Not a common find ;)
Theory goes that the commonest strains of HIV make use of CCR5 which is a chemokine receptor on immune response cells, especially T-cells. Those patients who are homozygous for this recessive allele have demonstrated a resistance to HIV.
This is because it is thought that HIV uses the CCR chemokine receptor as a point of entry to the T-cell lymphocytes. Those with the recessive allele dont have this entrypoint.
Since the ccr5 chemokine receptor is an important sensory aid in the T-cells ability to fight infections, it is likely that these rare individuals ( less than 10% of the population) would have a somewhat diminished immune response to more conventional viral/ bacterial challenges.
Bone Marrow Transplantation is a very high risk procedure, leaving the recipient open to all sorts of life threatening complications. Even were CCR5 delta 32 ( the particular mutation that appears to code for HIV resistance) more readily available through, say, lab based cloning, the process of bone marrow transplantation itself would be the limiting factor.
A more favourable approach as a long term preventative medication would be to develop drugs that interfere with the CCR5 receptor pathway.
http://en.wikipedia.org/wiki/CCR5