The AIDS virus hides out inside people's intestines, researchers said on Saturday in a report that offers new understanding of the incurable infection.

The virus replicates in the lining of the gut and does much of its damage to the immune system there, Satya Dandekar, chairwoman of the Department of Medical Microbiology and Immunology at the University of California Davis Health System, and colleagues reported.

Writing in the Journal of Virology, Dandekar said the study was the first to explain why the drug cocktails taken by HIV patients so often fail to work completely.

"The real battle between the virus and exposed individuals is happening in the gut immediately after viral infection," she said in a statement.

"We need to be focusing our efforts on improving treatment of gut mucosa, where massive destruction of immune cells is occurring. Gut-associated lymphoid tissue accounts for 70 percent of the body's immune system. Restoring its function is crucial to ridding the body of the virus."

HIV cannot be cured but the drugs, known as highly active antiretroviral therapy, or HAART, can keep the virus under control.

At first, doctors had hoped that years of treatment might eventually eradicate the virus, but, 25 years into the epidemic of AIDS, it is clear that cannot happen. That is because the virus can hide out quietly in reservoirs, which include certain immune cells.

The gut is clearly important, too, Dandekar's team said.

"We found a substantial delay in the time that it takes to restore the gut mucosal immune system in those with chronic infections," Dandekar said. "In these patients the gut is acting as a viral reservoir that keeps us from ridding patients of the virus."

The mucosa are the wet tissues that line the nose and throat, the genitals and the inside of the gut. HIV often infects people via the mucosa.

Dandekar's team has been studying HIV-infected patients who, even without treatment, have survived more than 10 years with healthy immune systems, including the T-cells that are attacked by the virus.

"We looked at their gut lymphoid tissue and did not see loss of T-cells there. This correlated with better clinical outcomes," Dandekar said.

So they started the current study, following 10 patients being treated with HAART, taking blood and gut samples before and after three years of treatment.

They found evidence of inflammation, which disrupts tissue function, promotes cell death and upsets the normal balance of gut bacteria.

Dandekar said these findings suggest anti-inflammatory drugs may help HAART work better.

One of the country's top AIDS researchers and an expert in international health will lead Duke University's new Global Health Institute, one of several recent moves that puts the school at the forefront of HIV research.

Dr. Michael H. Merson, former director of the World Health Organization's AIDS program and a professor at Yale University, will take over as institute director Nov. 1.

The university-wide program promises to go beyond medicine by bringing together students in engineering, business and other academic areas to address health issues worldwide.

"It's a very exciting opportunity," Merson said Tuesday in a telephone interview from New York. "When I was there (at Duke), I was so impressed with the plans and the commitment. It was a unique chance to make a difference in the world's health."

The appointment comes on the heels of last week's announcement that Duke would receive $46.5 million for AIDS vaccine research from the Bill & Melinda Gates Foundation. More than $350 million has now been given to Duke in the past 13 months for HIV and AIDS research, including grants from the National Institutes of Health.

School officials stressed the Global Health Institute would go beyond AIDS research with a special focus on the health inequalities between poor and affluent countries.

"The institute's mission is also to educate future global health leaders and scholars, with the real focus on the disparity that exists between the have's and have not's throughout the world," Merson said.

Faculty and students from throughout the university bringing their expertise in engineering, international law and economics to an area often centered on medicine. Such diversity is vital to global health because curing disease goes beyond finding vaccines, Merson said.

"You also need to think about patients taking their drugs, so you need to involve clinical psychologists and people trained in social work. And you want to make sure people don't get infected, so you need public health experts," Merson said.

Providing cheaper drugs is an area for law students focused on international property rights, while engineers could develop less expensive ways to purify water.

"Global health is not only a medical issue, it's a multifaceted social issue," added Victor Dzau, chancellor of health affairs, who helped develop the program with university President Richard Brodhead. "If we can bring together all these areas of expertise, we can really address the problem and find solutions."

Merson worked for the World Health Organization in Geneva, Switzerland, from 1978 through 1995, and spent the last five year's as director of the organization's Global Program on AIDS, which has worked to control the disease worldwide.

He joined Yale in 1995 as dean of Public Health at the School of Medicine. Merson now heads the university's Center for Interdisciplinary Research on AIDS, which operates research and projects in about 20 countries.

Merson earned his medical degree at the State University of New York Health Science Center in Brooklyn before completing his internship and residency at Johns Hopkins Hospital.

He spent three years working for the Centers for Disease Control and Prevention, where he was promoted to chief medical epidemiologist at the Cholera Research Laboratory in Bangladesh.

Merson has written more than 175 articles and is senior editor of International Public Health.

"We did an international search, and he was head and shoulders above all the other candidates if you look at what he's done," Dzau said.

Heat resistant anti-retroviral HIV-AIDS drugs manufactured in the United States have arrived in Nigeria, Africa's most populous country, Medecins Sans Frontiers (Doctors Without Borders), said.

The new version of the fixed-dose combination lopinavir/ritonavir (CPV/R), marketed as Kaletra by Abbott Laboratories, was approved for use last October.

On March 15 MSF had placed an order for the new drug with Abbott headquarters in the United States to use in MSF projects in nine countries: Cameroon, Guatemala, Kenya, Malawi, Nigeria, South Africa, Thailand, Uganda and Zimbabwe, it said.

The organisation stressed the need for Abbott to take necessary actions to register the drug and make it affordable in Nigeria, the country which has 3.5 million AIDS sufferers, placing it the second most hit in Africa, after South Africa.

Last April Abbott announced a price for the new formulation of 500 dollars per patient per year for least developed and African countries.