Looks like the WSUS product team announced that new SCE anti-malware definitions are now available for WSUS:
Microsoft Security Essentials antimalware definitions are now available via WSUS. Microsoft Security Essentials is a core antimalware service for consumers and home-based small businesses that Microsoft released in September of 2009. This was done because academic institutions around the world (particularly in Asia) provide students with low cost or free internet access and provide students with update services through WSUS. Many students are protecting their computers with Security Essentials, and the universities requested that the definition updates be provided via WSUS.
To continue reading see http://blogs.technet.com/wsus/archive/2010/03/31/microsoft-security-essentials-anti-malware-definitions-now-available-via-wsus.aspx
J.C. Hornbeck | System Center Knowledge Engineer