That’s going to be pretty difficult. I’m not sure if you have an NLP engine on hand but if not then I can offer a way to create something similar. From my limited knowledge about Cleverbot it actually doesn’t have pre-set responses but i’m positive in it’s initial life it had pre-set questions. At the very basic level it would probably read the entire string and pick up the keywords, “Why, how, when, where, how come, isn’t it…, ?” blah, blah, blah you get the idea. When those words are used it’s immediately sorted into a ‘question’ array and stores the entire question; horrible grammar and all.
So replicating something like this in UE4 is actually going to be a hell of a job. It’s hard enough to create the logic on web-apps dedicated specifically to it but putting something like this into a game is no small feat. Generally it’s why you don’t see it very often if at all. Though I don’t have a doubt in my mind that it’s possible. Technically what you could try to do is make a simple web-page with pre-defined responses and maybe a question or two. In Unreal do some HTTP requests via code(C++) and probe the logic from there. This would probably be the best step for this kind of AI.
I’m sure there might be other ways of going about it but in truth AI is really one of the most difficult subjects to perform in the most effective way possible. If I were to tackle the “learning” AI I would handle it via HTTP requests for a variety of reasons. I hope this was helpful to you and anybody else who is also curious on this topic.