猪细小病毒弱毒株（PPV_（s－1）A）及其疫苗的免疫效力

IMMUNOGENICITY OF ATTENUATED PPV STRAIN_(s-1)A AND VACCINE PREPARED FROM IT

以ＰＰＶｓ－１Ａ株弱毒肌肉接种后备母猪２头，每头注射１ｍＬ。接种后第８天的ＨＩ价为１２８～２５６。以后抗体上升，攻毒前ＨＩ价平均为１２８０。对照母猪２头ＨＩ抗体均为阴性。４头母猪配种后，怀孕至３８～４０ｄ时攻毒，结果从接种母猪的血浆中没有分离到病毒，而对照母猪的血浆中则分离到病毒。攻毒４０ｄ后宰杀，接种母猪共怀２５头胎猪，从它们的脏器中均没有分离到病毒，而对照母猪共怀２３头胎猪，其中有１０头的脏器分离到病毒。４批弱毒苗免疫１１头５．５月龄阴性猪，１周内全部产生抗体反应，１个月时平均ＨＩ价为５９９，免疫后１～７个月攻毒，结果免疫猪的血浆和内脏均未分离到病毒，相反，８头对照猪在攻毒前ＨＩ价保持阴性，攻毒后１周ＨＩ１０２４～４０９６，从血浆和内脏都分离到病毒。试验证明，弱毒苗免疫持续期至少为７个月；保存期１１个月。

mL of attenuated PPV strains-1A preparation was injected intramuscularly to each of two gilts which showed HI titres of 128 and 256,respectively, 8 days after inoculation. They and other two HI-negative gilts(as control)were mated thereafter. The four were challenged with virulent PPV strain 38～40 days after conception when the previouslyinoculated two showed an HI titre of 1 280. Viremia was seen in the two control gilts but not inthe two previously inoculated with the attenuated strain.Viruses were recovered from the internal organs of 10 of all the 23 fetuses collected from the two control gilts 40 days after challenge but not from all the 25 fetuses of the previouslyinoculated ones. Eleven 5.5 month-old HI-negative piglets were inoculated respectively with 4 batches of vaccines prepared from the attenuated PPV strain s-1A and all showed antibody in blood within one week and the HI titre reached 599 in average after one month after inoculation. The eleven were challenged with virulent PPV strain 1～7 months after inoculation and no viruses were recovered thereafter.In contrast, 8 HI-negative control piglets showed HI titres ranging from 1 024 to 4 096 one week after challenge and viruses were recovered from the internal organs of all of them. The result showed that the vaccine prepared from the attenuated PPV strains-1A could produce an immunity which could last at least 7 months and the vaccine could keep a shelf-life of 11 months.