Saturday, November 29, 2014

GSK's Candidate For Ebola Immunization May Not Be Durable -- Protection May Not Last Beyond 10 Months

Again, still only from a very small 20 person Phase I safety trial, here -- but the NIH/GSK candidate may not be particularly durable, according to a British virologist familiar with the early results. And durability will be important, in Africa.

From CNN, then, this morning:

. . . .Professor Andrew Easton, a leading virologist at Britain's Warwick University, told CNN that the trial was an "essential first step" toward a vaccine to prevent Ebola and justifies some optimism.

However, there are still some unanswered questions, he said.

"We know from some of the preliminary work that went on in animal studies previously that the antibodies that are generated in response to the [GSK/NIH Candidate] vaccine don't last as long as we would like -- there was a clear reduction over a fairly long period of time, about 10 months," he said.

"So it's possible that that might be a problem in humans, but the reality is we won't know until it's actually been tested in humans. . . .

We will keep you posted, here. Still cause for optimism with three potential paths to immunization. Therapeutic hot stone massage, and workout time!

1 comment:

Birdman said...

I do not believe that durability of the immune response is a critical issue during the outbreak and for curtailing the outbreak. The durability must be moderate...perhaps 6-10 months. Ten months was achieved with the ChAd3-EBOL vaccine which was boosted with MVA-EBOL. Durability IS an issue in populations which are exposed to endemic ebola virus after the outbreak has been stopped. To stop the outbreak one needs a single dose vaccine that generates fast, high level immune responses against ebola. The vaccine would also optimally NOT generate signs or symptoms commonly associated with EVD. This could lead to vaccinees and contacts thinking they have ebola.

Stanley clearly showed poor durability of ChAd3-EBOL as a stand alone vaccine in NHP and that heterologous boosting with MVA vectored GP was needed to achieve 10 months of protective immunity. Also shown was that MVA vectored GP was a very poor standalone vaccine.

Stanley, D.A., et al., 2014. Chimpanzee adenovirus vaccine generates acute and durable protective immunity against ebolavirus challenge. Nat. Med. 20, 1126–1129. doi:10.1038/nm.3702

Unfortunately we only have indirect evidence that the VSV vectored elola Zaire vaccine will elicit durable responses. There are no NHP durability data published for the VSV-Zaire vaccine...only the VSV-Marburg vaccine:

Mire, C.E., et al., 2014. Durability of a vesicular stomatitis virus-based marburg virus vaccine in nonhuman primates. PLoS ONE 9, e94355. doi:10.1371/journal.pone.0094355

However, As I mentioned in a previous post, I believe the human anti GP ELISA titers elicited with the VSV vector will be higher than those generated with the ChAd3 vector and this alone is likely to lead to a durability better than that generated with ChAd3.