As part of one of our current VDI projects, we've recently deployed Trend Micro Deep Security to enable VMware vShield Endpoint. This is a pretty handy technology that allows offload of anti-malware to the ESXi hypervsior, meaning that the individual Virtual Machines do not each need to run a traditional Anti-Virus software solution.
This is good news, as the cumulative load of several hundred or thousands of desktop VM's running traditional Anti Virus can quickly become quite a burden on the host servers, and managing updates can introduce problematic loads.
Trend have been integrating with vShield longer than anyone else. With vShield Endpoint and Trend Deep Security, issues with traditional Anti Virus are mitigated, and all anti-malware is simply and effectively managed at the hypervisor.