No you can not. If you upgraded an old host to version 5.1 that did have the host profile applied you can create a new host profile from that host.
Basically the host profile is version specific for the major versions, 4.0, 4.1, 5.0, 5.1. Even if you manage to apply an older profile to a newer host things might just break.
One example: How would the ESXi 5.1 host know about the service console ports? It only knows about vmkernel ports.
