AIDS conference sign
© of the downed Malaysia Airlines jet were heading to the AIDS 2014 conference in Melbourne, including world-prominent activist Joep Lange.
MELBOURNE - It was supposed to be a star-studded event filled with scientific discussion and a little socializing on the side.

Instead, after the crash of Malaysia Airlines Flight 17, one of the world's biggest AIDS conferences was turned upside down as researchers absorbed news that some of their field's top experts were killed.

The flight that went down in eastern Ukraine on Thursday was carrying a number of the world's prominent HIV/AIDS activists, led by Joep Lange, a researcher at the University of Amsterdam who had worked in the field since 1983, nearly the beginning of the epidemic.

Reports circulated that as many as 100 or more conference attendees were on board on the ill-fated flight, though only a handful were confirmed by Friday night. Some activists believed to be missing later appeared, having caught other flights to Australia.(Follow the latest updates on the Malaysia Airlines crash in Ukraine.)

"We are bracing ourselves to hear of the deaths of others who worked in the AIDS response as their names are officially released," said Michel Sidibé, Executive Director of UNAIDS. "The UNAIDS family is in deep shock. Our hearts go out to the families of all the victims of this tragic crash. The deaths of so many committed people working against HIV will be a great loss for the AIDS response."

Yet the uncertainty left a dark cloud over the assembled attendees and rippled throughout the global HIV/AIDS community. As academics gathered ahead of the main conference which begins Sunday, the downed aircraft was the first topic on everyone's minds.

"This is a huge tragedy for the HIV/AIDS research community," said Dan Barouch, professor of medicine at the Beth Israel Deaconess Medical Center at Harvard Medical School, who is in Melbourne for the International AIDS Conference event, which is organized every two years by the International AIDS Society.

"It's not just figures like Joep (Lange). It is a combination of a few very prominent researchers plus the junior researchers who could have made dozens of years of contributions."

Others who were confirmed dead en route to the event were Glenn Thomas, a former BBC journalist who had worked for the World Health Organization's press team for more than a decade, and Jacqueline van Tongeren, a former nurse who worked closely with Mr. Lange fighting HIV/AIDS in places like Thailand and Myanmar.

Organizers of the event said in a statement posted on its website that the conference would go ahead as planned "in recognition of our colleagues' dedication to the fight against HIV/AIDS." The conference was expected to draw some 12,000 participants and include speakers such as former President Bill Clinton and musician and activist Bob Geldof.

Drug-company representatives attending the event were rattled by the news. Employees at Bristol-Myers Squibb were told about the crash in an internal email, which Carey Hwang, medical director for discovery medicine based in Princeton, N.J., read on a layover Friday morning between Sydney and Melbourne.

"It was a shock. It will put a pall over the conference, which is already an emotionally charged event."

Opening prayer for victims
© Denis Napthine, Co-Chair of AIDS 2014 Prof Sharon Lewin, Melbourne Lord Mayor Robert Doyle, Victorian Minister for Health David Davis and YEAH CEO Alischa Ross observe silence at the opening of an AIDS conference in Melbourne on Friday night.
Sadness was also acute in Amsterdam, which has blossomed as a major hub for HIV- and AIDS-related advocacy in recent years.

Several people linked to its activist community were believed to be on the plane which departed from the city, including an AIDS-prevention lobbyist who posted a message on Facebook before leaving saying he planned to backpack in Australia after the conference.

At the center of this community for decades has been Mr. Lange, advocates said.

A former president of the International AIDS Society from 2002-2004, Mr. Lange is credited as the architect of numerous key trials on the use of antiretroviral therapy and advances in the prevention of mother-to-child transmission.

He made a name for himself in the early days of the AIDS epidemic by advocating that antiretroviral drugs like Azidothymidene, or AZT, be combined with others for a more-effective and less-toxic therapy. Along the way, he debunked some of the less-effective antiretroviral drugs rushed to market.

"He was never afraid to tell pharmaceutical companies to bury their favorite baby," said David Cooper, director of the Kirby Institute, an institute specializing in HIV/AIDS research at the University of New South Wales in Sydney.

Several attendees of the 20th International AIDS Conference, scheduled for July 20-25 in Melbourne, Australia, were travelling on the Malaysia Airlines flight MH17 that went down in Ukraine EPA

In the mid-1990s, Mr. Lange began to believe that the First World had gotten a grip on the virus, and switched his focus to helping deliver the drugs to low-income communities in places like Nigeria, Uganda and Tanzania. He enlisted the help of Dutch companies like Heineken International and Royal Dutch Shell PLC for financial backing.

In remote communities, Mr. Lange and his partners began setting up demonstration projects to prove that the delivery of new anti-HIV drugs could make an impact on the spread of the disease and mortality rates. His projects would prove models for large-scale rollouts of the drugs across Africa by the World Health Organization and others.

More recently he founded the Amsterdam Institute for Global Health and Development, which partners with public health bodies to improve care through everything from Internet-based drug distribution software to setting up mobile labs in rural Vietnam to diagnose infectious diseases.

"That I'm still alive is due to him," said Han Nefkens, an art collector who works with Artaids, a Barcelona-based organization that seeks to raise awareness of HIV/AIDS through art. Diagnosed with HIV in 1987, Mr. Nefkens had sought out Mr. Lange on the advice of a friend, beginning a friendship that bloomed to include philanthropic activity.

"This morning when I heard the news, I was in a state of paralysis," said Frits van Griensven, a senior adviser for HIV Prevention at Bangkok-based HIV Netherlands Australia Thailand Research Collaboration, or HIVNAT, which Mr. Lange helped found in the 1990s. He said Mr. Lange traveled so often in his work that "nobody" saw him very often.

"Everything will come to a stop because of his super-visionary leadership. But people will pick up pieces and continue what is needed to be done."