HTLV-1 is a single-stranded RNA virus that causes adult T cell leukemia. Even Though HTLV-1 infects between 12 to 25 million individuals, only 5% are symptomatic. 
Route of transmission; blood transfusions, sexual contact, and during parturition. 
Although it is not well understood how HTLV-1 causes adult T cell leukemia, researchers have seen a strong link with the specific CD8 T cells and the growth of T cell leukemia.


Northwestern University

- Hepatitis C Virus 
- Hepatitis B virus 
- Epstein-Barr Virus (EBV) and Human Herpesvirus 8 (HHV-8) 
- Human papillomavirus (HPV) 
- Human T lymphotropic virus type-1 (HTLV-) 


Viruses that cause cancer 

Hepatitis C is an RNA virus that infects 3% of the world's population. Hepatitis C can be acute or chronic. In the case of chronic infection it causes cirrhosis which can then lead to primary hepatocellular carcinoma in some individuals. 



Hepatitis C Virus 
 

Hepatitis B virus is a DNA virus and Hepatitis C virus has a very high mutation rate with 11 genotypes and many subtypes which can easily escape  the immune system recognition. It can cause cirrhosis and liver failure if it lasts for more than three months. Hepatitis C can lead to hepatocellular carcinoma and in some cases death. Treatments for hepatitis-induced liver disease can be surgical such as tumor incision or liver transplant. Nonsurgical treatments include“percutaneous ethanol injection, transarterial embolization, radiofrequency ablation, chemotherapy, and radiotherapy” (John 1). 
Treatment choices are made based on liver function and cancer prognosis. 


Interferons are used to decrease viral replication and thus eliminate or reduce liver complications. Medications such as lamivudine, adefovir, entecavir, and telbivudine target viral replication and have been  found to be effective. 
With transplantation, oral medications prevent Hepatitis B but not Hepatitis C recurrence. 


Hepatitis B virus 


EBV and HHV-8 are both herpes viruses which have large double stranded DNA. Nearly 95% of all adultes are seropositive. These viruses encode enzymes in DNA replication, repair and nucleotide biosynthesis. 

EBV is associated with B and T cell lymphoma, Hodgkin’s disease, post-transplant lymphoproliferative disease, leiomyosarcomas, and nasopharyngeal carcinomas. Research has shown individuals with immunodeficiency are more likely to develop such illness and thus immunosurveillance plays an important role in the prognosis of such conditions. 

Biopsies of Kaposi Sarcoma contained HHV-8 DNA,which suggested the cancer was caused by HHV-8. Kaposi sarcoma was a rare type of cancer before the AIDS epidemic but AIDS increased this kind of cancer. This underscores the role of immunosuppression in the development of Kaposi sarcoma. This suggests that immunotherapy  and targeted therapy are the best ways to eradicate this type of cancer.


Epstein-Barr Virus (EBV) and Human Herpesvirus 8 (HHV-8) 


Human Papillomavirus (HPV) is another virus that causes cancer in humans. Most HPV-induced diseases are benign such as warts but those caused by high risk strains of HPV such as 16 and 18 causes cervical and penile cancer. Other HPV-related cancers are head and neck cancer and some skin cancer. Immunosuppressed individuals are at particularly high risk of HPV-induced cancers.


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