You cut diamonds with diamonds, so why not fight viruses with viruses? A new trial has suggested it might be possible to recruit the less-than-loved pathogens that cause the common cold in our battle against HIV, using them to develop an experimental preventive vaccine.
After stitching parts of HIV into cold viruses and immunizing a group of people, researchers have shown that this approach is not only safe and well-tolerated, but also elicits an immune response that could offer some protection. That unfortunately doesn’t mean we’re anywhere near to creating an effective vaccine for this devastating virus, but it does help us creep towards that ultimate goal.
Various different approaches have been tried and tested in the search for a long-sought-after HIV vaccine, yet frustratingly we’re still empty-handed. One of these is to use a so-called “vector,” basically a carrier vessel, to safely introduce bits of HIV into the body so that an immune response can be mounted against them. A popular choice is to use other, harmless viruses since these can easily be engineered to produce molecules of desire and also quickly disseminate around the body.
A problem scientists have faced with this technique is that our body’s own immunity to these vectors can limit their use. If the body has encountered a delivery vehicle before, which we might expect if a common virus is used, then the immune system may mount a reaction against it and prevent any useful responses from being elicited. A way to get around this is therefore to use a vector that isn’t so common, which is where the present study comes in.
The international team, headed by researchers at Brigham and Women’s Hospital and Harvard Medical School, chose two relatively rare types of cold-causing adenovirus and stitched in genes for one of HIV’s surface molecules, called envelope. This protein is essential for HIV to get inside the cell and, since it’s located on the outside of the particle and thus presented to the immune system, has been the predominant focus for vaccine endeavors.
Model of an adenovirus. Kateryna Kon/Shutterstock
Described in Annals of Internal Medicine, either the experimental jab or a placebo was given to a group of more than 217 healthy individuals in the U.S., East Africa and South Africa. For those receiving the candidate vaccine, at least one dose was given, and those administered two were either given a double dose of one adenovirus/HIV combo or one of each trial vector.
Encouragingly, in all populations tested, the vaccine mounted significant immune responses, and booster shots increased the amount of protective antibodies produced by the body. They were also well-tolerated, with no serious adverse events occurring. Although, some did experience severe but brief reactions.
Another important find was that two doses given within three months were as effective as spreading them out over six months. “That is a big advantage, as more people are likely to complete their vaccination if the doses are closer together, and the immune response, if protective, will start protecting them sooner,” Dr. Susan Buchbinder of the San Francisco Department of Public Health explained in a statement.
While promising, it’s important to note that we don’t know whether the responses would actually be protective, or how long they would last. In addition, the vaccine only targeted one strain of HIV, and thus doesn’t cross-protect against the others. Still, progress is progress.