注射菌苗的生殖期黄颡鱼亲鱼的外周血细胞和体液免疫变化

The changes of cellular and humoral immunity of mature yellow catfish,Pseudobagrus fulvidraco Richardson,immunized with formalin-killed Aeromonas sobria

阐明生殖期亲鱼在注射灭活菌苗后的血细胞和体液免疫变化规律,是预防亲鱼产后虚弱患病和仔鱼染病死亡的理论基础。本研究在试验组和对照组黄颡鱼胸鳍基部分别注射0.2mL浓度为1.0×108CFU/mL福尔马林灭活温和气单胞菌苗(F-AS)和0.65%灭菌生理盐水,在免疫后第1、2、4、7、14、21、28、35天,从尾静脉采血,测定外周血液血细胞数量及组成比例,血细胞吞噬活性和抗体效价。结果显示:注射菌苗后白细胞数量和淋巴细胞的白细胞分类计数逐渐增加,显著高于对照;中性粒细胞、单核细胞的白细胞分类计数以及吞噬百分比(PP)、吞噬指数(PI)在4～7d显著高于对照;抗体效价逐渐升高且在第14天达到最高,随后逐渐下降;而红细胞数和血栓细胞的白细胞分类计数逐渐下降,显著低于对照组。结果表明:单次注射菌苗后亲鱼可以产生良好的免疫应答,1～7d以增强单核细胞和中性粒细胞等非特异细胞免疫为主;7～35d淋巴细胞增值,并大量释放抗体且在第21天淋巴细胞出现极显著升高,此后虽逐渐下降但仍显著高于对照,抗体维持在较高水平上的时间为1周左右,建议在黄颡鱼催产前10～14d进行单次菌苗注射以增强亲鱼免疫力。

Spawned yellow catfish （Pseudobagrus fulvidraco Richardson） and their fry usually die of infective diseases. In order to enhance the resistant ability of spawning yellow catfish and their fry against pathogens,it is necessary to illuminate changes of immune parameters of periphery blood in immunized mature yellow catfish. In this study,one hundred and thirty healthy mature yellow catfish were randomly divided into test and control groups. Each individual was intraperitoneally injected with 0.2 mL of bacterial suspension at a concentration of 1.0×10^8 CFU/mL formalin-killed Aeromonas sobria for the test group,and with 0.2 mL of 0.65% sterile saline solution for the control group. Then,approximate 2 mL of blood was taken from each fish caudal vein at 1,2,4,7,14,21,28,35 d post injection. Three yellow catfish were sacrificed at each sampling time. The haematological indices,such as leucocyte and erythrocyte number per microlitre,differential leucocyte count （DLC）,and serum antibody titer and activity of phagocytes,were investigated for each blood sample of the test and control group. The results were as follows ： The leucocyte number per microlitre of test group drastically increased and was significantly （or very significantly） higher than that of control from the 2nd day to 35th day post immunization （Fig. 2）. The differential leucocyte count （DLC） of the test group prominently increased and was significantly （or very significantly） higher than that of control for neutrophil and monocyte from day 4 to day 7 （Fig.5 ＆ Fig.6 ）,and for lymphocytes from the 4th day to 28th day （Fig. 4）. The phagocytic percentage and phagocytic index also gradually increased from day 1 to day 7 and peaked at 7 d,then dropped down to the control level （Tab. 2）. However,the test group was significantly lower than the control in erythrocyte number per microlitre between the 7th day and 35th day （Fig. 1）,and in DLC of thrombocyte between day 4 and day 28 （Fig. 3）. The serum antibody titer gradually increased from day 1 to day 14 and reached the highest value at 14 d,then,slowly decreased from day 14 to day 35,and maintained a higher level between day 14 and day 21 in comparison with the values at other sampling times （Tab. 3）. From what has been stated above,the immunized mature yellow catfish were enhanced in their resistant ability against bacterial pathogens by means of increment of non-specific cellular immunity,such as monocyte and neutrophil,during the early period （from day 1 to day 7） post single dose immunization,and of specific cellular and humoral immunity,such as lymphocytes and antibody,from day 7 to day 35 after the immunization. And the higher antibody titer level could last for a week from day 14 to day 21 post the immunization. Therefore,it is suggested that the mature fish should be immunized with single-dose vaccine at day 10-14 before breeding to enhance the resistant ability of spawn yellow catfish against pathogens,and further to reduce mortality rate of the spawned yellow catfish and their fry caused by infective diseases.