Microbiology: DNA Viruses Flashcards
Herpes simplex-1 (HSV-1)
Spreads via respiratory secretions and saliva
Lytic phase:
- virus infects epithelial tissues, uses host machinery to replicate itself, and then burst said epithelial cells to infect more
Latent phase:
- eventually, the virus particles move up neurons to cell ganglion and enter a dormant phase where they remain for life
- slowly, they release herpes copies down neurons and back into epithelial tissues to start up the lytic phase (this is common during stress, skin damage and viral illnesses)
- lesions develop on the ipsilateral side of the ganglia they infect*
Causes
- keratoconjunctivitis (branching dendritic lesion upon eye exam is classic for herpes)
- herpes liabialis (cold sores)
- enlarged lymph nodes
- pharyngitis
- herpetic whitlow lesions on fingers
- sporadic temporal lobe encephalitis
- erythema multiforme
- eczema herpeticum (infection of the skin at sites of atopic dermatitis)
- blisters on the vermillion border on the ipsilateral side of the face (only present during deactivation of the latent phase)*
- most common cause of sporadic encephalitis*
- often lies latent in the trigeminal ganglia*
Treatment: doesnt kill, only treats symptoms
- acyclovir
- famciclovir
- valcyclovir
- if neonatal herpes, give IV dose, otherwise can be PO/IM or topical*
What are all of the DNA virus families and the characteristics associated with them
1) Herpesviruses
- Double stranded
- Linear
- enveloped
2) poxviruses
- double stranded
- linear
- enveloped
* largest DNA virus*
3) Hepadnavirus
- partial double stranded
- Circular
- enveloped
* has RT enzyme*
4) Adenovirus
- Double stranded
- linear
- non-enveloped
* has a unique capsid with fiber-like projections*
5) papillomavirus
- double stranded
- circular
- non-enveloped
6) polyomavirus
- double stranded
- circular
- non-enveloped
7) Parvovirus
- single stranded
- linear
- non-enveloped
* smallest DNA virus*
human herpes virus-4
HHV-4/ EBV/MONO
Spread via respiratory secretions and saliva
“ kissing disease”
- most common cause of mononucleosis (MONO)*
Infects two types of cells
1) esophageal epithelium
- virus under goes lytic cycle and replicates in the host cell using host cell mechanisms. Destroy host cell and infect neighboring cells.
- eventually end up in the tonsil usually and infect B cells.
2) B cells: via CD21 cell marker
“must be 21 to drink at the Barr”
- latent phase begins where the virus lays dormant in B cells and spreads throughout the body via the B cell host
- is destroyed by CD-8 T cells which is why blood smears show reactive CD-8 T cells often
Signs/symptoms: “usually asymptomatic”
- fever
- severe fatigue*
- lymphadenopathy (posterior cervical lymph nodes)*
- pharyngitis
- increases spleen friability (cant play contact sports for 3-4 weeks min)*
- palatial petechiae
- hepatosplenomegaly
- tonsillitis (exudate may or may not be present)
- faint pink rash that is on trunk/arms (RARE)
Cancers related to HHV-4: more likely in immunocompromised individuals
- burketts lymphoma (B-cell cancer)
- Hodgkin/ non Hodgkin’s lymphoma (B-cell cancer)
- nasopharyngeal carcinoma
Diagnosis:
- clinical symptoms
- mono-spot test showing heterophile antibodies (be careful with the test since it can show false-negative)*
- Presence of EBVs capsid (IgM VCA) on testing
- atypical lymphocytes on blood smears
Treatment: usually self-limiting
- avoid contact, rest, acetaminophen and NSAIDs.
- if you give amoxicillin or ampicillin to someone with mono because you think they have strep throat, they will develop a itchy maculopapular rash (idiopathic reasons)
Varicella-Zoster virus
HHV-3/ chickenpox/shingles
Transmitted via respiratory secretions and fluid contact.
Lytic phase:
- Infects respiratory epithelium cells, uses host cell machinery to replicate itself until host cell is at max capacity, then bursts and infects new cells
Latent phase:
- goes 1 of 2 ways
1) travels to the lymph nodes, liver, spleen and resides inside them (chickenpox)
2) travels into dorsal root ganglia/trigeminal ganglia and resides inside them (shingles)
Chicken pox signs/symptoms
- little red pox papules on the skin (caused by infection of keratinocytes and formation or “tzanck cells” (multiple keratinocytes in the skin that infected morph into one large cell))
- headache/fever/malaise
- forms scabs and falls off over time
- painful mucosal sores in the mouth
Shingles signs/symptoms:
- scaly/itchy and sometimes painful skin/ rash that is along the dermatome of the ipsilateral posterior dorsal root ganglia
- herpes zoster ophthalmicus (inflamed swollen eye lids due to herpes inside CN5 V1 Branch ipsilateral ganglion)
- postherpetic neuralgia: pain in the effected dermatome that lasts 90 days after proper treatment and no longer rash on the dermatome
- commonly if not treated leads to secondary bacterial infections*
Treatment:
- topical antipruritic meds and NSAIDs
- DONT use aspirin, can trigger Reye’s syndrome at all ages
- VZIG (only in immunocompromised/pregnant)
- Acyclovir/famciclovir/valacyclovir
(only in immunocompromised)
- varicella/zoster vaccines (not useful in patients who already have it)
Herpes simplex virus 2
(HSV-2)
(Genital and neonatal herpes
Spread via sexual contact and perinatal from infected mothers
- more common type of viral meningitis with herpes virus (HSV-2 > HSV-1)
Lytic phase:
- virus infects epithelial tissues, uses host machinery to replicate itself, and then burst said epithelial cells to infect more
Latent phase:
- eventually, the virus particles move up neurons to cell ganglion and enter a dormant phase where they remain for life
- slowly, they release herpes copies down neurons and back into epithelial tissues to start up the lytic phase (this is common during stress, skin damage and viral illness)
- lesions develop on the ipsilateral side of the ganglia they infect*
Causes:
- genital herpes: (ulcers/pustules on the genitalia)
- neonatal herpes: (1 of 3 possibilities = skin/eye/mucus membrane infections at damaged skin. CNS infections. Disseminated infection/sepsis/organ failure)
- viral meningitis: (usually during reactivating only)
most commonly remain latent in sacral ganglia
Treatment: doesnt kill, only treats symptoms
- acyclovir
- famciclovir
- valcyclovir
- if neonatal herpes, give IV dose, otherwise can be PO/IM or topical*
Reye syndrome
Liver disorder that is caused by aspirin in young children or adults with certain infections
Causes toxic buildup of ammonia
Human herpes virus 5
HHV-5/Cytolomegalovirus/CMV
Transmitted via sexual contact, saliva, urine, transplants and transfusions
- also a congenital route so mothers can pass this
- uses integrin receptors to get into host cells*
- pretty much only dangerous in immunocompromised individuals*
Complications: only in immunocompromised individuals
- mono
- pneumonia
- esophagitis
- ADIS retinitis*
- vision loss
- Congenital CMV
Human herpes viruses 6/7
(HHV-6/7)
(Roseola infantum/6th disease)
Transmitted via saliva and respiratory secretions
virus attaches to APCs in respiratory mucosa, and latches onto T-cells when they come in contact with APCs
Undergoes lytic and latent phases also
- latent is in lymphocytes
Signs/symptoms Roseola infantum/6th disease (more common with HHV-6) - commonly seen in children 6mon-2yrs - *high fevers for several days - (+/-) seizures - *rosy macular diffuse rash that starts on trunk and moves to extremities (after fever only) - periorbital edema - rinorrhea - diarrhea/coughing/vomiting - *Nagayama spots (red spots on soft palate) - lymphadenopathy - acute Ottis media
Treatment:
- supportive only (is self-limiting)
- acetaminophen/ NSAIDs
- acyclovir/ganciclovir (immunocompromised individuals ONLY)
Human herpes virus 8
Kaposi sarcoma
Spread via sexual contact
pretty much exclusively seen in immunocompromised individuals (especially AIDS)
Enters tons of cells in the body to begin lytic phase. Latent phase it stays in endothelial cells on the skin
Known to cause kaposi sarcoma
- dark/violaceous plaques or nodules on the skin, GI system or pulmonary system due to endothelial cell tumors causing angiogenesis
Treatment:
- reverse (or better) immunodeficiency if possible
- chemotherapy/cryosurgery
What are the 7 Oncoviruses and what cancer do they cause?
Note: oncovirus are viruses that are known to directly cause cancer to prolonged exposure
HHV-8 = kaposi sarcoma
- Latent nuclear antigens (LANA-1) inhibits p53 in epithelial cells
HPV =
4 subtypes of kaposi sarcoma
1) classic
- found in older males, is slow growing and typically affects the leg skin
2) Endemic
- found in younger African males, and is rapid grower
3) epidemic
- found in AIDS patients and affects the entire body to some degree
4) immunosuppressive related
- found in organ transplant patients or serious doses of corticosteroids
- affects anytime of skin
What is a Tzanck test?
A test used to check for HSV-3 (sometimes HSV-1/2)
Take a swab from the affected skin vesicle/lesion
- note for the presence of viral DNA and Tzanck cells (large multinucleated giant cells)
Adenovirus
Cause respiratory, GI and GU issues such as:
- pneumonia
- Common cold
- febrile pharyngitis (sore throat)
- cystitis (bladder inflammation)
- unspecific diarrhea
- Gastorenteritis
- conjunctivitis (pink eye)
Spreads via fecal: oral route
- usually through contaminated water, fields or flies
- can also be spread congenitally
Makes a home in respiratory/ GI/GU epithelium by binding via the coxsackie-adenovirus receptors located on respiratory epithelium
- begins lytic phase and generates inflammatory response
More common among:
- children
- immunocompromised
- military recruits
Signs/symptoms URI - fever - nasal congestion - runny nose - sore throat LRI - coughing - dyspnea - chest pain GI - diarrhea - nausea/vomiting - fever
Diagnosis:
- viral cultures
- physical exams
- PCRs
Treatment:
- usually asymptomatic W/ symptomatic treatment
- Cidofovir/IVIG (immunocompromised only)
What are the 4 cardinal signs of inflammation?
Redness
Swelling
Warmth
Pain
Parvovirus-B19
5th disease/“slapped cheek syndrome”
spreads via respiratory droplets and saliva
- is also possible for congenital transmission
- it does not infect any cells until it gets to the bone marrow
Once inside bone marrow, infects proerythroblasts and start the lytic phase
- needs the P-antigen to get in* (hence why it chooses proerythroblasts
- also grows best in cells with S-phase activation (common in proerythroblasts)
causes aplastic crisis in sickle cell patients
Complications:
- 5th disease
- flu-like symptoms
- lace-like rash in a “slapped cheek” like appearance in children (can also be seen on trunk)
- in adults, causes arthralgia and RA-like symptoms
Fetal B-19 infection
- passed on to fetus
- causes hydrops fetalis (abnormal increase of fluid in soft tissue) due to overwhelming RBC destruction and leaky capillaries
- often is fatal to infants if ion 1st half of pregnancy
- NO DEFECTS if born with B-19 infection (just have to survive)
- Aplastic crisis
- seen in sickle cell anemia, thalassemia patients
- break down of RBCs due to infection cause a crisis low RBC count
- extreme fatigue
- pallor
- muscle weakness and difficulty breathing
Treatment:
- 5th Disease = symptomatic only
- aplastic crisis = symptomatic and transfusions
- immunocompromised infections = IVIG transfusions
- fetal infection = intrauterine blood transfusion (as long as 18-35 weeks)
