Herpesvirus 6 & 8 Flashcards
What are all herpesvirus?
- DNA viruses
- immediate, early, and late replication
- all enveloped so can be killed by detergents, heat, during, and acids
How is Epstein-Barr Virus (EBV) transmitted?
- through saliva
- mono= known as “kissing disease”
What are the characteristics of EBV?
- by 35-40 years, almost all people in the US are infected
- establishes latency in memory B cells
- shed virus in saliva throughout life after they are infected
- young adults: 50% of infected will get infectious mononucleosis
What are the characteristics of infectious mononucleosis?
- virus initially divides in oropharynx causing sore throat through lytic infection.. then infects its main target: B cells
- primary cause of symptoms: massive expansion of cytotoxic T lymphocytes
- LONG incubation time: 4-6 weeks and virus can shed in saliva before symptoms start
What is the cycle of EBV mononucleosis?
- causes generalized activation of B cells
- leads to heterophiles antibody production
- heterophiles antibodies are non-specific antibodies that react with certain animals, horses, sheep RBC’s
- test via monospot test
- once acute infection is over, some memory B cells have latent EBV genome without production proteins
- when B cells divide, they express a viral protein to make sure viral genome goes into both cells
- EBV can reactivation from memory B cell pool and make new infectious virus
- virus will go back to oropharynx and infect epithelial cells to now produce virus that can be detected in saliva
What are complications of mononucleosis?
- spleen enlargement (avoid sports for 3-4 weeks)
- mild hepatitis (avoid alcohol)
- airway obstruction due to enlarged tonsils
What is oral hairy leukoplakia caused by?
- EBV but increased risk with smoking
What are the characteristics of oral hairy leukoplakia?
- benign, non-painful lesion on lateral border of tongue
- can NOT be scraped off tongue (unlike oral candidiasis)
- can be the first sign of someone with an HIV infection or occur in people taking immunosuppressive drugs
- best tx: antiviral drugs to increase CD4 count
What are the cancers involved with EBV?
- oral hairy leukoplakia
- nasopharyngeal carcinoma
- burkitt lymphoma
What are the characteristics of Burkitt Lymphoma?
- very fast growing, aggressive
- also correlated with malaria infection
- endemic BL: starts as tumor of face and more likely in young children
- caused by chromosomal translation of c-myc gene to a chromosome that has immunoglobulin locus that causes unregulated c-myc expression giving uncontrolled cell growth
- sporadic BL: starts in abdomen and not highly ass
T/F: CMV infections are mostly asymptomatic
True!
- except CMV mono-like syndrome, congenital infections, and immunocompromised
How is CMV transmitted?
- saliva, urine, blood, breast milk, semen, cervical secretions
- spread through sexual contact, infected salvia, urine, and breastfeeding
T/F: CMV infects a wide range of cells. It is not possible to be infected with more than one strain
False.
CMV does infect a wide range of cells but it is very much possible to be infected with more than one strain
When is CMV most severe?
- in people with AIDS: retinitis
- big problem in transplant recipients
Where is latency established in CMV disease?
- myeloid precursors cells in bone marrow
In mononucleosis like syndrome of CMV, what cells do they infect?
- T cells… does NOT infect B cells
- no activation/production of heterophiles antibodies
- so it is antibody negative and mono spot negative
What is the #1 congenital infection in the US?
CMV
- due to primary CMV infection having a high risk of transferring to fetus
- but only 10% of babies are symptomatic
What is the difference between asymptomatic and symptomatic CMV diseased in congenital CMV?
Asymptomatic:
- only 10% risk of hearing loss which is delayed and progressive
Symptomatic:
- can have motor, cognitive deficits, hearing loss, or vision impairment
Why are children a major cause of adult infection of CMV?
- they can secrete CMV in saliva and urine for over a year
- most infections are asymptomatic
Who is HHV6 common in?
children
(very common childhood infection)
What does HH6 cause?
- roseola
- febrile seizures
Which is Kaposi sarcoma-associated herpesvirus associated with?
HH8
Who is HHV8 common in?
Men who have sex with men
What are the symptoms and transmission of HH8?
- usually no symptoms unless co-infected with HIV and/or lower CD4 count
- symptoms: oral lesions and lesions on other parts of body that often violet
- transmitted through sex/saliva/kissing
What are prions?
– proteinaceous infectious particle
- it is only protein nothing else
- normal protein found in the brain
- ** becomes pathogenic when it is a miss folded prion protein**
What do the infectious prions (PrPsc) have compared to normal prions (PrPc)?
- PrPsc have a higher number of B sheets
- PrPsc convert normal PrPc cells into the PrPsc and cause aggregates of amyloid plaque which then cause cell to die and releases the infectious misfolded prion protein: gives the spongiform appearance of parts of the brain (transmissible spongiform encephalopathy)
Although miss folded prions cause many different types of disease, which is the most common?
spontaneous Creutzfeld-Jacob disease
- no genetic component and no infection
- spontaneous mutation in prion gene (seen in certain families) or spontaneous misfiled protein that becomes infectious (seen in people older than 50)
- 1% of people who got this are due to an infectious cause: an external source like contaminated surgical instruments
What is the fatality of spontaneous Creutzfeld-Jacob disease?
after symptoms appear, life expectancy is rarely over a year (fatal condition)
Are prions easy to kill?
No, they are resistant to many disinfectants, proteases, and normal auto clothing making it VERY hard to kill prions
What are the infectious causes of transmissible spongiform encephalopathies?
- variant Creutzfeld-Jacob disease (vCJD)
- iatrogenic Creutzfeld-Jacob disease (iCJD)
What is variant Creutzfeld-Jacob disease (vCJD) caused by?
- eating beef contaminated with prion proteins
- cows that had spongiform encephalitis (mad cow disease) that were consumed
- incubation time: 5 years. 100% fatal
What is iatrogenic Creutzfeld-Jacob disease (iCJD) caused by?
- healthcare settings
- most cases from material harvested from cadavers (human growth hormone, dura mater graphs)
- some cases were from using prion-contaminated neurosurgical instruments (including dental instruments)
