Technology enhanced learning relies on a variety of software architectures and platforms to provide different kinds of management service and enhanced instructional interaction. As e-learning support has become more complex, there is a need for virtual campuses that combine learning management systems with the services demanded by educational institutions and users. However, nowadays, the functions of virtual campuses need to be enhanced with external e-learning applications. This paper deals with the issue of integrating these applications in virtual campuses using a software architecture based on the merging of mashup and multitier patterns. Our solution is based on an asymmetric architecture that provides seamless interconnection of the external tools with virtual campuses. We illustrate it with a real example of the integration of a research prototype that searches for and retrieves learning objects with a virtual campus designed independently of the underlying e-learning platform.