Interoperability is a challenge for constructing Live-Virtual-Constructive (LVC) systems. This study is a step toward LVC interoperability adhering to a gateway-based approach with a particular focus on two standard middleware, namely, Data Distribution Service for Real-Time Systems (DDS) and High-Level Architecture (HLA) for distributed simulation. A gateway is designed and implemented to achieve DDS-HLA interoperability. This gateway has the ability to realize two-way data transfer between DDS and HLA systems. The gateway design is based on the idea of a configurable connector that is equipped with variability capabilities. It can perform data-type conversions between these two systems according to the mappings specified by the user. In a case study, the gateway is integrated into a distributed tactical environment simulation system.