Saturday, June 12, 2010

Toward Resistance

Toward Resistance

If the virus were not so variable, one or two AIDS drugs would suffice. But the virus changes its genome with practically every copy. The reason for such flexibility is that RT lacks a proofreading mechanism and does not repair copy errors. Mutations in the HIV genome can result in changes in the composition of its proteins. Most of these changes are detrimental or even lethal to the virus, but with many millions to even billions of virus copies produced daily in the same patient, chances are high that a viral variant will arise quickly whose target protein remains functional even in the presence of a drug. Such a virus is resistant to the drug.

Suppressing viral replication means reducing the number of experiments the virus can perform to produce a resistant variant. In order to increase the barrier of the virus to escape toward resistance, several drugs targeting different viral proteins are given simultaneously. This scheme, called highly active antiretroviral therapy, or HAART, renders therapies effective for much longer periods of time. The virus always wins. Most current therapies remain effective for only months to a few years.

What medicines are used for HIV infection?

What medicines are used for HIV infection?

There are several kinds of medicines are used to fight HIV infection. The first kind is called nucleoside analog reverse transcriptase (say trans-krip-tase) inhibitors, or "nukes." When HIV infects a healthy cell, it needs the cell's DNA, or genetic instructions, to build copies of itself. These drugs act by blocking the HIV's ability to copy a cell's DNA. Without complete DNA, HIV can't make new virus copies. These medicines include the following:
  • Abacavir
  • Didanosine
  • Emtricitabine
  • Lamivudine
  • Stavudine
  • Tenofovir DF
  • Zidovudine
  • Combination of Abacavir, Lamivudine and Zidovudine
  • Combination of Abacavir and Lamivudine
  • Combination of Emtricitabine and Tenofovir DF
  • Combination of Lamivudine and Zidovudine
The second kind of medicine is called a non-nucleoside reverse transcriptase inhibitor. These drugs also prevent HIV from using a healthy cell's DNA to make copies of itself, but in a slightly different way. This group includes the following medicines:
  • Delavirdine
  • Nevirapine
  • Efavirenz
  • Etravirine
The third kind of medicine is called protease (say pro-tee-ase) inhibitors. These medicines work by preventing infected cells from releasing HIV into the body. This group includes the following medicines:
  • Amprenavir
  • Atazanavir
  • Darunavir
  • Fosamprenavir
  • Indinavir
  • Nelfinavir
  • Ritonavir
  • Saquinavir
  • Tipranavir
  • The combination of Lopinavir and Ritonavir
The fourth kind of medicine is called a fusion inhibitor. This medicine works by preventing the entry of the HIV virus into your body's healthy cells. This medicine is injected by a doctor. This group includes the following medicines:
  • Enfuvirtide
  • Maraviroc
The last type of medicine is called an integrase inhibitor. This medicine works by disabling integrase. Integrase is a protein that HIV uses to insert its genetic material into the genetic material of CD4 cells. This group includes the following medicine:
  • Raltegravir
The different kinds of medicines are often used together (in combination) to reduce the amount of HIV in the body.

When different drugs are combined with the purpose of reducing the amount of HIV in your blood to very low levels, the resulting treatment regimen is called highly active antiretroviral therapy (HAART). Your doctor must watch you closely when you are being treated with these drugs to see how well they lower the amount of virus in your body. Your doctor also wants to make sure you aren't having side effects like nausea, vomiting, fatigue, anemia or peripheral neuropathy (a numb feeling in your hands or feet).

Sunday, June 6, 2010

What about subtypes of HIV?

What about subtypes of HIV?

Thus far, 11 distinct subtypes, also known as "clades" or "genotypes," have been recognized of HIV-1. More than 96% of the HIV-1 infections in the United States and Europe are caused by subtype B. Subtypes B and F predominate in South America and Asia. Subtypes A through H of HIV-1 are found in Africa, along with HIV-2 in sub-Saharan Africa.

The ELISA/Western blot tests can detect antibodies to all HIV-1 subtypes. Viral load tests can also detect and quantify subtypes of HIV-1. The viral load tests can also detect and quantify HIV-2.