Malarial vaccine poised for imminent mass-distribution

So, it seems that there have been some significant leaps forward in the effort to create a vaccine to fight malaria, a disease particularly prominent in Sub-Saharan Africa and caused by the parasite Plasmodium.falciparum. GlaxoSmithKline (GSK Biologicals), a global pharmaceuticals industry with a history of developing vaccines, has recently entered phase III trials, the ultimate stage of clinical testing! I say recently, I mean finally; they started developing the vaccine in 1987 and have been testing it ever since. But! There have been some tasty results. Do read on…

GlaxoSmithKline and Mosquirix

It’s difficult to create a vaccine to prevent parasitic disease. Not only are parasites more structurally complex  than your average run-of-the-mill bacterium or virus, but they also have a multistage life-cycle during which they evolve, residing in different hosts and environments. In collaboration with PATH, GSK created RTS,S, also named Mosquirix, a promising candidate to be the first malarial vaccine, which targets the first stage of the plasmodium life-cycle: the sporozoite.

Plasmodium life cycleClick to enlarge

RTS,S is a protein which can be injected intravenously to prime the immune system such that upon eventual malarial infection, the body is more ready than it otherwise would have been to fight off the disease.

How does it work?

RTS,S was constructed by combining two proteins:

  • Circumsporozoite protein: a protein found on the surface of P.falciparum
  • Hepatitis B surface antigen: a protein found on the surface of Hepatitis B viral particles
  1. RTS,S is injected into the body along with the adjuvant system AS01. Specific B lymphocytes (immune cells) circulating in the blood recognise the hepatitis B surface antigen component of the vaccine via antibodies bound to the surface of the B cell.
  2. The B cell then engulfs the whole protein, digesting it into smaller fragments which are then presented on the outer-surface of the cell.
  3. Fragments derived from the circumsporozoite protein may then be recognised by another type of immune cell: the T cell.
  4. The T cell stimulates the B cell to proliferate and differentiate into plasma cells, such as memory cells, which specifically recognise the circumsporozoite protein on the surface of the parasite.
  5. Therefore, upon subsequent infection, parasites are identified quickly, efficiently activating an immune response against the infection before the person gets sick.

B cell

Click to enlarge

Does it actually work some?

RTS,S is GSK’s most promising attempt at creating a working malarial vaccine. Recent results from the phase III trials indicate that the vaccine reduces the frequency of episodes of clinical malaria by 35% and severe malaria by 49% over an eight month follow-up period and also remains effective for up to 18 months after administration. So yeah, it seems to work! It may not be 100% effective, but the numbers don’t lie, it’s definitely helping. As malaria claims around 660,000 lives a year, most of which are children (the study group in which the vaccine was most effective), the eventual use of this vaccine on a large scale is inevitable.

It looks like these studies, which by the way were funded by the Bill and Melinda Gates Foundation, are going in the right direction, which I personally think is a good thing. How about you? Do you think it’s fantastic that there’s the possibility of saving hundreds of thousands of lives, or are you worried about the possible ramifications this may have on overpopulation and the such like. Share your views in the comments below, we’d love to hear ’em. And finally, to paraphrase Toto…

It’s taken a lot to reach these phase III trials,

It took like 100 scientists or more to get this far.

To address the pains down in Africa,

It’s gonna take some (more) time but at least it’s getting there!

Till next time,

James.

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