(CNN) Six members of the Presidential Advisory Council on HIV/AIDS resigned last week, owing to "a president who simply does not care," one member wrote in a Newsweek op-ed on Friday headlined "Trump doesn't care about HIV. We're outta here."

"We cannot ignore the many signs that the Trump Administration does not take the on-going epidemic, or the needs of people living with HIV, seriously," wrote Scott Schoettes , the HIV project director for Lambda Legal , a civil rights organization focused on the LGBT community and people living with HIV. Schoettes was appointed to the advisory council during the Obama administration.

Schoettes said that advisers on the council, known as PACHA, had suspected the president's "lack of understanding or concern" for HIV/AIDS issues during the presidential race, but decided to stick around in hope of making change from within the administration.

On Inauguration Day, however, they noticed that the Office of National AIDS Policy website had been taken down.

"There was no mention of people with HIV anywhere (on the government website)," Schoettes, who is openly HIV-positive, told CNN.

Since becoming president, Trump has not appointed anyone to lead that office, vacant due to the change in administration, said Schoettes.

"This means no one is tasked with regularly bringing salient issues regarding this ongoing public health crisis to the attention of the President and his closest advisers," Schoettes wrote in the op-ed. He said the piece was endorsed by other council members who resigned: Lucy Bradley-Springer, Gina Brown, Dr. Ulysses W. Burley III, Grissel Granados and Dr. Michelle Ogle.

The final straw, he said, came with the House Republicans healthcare plan. The current draft removes protections for people with pre-existing conditions. The bill also rolls back the expansion of Medicaid, which covers over 40% of people who receive care for HIV.

proposed healthcare bill also ends the requirement that Medicaid cover addiction treatment in states that expanded the program, which could put some people at greater risk of HIV, said Beyrer. Injectable drugs can directly transmit HIV, and other drug use has also been associated with HIV risk, according to the Theproposedhealthcare bill also ends the requirement that Medicaid cover addiction treatment in states that expanded the program, which could put some people at greater risk of HIV, said Beyrer. Injectable drugs can directly transmit HIV, and other drug use has also been associated with HIV risk, according to the US Centers for Disease Control and Prevention.

Beyrer described the PACHA resignations as "an important gesture" that reflects the anxieties of many HIV/AIDS advocates.

"This is part of a much larger challenge that we're all facing," he said. "The repeal and replace of the Affordable Care Act is an existential threat to people with HIV in this country."

Talento has met with officials from groups such as CDC's A White House representative told CNN that members of the Domestic Policy Council have met with representatives from HIV/AIDS groups several times, and that one of its members, Katy Talento, was hired as the council's health policy lead.Talento has met with officials from groups such as CDC's National Center for HIV/AIDS and the US President's Emergency Plan for AIDS Relief , or PEPFAR, according to the representative.

The White House representative also said that the PACHA members did not reach out to Talento or the Domestic Policy Council director with their concerns.

Schoettes said that PACHA, which provides its guidance to the secretary of Health and Human Services , was instructed that their communication was not to be sent directly to the White House.

"They really shut down that line of communication," Schoettes said to CNN.

He added, "I don't know about these meetings that have been held internally ... but we certainly were not party to those."

Schoettes expressed concern that Talento "doesn't embrace the actual science around the epidemic," pointing also to her anti-abortion stances. In a 2015 column , she espoused that oral contraceptives cause abortions, which runs counter to scientific consensus.

The White House representative defended Talento's views, saying that being pro-life is consistent with fighting HIV/AIDS.

PACHA was founded in 1995 under the Clinton administration to provide guidance on HIV treatment and prevention. There are 25 seats, of which 21 were filled before Schoettes and his five colleagues stepped down. Now there are 15 members, Schoettes said.

Advocates for HIV/AIDS issues worry that the administration's current direction, including health care reform, could roll back the gains made to curb the epidemic. These losses may hit some harder than others , including LGBT communities, people of color and poor areas in the South.

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"We really cannot afford to be turning back the clock on these communities," said Beyrer.

Schoettes said that the response to the op-ed has been "overwhelmingly positive," and that he and his five colleagues believe that they will be more effective "from the outside" in the fight against HIV/AIDS.

"I want the Republican senators to know that we are ready to engage them on this. We're ready to do that," Schoettes said.