The prospect of a vaccine that could prevent new HIV infections is now possible, thanks to developments in antiretroviral medications that were first created in the mid-1980s and improved over the years by researchers working with animal models. Today, May 18, marks the NIH-sponsored HIV Vaccine Awareness Day, an annual observance that recognizes efforts to reach this milestone in the treatment of a condition that was, in our not-too-distant past, little understood and widely feared.

The first antiretroviral, AZT, hit the market in 1986, a year in which an HIV diagnosis was still considered a death sentence—and a source of widespread panic and consternation. “Well, everybody is worried about everybody now,” Susan Sontag wrote in a seminal short story published in the New Yorker that same year. “That seems to be the way we live, the way we live now.”

Clinical trials of AZT showed dramatically increased life expectancy in human patients, a breakthrough that forever changed the virus’s prognosis, and with that, our understanding of what it means to live with HIV. The drug was developed by researchers who first sought to understand the mechanism by which the retrovirus works. In studies with monkeys, they identified a related virus called SHIV, concluding that both are lentiviruses, which are characterized by their long incubation periods followed by chronic, deadly diseases (in human patients, AIDS-related complications after patients reach the late stages of HIV infection).

Pioneering research with monkeys and mice, to which the development of AZT is credited, has paved the way for the combination therapies that are prescribed today. Thanks to these drugs, people living with HIV can now generally expect to lead happy, healthy lives well into late adulthood. This would not have been possible without the knowledge gained by the research community from studies with animal models, which provided the basis for understanding how the disease is transmitted and how it progresses.

The prognosis of HIV has improved dramatically, however, HIV/AIDS remains a global pandemic that has claimed a staggering 39 million lives between its discovery and 2014. HIV-positive patients in the United States still have an average life expectancy that lags 13 years behind those who are HIV-negative. Its impact is felt in the public health sphere, as an illness that infected an estimated 37,600 Americans in 2014, and in reverberative waves of economic hardship and discrimination, or stigma, that are witnessed around the world.

In recent years, the world has witnessed progress above and beyond the existing therapies used to treat people living with HIV. Beginning in 2014, populations who are HIV-negative but have substantial risk of contracting HIV may take a daily antiviral drug, which has been shown to reduce the risk of infection by up to 92%. The regimen, pre-exposure prophylaxis (PReP), is a powerful tool in the fight against HIV/AIDS. These drugs and promising new therapies were made possible by mouse and non-human primate models, which enabled researchers to conduct preclinical testing and develop pharmaceuticals that prevent HIV from incorporating its genetic material into the host’s genome.

Generally, within three weeks of exposure to HIV, patients will develop antibodies that become detectable. This process, called seroconversion, can be stopped with a post-exposure prophylaxis (PEP) treatment regimen shortly after the patient’s exposure, or possible exposure, to HIV. With PEP, people who have engaged in high-risk behaviors can stay HIV-negative, even if the virus has entered their bloodstream. Before studies were conducted with primates, researchers believed that antiviral treatment of newly infected patients who did not display symptoms was both risky and ineffectual.

The use of antiviral medications to prevent seroconversion and infection with HIV has equipped patients and healthcare providers with new ways to fight HIV/AIDS, but this is not enough. A safe and effective vaccine is widely acknowledged as the only means to stem the pandemic.

Cases of measles, mumps, rubella, and chickenpox have declined sharply, often by more than 90%, thanks to lifesaving vaccines that are attenuated (or “live”). An important step in the curation of a viable vaccine against HIV included a study with primates, in which it was determined that an attenuated strain of SHIV caused AIDS in the research subjects. Without this information, scientists would not have understood the need for additional safeguards, and clinical trials on humans may have ended disastrously.

This year, we can expect the second phase of human clinical trials for SAV001, a vaccine that is safe, well tolerated, and effective in generating anti-HIV immune response in HIV-positive patients. SAV001 is a killed (inactivated) whole HIV-1, marking a significant departure from previous HIV vaccine attempts that used live strains of the virus. The efficacy of this method was first demonstrated in studies with non-human primate models. “If we can show that this vaccine is effective in preventing people from contracting HIV, we can stop the AIDS epidemic,” said Chil-Young Kang, who presides over the research team that developed and tested the vaccine.

As researchers close in on a cure for the global HIV/AIDS pandemic, and as we honor those efforts on HIV Vaccine Awareness Day, it’s important to also remember that research with animals has enabled both the tremendous strides that have been made and the milestone that now seems within our grasp. It is to this that we owe “the way we live now,” looking toward a future without HIV/AIDS, free from the crippling fear and anxiety that gripped those who lived through the pandemic’s early days.

Learn more about The Critical Role of Nonhuman Primates in Medical Research.

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