More than 30 years have passed since the human immunodeficiency virus (HIV) was identified, and yet we still do not have an effective vaccine to prevent its spread. And, although in countries like ours AIDS seems like a disease of the past, we must not forget that, according to the World Health Organization, HIV continues to be one of the biggest health problems worldwide, having already claimed more than 35 millions of lives.
Why is it so difficult to find an effective vaccine? HIV has a great capacity to mutate rapidly, in addition to being able to ‘camouflage’ itself in the body and remain inactive to reactivate years later. As a result: we are fighting a very elusive virus that comes in many different forms, and we also need a vaccine that is effective in the long term.
The latest data have been published in The Lancet journal and show the results of phase 1 / 2a (administration to healthy volunteers and early administration to patients) of a vaccine against the HIV-1 virus, which causes the majority of infections, which it uses an adenovirus serotype 26 (Ad26) as a vector. Adenoviruses are a family of viruses that are very frequently used to carry genes, in this case genes that encode antigens against HIV. In short, a kind of molecular Trojan horses that carry parts of different types of HIV to provoke an immune response against different strains of virus from all over the world.
The work shows the results of two parallel trials: the first in 393 healthy, low-risk adults from East Africa, South Africa, Thailand and the United States. Volunteers received either the placebo or one of the different vaccine combinations. In this phase of the clinical trial, the most important thing is to make sure that the vaccine is safe and does not cause adverse reactions. In this case, only five people (1% of the sample) experienced any discomfort: abdominal pain and diarrhea, dizziness, back pain and general malaise.
Promising but not definitive results
According to Dan Barouch, a professor at Harvard Medical School and leader of the research, in statements to the AFP agency, “the vaccine induced robust immune responses in the participants.” More significant are the results of the second study, carried out in rhesus monkeys ( Macaca mulatta ) that were subsequently inoculated with a virus similar to HIV: the vaccine offered total protection against infection in two thirds of the 72 individuals in which it was tested.
The results are promising, but preliminary. The next step is to see what happens on a large scale when the virus attacks people potentially immunized with the vaccine. This is what will be verified in phase 2b of the clinical trial, which has already begun. It is testing the effectiveness of the vaccine in 2,600 southern African women at risk of HIV infection, and results are expected in 2021 or 2022. “The fact that the vaccine protects two-thirds of monkeys in a laboratory test it does not mean that it protects humans, and therefore we must wait for the results of the next phase before knowing whether or not it will protect humans against HIV infection ”, Barouch warned.
If anything, the new research is encouraging, and we hope that the AIDS vaccine is finally getting closer.
Referencia: Barouch et al. 2018. Evaluation of a mosaic HIV-1 vaccine in a multicentre, randomised, double-blind, placebo-controlled, phase 1/2a clinical trial (APPROACH) and in rhesus monkeys (NHP 13-19) The Lancet, https://doi.org/10.1016/S0140-6736(18)31364-3
