I think you’d need to call getMendixObject() on this.HttpResponse when you pass it as a parameter. Try the following...
Map<String, Object> params = new LinkedHashMap<String, Object>();
params.put("httpResponse", this.HttpResponse.getMendixObject());
params.put("listObjects", listObjects);
MicroflowCallBuilder result = Core.microflowCall(MicroflowName).withParams(params).execute(this.context());
Hope this helps.