Oncogenic Virus

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Oncogenic virus

Virus that produce tumor in their natural host, experimental animals or cell culture
Viruses associated with malignancies
DNA Virus:-
Papilloma virus, EBV, HBV
RNA virus:-
HTLV I,III, HCV
20% has viral risk factor

Terminologies

Immortalization – ability of the virus to establish persistent infection, that can also stimulate uncontrolled growth indefinitely

Transformation- ability of the virus infected cell to cause malignant growth in immunodeficient or immunocompromised animals

Characteristic of transformed cells
Possession of viral genome
Integration or plasmid like
Morphological change
Loss of cell contact inhibition growth
Decrease growth factor requirement
Increase efficiency of clone formation
Changes in membrane transport  properties
contd
Expression of tumor associated antigen
Changes in plasma cell membrane composition-
↓density & cellular glycolipids
↓fibronectin
↑oligosaccharides
Chromosomal alteration- partial deletion, translocation & partial or complete duplication


Mechanism of viral oncogenesis 


DNA virus :-
A portion is integrated in the host cell genome
Encodes protein which binds & inactivate growth regulatory protein (RB/p53 genes)
Loss of p53 gene product makes cell susceptible to mutation
EBV – stimulates cell growth as B cell mitogen and by inducing expression of bcl-2 oncogene, it prevents cell death (apoptosis) 
Mechanism of viral oncogenesis- contd
Integrated viral genome often has – rearrangement or deletion
As viral DNA is defective or incomplete, no infectious virus is produced
Host cell undergo neoplastic transformation
Retro viruses
Reverse transcriptase –
Construct DNA copy of RNA
DNA integrates with DNA of host
Adopts two approaches to oncogenesis
Encodes oncogenic proteins (sis, ras, src, mos, myc, jun, fos)
These oncoproteins are identical to cellular proteins
Stimulates cell growth ( Tumor)
Seen in animals ( not in human )
Second approach
HTLV
Encodes protein (tax)
Transactivates gene expression of T lymphocytes
Clinical manifestation- DNA
DNA  has limited oncogenic potential
Viral genome codes for protein which inactivates protein coded by tumor suppressor genes
Papova virus
HPV 6 & 11
benign warts and premalignant lesions
carcinoma of female and male genital tract
Herpes
Herpes simples 1 and 2 – cervical carcinoma
Virus causes insertional mutagenesis
EBV – Burkitt’s lymphoma, Nasopharyngeal carcinoma
Transform lymphocytes to lymphoblast
Hepatitis B virus
Hepatocellular carcinoma
No oncogenes
Tumor cell contains integrated viral DNA
Probably acts by insertional mutagenesis or transactivating
Oncogenic retro virus
Causes tumor of RE/haemopoietic system
Leukaemia/lymphoma

Oncogenes
Oncogene  is a gene that (when mutate or expressed at abnormally high level) contibutes to the conversion of normal cell to cancer cell.

Oncogene
Viral oncogene (v-onc)-  codes for protein that trigger transformation of normal cells into malignant cells
Cellular oncogenes- oncogene isolated from cancer cell
Proto-oncogene- counterpart in normal cell
Nomenclature
v- viral oncogene
c- cellular genes
v- src (sarcoma)
c- src
src- tyrosine specific protein
sis- platelet derived growth factor
mye- DNA binding protein 
Function
Protein kinases- (v-src) codes for tyrosine –specific kinase-  loss of contact inhibition
Transactivating proteins- over expression of cellular replication and differentiation
Identification of oncogenes
Transfection-  NIH 3T3 mouse fibroblast
DNA probes
Antioncogenes
Tumor suppressor gene/growth suppressor gene/ anti-oncogenes
Retinoblastoma (Rb) gene
Retinoblastoma

Comments

  1. Donna RobertApril 21, 2021 at 10:52 PM

    The worst time has passed”However, it is true that there are more improvements than before...because of the rising numbers of people living with HIV in the state of Nevada. How could they stigmatize all of them? Therefore everything becomes a little easier and we start to share everything... We also started to invite and visit each other in a community. You know, it is six years since I started taking antiretroviral drugs...Yet whatever problems I face, the worst time has passedWhen I was evicted from the family home by my mother, my father rented a small room for me. But my mother and brothers believed that having HIV was my own fault – and that I deserved to be punished...I also considered myself unworthy and without hope... But I have a child and eventually I convinced myself to live for my child’s sake.
    My mother knew nothing [about HIV]. She didn’t understand anything. Do you know why? She didn’t have [the chance] to go out of the house and communicate with society. However, my father does interact with the community. I know his friends are mature and dignified africa america. So he has a better understanding than her.My father came call me on a sadfull day sitting on my couch about a friend of his from africa who introduce him to Dr Itua herbal  cure in africa in which he advise we should purchase his herbal medicine to cure my hiv so we did and Dr Itua prescribed I should drink the herbal medicine for two weeks to cure although we were so curious about the whole thing ,I finished the herbal medicine like he advised then he talked to me to visit my nearest clinic for check up I did and now I'm totally cured from Hiv my father was my rock and I and my family are now happy together also Dr Itua has be helpful in my community ever since he cure my Hiv so why I'm leaving  my story on here today is to reach out someone out here to hope on God and never give up no matter the situation you that you are facing especially through this pandemic seasons which has really taught us all on how we should be helpful to each other and cherish one another.Dr Itua cures the following diseases.....  Herpes,Liver cancer,Throat cancerLeukemia.,Alzheimer's disease,Chronic Diarrhea,Copd,Parkinson,Als,Adrenocortical carcinoma  Infectious mononucleosis.
    Intestinal cancer,Uterine cancer,Fibroid,Bladder cancer,Hiv,Esophageal cancer,Gallbladder cancer,Kidney cancer,Hpv,Lung cancer,Melanoma,Mesothelioma,Multiple myeloma,Oral cancer,Sinus cancer,Hepatitis A,B/C,Skin cancer,Soft tissue sarcoma,Spinal cancer,Stomach cancer,Vaginal cancer,Vulvar cancer,
    Testicular cancer,Thyroid Cancer.You can contact Dr Itua Herbal Center on E-Mail: drituaherbalcenter@gmail.com  Or Whats-App Chat : +2348149277967

    ReplyDelete

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