First off, good topic.
While the adaptive immune system is very crucial to human survival it is also important not to forget innate immunity. A very important mechanism is our Toll-like Receptors (TLR's). These are homologous to the immune receptors in species (e.g. Drosophila sp. where the proteins were first found) that do not have an adaptive immune system. These proteins are still very important in recognizing foreign invaders. I would strongly suspect that these proteins are under selection, as are the proteins in pathogens that the TLR's bind to. TLR's are just one example of the mechanisms involved in innate immunity. There are several more such as complement binding.
As to the question in the OP:
And in terms of human (or more correctly-vertebrate) and pathogen interaction, do you think that we have evolved an adaptation that actually prevents any further evolutionary adaptation to disease?
My answer would be no. The adaptive immune system is built on top of a very important innate immune system which is still under selection.
Edited by Taq, : No reason given.