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  • Researchers are using Moderna’s mRNA vaccine technology to target HIV.
  • The eventual goal is to stimulate the immune system to produce broadly neutralizing antibodies that target multiple HIV strains.
  • Over the past few decades, finding a safe and effective vaccine to prevent HIV infection has proven to be very challenging.

An early stage clinical trial of an mRNA-based HIV vaccine could begin this month, according to the U.S. National Library of Medicine clinical trial registry.

This vaccine candidate uses technology developed by biotech company Moderna — the same technology used for its highly effective COVID-19 vaccine.

The trial, which builds on earlier research by the International AIDS Vaccine Initiative and Scripps Research, would test the first stage of a multistep vaccine regimen.

The eventual goal is to stimulate the immune system to produce broadly neutralizing antibodies that target multiple HIV strains.

Additional clinical trials will be needed before a vaccine capable of preventing HIV infection is available.

Many people are familiar with the coronavirus spike protein: mRNA vaccines train the immune system to produce antibodies that target the spike protein and prevent the virus from infecting cells.

HIV also has a spike-shaped virus protein known as Env, or the envelope protein. The shape of this protein varies among different strains of the virus, making it harder to target with antibodies.

“Antibodies against one virus — against one HIV spike — will not block another HIV spike,” William Schief, PhD, a professor and immunologist at Scripps Research, said in a YouTube video released by Scripps.

“We have to elicit antibodies that bind to specific patches on the spike that don’t change very much,” he said.

In the early 1990s, scientists first isolated broadly neutralizing antibodies that target these non-changing, or conserved, areas of the HIV envelope protein. Additional antibodies have been identified since then.

However, going from vaccine to broadly neutralizing antibodies requires multiple steps.

Schief and his colleagues at Scripps and the International AIDS Vaccine Initiative developed a candidate vaccine that stimulates the immune system to produce precursor cells needed to start this process.

Results released earlier this year from a phase 1 clinical trial showed that 97 percent of participants who received the vaccine showed the desired immune response.

This “priming step” is the first of several that researchers hope will lead to broadly neutralizing antibodies against HIV.

The immune cells generated during this initial trial in response to the candidate vaccine “don’t know how to neutralize HIV yet,” Schief said in the YouTube video, “and we didn’t expect that they would.”

“But we have studied them, and now we have a good idea for what our second shot should look like.”

The International AIDS Vaccine Initiative and Scripps have partnered with Moderna to test an mRNA-based vaccine version of this approach.

Messenger RNA, or mRNA, contains a blueprint for making a specific protein. MRNA vaccines deliver these instructions to the cells, which then produce the protein.

In the phase 1 trial using Moderna’s technology, the mRNA vaccine will carry the instructions for a protein that stimulates the immune system in the same way as the earlier Scripps and International AIDS Vaccine Initiative trial.

This trial will enroll 56 healthy people without HIV, and will test two versions of the vaccine candidate.

Two groups of people will receive a mix of the two vaccine candidates, and the other two groups will receive one or the other.

Researchers will look to see whether the vaccine generates the desired immune response — the immune precursors cells — and whether there are any safety concerns.

This is only the first of several clinical trials, so it will take some time before scientists know whether this approach can prevent HIV infection.

However, many people will be watching closely to see whether the mRNA technology does for HIV what it did for COVID-19.

“If nothing else, I hope that we’re able to leverage the lessons learned from the COVID-19 trials for developing a safe and effective HIV vaccine,” said Anthony J. Santella, DrPH, a public health researcher at the University of New Haven.

Although the mRNA technology looks promising, over the past few decades, finding a safe and effective vaccine to prevent HIV infection has proven to be very challenging.

The latest blow comes from a clinical trial of an HIV vaccine that uses the same technology as Johnson & Johnson’s COVID-19 adenovirus (Ad26) vaccine.

The study, known as Imbokodo, enrolled around 2,600 women in southern Africa at high risk of HIV infection.

Results released this week show that the vaccine only had an efficacy of 25 percent, well below the 50 percent goal.

“Despite the use of the Ad26 technology, which is effective for COVID-19, the Imbokodo study illustrates that HIV is a virus that requires a higher degree of immune response to achieve effective protection,” Dr. Larry Corey, a virologist at the Fred Hutchinson Cancer Research Center and lead investigator on the study, said in a news release.

A second HIV vaccine trial that’s testing a different vaccine regimen in a different population will continue.

Carl Schmid, executive director of the HIV+Hepatitis Policy Institute, cautions that even if a potential HIV vaccine candidate is identified soon, it will take time to test it in clinical trials and roll it out to the world.

“In the meantime, we can prevent additional [HIV] transmission and infections through testing and treatment,” he said, “and now people can protect themselves through PrEP [pre-exposure prophylaxis].”

Around 37 million people in the world are living with HIV. In 2020, 1.5 million people contracted HIV, according to UNAIDS.

In addition to the mRNA vaccine technology, Santella sees other lessons for the HIV community coming from the COVID-19 pandemic.

“We saw firsthand [with COVID-19] what can be accomplished when local, state, and federal government officials and policymakers want to prioritize something,” he said.

“So I expect the HIV community will now use our COVID experience to put those who are in positions of power and privilege on standby, and demand the same efforts to end the HIV epidemic.”