You can acheive this by changing the destination property of MQ Output Node to Reply To Queue,Take another message flow place MQ Input and give the queue name which was provided in MQ Output Node.As it is coming in XML format, if it contains SOAP Headers no issues but if there are no SOAP headers add SOAP headers using compute node and connect to SOAP Request Node from SOAP Request Node it connects to SOAP Input Node.
I think this will work