A Smart TV is technically a computer
So, technically, yes. It can be infected.
From a practical standpoint, though, I think you'll find that there are not going to be any anti-virus systems that run on the TV as-is. You would have to hack the TV yourself and install your own OS (probably some flavor of Linux) in order to load software that isn't written by the TV's manufacturer. I haven't looked, but I suspect that there are hacks published for many TVs on the market. Hobbyists enjoy hacking everything from digital cameras to digital picture frames. A TV would be right in their wheelhouse.
OTOH, while it is technically possible for your TV to get infected, I'm not sure what the bad guys would do with it. I don't think those TVs have a lot of computing power, nor much memory. The culprits might try to use it as an entry point past your hardware firewall (you are using a router with a firewall built in, right?) But, if your computers, phones and other devices are running virus software, then that doesn't gain them much. And, the TV market is fragmented enough that any target they aim for would be a pretty small population of devices. So, it's probably not worth their time.
A more lucrative target would probably be a DVR. Those are computers, too. Those machines wouldn't be called high-powered, but they would make for a nice zombie to send spam from. Again, you're not going to find any anti-virus system readily available that you can put on there to protect them. Those companies are very jealous of what goes on their systems. That's good news for virus protection, though. Because in protecting themselves from hobbyists they're also protecting themselves from virus writers.
To wrap up, the new TVs are technically at risk. But, from a practical point of view, at this point, I don't think it's worth spending any time worrying about.