igA1 gene assisted S. suis strains to break the host mucosal immune barrier [56], mutT, pnuc, and nadR genes involved in the biosynthesis and utilization pathway of NAD (Nicotinamide Adenine Dinucleotide) that were responsible for the resistance to oxidative stress and evasion of host immunity phagocytosis during the infection [57–59]. This evidence concerns the gene IGHA1 and infection.