Microbiology Notes Exam 3. Set 1 – Flashcards

Dead-end hosts

Note: Humans and horses are both dead end hosts for West Nile Virus and Eastern Equine Encephalitis, both are arboviruses.

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A dead end host is a host who is unable to transmit the disease. 

Horses and humans are both dead end hosts for Eastern Equine Encephalitis and West Nile 

• Serovars are serological variants, or different strains of the same virus.
• The more serovars there are, the more difficult it is to make an effect vaccine against a virus. 

Safest - Component

Second Safest -  Killed

Third safest - Attenuated

Most effective - Attenuated vaccine

Second most effective - Killed

Third most effective - Component

• viremia is a condition in which a viral infection enters the bloodstream and gains access to the body through it. 
• A viremic phase indicates the time when the virus travels through the blood stream. 

Primary Cell Line

Diploid Cell Line

Continuous Cell Line

Reverse Transcriptase

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The enzyme, reverse transcriptase, is released into the host cell at uncoating. 

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• Reverse transcriptase allows the organism to create a strand of DNA using RNA as a template. 
• It is found it retroviruses

The enzyme is called "reverse transcriptase" because it enables the transcription process to happen in the reverse of its normal order.

Instead of an RNA copy being produced from the original DNA template, a copy of DNA is created from an RNA template. 

The DNA goes into the host cell's nucleus and inserts itself into the host cell's DNA as PROVIRUS[image]

• Retroviruses tend to be lifelong viruses, they establish latency and remain with the host till death. 

• Reverse transcriptase is an enzyme specific to retroviruses, giving it a high degree of selective toxicity.  
• This means drugs that target reverse transcriptase are very unlikely to harm the host. 

• AZT inhibits the enzyme reverse transcriptase that HIV uses to synthesize DNA, thus preventing viral DNA from forming.

• AZT inhibits reverse transcriptase by binding to its active site.
• It was used as an early HIV anti-retroviral and is still used.
• The virus was able to reconstruct the active site elsewear on the enzyme, and so functioned regardless of the presence of AZT

Pox viruses

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small pox

POX VIRUSES ARE GENERALLY LETHAL

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SMALLPOX

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• Vaccines originated with smallpox and the observation that having had cowpox conferred immunity to small pox. 

Cowpox confers immunity to smallpox. Cows are the hosts of cowpox. 

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• Smallpox is a respiratory disease that ultimatly manifests in the integumentary system as a skin based disease.

• Through direct contact with an individual harboring the disease, through indirect contact with a fomite or by introduction of the virus into the respirtory system through airborne infectious droplets.

None

This is a child with an adverse reaction to the smallpox vaccine

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Herpes simplex I generally resides in the trigeminal nerve

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Herpes Simplex II usually resides in the sacral nerve plexus

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• Herpes Simplex is usually kept in check by the immune system. 
• When the immune system is taxed by stress of one kind of another, Herpes outbreaks occur because the immune system is spread too thin to keep it in check. 

• The sympathetic portion of the autonomic nervous system is activated by stress. 
• This makes sense because the autonomic nervous system is the part of the nervous system that is outside of our conscious control. We don't consciously choose to breathe more rapidly or to raise our heart rate in stressful circumstances.
• The sympathic portion governs responses that help us respond to stress, as in the classic "flight or fight" responses. 

• Activation of the sympathetic branch of the autonomic nervous system stimulates the immune system.  

• Because the immune system can only be at the top of its game for so long. 
• When it is not at the top of its game, a reemergence of the viral symptoms occur.

Many babies will titre positive for Herpes Simplex I by 6 months of age. 

This is most likely the result of being kissed on the mouth by adults. 

YES!

• One can get Herpes even if the person who is "sharing" it is manifesting no symptoms. 

• Vericella Zoster is commonly known as chicken pox.
• It belongs to the Herpes family of viruses. 

An aging population, people over forty.

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Herpes Zoster is commonly called shingles

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Children

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• Yes, it can come on at any point after the virus is in the body, but it typically manifest in middle to later adulthood.

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Herpes Simplex I

Herpes Simplex II

Varicella Zoster

Herpes Zoster

EBV- Epstein Barr

CMV or Cytomegalo Virus 

One catches chicken pox or Varicella Zoster, not shingles or Herpes Zoster?

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Those with Herpes Zoster are actively shedding the virus that causes chicken pox and Shingles.  Those with compromised immune systems will require a lower ID₅₀ than those with healthy immune response and may develop chicken pox or Varicella Zoster as a result of the contact. 

 Herpes Zoster or shingles follows the nerve tract causing tremendous pain.

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Serocoversion

• Seroconversion is the development of detectable specific antibodies to microorganisms in the blood serum as a result of infection or immunization. 
• Before the seroconversion point, the antigen is prevalent and the corresponding antibody is not detectable in sera. 

• It was suggested but not stated that because Varicella Zoster tends to lose vigor within a apopulation, those who receive a small exposure to the disease may end up harboring the virus without producing suffient immunity to it, resulting in an increased likelihood of Herpes Zoster manifestation.
• This may not be the case, but the lecture seemed to suggest it. 

• YES. If one does not seroconvert they are able to get the virus over and over. 
• Because Herpes Viruses establish latency, they are likely to reemerge. 
• If a person never seroconverts to the virus, they may have bouts of the disease throughout their lifetime. This manifests in shingles.

• The fact that there is a portion of the population who will not seroconvert to the vaccine. These people will never develop immunity no matter how many times they are vaccinated or are exposed to the virus.

• Anyone who has had chicken pox, or Varicella Zoster, has the potential to develop chicken pox. 

ALL HERPES VIRUSES ESTABLISH LATENCY

These are the ones learned about:

1. Herpes Simplex I
2. Herpes Simplex II
3. Varicella Zoster
4. Herpes Zoster
5. Epstein Barr Virus
6. Cytomegalo Virus

HIV

Kaposi Sarcoma is one such cancer[image]

Burkitt's Lymphoma is associated Epstein Varr Virus

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Burkitt's Lymphoma, associate with the Epstein Barr Virus, is most commonly seen in youth and children in Equatorial Africa. 

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When the cancer was first discovered it was found that all the children who had the cancer had antibodies to the virus. 

Malaria. [This is due to adcquired immunity.]

• People with Burkitt's Lymphoma have had malaria. They all have the Epstein Barr Virus as well. The combination of malaria and Epstein Barr increase the likelihood of this type of cancer. That is why the disease is mostly seen in the areas of Africa where malaria is endemic. 
• Most adults have Epstein Barr. It's not a big deal unless you've also had malaria. 

Malaria is a protozoal disease

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