to reach full immunity. Whole vaccines can sometimes trigger an unwanted and painful inflammatory response, not an issue with subunit vaccines. All antigens are recognized as exogenous antigens, only generating an antibody-mediated response.

Question 11

Toxoid vaccines

Answer 11

Induce and immune response against toxins produced by the pathogen. Introduces toxins into the body, not the disease itself. Used for bacterial diseases tetanus and diphtheria. Use chemically or thermally modified toxins. Toxins possess fewer antigenic determinants (epitoes). Multiple childhood doses and frequent boosters are required. Stimulate only antibody-mediated immunity.

Question 12

Combination vaccines, what are they? Give examples.

Answer 12

Combines antigens from several attenuated and inactivated pathogens and or/toxoids for simultaneous administration.

e.g MMR is a vaccine against measles, mumps, and rubella. E.g DTaP is a vaccine against diphtheria, tetanus, and pertussis. E.g Gardasil 9 is a vaccine against 9 different strains of human papillomavirus (HPV).

Question 13

Recombinant gene vaccines

Answer 13

Recombinant gene technology can be used to create vaccines in multiple ways.

Virulence gene deleted from a pathogen.

Large quantities of pure antigens can be produced for use in vaccines.

A gene encoding an antigen of pathogen can be introduced into a harmless microbe, which can be used as a vaccine.

DNA encoding a pathogens antigen can be used as a vaccine.

RNA encoding a pathogens antigen can be used as a vaccine. Used to make Covid 19 vaccines.

Question 14

Which type of vaccines did Louis Pasteur make?

Answer 14

attenuated vaccines

Question 15

What type of vaccine is the Covid-19 vaccine?

Answer 15

Recombinant vaccine

Question 16

Why might a subunit vaccine be superior to a whole agent vaccine?

Answer 16

Subunit vaccines do not run the risk of triggering an unwanted and painful inflammatory response like whole agent vaccines do.

Question 17

In what way or ways is an attenuated vaccine superior to an inactivated vaccine? In what way is an inactive vaccine superior to an attenuated vaccine?

Answer 17

Inactivated are safer since the microbes are dead. However they only generate antibody-mediated response and fewer antigen molecules produced. Attenuated have higher risk for causing disease especially in non-health individuals. However better immune response form the body is generated producing a large number of antigens.

Question 18

Why are some people unable to get vaccinated?

Answer 18

Age-infants, elderly, and immunocompromised people cannot be safely vaccinated. However unvaccinated people should still be protected by herd immunity.

Question 19

What is herd immunity and how does it function?

Answer 19

Occurs when so many people cannot be infected that the pathogens spread is effectively halted. Either due to vaccination of recovery from the infection by the pathogen. The very few infected people in the population are unlikely to interact closely with the very few unvaccinated people in the population. This requires that the vast majority of the population is vaccinated.

Question 20

What percentage of a population needs to be immune to a pathogen through either vaccination or prior infection for herd immunity to function?

Answer 20

> 95%

Question 21

Why is herd immunity difficult to achieve?

Answer 21

Because it requires compliance but the majority of the population. In most cases this compliance is voluntary and generally not enough people get vaccinated.

Question 22

Why is it difficult if not possible to reach herd immunity in the United States against the virus that causes Covid-19.

Answer 22

Due to lack of vaccine compliance.