Molecular Genetics - HPV and HBV (II) Flashcards
Structure of HPV
Non-enveloped dsDNA virus with supercoiled genome
List 2 high risk and 2 low risk HPV genotypes.
Associated diseases?
High risk: 16,18
Oncogenic, HSIL, Cervical cancer
Low risk: 6,11
Anogenital warts, LSIL
2 oncogenes commonly detected in cervical cancer.
Activity in low risk and high risk HPV types?
Function of these oncogenes?
HPV oncogene E6 and E7
high transforming activity in high risk HPV
Interact with growth-regulating targets in host cells.
E6»_space; p53, E7»_space; pRb
> > Maintain malignant phenotype of cervical carcinoma cells
Primary prevention against cervical cancer?
- HPV vaccination
- Avoid risk factors
Secondary prevention against cervical cancer?
- Cervical cytology/ HPV test screening
- Detect pre-invasive lesion of uterine cervix (HSIL)
3 reasons HPV infection persists?
- Evades normal immune mechanisms
- Do not produce humoral immune response
- Diagnostic serology test not widely available
3 main types of HPV DNA test
1) HPV pooled DNA test
2) HPV genotyping
3) HPV pooled test + High risk HPV 16/18 genotyping
3 purposes of HPV genotyping test
- Epidemiology
- Assess clinical behavior of subtypes
- Design targeted therapy and vaccine
Most important factors that validate HPV molecular tests
1) Quality control and clinical validation in diagnostic settings
2) Adequate data to correlate between cut-off point and detection of cervical cancer and precursor lesion
In situ hybridization.
used for which type of HPV test?
Early HPV detection
PCR sequencing
- used for which type of HPV test?
HPV detection
HPV genotyping
(+/- Detect multiple HPV)
Describe HPV DNA chips function
PCR products of L1 and E6, E7 gene sequences are hybridized to arrayed probes on the chip»_space; DNA sample with target genes bind to probes
HPV genotypes identified by fluorescence scanner
List techniques for HPV testing *****
- HPV DNA chip: Genotype by gene products
- Qualitative multiplex assay and RT-PCR
HPV detection
HPV high risk genotype 16,18
Identify multiple HPV infection - RNA transcription detection
Persistent HPV infection
Qualitative multiplex assay
- used for which type of HPV test?
HPV detection
HPV high risk genotype 16,18
Identify multiple HPV infection
RT-PCR
- used for which type of HPV test?
HPV detection
HPV high risk genotype 16,18
Identify multiple HPV infection
Which targets are tested in extended HPV genotyping (check)
E6,E7 DNA regions
Screen for all 14 high-risk HPV types
Best test for persistent HPV infection?
RNA test:
RNA transcript detection
more specific for detection of persistent infection and detection of HSIL than DNA test
Invasive cervical cancer and high grade lesion is suspected based on clinical exam
Order 2 tests for confirmation
Co-testing:
Pap-smear + HPV DNA testing
Define ASC-US and associated risks
Atypical squamous cells of undetermined significance
- Cytological abnormalities, higher risk of LSIL or HSIL
Triage of ASCUS
- Next step after detection of ASCUS through cytology testing
Cytology and HPV co-testing
1) Repeat cytology again at 6 months and 12 months
a) Positive for ASCUS or LSIL/ HSIL in both tests = colposcopy
b) Both Normal results = repeat cytology again in 3 years
2) HPV testing
a) High risk HPV positive = Colposcopy
b) High risk HPV negative = Repeat cytology or co-testing at 3 years
Purpose of ASCUS triage?
Reduce patient anxiety
Decrease cost of repeat smears
Earlier Dx of HSIL
One other cancer associated with HPV
Testing method?
HPV 16»_space; Oropharyngeal squamous cell carcinoma
Increase incidence in men with age
IHC for p16 as surrogate marker from tissue specimen
3 un-recommended use of HPV tests
Low risk test
Test under 25
Reflexive HPV test after Pap smear of HSIL
HPV +ve and HPV -ve cervical cancer
- Associated with which risk factors
- Which has better prognosis
HPV +ve = sexual behavior
HPV -ve= smoking and tobacco
HPV +ve has better prognosis
