Robert C. Gallo*
The Early Years of HIV/AIDS
Animal retroviruses were among the earliest viruses discovered, and by the 1960s some were shown to cause cancer. These findings prompted the formation of the U.S. Virus Cancer Program, which aimed to identify human tumor viruses, especially human retroviruses. By the late 1970s, however, a mistaken consensus emerged that viruses did not cause human cancer and that human retroviruses did not exist, leading to termination of the program. Even more perplexing was the assertion that serious epidemic diseases were limited to the "Third World," culminating in the closure of certain U.S. medical school microbiology departments and a disturbing lack of support for the U.S. Centers for Disease Control and Prevention (CDC). In the midst of this complacency, my co-workers and I made human retroviruses one of our primary research objectives. We were interested in leukemia and began to characterize the DNA polymerases in blood cells (1, 2). Howard Temin had proposed that retroviruses replicate through an integrated DNA intermediate, a notion supported by his discovery with David Baltimore of a retroviral reverse transcriptase (RT).
This discovery provided me with an entry point into the field because RT is a DNA polymerase. We developed sensitive assays to detect RT in order to search for retroviruses at low levels in cell supernatants, membrane preparations, and long-term cell cultures. In 1972, we reported purification of an RT from human lymphocytic leukemia cells. We realized that to detect the human retrovirus producing the RT, we would need to culture human blood cells for long periods and in greater numbers than possible with the available system of colony growth on agar. So, we began to analyze conditioned medium from various cell types, including activated T cells, for the presence of growth factors. We found a growth factor that promoted myeloid cell growth, enabling establishment of HL-60, the first human granulocytic cell line. Next, with Doris Morgan, our group discovered interleukin-2 (IL-2), which we called T cell growth (mitogenic) factor (3-5). This enabled my colleagues and I together with my postdoctoral fellow Bernard Poiesz to isolate the first human retrovirus, human T cell leukemia virus-1 (HTLV-1), in 1979 from a patient with a T cell malignancy (6-8). Independent work the following year from several Japanese groups further documented that HTLV-1 caused a very specific adult T cell leukemia endemic to Japan. HTLV-1 targets CD4+ T cells; it is transmitted from mother to child, and through blood and sexual contact (9-11). This human retrovirus is prevalent in parts of Africa, is closely related to Old World primate leukemia viruses, and causes minor immune impairment. In 1982, we reported the isolation of the second human retrovirus, HTLV-2, from a case of hairy cell leukemia of the T cell type (12). The characteristics of HTLV-1 and HTLV-2 foreshadowed the discovery of an even more sinister human retrovirus.
I first heard about AIDS in 1981 from newspaper reports but more informatively from lectures given by Jim Curran of the CDC, who challenged the audience, asking "where are the virologists?" Theories of the cause of AIDS abounded, but Curran was already thinking of an infectious etiology, most likely a new virus (13). Max Essex reminded us that the feline leukemia retrovirus not only causes leukemia, but that its variants could also cause immune disorders. We knew that the risks for HTLV-1 infection included blood exposure, sexual contact, and birth to a mother with the disease, and also that HTLV-1 targeted CD4+ T cells. The same risk factors were described for AIDS, and combined with clinical evidence that CD4+ T cells were abnormal in AIDS patients and epidemiological hints that AIDS may have originated in equatorial Africa, this led us to propose that AIDS might be caused by a new retrovirus of the HTLV family. In May 1982, using protocols similar to those for isolating HTLV-1, we tested blood cells from AIDS patients for cross-reactivity with HTLV proteins and for HTLV-like DNA sequences. But by early 1983, we had found HTLV-related DNA sequences in only 2 of 33 AIDS patients and had obtained virus isolates with equal infrequency.
It was in 1973 that I first met Luc Montagnier of the Pasteur Institute (14). In January 1983, Montagnier and his colleague Jean-Claude Chermann were beginning to study blood cell cultures from patients with suspected AIDS. They told me of their first positive result: the culturing of a virus from the peripheral blood cells of a patient with lymphadenopathy. They were able to identify the virus as a new human retrovirus, but were unable to characterize it in detail. Essex and I suggested to Montagnier and Chermann that we submit our findings jointly, and three reports from the two groups were published in May 1983. Montagnier and Chermann had not named the virus, but later called it LAV (lymphadenopathy-associated virus, isolated from patient BRU).
There was still another "curve ball" to come. In February 1983, a clinician (Jacques Leibowitch) arrived from Paris with cell samples from AIDS patients. One of these samples came from a man (CC) who had received blood transfusions in Haiti. My co-worker Mika Popovic succeeded in growing CD4+ T cells from the sample. These T cells were highly positive for RT, and electron microscopy revealed that they contained two viral forms, which we called "mature" and "aberrant," believing that they were from the same virus. The virus from these T cells cross-reacted with antibodies to HTLV core proteins, yet unlike HTLV, it killed target T cells. Using more sophisticated methods, we quickly discovered that these T cells contained two distinct retroviruses: HTLV-1 and the aberrant form, later defined as HIV. We had assumed that we could only find HTLV-like viruses in 5 to 10% of our AIDS patients because our assays were not sensitive enough, and had not considered the possibility that our HTLV-positive cells were in fact infected with two separate retroviruses.
In our May 1983 paper, we had not separated and adequately cultured a retrovirus that was free of HTLV. Thus, the paper by the Montagnier/Chermann group is unequivocally the first reported true isolation of HIV from a patient with lymphadenopathy. However, the cause of AIDS was still unknown. By the summer of 1983, our group had obtained evidence for a retrovirus related to HTLV in many patients with AIDS and pre-AIDS. With a more detailed molecular analysis of the virus from patient CC, we concluded that the HTLV-positive results in samples from 5 to 10% of AIDS patients were due to a double infection with HTLV and a new human retrovirus. Moreover, the early 1983 experience with sample CC proved that the new retrovirus could be grown in continuous culture (something that Montagnier and Chermann believed impossible because, even to this day, their LAV/BRU virus cannot be cultured).
In late 1983, Popovic and my technician Betsy Reed-Connole had a second breakthrough: They grew several viral isolates in CD4+ T cells in continuous culture. Several of these viral isolates--RF (1983), IIIB (1983), and MN (early 1984)--became standard tools for AIDS researchers and crucially enabled development of a blood test. In March 1984, we submitted four papers to Science (15) and shortly thereafter one to Lancet (16). In these papers, we described isolates of the new retrovirus, methods for its continuous production, analyses of its proteins, and evidence that it was the cause of AIDS. The rapid development of a blood test not only safeguarded the blood supply, but also allowed public health officials to follow the course of the disease in infected individuals before they developed full-blown AIDS. The blood test also yielded a grim vision of the future--although sera from hemophiliacs in Japan all tested negative in early 1984, by the end of that year, 20% of the sera were positive for HIV because the hemophiliacs had been treated with HIV-tainted blood products from the United States.
We visited Montagnier in Paris and gave him our cell line continuously producing HIV (called HTLV-IIIB/H9), so that he could compare it with his LAV/BRU isolate. We agreed to a joint press conference if our IIIB retrovirus turned out to be the same as their LAV/BRU isolate. However, a leak from a freelance journalist prompted Margaret Heckler, secretary of the U.S. Department of Health and Human Services (DHSS), to call an urgent press conference to which I was summoned home to attend, and from which, very regrettably, the French group was excluded.
The scientific achievements were overshadowed by a dispute between the United States and France over the patent rights to the blood test, and a temporary disagreement among the scientists. Although patents were not common at the National Institutes of Health back then, we were instructed by DHHS officials to patent the blood test so that pharmaceutical companies would be able to rapidly deploy the test worldwide. Because it grew so well in T cell lines, we selected the IIIB isolate to develop the blood test. The dispute over the origin of this isolate became sensationalized. In fact, our IIIB isolate was accidentally contaminated with a sample sent to us by Montagnier. This HIV strain (IIIB/LAI) later contaminated the cultures of several other laboratories (17).
Years later, we learnt that the same HIV strain had earlier contaminated viral isolates of the French group. Montagnier and Chermann did not realize that virus from a patient called LAI had contaminated their LAV/BRU isolate. Although Montagnier believed he was sending LAV/BRU to us--and so did we--one culture consisted predominantly of LAI. The properties of LAI are very different from those of LAV/BRU, which does not grow in cell lines. Compounding the complexity, although IIIB was clearly derived from LAI, it is not identical with LAI, but rather is a variant that grows vigorously because of mutations in some of its regulatory genes. All of this was acknowledged by our group and the French group in 1991 (18) (see the Viewpoint by Montagnier, on page 1727).
The period after the May 1984 publication of our papers was marked by rapid advances (15, 19). The HIV-1 genome was sequenced, HIV antigenic variation was discovered, the virus was found in the brain of AIDS patients, genomic sequence variation was found in viral populations from the same patient, macrophages were found to be targets for HIV, various modes of HIV transmission were elucidated, all of HIV's genes and most of its proteins were defined, and the blood supply in most developed nations was rendered safe as a result of screening for HIV. Next, came identification of the HIV receptor (CD4), the discovery of SIV in chimps, and the development of the first anti-HIV drug, AZT.
The late Jonathan Mann heralded the years 1982 to 1985 as a period of intense discovery, noting that the pace of research was the fastest in medical history. For some scientists, these were also years of disquiet and frustration; years in which we would encounter in an unprecedented manner the negative face of politics, the media, patient activists, and legal issues. For myself and others trained in science and disciplined by the rigor and analysis that are the essence of scientific endeavor, the rough and tumble of the outside world provided harsh and bitter lessons. In retrospect, it is clear that these lessons needed to be learnt, and I can say we are better for the experience. But our job is far from over, and it is up to the scientists to ensure eradication of the AIDS epidemic that continues to rage in many regions of the world.
References and Notes
- M. G. Sarngadharan, M. Robert-Guroff, R. C. Gallo, Biochim. Biophys. Acta 516, 419 (1978). [Medline]
- M. G. Sarnagadharan, P. S. Sarin, M. S. Reitz, R. C. Gallo, Nature New Biol. 240, 67 (1972). [Medline]
- S. Z. Salahuddin, P. D. Markham, F. W. Ruscetti, R. C. Gallo, Blood 58, 931 (1981). [Medline]
- S. J. Collins, R. C. Gallo. R. E. Gallagher, Nature 270, 347 (1977). [Medline]
- D. A. Morgan, F. W. Ruscetti, R. C. Gallo, Science 193, 1007 (1976). [Medline]
- F. W. Ruscetti, D. A. Morgan, R. C. Gallo, J. Immunol. 119, 131 (1977). [Medline]
- J. W. Mier, R. C. Gallo, Proc. Natl. Acad. Sci. U.S.A. 77, 6134 (1980). [Medline]
- F. Wong-Staal, R. C. Gallo, Nature 317, 395 (1985). [Medline]
- R. C. Gallo, J. Hum. Virol. 3, 1 (2000). [Medline]
- ------, Nature Med. 1, 753 (1995). [Medline]
- M. Yoshida, Annu. Rev. Immunol. 19, 475 (2001). [Medline]
- V. S. Kalyanaraman et al., Science 218, 571 (1982). [Medline]
- R. C. Gallo, Virus Hunting AIDS, Cancer and the Human Retrovirus: A Story of Scientific Discovery (Basic Books, New York, 1991).
- J. C. Chermann, J. Hum. Virol. 4, 289 (2001). [Medline]
- R. Kulstad, Ed., AIDS: Papers from Science, 1982-1985 (AAAS, Washington, DC, 1986).
- B. Safai et al., Lancet 1, 1438 (1984). [Medline]
- Repetitions of IIIB/LA1 contamination occurred in Robin Weiss's laboratory in London, at the Frederick National Cancer Institute laboratories, at Duke University, and very likely in several other laboratories, as well as the original contamination in France.
- S. Wain-Hobson et al., Science 252, 961 (1991). [Medline]
- R. C. Gallo, Immunol. Rev. 185, 236 (2002). [Medline]
The author is at the Institute of Human Virology and Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201, USA.
Issue of 29 Nov 2002,
Copyright © 2002 by The American Association for the Advancement of Science. All rights reserved.