3.6 Protective immunity induced by recombinant PCP antigen against A. pleuropneumoniae
Mice injected intraperitoneally with A. pleuropneumoniae serotype 7 (APP7) were used as protective models to examine the protective immunity of PCP antigens produced here.[5,10] As the 6×His tag has a small molecular weight and is not charged under physiological conditions, it is speculated that the retention of the 6×His tag will not affect the immunogenicity of recombinant antigens.[12] As shown in Fig. 6G , Oml1 and ApxII antigen-immunized mice were all well protected against lethal challenge with APP7, 90% and 80% of the mice were still alive even 168 h after infection, respectively. However, unlike the high protective effect of Oml7 previously observed in C. glutamicum ,[12] Oml7 showed a relatively low protective effect among the three antigens tested. Only 50% of the mice survived, but the survival rate was still higher than that of the control (20%). This low protection of Oml7 may be due to the damage of protein activity during the purification or storage process. In the challenge experiment with APP7, the good immune protective effect of Oml1 observed here once again proved the good cross-protection effect of the subunit vaccine on different serotypes and its great application prospects for PCP prevention.