The Department of Justice has launched a review of a government patent for use of a drug that prevents HIV infection, according to a retired Centers for Disease Control scientist who was among scientists who spoke with a department lawyer last week.

Thomas Folks said a Justice Department lawyer visited the CDC in Atlanta on April 16 to question government scientists who pioneered the use of the drug Truvada for prevention.

Folks, who retired from the CDC in 2007, participated in one of the meetings via telephone and helped explain the scientific discoveries his government team made 15 years ago.

The meetings are the first indications the government is considering action against Truvada’s manufacturer, Gilead, which contends the government’s 2015 patent is invalid and has publicly rebuffed requests for royalty payments.

The government has declined to take the rare next step and sue for patent infringement, The Washington Post reported last month.

The lack of action has enraged HIV activists,with some protesters hecklingthe CDC director at a meeting in Virginia on April 1. It also has attracted attention on Capitol Hill. Sen. Debbie Stabenow (D-Mich.) led a small group of senators this week in writing to Health and Human Services Secretary Alex Azar, citing The Post article. The senators said taxpayers should be able to recoup public investments and help make vital drugs more affordable.

“The government should also be willing to enforce its patents and take legal action against companies that appear to be infringing on their patents,’’ the senators wrote, “to prevent multinational companies from reaping billions of dollars in profits without properly compensating the government for its investments.’’

Truvada for PrEP, as the prevention use of the drug is known, is expected to form the backbone of President Trump’s promised plan to eradicate HIV by 2030. But the drug costs $1,600 to $2,000 a month, which patient advocates say makes it prohibitively expensive. The drug is distributed for as little as $6.50 a month in Africa, according to researchers.

During the previously undisclosed meeting at CDC on April 16, the Justice Department lawyer was gathering facts about the strength of the government patent but stopped well short of saying the government planned to sue Gilead, said Folks, who ran a CDC monkey research lab and lives in Texas. Folks confirmed the meeting took place after being contacted by The Post.

“I hope they get some good Department of Justice lawyers who can help them and come in and give them some teeth,’’ Folks said of the CDC.

Folks said he believed the Justice Department lawyer leading the meeting was Walter W. Brown, an intellectual property attorney in the commercial litigation division.

Brown did not respond to a request for comment. He forwarded an email from The Post to the Department of Justice media team, which declined to comment.

Launching a DOJ review — with its potential to lead to a patent infringement suit — could merely be intended to give officials greater leverage in ongoing negotiations with Gilead about cutting Truvada for PrEP prices and making the treatment more widely available. The Department of Health and Human Services would not comment but pointed to recent public statements by top department officials.

“The royalties that would be owed to the department would take years in the making to get to the department’’ in a patent infringement lawsuit, said Admiral Brett P. Giroir, assistant secretary of health and human services, speaking at an event Monday sponsored by the Kaiser Family Foundation. “It wouldn’t really make a difference on the pricing. We’re really going down different avenues to make sure the pricing is lower moving forward. Those negotiations are ongoing.’’

Azar cited those negotiations in an interview with NPR earlier this month — the first high-level confirmation of negotiations with Gilead.

In an emailed statement, Gilead said there were no ongoing negotiations with HHS about the patents owned by the government.

“We are in discussions with the government to determine the best ways to broaden access to Truvada for PrEP to vulnerable populations in the United States and support the federal plan to end the HIV epidemic.’’

HIV activists under the banner PrEP4All Collaboration spent months last year digging into the government’s patent for the development of Truvada for HIV prevention. The group has demanded input into CDC deliberations about how to distribute HIV prevention drugs more widely.

“It is completely unacceptable that CDC and HHS continue to go through this process with zero input by the communities most impacted by HIV,’’ said James Krellenstein, a co-founder of the group. “There has been no public transparency into this process at all.’’

Gilead’s Truvada was approved in 2004 as HIV treatment for people who already had contracted the virus. Gilead supplied the drugs given by CDC scientists to CDC monkeys to test whether it worked for prevention. Gilead then won FDA approval in 2012 to market the drug for that additional use.

Folks, the retired CDC scientist, said the DOJ lawyer who visited Atlanta last week asked CDC officials involved in development of Truvada for PrEP how they came up with ways to test the treatment in monkeys. The CDC’s novel idea was to repeatedly infect the monkeys with a relatively small amount of HIV, an level that would mimic the volume of virus in semen, to prove the drug would work for prevention, Folks said. Earlier experiments had used excessively large volumes of virus, he said.

“We developed the model,’’ he said. “Without the model, you might not have found this.’’