May 13, 2011

Early Anti-retroviral Therapy Prevents HIV Transmission

An HIV-positive person who takes anti-retroviral drugs immediately after diagnosis, rather than waiting until their health begins to decline, can reduce the risk of spreading the virus to uninfected partners by 96%, according to a major international study.

Although antiretroviral therapy was long known to improve the health of people infected with HIV, this is the first study to show a definitive impact on preventing transmission to an HIV-negative partner.

"This is excellent news," said Myron Cohen, the study's lead author.

"This is the first randomized clinical trial to definitively indicate that an HIV-infected individual can reduce sexual transmission of HIV to an uninfected partner by beginning antiretroviral therapy sooner," said Cohen, who serves as director of the Institute of Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill.

The trial began in 2005 and included 1,763 couples -- 97 percent of which were heterosexual "“ in Africa, India, Thailand and the Americas.  The HIV-infected partners included 890 men and 873 women.

The randomization phase of the trial was halted early after researchers observed that the drug therapy was having such a dramatic blocking effect on the risk of spreading the infection.

Some couples were placed into a delayed group, in which the infected partner began taking antiretroviral therapy (ART) only when a type of T-cell known as CD4 dropped below 250 cells per millimeter cubed, or if he or she developed an AIDS-related illness.

The other group immediately began ART, which resulted in just one case of HIV transmission to an uninfected partner.

However, within the delayed group there were 27 HIV transmissions that could be traced directly to the infected partner.

Researchers called the difference between the two groups "highly statistically significant."

"Previous data about the potential value of antiretrovirals in making HIV-infected individuals less infectious to their sexual partners came largely from observational and epidemiological studies," said National Institute of Allergy and Infectious Diseases chief Anthony Fauci.

"This new finding convincingly demonstrates that treating the infected individual -- and doing so sooner rather than later -- can have a major impact on reducing HIV transmission," he told the AFP news agency.

According to Wafaa el-Sadr, executive committee member of the HIV Prevention Trials Network (HPTN), the organization that conducted the study, the results should have a major impact on HIV treatment recommendations.

"I think HPTN 052 will always be recognized as a landmark study that truly may transform treatment as well as prevention of HIV globally," she told AFP.

Sadr, who is also a professor of medicine and epidemiology at Columbia University in New York, said researchers would continue to follow the study participants.

"Everybody who was not offered immediate treatment is now being offered immediate treatment, now that we know what we know," she said.

Although the study was initially set to continue until 2015, the independent safety and monitoring board halted the randomization phase early "because of the very clear and remarkable benefits that were shown," she explained.

"They determined that these findings were so profoundly important that they had to be shared immediately."

AIDS has claimed more than 25 million lives worldwide, with more than 60 million people having become infected with the virus since 1981. Some 80 percent of new infections are sexually transmitted, according to United Nations data.

Antiretroviral treatment is a combination of drugs that can reduce the level of virus in the blood to below detectable levels.  However, the therapy can also cause harsh side effects such as nausea, diarrhea, vomiting and weight loss.

The 11 HIV drugs that were used in various combinations in the study included the following:

"¢ atazanavir (300 mg once daily)
"¢ didanosine (400 mg once daily)
"¢ efavirenz (600 mg once daily)
"¢ emtricitabine/tenofovir disoproxil fumarate (200 mg emtricitabine/300 mg tenofovir disoproxil fumarate once daily)
"¢ lamivudine (300 mg once daily)
"¢ lopinavir/ritonavir 800/200 mg once daily (QD) or lopinavir/ritonavir 400/100 mg twice daily (BID)
"¢ nevirapine (200 mg taken once daily for 14 days followed by 200 mg taken twice daily)
"¢ ritonavir (100 mg once daily, used only to boost atazanavir)
"¢ stavudine (weight-dependent dosage)
"¢ tenofovir disoproxil fumarate (300 mg once daily)
"¢ zidovudine/lamivudine (150 mg lamivudine/300 mg zidovudine taken orally twice daily)

Antiretrovirals were originally designed as a HIV treatment, they are now being tested for prevention, as a pill taken by high-risk gay men and as a vaginal gel for women.


Image Caption: Scanning electron micrograph of HIV-1 budding from cultured lymphocyte. This image has been colored to highlight important features. (CDC) 


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