Why isn't "T-cell adoptive transfer" immunotherapy panacea?

[cave_cat]

in wikipedia Immunotherapy article it talks about how they treat some cancers with "T-cell adoptive transfer" involving cloning patient's white blood cells, sometimes modifying / improving them and then injecting them back into the patient. It says that research started in the 80s and seems to still go on, mostly with cancers.

So I am wondering, why isn't this general approach a generic panacea for all bacterial and viral diseases? E.g. if flu vaccine in vivo makes immune system eventually suppress the current flu strain (and in fact young people do it themselves without vaccine) why can't vaccine be replaced with massive infusion of these cloned T-cells with "vaccine" / response to the strain inserted in the lab?

Likewise, why can't HIV be eliminated by using cloned T-cells whose membranes are modified to eliminate whatever feature involved in allowing the virus enter and attack them?

I guess the main gist of this question is, I understand that if the above isn't happening, there are major limitations to the procedure that are not elaborated in the brief description in wikipedia. So, anybody knows what they are? What makes this procedure so limited that it remains experimental cancer treatment instead of a panacea for everything under the sun?

 

[Ygggdrasil]

This idea has, as you suggested, been applied to the treatment of HIV. One of the first studies occurred in 2008 when an HIV-positive individual who also had leukemia was in need of a bone marrow transplant. Scientists have known that about 1% of Europeans carry a mutation in both copies of the CCR5 gene that greatly decreases their susceptibility to HIV (CCR5 is a protein on the surface of T-cells required for HIV entry). So, the doctors found a bone marrow donor carrying the CCR5 mutations, and replaced the patient's bone marrow with that of the HIV-resistant donor's. Although the initial reports seemed to suggest the transplant cured him of HIV, the infection recently re-emerged. Still, scientists are experimenting with modifying a patient's own T-cells to alter the CCR5 receptor in the hopes of generating resistant T-cells that can help fight HIV infection.

Now as to why the procedure is not so widespread, there are a few reasons. First, it is a very new treatment and we are not fully aware of the risks. Genetic modification of any cell type always carries the risk that you will inadvertently convert the modified cell into a cancerous or pre-cancerous cell. While such risks might be acceptable when treating severe diseases like cancer, such risks are not acceptable for more routine cases where less risky (and much cheaper) alternatives are available. Newer, better targeted genome editing technologies may reduce these risks, but further testing of these technologies is still needed.