D.7+Antiviral

__**OBJECTIVES:**__

// Antiviral drugs may work by altering the cell’s genetic material so that the virus cannot use it to multiply. Alternatively, they may prevent the viruses from multiplying by blocking enzyme activity within the host cell. // || // Specific proteins on the HIV virus bind to a receptor protein on certain white blood cells (T cells). Because of the ability of the HIV viruses to mutate, and because their metabolism is linked closely with that of the cell, effective treatment with antiviral drugs is very difficult, as is vaccine development. The control and treatment of HIV is exacerbated by the high price of anti-retroviral agents and sociocultural issues. // ||
 * D. 7. 1 State how viruses differ from bacteria. ||
 * D. 7. 2 Describe the different ways in which antiviral drugs work.
 * D. 7. 3 Discuss the difficulties associated with solving the AIDS problem.

__ Virus vs. Bacteria __ Viruses have no nucleus, no cytoplasm, do not feed, excrete or grow, cannot reproduce on their own (they need to use the materials provided by a "host cell") Virus:
 * **Virus** || **Bacteria** ||
 * Central core of DNA/RNA || Nucleus ||
 * No Cytoplasm || Cytoplasm ||
 * Needs a host cell || Reproduces on own ||
 * Doesn't feed, excrete or grow: non-living || Is Living ||

__** Antiviral Drugs (and how they work) **__

__ Difficulty with treating viral infections: __ The speed that the virus multiplies Therefore, by the time the symptoms are shown, the virus has multiplied so much that the antiviral drugs will have little effect. It's difficult to eliminate the virus completely, so it can reappear later on. The viruses are constantly mutating.

__ How the drugs work: __ Altering the cell's genetic material so that the virus can't use that cell to multiply. Eg. Acyclovir: applied to the skin to treat cold sores caused by herpes virus. Structurally similar to deoxyguanosine (one of the building blocks of DNA), the virus is tricked to use acyclovir for a building block for their DNA, which prevents the virus from multiplying. Preventing the new viruses (after the original virus reproduces) from leaving the cell. Eg. Amantadine: works against the influenza virus. This drug makes one of the enzymes (called neuraminidase) that the virus uses to stick onto the host cell as the virus tries to leave inactive, so that the virus cannot leave the original cell.

Link to an animation on virus replication: [] (This specific animation is about HIV, a retrovirus mentioned below, but the idea is very similar to all viruses.)

(first two bullet points are not needed for the syllabus, but provide a nice background (AIDS and Current Solutions)
 * __ Difficulties with solving AIDS: __**

__ AIDS: __ Caused by a retrovirus, it contains RNA instead of DNA. This virus infects T helper cells (a kind of white blood cell) that alerts other cells in the immune system, leaving the body unable to fight other infections. Upon invading the cell, the retrovirus makes viral-DNA from the RNA template (reverse transcriptase). (This is opposite to what normal cells do-make RNA from DNA template.)

__ Current solutions: __ ATZ (zidovudine), clogs up the active site (is a reverse-transcriptase inhibitor). This doesn’t affect normal cells.

__ Problems: __ The HIV virus has a high ability to mutate. Their metabolism is linked closely to the cells, (making it difficult to attack only the virus and not the cell itself also) High prices of anti-retroviral agents Sociocultural issues Too many symptoms-all kinds of diseases can infect you.