猪圆环病毒2a/2b亚型病毒株灭活疫苗及其重组Cap蛋白亚单位疫苗的交互免疫实验

摘要

为评价猪圆环病毒(PCV)2a/2b两种基因型病毒株及其重组Cap蛋白(rCap)之间的交互免疫,本研究采用PCV2a-LG株和PCV2b-YJ株制备了2种病毒灭活疫苗,及其重组杆状病毒表达的2种Cap蛋白(PCV2a-rCap和PCV2b-rCap)亚单位疫苗.选用8周龄BALB/c鼠165只,随机分成11组,每组15只,用上述4种疫苗各免疫2组,以PCV2a或PCV2b株攻毒.攻毒后,所有鼠均未见肉眼可见的临床症状和病理变化.采用IPMA法检测抗体,4种疫苗于免疫第3周抗体转阳,第5周抗体效价达到1:200～1:800倍,其中PCV2a-rCap免疫组抗体效价最高.2种灭活苗和PCV2a-rCap免疫组攻击同型或异型病毒株均可以获得完全保护.以PCV2a和PCV2b各为指示病毒对病毒抗血清和rCap蛋白抗血清进行交叉中和试验,同型病毒株与同型血清的中和抗体效价均高于异型病毒株.病理观察显示,免疫鼠均未见明显病理变化,攻毒对照鼠肺脏出现一定程度的病理损伤.本研究表明,病毒灭活疫苗及其rCap亚单位疫苗PCV2a和PCV2b可提供交叉保护.%To valuate cross-protection between porcine circovirus (PCV) genetype 2a and 2b, four kinds of vaccines were prepared, respectively, including two virus inactivated vaccines of PCV2a-LG and PCV2b-YJ strains and their recombinant Cap subunit vaccines of PCV2a-rCap and PCV2b-rCap expressed by recombinant baculovirus. Eight-week-old BALB/c mice (n=165) were randomly divided into 11 groups (15 mice each). Each vaccine was immunized for 2 groups of mice and challenged with either homologous or heterologous genetype PCV2, with 2 challenge only and one blank control groups. No clinical signs were observed in all groups post challenge. However, the antibody titers were from 1=200 to 1=800 in all immunized groups at 5 weeks post immunization detected by IPMA. Of which the highest titers were found in PCV2a-rCap groups. The two inactivated vaccines and the PCV2a-rCap showed 100% protection against challenge with either PCV2a or PCV2b according to the virus load which was significantly reduced in the mice lung. Furthermore, the serum neutralization test demonstrated a high level cross-reactivity between the two genotype strains of PCV2. Histopathologic changes were developed in lung of control mice post challenge and noobvious changes were present in vaccinated mice. This study suggested that even though there were a certain degree of antigenic differences between two genotypes of PCV2 strains, the cross-immunization protection could be provided by both inactivated vaccines and PCV2a-rCap protein subunit vaccines.