2.1.2 Adeno and Pox Viruses Flashcards
What is the smallest known virus?
Parvoviruses
What allows parvoviruses hybridize and form hairpin loops?
Inverted repeats
Parvovirus
Responsible for the classic slapped cheeked rash that kids get, it also goes by fifth disease (one way to remember this is when you get slapped there are 5 fingers left on your cheek) and erythema infectiosum.
Parvovirus full name is parvovirus B19.
It is a naked virus.
Parvovirus is the smallest DNA virus that we will learn about, also it is the only DNA virus which has a straight single DNA virus
Transmitted through respiratory droplets.
Can also be transmitted through mother to baby, part of TORCH infection.
Erythema infectiosum is when a kid gets low grade fever which usually lasts about a week. Then the fever breaks and the kid develops slapped cheek rash on its face. This then progresses to a lacy, reticular pattern that travels down the body. It is important to know this progression because we will have to differentiate it from Roseola because it is a high grade fever that can cause febrile seizures. It is important to know that rash of erythema infectiosum starts at the face and travels downwards.
Besides slapped cheeks, there are 3 more clinical findings associated with parvovirus that we need to remember. The first is related to adult disease, we will often hear this as a test questions in which a school teacher becomes ill with joint pain, arthritis and possible some edema. The second associated is between the parvovirus and transient aplastic anemia, especially in people with sickle cell disease (this anemia is caused by depletion of the bone marrow, when all the cell lines are depleted the bone marrow is only left with adipocytes, that when packed together has a cobble webbed look. This is transient and will fade as the virus clears out.
Parvo is a TORCH infection, when a baby in utero is exposed to the parvo virus the consequences can be severe, if it contracts the virus in the first 2 trimesters of the pregnancy, hydrops fetalis can occur, this is where when there is severe fetal anemia which basically leads to fetal version of congestive heart failure, the massive edema will eventually lead to fetal demise, this is also what happens in alpha thalassemia which is when the fetus only makes hb barts.
What is the process of DNA replication of parvoviruses?
What condition?
B19 Virus - Fifth’s disease
What is the mechanism of spread of B19 Virus?
What immunological component is important in resultion of fifth’s disease?
Antibody
What type of disease is caused by B19 virus?
Biphasic disease
Which cell in erythropoeisis does parvo B19 infect in order to disrupt the process?
Proerythroblast
Name 3 complications associated with parvo?
Transient aplastic crisis - abrupt cessation of RBC prod in the BM
Cell Red Cell Anemia - pts with an underlying immunodeficiency leading to BM suppression
Hydrops fetalis - seronegative pregnant woman is infected w/ B19, virus crosses the placenta causing anemia and CHF
What virus has been extensively studied as a potential vector for gene therapy?
Adeno-associated viruses (AAV)
What do you see in this image?
Adenovirus
It is a DNA virus, it is named as adeno because it was first isolated from adenoids, since it the number one cause of adenoids and tonsillitis, they highlighted this right off the bat. Most common cause of tonsillitis.
It is a naked virus.
It is transmitted in a couple ways, it is transmitted via respiratory droplets and through fecal-oral route. Most commonly it affects children who don’t wash their hands, military recruits as they are in close quarters and people who frequently visit public pools. Know that children are commonly effected.
Adenovirus causes hemorrhagic cystitis, it causes gross hematuria. The third infection it causes is viral conjunctivitis, it is actually a common cause of viral conjunctivitis.
There is a live attenuated vaccine for adenovirus, it is only recommended for military recruits.
What is seen in this renal biopsy?
Basophilic intranuclear inclusion bodies of adenovirus
What is true about the different clinical syndromes of adenovirus?
Different types of adenovirus are associated with different clinical syndromes
What is the mechanism of adenovirus spread within the body?
What do you see in this image?
Poxvirus
It is a DNA virus, what makes poxvirus different from other viruses is that it already packs everything that it needs to replicate.
Poxviruses make their own envelopes, for some reason this is a big deal and we should know this.
Poxvirus is the only DNA virus that completely replicates in the cytoplasm. It has packed along a special DNA dependent RNA polymerase which is just a fancy word for RNA polymerase that reads DNA. It never has to go inside the nucleus since it can make all the proteins it needs using the host ribosomes.
An extension of this understanding is that poxvirus makes intracytoplasmic inclusion bodies in the cell it infects, the most important ones to remember are type B inclusions or Guarnieri bodies which are sites of viral replication, it is important to know that they are intracytoplasmic because that is where the replication occurs, so finding these on a biopsy for skin lesion is diagnostic for poxvirus.
Another fun fact to know is that poxvirus has a dumbbell shaped core, you can tie in the fact that poxvirus is the largest known DNA virus.
The poxvirus family has a few important members that we should know. We can start off with the smallpox virus. It is also caused variola. It causes raised blisters on the skin and mucosal surfaces, (don’t confuse variola with varicella which is chicken pox, both the chicken pox and smallpox presents with scattered ulcers and blisters, but you can tell them apart clinically). The key for the distinction is that the lesions are the same age for smallpox, varicella or chicken pox has new and old skin blisters
Another poxvirus called cowpox causes symptoms similar to smallpox, first cowpox is transmitted by contacting infected cows, like cow herders get it first. Smallpox has been completely eradicated due to vaccination efforts.
The last virus we will talk about is Molluscum Contagiosum virus, it is named after the skin condition it causes which are flesh colored, dome shaped, umbilicated skin lesions, the word umbilicated means that it has a little dimple in the middle, just like our belly, and this is an important buzzword associated with MC virus, it is most common in children, the rash can be found anywhere except for the palms and soles but it is more often seen in the trunk, axilla, the antibubiteal fossa and palpiteal fossa. When this disease occurs in healthy adults, it usually indicates sexual transmission and appears as a single lesion. However if it is spread diffusely in an adult, the person likely has HIV or is somehow immunosuppressed.
What is the disease course of smallpox?
Name this virus
Orf virus
- single nodular lesion forms at the point of contact
- becomes granulomatous
- usually forms and regresses within 25-35 days
Name this virus
Molluscum contagiosum
Name this virus
Molluscum contagiosum
What is the structure of adenovirus?
Non-eveloped icosahedral virus that has fibers at the vertices
Linear dsDNA
