Tumor viruses Flashcards
(18 cards)
7 human cancer viruses
Epstein barr - dsDNA
hepB - ss/dsDNA
human t lymphotropic virus-I - +ssRNA retro
HPV16 and 18 dsDNA
hepC +ssRNA
Kaposi’s sarcoma herpesvirus - dsDNA
Merkelcell polyomavirus - dsDNA
Which virus uses indirect carcinogensis?
hepatitis:
chronic viral infection -> inflammation
which viruses use direct carcinogenesis?
EBV, HTLV I, KSHV, Papilloma, MCV
Which cancers are virus necessary factors?
HPV and cervical cancer
KSHV and KS
When are cancers both virus + and -
merkel cell carcinoma (MCV)
head and neck cancer (HPV)
Epstein barr virus
discovered in 1964 due to plane delay (latency) by electron microscopy in Burketts lymphoma tumors
causes lymphoma, nasopharyngeal carcinoma, gastric cancer, MS, mono
Large dsDNA
present in >95% of adults
HepB virus
discovered in 1965
causes hepatitis and hepatocellular carcinoma
Small ssDNA virus
chronic infection
vaccine preventable
Human t cell lymphotropic virus I (HTLV-I)
discovered in 1980
causes acute T cell leukemia
tropical spastic paraparesis/myelopathy
first human retrovirus
spread via sex, breast milk, transfusions
Human papillomavirus (HPV)
discovered in 1983
causes cervical cancer, head-neck cancer, anal cancer, penile cancer
sexual transmission (Related to site of inoculation)
vaccine preventable
why has Oropharynx cancer has stayed steady despite decreasing rates of smoking?
Rates of HPV+ has increased, HPV- has decreased
HepC virus
discovered in 1989
causes hepatitis and hepatocellular carcinoma
+ssRNA flavivirus similar to dengue/west nile
IDU, transfusion, transplantation
drug treatment can eliminate HCV
How can we prove causality?
- necessary and sufficient
- causality as a human device
- KOch’s postulates
- Hill’s criteria for causality
What are Koch’s postulates and why are they insufficient for proving HPV’s cause of cancer?
- can be isolated from lesion
- can be grown in pure culture (not possible for all viruses)
- induces disease in susceptible host (Humans are the only susceptible host for HPV and that would be unethical)
- can be reisolated from infected susceptible host
Hill’s epidemiological criteria for causality
association
generalizability
temporality
specificity
biologic gradient
coherence
biological plausibility
experimental evidence
What are host factors of cancer viruses
age
sex
previous exposure
underlying disease
malnutrition
immunosuppression
what are environmental factors for tumor viruses?
seasonality
sanitation
irradiation
other infections
What are organism factors for tumor viruses?
strain/genotype
antibiotic/antiviral resistance
virulence factors
Kinetic model for risk infection
exposure -> transmission vs no transmission
of infected individuals -> tumorigenesis or not
