Page 17 of articles about vaccine
Porcine circovirus type 2 (PCV2) infection decreases the efficacy of an attenuated classical swine fever virus (CSFV) vaccine

PRRS Immunology
Resolving the basis of viral and host variation will require identification and characterization of key B- and T-cell epitopes conserved among diverse PRRSV, and of the molecular and structural details of key effector antibodies, T-cell antigen receptors, and MHC molecules that mediate broad, cross-protective immunity.

Mycoplasma hyorhinis - not just a commensal
Although a commensal, M. hyorhinis may cause serious systemic disease through mechanisms that are not fully understood.