The retroviruses (HIV) carry 2 strands of ___ ___and its own polymerase called _____ _____ which converts the + stranded RNA to DS DNA. This DNA incorporates into the host cells DNA as a _____. This provirus never comes out of the ____DNA. It may be transcribed and translated to produce more _____. The virus may also convert the host cell into _____or tumor cells.
+ stranded RNA , reverse transcriptase, provirus,host ,viruses,cancer
Symptoms: Remember for all the RNA viruses, fidelity in the replication of RNA is not as high as for DNA so more mistakes occur. Therefore there is higher rate of change. The stages of cellular infection are as follows:
1. HIV attaches to receptors on a host cell and release HIV RNA into the cytoplasm.
2. An enzyme called reverse transcriptase converts the SS viral RNA into DS viral DNA which travels to the nucleus.
3. The enzyme called integrase splices the viral DNA into the host cells DNA.
4. The infected cell produces more viral RNA which in turn can be translated to form large viral proteins.
5. A protease enzyme cuts the viral proteins into functional protein shorter in length.
6. New viral proteins and RNA come together to form new viral particles.
7. New HIV particles bud from the surface of the infected cell and infect new cells.
Human Immunodeficiency Virus (HIV)
Disease: Acquired Immunodeficiency Syndrome (AIDS)
Route of Transmission: Sexually, IV drug use, Tissue transplant, blood transfusion
HIV Replication Animation
An HIV positive individual undergoes and intense battle from the time of infection until development of disease in which the immune system is counteracting the destruction of T cells by increasing new T cells at a higher rate. The battle to keep up is eventually lost and then the disease symptoms begin.
HIV disease: fatigue, mild fever, sore muscles, occasional diarrhea, swollen lymph nodes, T cell count drops to 800/cc.
AIDS Related Complex: exaggerated symptoms of HIV disease, persistent fatigue, swollen lymph nodes, diarrhea, weight loss, night sweats, candidiasis, T cell count drops to 400/cc, psychological stress and fear.
AIDS: T cell count reaches 25/cc, constant swollen nodes, nausea, intense fatigue, vomiting, headaches, heavy night sweats, brain disease with dementia and disorientation, wasting with cholera like diarrhea and severe weight loss, opportunistic diseases.
HIV antibodies determined by ELISA followed by Western blot and gene probes for definite identification, AZT and nucleotide analogs can be given to interfere with DNA synthesis by reverse transcriptase but these drugs also poison the body, ____ can be given to prevent HIV attachment to T cells, Predicted to be 20 million cases in work by year 2000.
a. contains positive single-stranded RNA
b. infects B and T cells.
c. is a retrovirus.
d. Both A and C are correct.
e. A, B and C are correct.
Enveloped viruses can exit a host cell by a process called ______which usually does not result in lysis of the cell. Nonenveloped usually ____the host cell.
A variety of ____may result from viral infection.
One is_____ ____ which are often filled with viruses or parts of viruses. Rabies virus forms ____ bodies (dark inclusion inside nerve cells) which may be seen in the brains of infected animals.
Some viral infections form giant cells called _______.
Others cause _______ breakage.
Still others express altered levels of _______. This may be beneficial because some virally infected cells produce increased levels of _____(a natural antiviral agent) which can protect neighboring cells from viral infection.
CPE , inclusion bodies, Negri, polykaryocytes,chromosomal,
Viruses are often associated with cancer. A cancer is the _________ ______ of a given type of cell in the body. The tissue is then called a tumor which may be malignant or benign. The suffix "____" is associated with tumors and the prefix designating the type of tissue affected. Not all form solid tumors for example ______occur when WBCs in the body become cancerous. _____are connective tissue tumors. ____are tumors of glandular epithelial cells.
uncontrolled multiplication,oma, leukemias, Sarcomas ,Adenocarcinomas
Many normal cells are ______into tumors when oncogenes are activated. All nucleated cells have _______(Bishop and Varmus). Under normal conditions these genes encode normal proteins until triggered to form ________proteins. In normal form these genes are called ________.
Proto-oncogene >> Cells Grow Normally
Oncogene >> Cells Grow Abnormally
transformed ,oncogenes ,abnormal ,proto-oncogenes
Ultraviolet light, Radiation, Carcinogens
Replication Mistakes (non-induced)
All ______viruses have the ability to integrate into the host cell's DNA and replicate there.
Signs that cells have become cancerous:
Most will lose contact inhibition.
Many infected cells express viral antigens on their surfaces.
Others have broken chromosomes or unusual numbers of chromosomes.
Methods of Oncogene Activation:
Single base pair mutation
Transduction - oncogene moved from one cell to another
Translocation - oncogene is moved from one area in a chromosome to another chromosome all together in the same cell.
Gene amplification -an oncogene is duplicated many times in a cell causing overproduction of a protein.
Known Oncogenic Viruses
Adenoviruses, Herpesviruses, Poxviruses and Papovaviruses are all oncogenic viruses.
Papilloma viruses may cause benign warts or cervical cancer.
Herpesviruses (Epstein Barr virus) is associated with Burkitt's Lymphoma, a cancer of the lymphatic system; nasopharyngeal cancer, and Hodgkin's Disease another lymphatic cancer. 90% of our population probably carries EBV in a latent stage.
HHVI causes cold sores.
HHVII causing genital herpes infections. Latency is also associated with HHVI and II. HHVI may be triggered by fever or sun (hence the name fever blisters) and it is carried by most of our population.
Varicella zoster virus (HHV3 also a herpes virus) may exist in a latent state. Varicella causes Chicken pox, and is the same virus as the one causing Herpes Zoster (shingles) in adults. There is a connection between HHVII infection and cervical cancer.
HBV virus is associated with liver cancer.
Among the RNA viruses only the ______seem to be oncogenic. HTLV I and II, feline leukemia virus and HIV. These viruses may be _____for long periods of time with the apparent exception of HIV.
retroviruses , latent
What is the fole of proto-oncogenes in theories of how viruses cause cancer?
a. They play a role in the control of cell division.
b. They make cells more susceptible to infection by cancer-causing viruses.
c. They prevent the immune system from attacking cancer-causing viruses.
d. They cause cancer viruses to replicate faster.
e. They prevent cancer-causing viruses from leaving the cell.
A____ _____ infection is a disease which occurs slowly over a long period of time. Many are caused by _______viruses such as the paramyxovirus (measles) which can cause subacute sclerosing panencephalitis (SSPE) many ____after causing measles. All documented slow viral infections cause slowly progressing, ____, neurological diseases.
slow viral, conventional ,years , fatal
_______agents may also cause slow viral disease such as _____which is a sheep neurological disease in which the sheep scrape or rub against something until parts of their bodies become raw.
Unconventional , scrapie
It appears a _____for proteinaceous infectious particle or ____ protein is the cause of the disease.
Prion , pure
All known diseases of prions are neurological diseases such as ______-_____ disease (has been transmitted through transplanted corneas and scalpel nicks during autopsies), ____ (associated with tribes in New Guinea undergoing cannibalistic rituals), _____ ____ Encephalopathy (BSE or Mad Cow Disease) and Gerstmann-Straussler syndrome.
Creutzfeldt-Jakob, Kuru, Bovine Spongioform
Because of BSE research in Europe, it is now known that the prions which cause human disease differ from the cattle prion by 30 _____ ____. The cattle and sheep prions differ by ___ amino acids. The infectious prion has a distorted shape and has the ability to change the shape of normal prions in animal brains to the _____ shape.
amino acids, 7, abnormal
The process of changing normal prions to deformed ones takes _____. Prions are very heat resistant up to _____, resistant to common sterilants and disinfectants, extreme pH, UV and ionizing radiation and resists _____digestion in the stomach.
years, 120oC, protease
Proteinaceous infectious agents
Composed of ____ ___ ____.
All mammals contain gene that ____for primary sequence of amino acids in PrP
Two stable ____structures of PrP
Normal functional structure with α-helices called _____ ___.
Disease-causing form with β-sheets called ____PrP
Prion PrP converts cellular PrP into prion PrP by inducing ________change
single protein PrP, codes , tertiary , cellular PrP, prion , conformational
All of the following are diseases known to be caused by prions EXCEPT:
b. Cheutzfeldt-Jakob disease.
c. Alzheimer's disease
e. bovine spongioform encephalopathy
How are prions different from all other known infectious agents?
a. They cannot reproduce outside a cell
b. The cause disease in a way similar to slow viral infections.
c. They cause neurological disease.
d. They can be destroyed by incineration.
e. They lack nucleic acid.