Let's look at its composition:
MVA stands for Modified Vaccinia Ankara virus, a very attenuated strain of the vaccinia virus, engineered to function as a vaccine delivery system for antigens and previously used to treat, and eventually eradicate, smallpox. The MVA-B, a variation of MVA, has been designed to work against the most common subtype of HIV in Europe, indicated by the letter "B". Its composition differs from the original MVA strand by 4 extra HIV genes, called Gag, Pol, Nef and Env, inserted into MVA's genetic sequence. These genes are able to stimulate B and T lymphocytes, and lack the ability to self-replicate, which makes them rather safe candidates for this type of vaccine. Could this be sufficient proof for their safety?
In addition, this study led by Professor M. Esteban showed that over three-quarters of the 24 treated volunteers had developed HIV-specific antibodies 48th weeks after vaccination. 38.5% of these participants also demonstrated the production of lymphocytes T CD4+ (a type of T helper cell that fights HIV), while 69.2% had produced the T cell receptor CD8+ in comparison with a total of 0% in the control group.
While the robust results of this small-scale study illustrate the potential success of a world-changing solution, they do not tell us anything about the therapeutic aspect of the vaccine. How will the four genes act in the immune system of a patient already infected with HIV?
The need for many more clinical trials (preferably large-scale!) in the future is evident. What is more unclear, however, is whether more participants will be willing to take part in testing a vaccine that may not even hit the production phase.
For more information, here is a very detailed Science Daily Article with more recent results (6th October 2011): MVA-B Spanish HIV Vaccine Shows 90 Percent Immune Response in Humans
- Julie Saffarian