Experts on Thursday sought urgent work on HIV-killing gels that could help protect women who can't rely on condoms, while former South African leader Nelson Mandela (search) told the world not to ignore tuberculosis as it battles AIDS.

With research over the past two years showing that an AIDS vaccine (search) is still a long way off, HIV-killing gels and creams, female condoms and diaphragms that could bolster prevention in the interim have become more of a priority.

"Developing an HIV vaccine is probably one of the most difficult challenges that biomedical science is confronting," vaccine researcher Jose Esparza told a session at the International AIDS Conference (search) that runs through Friday.

It's the biggest gathering ever of AIDS scientists, activists, policy-makers and HIV-infected people, also drawing international dignitaries like Mandela, the former South African president.

"The world has made defeating AIDS a top priority. This is a blessing, but TB remains ignored," said Mandela, who turns 86 on Sunday.

Tuberculosis (search) is one of the most common diseases that attacks AIDS patients after their immune system has been destroyed, with the lung disease causing from 15 percent to 40 percent of the 3 million AIDS deaths worldwide last year.

On Thursday, the Bill and Melinda Gates Foundation (search) announced a $44.7 million grant to support a consortium that will research TB control strategies in communities with high levels of HIV.

The consortium, led by Johns Hopkins Center for Tuberculosis Research (search), will conduct three large-scale community studies over seven years in Zambia, South Africa and Brazil.

Mandela called the grant "critical" in the fight against TB.

Mandela, who survived tuberculosis in prison during South Africa's apartheid era, noted that the world has known the cure for TB for more than 50 years but that too many people are not being diagnosed and treated.

Curing TB can cost as little as $10 per patient, said Dr. Jack Chow of the World Health Organizatio (search)n.

"We can't fight AIDS unless we do much more to fight TB as well," Mandela said to loud applause from scores of activists, admirers and staff at a packed news conference.

There have been daily protests at the conference over the HIV policies of President Bush, such as his emphasis on abstinence — rather than condoms — in the fight against HIV. Much of Bush's foreign aid on AIDS is tied to abstinence programs.

Critics say a vow of abstinence is difficult to maintain and, when broken, can lead to unprotected sex, raising the risk of HIV infection that could effectively be blocked by a condom.

About 20 youth protesters briefly seized a U.S. government booth at the conference, shouting, "Bush is a jerk. Condoms work."

Much of Thursday's focus was on women, who are now nearly half of the world's 38 million people living with HIV. Their infection rates in many regions are climbing much faster than men's.

With many cultures denying women the power and confidence to demand that partners wear condoms, scientists are addressing ways women can protect themselves.

Vaginal gels, which can be applied long before intercourse and used without a partner's knowledge, could be such a way, and Dr. Zeda Rosenberg, chief executive of International Partnership for Microbicides, urged that more resources be poured into the effort.

"Unlike vaccines, there has been virtually no private sector investment in microbicide development," Rosenberg said. "The science is there. The technology is there, and most of all, the passion and dedication of those in the field is palpable."

Early versions of these gels and creams would attack a broad spectrum of bacteria, viruses and perhaps even human cells. Among complicating factors for developers are that microbicides also can kill cells in the vagina that help block HIV, Rosenberg said.

Rosenberg says microbicides may initially be only about 30 percent effective, but that second-generation products already in early development would more specifically target HIV and be more powerful.

She told The Associated Press that $1 billion is needed in research over the next five years if a viable product is to be made available commercially by 2014.

Other experts think it will take longer.

"It will certainly be more than 10, probably 15 to 20 years, if ever, before we have an effective microbicide," said Dr. Frederick Altice, an infectious diseases expert at Yale University.

Some health specialists also worry that such gels could reduce the use of condoms, which are far more effective at preventing the spread of HIV.

Those same concerns apply to female condoms, although many studies have shown them to block HIV as effectively as men's condoms, said Quarraisha Abdool Karim, an epidemiologist from University of Natal in South Africa.