Recent findings indicate that a two-phase approach to vaccination might hold promise for HIV treatment, where an initial ‘priming’ shot which fires up the immune system is followed by one or more ‘guiding’ shots, which shepherd it to develop a broadly active arsenal against a potential encounter with the virus.
Vaccines work by teaching the immune system what dangerous viruses ‘look’ like; they’re similar to sending out a ‘wanted’ notice for your body, so the defence force can be on the lookout. Frustratingly, HIV is a master of disguise – because it mutates so rapidly, it is always changing how it appears. This is not only a major stumbling block in developing a vaccine, but also in the generation of a natural immune response; HIV simply outfoxes the ability of most individuals to get a lock on the target.
Most – but not all. Some individuals begin to produce antibodies which can somehow get a lock on the virus no matter how many times it mutates. These ‘broadly neutralising antibodies’ (bNAbs) target several sites on the virus that are normally camouflaged. Analysis of these antibodies has shown that they have undergone several rounds of mutation and change – indicating they’ve evolved along with the virus rather than simply being produced in one event.
And, when these antibodies are transferred into HIV- mice and monkeys, they protect against the virus. In fact, bNAb therapy is under consideration as both a form of HIV treatment and prevention in itself.
However, better than transplanting bNAbs would be teaching an immune system how to make them itself, possibly paving the way for a viable HIV vaccine. This is just what this study has done.
In the study – published in Cell – researchers found that giving two shots helped the immune systems of genetically modified mice generate these bNAbs. The first shot involved a very ‘artificial-looking’ strand of material (think of a caricature) to prime the immune system, the second with a more natural looking one (think of a portrait), meant the immune system was guided into making these very powerful bNAbs.
While this all sounds very exciting, work on mice is a long way from work in the clinic, and there are still several unanswered questions. As one of the researchers involved says “while our results suggest sequential immunizations may make it possible to vaccinate against HIV, we have only just begun to understand how this sequence would work; we know the beginning and the end, but we don’t know what should happen in the middle.”
With hopeful results such as these, that might sound like nitpicking, but anyone who has followed advances in HIV treatment will know that findings such as this should be treated with cautious optimism. The recent history of HIV vaccine research has not been very hopeful – maybe this new approach is a sign of changing fortunes.