For years, researchers have tinkered with adenoviruses, which can cause illnesses such as the common cold, using disabled versions of the pathogens to build vehicles for vaccine delivery. And now there’s a new spin from a different species. This week, scientists reported that chimpanzee adenoviruses could be used as the backbone for a vaccine against hepatitis C virus (HCV); the findings, published in Science Translational Medicine, were met with an enthusiastic response. Two teams published back-to-back work; the first group isolated more than two dozen chimp adenoviruses from thousands of the animals’ stool samples and identified the one that induced the biggest response in two types of T-cells in the immune systems of mice and non-human primates, making it a potential tool for vaccination against HCV. The second tested that viral vector in a phase 1 clinical trial and saw that healthy people showed an immune response comparable to that produced by a human adenoviral vector vaccine.

Paul Klenerman, an immunologist at Oxford University in the UK, was a member of the second group and says the team was excited to see an increased immune response from two classes of T-cells “that was at least as strong as what we see in people who clear HCV naturally.”

Virologists have proposed potential chimp adenovirus vaccines for everything from malaria to HIV to cancer. Klenerman says they offer an excellent alternative to human adenoviruses, to which we may have pre-existing immunity that could potentially disable the vaccines based on them. He’s not the only one to raise that possibility—ever since the still-unsolved failure of the STEP HIV vaccine trial, which tested a human adenovirus-based HIV vaccine, immunologists have puzzled over pre-existing immunity.

But is it time to go bananas over chimp adenoviruses? The bigger picture is that immunologists are not in lockstep when it comes to the effects of pre-existing immunity on adenovirus-based vaccines. Michael Betts, an immunologist at the University of Pennsylvania in Philadelphia, was one of the authors of one of two studies published in Nature Medicine in 2009 that provided evidence against pre-existing immunity as the cause of the STEP trial meltdown. He says that ultimately the question of viral immunity in vaccines is still a black box: “Without knowing more about immunity, it’s hard to say that chimp adenoviruses are likely to be any better than any other adenoviruses.” And although the preliminary results published this week are positive, they are far from conclusive; a second trial to test the protective ability of the vaccine is currently underway. With some luck, this field of research should shed light on whether chimp vectors mean more than just swinging from the trees.

Image by Steve Snodgrass via Wiki Creative Commons