This is the sixth and final post in The Scope blog series “HIV: A Scientific Discovery,” a collection of pieces that explore the major scientific milestones in the discovery of the HIV virus.
Luc Montagnier’s laboratory at The Pasteur Institute immediately began efforts to identify and characterize their newly discovered virus, which they named the Lymphadenopathy-Associated Virus (LAV). To study the virus, however, they needed more of it. Much more. They had to find a way to grow the virus and replicate it in cell culture, a task that proved to be stubbornly difficult for the particular strain they had isolated.
An ocean away, Robert Gallo’s group at the National Cancer Institute was facing a different problem: HTLV was still the only retrovirus they could find in AIDS patients. If Gallo couldn’t find the French virus in his own patients, perhaps Montagnier had been mistaken – the new virus Montagnier had found might not be the AIDS virus after all. Furthermore, as the man who had discovered HTLV, the only known retrovirus at that time, Gallo was convinced that the AIDS virus was simply a newly mutated form of HTLV.
Gallo found two forms of HTLV in his patients’ T cells which he interpreted as different stages of the HTLV virus’ development. He called these the “mature” and “aberrant” forms of HTLV. In order to characterize the differences between the two forms, Gallo placed the two forms into separate cultures and allowed them to infect T cells.
The results shocked him. The mature form infected T cells with the expected outcome of HTLV infections: the cells became cancerous and rapidly outgrew the culture. The aberrant form, however, produced the opposite effect: it killed off the cells, leading to diminished cell numbers. The two populations were not merely different forms of a virus; they were different viruses altogether.
The new virus nevertheless did exhibit features very similar to the previously discovered HTLV-I and HTLV-II viruses, so Gallo named it HTLV-III. Favored by slightly more luck than Montagnier, Gallo had no difficulty growing this viral isolate in culture. When he mixed the virus with blood samples from AIDS patients, antibodies against the virus were present in 90% of patients, including those at early stages of the disease. The Pasteur group announced a similar detection rate for the LAV virus. If there was truly a virus responsible for the AIDS epidemic, they had found it.
But which virus was it – LAV or HTLV-III? Close examination of the two virus’ structures by electron microscopy showed that the two viruses were nearly identical physically. Additionally, antibodies bound to the same proteins on both viruses, giving further credence to their equivalence. Montagnier and Gallo agreed that they had discovered the same virus and named it the Human Immunodeficiency Virus (HIV).
There was no doubt that the HIV virus was the root cause of AIDS. The virus was the first virus that could be detected in nearly all AIDS patients sampled, it was a retrovirus as virologists had predicted, and it preferentially killed T cells, thus offering a clear explanation for the immune deficiency that was the disease’s hallmark.
With identification of the virus also came a way of finding it. After the discovery was made in the summer of 1984, health officials tested the entire American blood bank for the presence of HIV, and the blood supply was shortly thereafter cleared of the virus. By then, nearly 50 people had acquired the virus from infected blood transfusions. They were among the 4000 people who had by then been infected with HIV, nearly half of whom had died.
In the following months, HIV research boomed. The genetic sequence of the virus was determined, its key proteins were identified, and its modes of transmission and pathogenesis were pinned down. For the next three decades, scientists piece by piece unveiled the basic function of the virus and crafted varying strategies to limit HIV’s spread and to bring about its utter elimination.
Significant progress has been made in HIV research and treatment in the 30 years since the discovery of the virus. A disease that initially boasted a mortality rate of nearly 50 percent now claims only 3 percent of its victims. Nevertheless, in the same time span that science has been honing its counterattack, the virus has spread across the globe to the point that, at this moment, nearly 37 million people live with HIV. One million of these people die every year.
As we continue the scientific fight against HIV, it is with no doubt important to look back on the stories of scientific discovery that launched the fight in the first place, and to remember that these discoveries are indeed stories. They are not isolated mile markers along the trajectory of scientific progress, but rather stretches of road that are neither straight nor without their branches. It would do us well to remember this as we await the breakthroughs that are still yet to come in the war on AIDS.
Kevin Wang is a junior in Ezra Stiles College. Contact him at firstname.lastname@example.org. Follow Kevin on Twitter at @kkwang23.
(Featured Image courtesy of the National Institute of Allergy and Infectious Diseases.)