Prions & DNA Viruses Flashcards
1
Q
What disqualifies prions from being viruses?
A
lack of genome
2
Q
Do prions elicit a immune/inflammatory response?
What are characteristics of prions?
A
no because altered self
30 kD, infectious, glycoprotein, no immune response
3
Q
Describe characteristics of prion infection.
A
- slow progression
- lose muscle coordination
- dementia, progressive insomnia
- amyloidosis
- spongiform encephalopathy
4
Q
Describe the steps of propagation of a prion.
A
- PrP gene, found on chromosome 20, contains 2 exons but the two mRNA’s ligated into a single mRNA (mutation) which is translated into a protein named PrPc
- mutation causes PrPc undergoes post-translational events to become glycosylated prion protein, PrPsc
- normal PrPc forms alpha-helix while PrPsc forms beta sheets
- B-sheet forming peptides form amyloid fibrils which kill thalamus neurons
5
Q
What are examples of trans human prions? inherited?
A
trans: Kuru, vCJD
inherited: CJD
6
Q
PrPsc aggregates to form amyloid in cerebellum causing _____ (x3).
A
- astrocyte gliosis
- depletion of dendritic spines of neurons
- apoptosis
7
Q
Parvoviruses
- example
- describe
- transmission
- pathology
- disease (x4)
- diagnosis
A
- Erythrovirus B19 (also Human bocavirus that was found in cattle and cause severe respiratory diseases in young children)
- DNA, naked, icosahedral, 1 type, ssDNA
- respiratory droplets or transplacental; kills erythroid precursors
- (1st) viremia and anemia, (2nd) rash and arthralgia
- (a) fifth dz - erythema infectiosum, slapped face rash; 1 of 5 exanthems
(b) aplastic crisis in chronic hemolytic anemia patients (sickle cell anemia)
(c) acute polyarthritis
(d) spontaneous abortion - when a seronegative mother becomes infected - clinical presentation, ELISA, PCR
8
Q
Papillomaviridae
- example
- description
- epidemiology (types)
- transmission (x4)
- pathology
- diseases (x4)
- diagnosis
- immune response
- vaccine
A
- human papiloomarvirus
- DNA, naked, icosahedral, 75 types, dsDNA
- types 1-4 are common; 16, 18, 31, 45, 52, 58 lead to cervical cancer (*highest risk)
- breaks in skin, mucous membrane; STD; formites, chewing on warts
- warts occur in keratinized skin; viral stimulated hyperplasia; koiocytes (well-vacuolated wart with dark nuclei); gene product E6 and E7 inactivate p53 (normally has proofreading function, a tumor-suppressing gene) leading to enhanced growth and more mutations
- (a) papillomas (warts)
(b) laryngopapillomas (types 6, 11), block airways in children
(c) condylomata acuminata aka genital warts (types 6, 11),
(d) cervical dysplasia, CIN, and carcinoma (types 16, 18) - pap smear showing koilocytosis
- CD8 T cells eventually kill HPV infected cells
- HPV9, Guardasil
9
Q
Polyomaviruses
- examples (2)
- epidemiology
- transmission
- diseases (2)
- diagnosis
A
- BK and JC virus
- very common, bu cause disease only in immunocompromised; most people latently infected by 15 y/o
- respiratory droplets to epithelium to lymphocytes to kidney where it remains latent; JC lysogenizes kidney, B cells, monocytes, astrocytes, and oligodendrocytes; virus shed in urine during acute phase and reactivation
- **IC individuals only (AIDS, transplantation, pregnant)
(a) hemorrhagic cystitis, nephritis, urethritis (BK virus)
(b) PML (progressive multifocal leukoencephalopathy) - lytic infection leads to demyelination of oligodendrocytes (JC virus) *on MRI of brain, will see white areas = lesions in white matter - PCR of CSF, CT or MRI, DNA analyses of urine, CSF or biopsies tissue are effective for detecting BK and JC
10
Q
Adenoviridae
- example
- describe
- epidemiology
- transmission, resistance towards, infects what, most common types are
- diagnosis
- biogenetical importance
- vaccine
- diseases (6ish)
A
- adenovirus
- dsDNA, naked, icosahedral, 12 vertex fibers, hemagglutinin
- 1st example isolated from adenoid tissue; 52 types determined by the vertex fiber antigen; terminal knob is a humaglglutinin
- aerosol, close contact, fecal-oral; resists desiccation, detergents stomach acid, bile, mild chlorination; infects mucoepithelial cells that then reach lymphoid tissue; types 1-7 are most common
- easily cultured, displayed characters inclusion bodies; DNA analysis
- used as a vehicle in human gene replacement therapy
- oral vaccine comprised of serotypes 4 and 7 for military recruits
- (a) acute febrile pharyngitis and pharyngoconjunctival fever = pharyngitis and pinkeye, resembles strep, flu like, nasal congestion
(b) acute respiratory tract disease (military recruits. Types 4 and 7) = fever, cough, pharyngitis
(c) colds, laryngitis, croup
(d) conjunctivitis and keratoconjunctivitis
(e) gastroenteritis and diarrhea
(f) other: intussusception, acute hemorrhagic cystitis, musculoskeletal disorders; systemic infection, PNA, hep
11
Q
Herpesviruses
- examples (2)
- things that are true of all 8 types
- most common
- pathogenesis
- Histology
- transmission
- disease (4 main ones) (which type?)
- Diagnosis
A
- HSV 1 and 2
- (a) dsDNA, enveloped icosahedral
(b) latent, recurring infections
(c) envelope confers sensitivity to acid, detergents, and drying
(d) encodes its own DNA polymerase
(e) infections are common and benign except in IC - HSV-1 and HSV-2
- mucoepithelial cells then latent infections in peripheral sensory gingival (usually trigeminal or sacral) then vesicular lesions at infection site; CMI is important; host cells lyse
- cowry type A, sancta (giant cells)
- HSV-1: direct contact, vesicular fluids, infections above waist
HSV-2: STD, at birth; infections below waist - (a) Herpes genitalis (HSV-2) - vesicles and ulcers on genitals
(b) Herpes labials (cold sores, fever blisters)(HSV1) - lips
(c) Herpes encephalitis (HSV1) - most common sporadic encephalitis in US
(d) Postnatal herpes encephalitis (HSV 2), 15% of newborns die - (a) Tzank smear of pap test material scraped from base of a vesicle to reveal syncytia and cowry type A inclusions
(b) confirmation by immune- or DNA-based methods, culture
(c) serology (but only for primary infection bc recurrent infections don’t show increases in titers
12
Q
What does the CSF of patients with encephalitis caused by HSV1/2 show?
A
- lymphocytic pleocytosis (increase of lymphocytes in CSF)
- nml glucose
- mildly elevated protein
- absence of pathogens using gram stain and culture
13
Q
Humans herpesvirus 3 (HHV 3)
- common name
- describe
- epidemiology
- transmission
- pathology
- diseases
- vaccines
- diagnosis
A
- varicella-zoster virus (VZV)
- DNA, enveloped
- chickenpox: ages 5-9, extremely contagious, life-long immunity
shingles - late reactivation of chickenpox and is a recurrent disease - respiratory droplets or skin contact then infects respiratory epithelium leading to viremia; travels to liver; vesiculopustular rash with crops of lesions form
- VZV causes latent infections in ganglia; reactivate periodically (with immune suppression and aging); entire dermatome with shingles
- (a) chickenpox (virecella) - epithelial cell infection resulting in an exanthema of macule, papules, pustules, vesicles and shallow ulcers; mild in children, severe in adults; 20-30% of adults may show interstitial PNA; prenatal infection (<20 weeks) can lead to CNS abnmls
(b) shingles (zoster) - peripheral nerve cell infection with an eruption in overlying epidermis; belt or girdle; server pain precedes rash and may be followed by postherpetic neuralgia (chronic pain) - for chickenpox: varivax, live
for shingles: zostavax, live - Tzanck test, CPE, sancta, immuno- and DNA-based methods; serology useful to determine immunity
14
Q
Human herpesvirus 4
- common name
- description
- transmission
- immune response
- diseases (4)
- diagnosis of diseases
- associated cancers
A
- Epstein-Barr virus (EBV)
- herpesvirus, DNA, enveloped
- infective via saliva, invades oral epithelia cells and B cells (tonsils), infections can be latent or lytic
- t-cells resolve infection by destroying the infected B-cells which produces the symptoms of mononucleosis (fatigue, t-cell lymphocytosis, downey cells, herteophile mononucleosis)
- (a) Infective mononucleosis (b-lymphocyte infection), overactive immune response, more severe in young adults (fatigue, fever, malaise, pharyngitis, lymphadenopathy)
(b) laryngitis - hoarseness, loss of voice
(c) hepatitis - elevated liver enzymes and jaundice
(d) encephalitis, aseptic meningitis
(e) clinical picture, atypical lymphocytosis, heterophiles antibody (monospot test) - (a) Burkitt’s lymphoma - endemic in African malaria areas
(b) Hodgkin’s lymphoma - lymphoid tissue cancer, deficient immune response
(c) Nasopharyngeal carcinoma - endemic in china
(d) Hairy oral leukoplakia (in IC, AIDS)
15
Q
Human herpesvirus 5
- common name
- description
- epidemiology
- transmission
- disease (3)
- diagnosis
A
- Cytomegalovirus (CMV)
- DNA, enveloped; opportunistic; primarily in IC or neonates
- common lymphotrophic lifelong recurrent infection;
- acquired transplacentally, during birth, from milk, saliva, tears, urine in infants; from semen or blood in adults
- (a) CMV mono: similar to, but milder than, IM; heterophiles negative monophile
(b) cytomegalic inclusion disease (salivary gland disease)
(c) transplant or transfusion infections - Owl’s eye cells
