Semester 2 - Enveloped DNA Viruses Flashcards
What are characteristics of herpesvirueses?
Large dsDNA viruses, enveloped
Latency a hallmark feature
Replicate in the nucleus
No Non-human reservoirs for any human herpesvirues
What is a tegument?
An amorphous layer between icosahedral capsid and lipid envelope of herpesvirueses
What are the three stages of herpes infection?
Immediate-early: genes that regulate early and late gene expression
Early: Non-structural/regulatory genes (enzymes)
Late: Structural genes
What is HHV1?
Herpes simplex type 1
What is HHV2
Herpes simplex type 2
What is HHV3?
Varicella Zoster Virus (VZV)
What is HHV4?
Epstein Barr Virus (EBV)
What is HHV5?
Cytomegalovirus (CMV/HCMV)
What is HHV6/7?
Roseola Infantum
What is HHV8?
Kaposi’s sarcoma Virus (KSV/KSHV)
What are LATs?
Latency associated transcripts
Interfere with the function of viral proteins
Affect chromatin organization, preventing viral gene expression
miRNA against apoptosis-promoting genes
What is reactivation from latency?
Typically occurs in the first few years following primary infection, but may occur anytime
Is associated with immune competency, stress
What is shedding during latency?
Occurs at a higher level in the first few years following primary infection but may occur any time
Infection may be passed on in the absence of symptoms (WHY?)
What are some characteristics of Herpes Simplex Type 1?
Oral cold sores (70%) accounts for 30% of genital herpes cases
Latent in trigeminal ganglion
What does a herpes labialis infection look like?
Oral cold sores
Small fluid filled blisters, may occur in clumps
Broken blisters crust over, resolve in approx 2 weeks without treatment
Reccurent - reactivation from stress, immune compromise
How is Herpes simplex 1 transmitted?
Contact, mucous, sexual
What are the signs and symptoms of a herpes whitlow infection?
Occurs on tips of fingers/thumbs, more common in health care workers
Burning tingling of fingers
Fluid filled vesicles over erythematous base - fluid may be cloudy or bloody
What is herpes keratitis/conjunctivits?
Inflammation of the cornea or conjunctiva of the eye
Redness, pain, swelling of the eye, itching and lesions
Typically infects one eye at a time
What is Herpes encephalitis?
Most common cause of viral encephalitis. Follows an acute infection or reactivation
Headache, fever, fatigue, cognitive impairment, altered consciousness, confusion, disorientation, clumsiness
Complications - Seizure, memory loss, paralysis
What are some characteristics of herpes simplex type 2?
Genital cold sores (70%) and accounts for 30% of oral herpes cases
Latent in sacral ganglion
What is herpes genitalis?
Genital lesions - small fluid filled may crust over
Risk maternal transmission (congenital herpes)
What are some characteristics of Varicella zoster virus?
Chicken pox (varicella) Reactivation as shingles (zoster) Latent in dorsal root ganglion
What are signs and symptoms of chicken pox?
Small, itchy blisters/pustules, widespread rash
Fever
Complications: pneumonia, sepsis, joint/bone infections
Adults at greater risk for complications (Skin and soft tissue, septic arthritis, osteomyelitis, pneumonia)
What are the signs and symptoms of shingles?
Asymmetric blisters/pustules
typically on the neck, trunk or leg
Radates from one dermatome (asymmetry)
Neuralgia, which may occur prior to blister appearance
How is VZV transmitted?
Aerosol, contact
What is the difference between chicken pox and shingles?
Chicken pox occurs after first exposure
shingles is a reactivation of infection after latency
Chicken pox may occur in children or adults, and is more severe in adults
Shingles most often occurs in adults
When is a VZV vaccine administered?
May be given prophylactically, or post-exposure to shorten the course of disease and reduce severity/complications
What are some characteristics of the epstein barr virus?
Infectious mononucleosis
Latent in B cells
Occurs most commonly in teens/young adults
What are the signs and symptoms of mono?
Fever, sore throat, extreme malaise, nausea
Exudative pharyngitis, tonsillitis
Lymphadenopathy, splenomegaly, hepatospenomegaly
Arthritic symptoms sometimes present
Mild, non-itchy rash may be present
What are some complications of mono?
Risk of splenic rupture - patients should refrain from aggressive physical activity for several months following infection
Risk of hemolytic anemia, infective cardiopathies (very rare)
What are some long term complications of mono?
Burkitt’s lymphoma
Nasopharyngeal carcinoma
How is epstein barr virus transmitted?
Mucosal (saliva, sexual)
Shedding may occur in the absence of symptoms - easily transmissible
Where is cytomegalovirus latent?
lymphocytes
What are the signs and symptoms of a cytomegalovirus infection?
Most people seropostive with no symptoms
Immunocompromised individuals - mono like illness
Risk of passing to child during pregnancy: congenital CMV = developmental disabilities, hearing loss, low birth weight, jaundice, CNS abnormalities
How is CMV transmitted?
Bodily fluids: saliva, urine, breastmilk, sexual contact
What are the signs and symptoms of CMV mononucleosis?
Primary cause of seronegative mononucleosis cases
Fever/systemic symptoms predominate, while hepatosplenomegaly and lymphadeopathy less severe
What are some CMV related diseases in immunocompromised individuals?
CMV colities - ulceration, pseudomembrane formation
CNS infection - encephalitis
CMV pneumonia
CMV retinitis
What are diseases that CMV is associated with?
Atherosclerosis, cardiopathies
Guillan-Barre syndrome
Autoimmune arthritis (SpA, ReA, PsA)
What are some characteristics of HHV6 and HHV7
Roseola infantum (exanthema subitum): Three day fever, baby measles
High seropositivity rate (60%)
Latent in thymocytes
What are the signs and symptoms of roseola infantum?
Sudden transient non-itchy rash in young children
Self-resolving lasts 3 days
What are the signs and symptoms of roseola infantum in an immunocompromised individual?
Mono-like illness, fever, lymphadenopathy, encephalitis, post-transplantation complications (GVH)
Associated with CNS diseases, autoimmune exacerbation, AIDS dementia, complex development
What are some characteristics of Kaposi’s Sarcoma Virus?
Latent in B cells
Associated with HIV progression to AIDS
Small tumors of the connective tissue lining blood vessels
What are the signs and symptoms of Kaposi’s Sarcoma virus?
Blue-red or purple macules/nodules localized to lower extremities, diffusing throughout the body
Heterogeneity of dermatological morphologies
Nodules may bleed easily
Bloody sputum, SOB
Progressive - ulceration of mucous membranes of the mouth, GIT, lymph nodes
What are characteristics of Poxviruses?
Large dsDNA virus with a double membrane
Replicates in cytoplasm: encodes viral DNA-dependent RNA polymerase
What are human pathogens of poxviruses?
Variola virus: smallpox
Vaccinia virus: vaccination
Zoonotic infections: cowpox, monkeypox
How do poxviruses replicate?
Two uncoating steps
Replication occurs in the cytoplasm: viruses encodes replication machinery
Assembly/Maturation involves acquisition of two envelopes
Golgi wrapping leads to IMV formation: can spread to neighboring cells
Egress from cell membrane leads to EEV formation: can spread to any cell, can survive extracellularly.
What are clinical features of smallpox?
High fever
Deep set maculopapular rash with papules at the same stage of development
Progress to fluid-filled blisters
Leads to hemorrhagic disease, high mortality rate
