THE EDITOR, Sir:

The person who wrote the letter, 'Some questions about HIV vaccine trials', had some concern about the clinic trials for HIV and other vaccines. I wanted to clarify some points for him/her. First, I do not work in the medical field, but I majored in microbiology (study of bacteria/viruses) at university here in Canada.

Vaccines are made to stimulate the body's own immune system; all viruses, bacteria, etc., are seen as foreign entities by the immune system. The vaccine will immediately launch an attack by activating defences called T-cells and B-cells initially; there may be other cells that come later. Essentially, what the body does is create cells called antibodies that stay in the body forever. The purpose is for the body to recognise the invading entity the next time it attacks the body, the immune system will immediately launch an attack against the virus or bacteria.

So the vaccines are roughly a serum with some cells of the virus or bacteria in question, in this case, HIV. The researchers will use a piece of the cell that is non-disease causing, when the vaccine enters the body, these cells will cause the body's immune system to create antibodies to the virus, thus protecting the body from a new attack. Basically, this is how your immune system works in general terms. I hope this clarifies things.

I am, etc.,

DAVID McRAE

Montreal, Canada

Via Go-Jamaica

mcraedg@hotmail.com