Birkbeck T Harry, Rennie Shona, Hunter Douglas, Laidler L Anthony, Wadsworth Simon
Institute of Biomedical and Life Sciences, Division of Infection and Immunity, Joseph Black Building,University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
Dis Aquat Organ. 2004 Aug 9;60(2):97-103. doi: 10.3354/dao060097.
A Scottish isolate of Piscirickettsia salmonis (SCO-95A), previously shown by intraperitoneal injection to have a lethal dose (LD50) of < 2 x 10(3) infectious rickettsial units, was tested for virulence by bath challenge, surface application to the skin, or dorsal median sinus injection. Atlantic salmon Salmo salar post-smolts were used in all experiments, and exposure to 1 x 10(5) tissue culture infective doses (TCID) of P. salmonis ml(-1) for 1 h in a bath challenge resulted in only 1 mortality, 18 d later, in 10 exposed fish. Application of 2.5 x 10(6) TCID of P. salmonis SCO-95A to paper discs on the skin failed to induce any mortalities within 42 d. Intraperitoneally, fish were administered vaccines containing 10(9) heat-inactivated (100 degrees C, 30 min) or 10(9) formalin-inactivated P. salmonis SCO-95A in adjuvant, with a control group receiving phosphate-buffered saline (PBS) in adjuvant. After an induction period of over 6 mo fish were challenged by injection of P. salmonis into the dorsal median sinus. Mortalities in the control group reached 81.8% and the heat-inactivated and formalin-inactivated vaccines gave significant protection from P. salmonis, with relative percentage survivals of 70.7 and 49.6%, respectively. The nature of the protective antigen is unknown, but could be lipopolysaccharide or a heat-stable outer membrane protein. Fish that survived a dorsal median sinus challenge of P. salmonis or were cohabitants showed a strong immune response to P. salmonis.
一株鲑鱼立克次氏体（SCO-95A）的苏格兰分离株，此前通过腹腔注射显示其致死剂量（LD50）<2×10³感染性立克次氏体单位，通过浸浴攻毒、皮肤表面接种或背中窦注射来检测其毒力。所有实验均使用大西洋鲑（Salmo salar）后仔鱼，在浸浴攻毒中，将鱼暴露于1×10⁵组织培养感染剂量（TCID）的鲑鱼立克次氏体/ml中1小时，18天后，10条暴露的鱼中仅1条死亡。将2.5×10⁶ TCID的鲑鱼立克次氏体SCO-95A接种于皮肤的纸片上，在42天内未诱导出任何死亡。通过腹腔注射，给鱼接种含有10⁹热灭活（100℃，30分钟）或10⁹福尔马林灭活的鲑鱼立克次氏体SCO-95A的佐剂疫苗，对照组接受含佐剂的磷酸盐缓冲盐水（PBS）。经过6个多月的诱导期后，通过向背中窦注射鲑鱼立克次氏体对鱼进行攻毒。对照组的死亡率达到81.8%，热灭活疫苗和福尔马林灭活疫苗对鲑鱼立克次氏体均有显著的保护作用，相对存活率分别为70.7%和49.6%。保护性抗原的性质尚不清楚，但可能是脂多糖或热稳定外膜蛋白。在背中窦受到鲑鱼立克次氏体攻毒后存活下来的鱼或同居的鱼对鲑鱼立克次氏体表现出强烈的免疫反应。
