Causes Burkitt’s lymphoma – aggressive, malignant cancer characterized by a solid tumour composed of aberrant B-cells
Hits teens and young adults by causing infectious mononucleosis
Passed through saliva of an infected person, hence called kissing disease, sharing glass, utensils or straw
Incubation period – 4-7 weeks
Initial signs – sore throat, tonsillitis, fatigue, anorexia, headache, white patches in the back of throat
Mononucleosis – enlarged spleen, may even rupture
Burkitt’s lymphoma occurs when a person is immunocompromised with AIDS or chronic malaria. EBV persistently infects B cells causing latent infection. Affects jaws, rapidly spreads to soft tissues and parotid glands. Involves chromosomal translocation between chromosome 8 (invariably) and 14, rarely with chromosome 2 or 12. This moves c-myc oncogene on chromosome 8 downstream of immunoglobulin heavy chain gene on chromosome 14 resulting in abnormal expression of the oncogene.
Named after Anthony Epstein and Yvonne Barr who first isolated the virus
Kaposi’s Sarcoma
1st described by Moritz Kaposi in 1872
Occurs in elderly men with an incidence ratio of 10-15 men:1 women
Average age of onset – 50-70 years in men of Mediterranean, Middle Eastern or Eastern European ethnic descent
Single or multiple lesions in lower extremities – ankles, soles
1981 – 1st reported as a part of AIDS in young homosexuals & bisexuals
Poses problems in patients under HAART (Highly Active Anti-Retroviral Therapy) and transplant patients undergoing immunosuppressive drugs
Belongs to class Human Herpes virus 8
Viral DNA sequence is detected by PCR in biopsy material from patients
<3% cells show lytic infection. mRNA transcripts of latent viral genes found in most infected host cells
Encodes D-type cyclin, IL-6 homolog, Bcl 2 homolog etc. that help in transformation of human cells
Hepatitis B & C Virus (HBV, HCV)
Cause chronic hepatitis that could lead to liver cirrhosis and hepatocellular carcinoma (HCC)
HBV – ds-DNA genome
HCV – RNA genome, replicates in cell cytoplasm
Both infect hepatocytes, HCV also infects B-cells
In HCC, in tumours caused by HBV, integrated viral DNA is seen whereas in case of HCV , having an RNA genome does not contain an obvious oncogene & no integration is seen
HCV causes chromosome instability. Rises mutation by 5-10 fold in certain genes – Ig H chains, bcl-6, p53, β-catenins
Transmission – entry via blood or body fluids into non-immunized persons, infected needles, infected mother to baby during birth
HBV can also be sexually transmitted
Rate of progression from chronic hepatitis to cirrhosis to cancer is higher for HCV than HBV
HCC – not detected until an advanced stage. Hence, liver cancer is usually fatal within a year of diagnosis
5th most common cancer in the world
Hepatitis B vaccine has lowered the incidence rate. No vaccine for HCV is available as of now
Donated blood is screened for
HBV & HCV – US, Canada
HBV – South East Asia
Human Papilloma Virus
Common among sexually active adults and adolescents
One of the most prevalent STD of the world today
Causes cervical cancer which becomes the major cause of death among women in developing countries and is the 2nd most common cancer among women in the world
PAP screening programs have reduced cervical cancer mortalities
118 types of virus discovered. Common host is humans. Also found in other mammals & birds
Cause benign papillomas or warts in skin of hands and soles, genitals or mucus membrane
3 categories :
High risk types – cancer of cervix, vulva, vagina, anus, penis (eg., Type 16 & 18). 4-20 years latent period of infection
Intermediate type – HPVs are frequently found in pre-cancerous lesions, less often cause cancers (eg., Types 31, 33, 51, 52, 83)
Structure Of Virus
Small, non-enveloped, icosahedral, ds-circular DNA virus, 52-55nm diameter, 8000bp
Can infect only multiplying basal epithelium cells which are metabolically active
Enter through cuts and abrassions
Replication and virion assembly occurs in nucleus
Some Useful Information
Bivalent vaccine for HPV is available that is 100% effective against persistent HPV – 16 & 18 infections. Reduces incidences of cervical cancer.
Vaccine preparation – HPV 16 & 18 L1 genes expressed in S.cerevisiae cells in high quantities. The proteins self-assemble to give a virus – like particle (VLP) without the genome. It infects human epithelial cells of cervix and causes papillomas. Injected intramuscularly into arms.
This vaccine is 62% efficient in females and 64% in males
GARDASIL – Manufactured by Merck and licensed by FDA in 2006. CDC recommends 11-12 aged females to get vaccinated in order to reduce cases of cervical cancer. Several states are mandating the use of this vaccine.
