The concept of UTM (otherwise known as Unified Threat Management) runs under the assumption that it's possible to merge existing security measures—from anti-spam to firewalls—into one all-inclusive package, regardless of whether it's software or hardware. In turn, aUTM appliance is a unit that merges common IT security services into one device, with the added advantage of effortless external inspection, examination, troubleshooting, reporting, and problem solving without the risk of compromising the unit itself from the threat it's suppose to solve.
The UTM Appliance Anti-Virus is just one feature in an all-inclusive package that handles the detection and removal of viruses. However, it benefits a lot from being under the UTM helm because other services such as anti-spam and firewall can help alleviate its workload by leaps and bounds. Once 2004 came about, security experts quickly realized the viability of combining common protection schemes such as anti-virus, anti-spam, anti-spim, pen testing, and so on together in one medium.
Since then, the relatively new UTM methodology has gained worldwide acceptance and acclaim as the foremost network gateway security solution for organizations everywhere. The traditional firewall's tendency to incorporate features such as anti-virus and anti-spyware scanning into its software suite has a lot to do with the development of the UTM. In fact, many standalone anti-virus solutions also utilize a modicum of UTM comprehensiveness in their products as well in the form of services like firewall and anti-spam assistance.
Arguably, both the anti-virus program that uses different defense services and the UTM application that has an anti-virus feature can be considered as practically the same service. Compound that with the fact that most UTM solutions are currently in appliance form, and it's quite understandable why it's so difficult to classify just what exactly a UTM Appliance Anti-Virus is supposed to be. The only real difference between the two is what they cater to: the anti-virus suite has more emphasis on virus removal while the UTM suite is more focused on overall protection.
Regardless of whether you have an anti-virus appliance sporting UTM features or a UTM unit containing an anti-virus option, they basically fill in the same function of protecting your machine from security threats via benefits like on-appliance reporting, load balancing, content filtering, VPN, gateway anti-spam, and gateway anti-virus.