Hopes raised for HIV vaccineBMJ 1997; 314 doi: https://doi.org/10.1136/bmj.314.7091.1365i (Published 10 May 1997) Cite this as: BMJ 1997;314:1365
American scientists have blocked the transmission of HIV-1 in chimpanzees with a new vaccine based on DNA. It is the first time anyone has managed to protect against HIV infection in the chimpanzee, the closest relative to humans in terms of immunological responses.
The research team concludes that at the very least their study shows that their DNA vaccine is capable of “interrupting the establishment of persistent infection,” describing it as an “unprecedented” effect (Nature Medicine 1997;3:526-32).
The researchers developed their vaccine from the genes of a weakened virus, rather than the proteins produces by those genes. They then immunised three chimpanzees with the vaccines, while a fourth animal was used as a control. Two immunised chimpanzees and the control were then challenged with 250 times the HIV needed to cause infection and followed up for 48 weeks.
Two tests were used to assess whether the virus was duplicating. A test that could detect 500 copies of the virus in 1 ml of blood was negative for both the immunised animals while the chimpanzee that had not been immunised was found to have 10000 virus copies per millilitre. A second test showed that the control animal became infected within two weeks of challenge and remained HIV positive for the remainder of the study. The chimpanzees that had been immunised had a small amount of the virus for a short time (at week 6 and week 8), but that disappeared and could not be detected again.
Jonathan Weber, professor of communicable diseases at Imperial College School of Medicine in London, said that to be able to produce a vaccine that produces a cellular and immune response (as in this case) was important to protect against HIV infection. “This is quite an important step forward, but it is a long way from a vaccine for everyday use,” he added.
Previous vaccines against HIV that have been shown in chimpanzees to produce an immune response have so far been unable to elicit a powerful enough response in humans to prevent infection, explained Professor Weber. The next step is to test the DNA vaccine in healthy volunteers. Human studies to test the safety of DNA vaccines have already begun in HIV positive volunteers.
Dr Ron Kennedy, from the University of Oklahoma Health Sciences Center and a veteran of research into HIV vaccines, writes in an accompanying editorial: “Perhaps my level of overt pessimism as it relates to developing a successful HIV-1 vaccine for use in humans could be raised to guarded optimism.”