Hi, while it may technically be possible to install additional software on a VRA, that is not supported. Whenever a VRA is redeployed (as part of an upgrade or for some other reason), any modifications to the VRA will be wiped.
VRAs replicate disk blocks (VMDKs or RDMs) instead of filesystem data, so the added value of running antivirus-scanning on a VRA might be more limited than you expect.