I think all this is a bunch of hooey. The plauge is bacterial and aids is a virus - I am not aware of bacterial resistance providing antiviral immunization.
Actually, there have been new studies saying that the 'black death' was likely not caused by bubonic and/or pneumonic plague. It moved too fast and was more in line with a hemmoraghic fever such as ebola. One such 'sweating sickness' did kill many in England. One of the many theories was that these diseases came out of the forests of Europe... which still existed at that time and were being slowly cleared. The same thing is true of Ebola and other hemorraghic fevers.
It is unlikely that rat fleas spread plague so far, wide and fast.
It has nothing to do with whether the attacking organism is a virus or a bacteria ~ the question concerns the cell receptors both the virus and bacteria use to gain access to the cell. Without that receptor, neither get in.