This is particularly important for targeting anti-viral therapy—meaning combinations of medicines need to be taken to help prevent the emergence of viral resistance.
This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now, Wondrium. Virus infections can be classified as either localized or body-wide, also known as disseminated.
In localized infections, the virus remains at the site of entry. Examples of local infections include respiratory viruses like the common cold, the herpes viruses that cause a cold sore, or wart viruses like a foot wart. An example of a disseminated infection would be the varicella-zoster or chickenpox virus.
After local replication in the respiratory tract, the chickenpox virus spreads throughout the body, and multiple organs can be infected, including the skin, which causes pox. Viruses are classified by their genetic material—either DNA, RNA, or retroviruses—and by their outer component—either enveloped or non-enveloped.
Enveloped viruses have different shapes, such as the rabies virus which is bullet-shaped. It is important to know since viruses are structurally different than bacteria and no antibiotics will work in preventing virus replication. Compared to antibiotics, the number of anti-viral medications is much less. This is another reason that vaccination against viral diseases is especially important.
Learn more about how to stay out of the hospital. The full-length RNA is actually the virus genome; it binds to the Gag protein and is packaged into new virus particles. The final step of the viral cycle, assembly of new HIV-1 virions, begins at the plasma membrane of the host cell. The Env polyprotein goes through the endoplasmic reticulum and is transported to the Golgi complex. These are transported to the plasma membrane of the host cell where gp41 anchors gp to the membrane of the infected cell.
The Gag p55 and Gag-Pol p polyproteins also associate with the inner surface of the plasma membrane along with the HIV genomic RNA as the forming virion begins to bud from the host cell. Maturation occurs either in the forming bud or in the immature virion after it buds from the host cell. This cleavage step can be inhibited by protease inhibitors.
The various structural components then assemble to produce a mature HIV virion. The mature virion is then able to infect another cell. Privacy Policy. Skip to main content. Search for:. Learning Objectives Identify the unique features of retroviruses. When integrated into a host genome, a retrovirus is hard to detect and can lay dormant for prolonged periods, having no discernible effect on the host.
Retroviruses can be human pathogens, and cause many diseases, but have also proven to be invaluable tools when used by molecular biologists. After attaching to the host, many of the receptors on both the cell and invading virus bind together for fusion of the virus with its host. Key Terms glycoprotein : A protein with covalently bonded carbohydrates. T cells : A lymphocyte, from the thymus, that can recognise specific antigens and can activate or deactivate other immune cells.
Retroviral RNA Genome The retroviral genome contains the elements needed for reverse transcription and all other activities of a retrovirus. Learning Objectives Discover the features of retroviral genomes. Key to the unique attributes of a retrovirus is the pol region, which encodes a reverse trancriptase RT , RT is the enzyme which takes the RNA form of the retrovirus genome and converts into DNA, the DNA form of which can integrate into the host genome.
Because viruses don't have cells of their own, they need to invade a host cell to reproduce. This normally destroys the host cell and causes disease. A retrovirus is a particular type of virus that uses RNA ribonucleic acid as its genetic material, and this is the key element of the retrovirus definition. Retroviruses do not kill the host cell at first because they can insert their genome into the host genome. This process is called reverse transcription and is done by the viral protein reverse transcriptase.
Examples of DNA viruses are the herpes simplex virus and the poxvirus. The retrovirus then integrates its viral DNA into the DNA of the host cell, which enables replication of the retrovirus. The extra step makes retroviruses more prone to mutation than most viruses, causes them to evolve more quickly than other viruses.
For example, scientists have used retroviruses to help diabetic rats make their own insulin. Get information on prevention, symptoms, and treatment to better ensure a long and healthy life. Bodine DM. National Human Genome Research Project. Origin and diversity of human retroviruses. AIDS Rev. Sluis-Cremer N. The emerging profile of cross-resistance among the nonnucleoside HIV-1 reverse transcriptase inhibitors. Alpharetroviral vectors: from a cancer-causing agent to a useful tool for human gene therapy.
Reversal of diabetes through gene therapy of diabetic rats by hepatic insulin expression via lentiviral transduction. Mol Ther. Goldsmith CS. Morphologic differentiation of viruses beyond the family level.
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