Really?
First, where is/are the citation(s)?
I would like to know how the researchers are completely certain that those antibodies were actually induced by SARS1 and not one of the commonly circulating coronaviruses that cause the common cold? Antibodies tend to be cross-reactive. In my experience doing western blots, antibodies against a certain protein worked on extracts from a variety of species--human, mouse, rat, guinea pig, monkey, hamster, etc. And there was considerable cross-reactivity in each sample, as well, against proteins that were not the protein I was studying.
Since coronaviruses all have pretty much the same proteins, I would expect antibodies against coronaviruses to be fairly reactive against all strains.
Western blot analysis of G proteins of wheat seedlings grown in different light regimes.
This is a random western blot image that I pulled off the internet to illustrate the cross-reactivity of antibodies. Look at how many protein bands the antibody highlighted. The only way you can tell which protein is the "right" one is through size analysis (which is not included on this blot).