Exploration with new vaccine technologies is moving forward rapidly, although given the usual pace of the science and then necessary tests for safety and efficacy it isn’t likely we will have a bird flu vaccine sooner than two or three years from now. Maybe that’s enough time. Maybe it isn’t. It would have been good if we’d have started earlier, but we didn’t. Anyway, here’s the latest entry, a skin patch vaccination (TransDermalImmunization, TDI). Naturally the news comes to us not through a scientific publication but through a press release. How else do you raise money these days? (That’s a rhetorical question).
Still, it’s not a far out idea. That’s because the skin is richly endowed with a type of immune cell call a dendritic cell (aka a Langerhans cell). The idea is to present the viral antigen to these skin cells with a patch, worn for a few hours and then discarded. Viral antigen is protein or protein fragment made by the virus which the immune system “sees” and then makes antibodies to. The first step in this process is for the antigen to be taken up by an “antigen presenting cell” (APC) which then breaks it into pieces and displays these fragments on its surface in conjunction with some other cell components to signal to the immune system it has an enemy it wants to call out the troops for. The immune system then fingerprints the fragment and arms other immune cells to make antibodies whenever it sees the antigen. Think of the APC as the “booking officer” that identifies, fingerprints and takes the mugshot of the virus (or in this case, a fragment of viral protein) and sends it to the immune system police force to watch for. If the immune police see it again they attack it with antibodies. The dendritic cell is an APC.
The APC must first go to the station to book the suspect. The station in this case is a regional lymph node which has the other kinds of immune cells in it (the ones that make antibodies, for example). You can enhance this process by adding other materials to the antigen called “adjuvants.” This combination of adjuvant with viral antigen in a skin patch is what the Department of Health and Human Services just awarded a $128 million contract the Iomai Corporation to develop. The Iomai product page has cartoons here to give you the idea. There is an arrow below the picture on the right to click through to get two more pictures.
Maybe it will work and maybe it won’t. In 2004 a flu shot for regular seasonal flu was shown to require much less viral antigen if administered by injection into the layer of skin (intradermal) rather than deep into the muscle (intramuscular) as usual. One of the problems with the H5N1 vaccine trials was that they needed far too much viral antigen from egg based vaccines to be practical, so the hope was that using intradermal injections with an adjuvant might get around this. Unfortunately, a recent H5N1 trial did not show a boost for this method of administration.
An effective vaccine patch would help the vaccine distribution and administration problem. Patches could be left in mailboxes or passed out wholesale for self-administration. If you could make enough of them, cheaply enough and in time. If you could make them at all.
We’ll let NIH’s Tony Fauci have the last word:
“It is a very interesting technology,” said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. “If it works.” (WaPo)