Research On Lifecycle Of Isospora Suis And Establish Of Monoclonal Antibodies Against It

Twenty 3-day-old artificially-reared coccidian-free piglets were inoculated Orally with 2.0 ×10~5 sporulated oocysts of Isospora suis,respectively,and killed at intervals from 6h to 144h after inoculations.Samples were taken from various sections(duodenum, jejunum, ileum, caecum, colon, rectum, lung, tracheainte, intestinal lymph node, liver and cholecyst) to determine the region that was most affected.Tissue sections were fixed in 4% polyformaldehyde and processed for routine histological tests using haematoxylin and eosin,examined and photographed,measured the size of different parasites with Olympus micrometer.The life cycle of I.suis was observed chronologically. The results showed that Isospora suis had 3 asexual and 1 sexual intra-intestinal conventional life cycle. The first asexual generation was most prominent at 2～3 days p.i.(post inoculation).Type I meronts were elongate,and the size was 7.5～12.5μm by 4— 6μm,the average was 10μm by 4.7μm.The shape of type I merozoite was similar with type I meront,and the size was 7.5～ 2.5 μm by 2.5—5.0μm .The second completed maturation at 3 to 4 d after inoculation.These meronts were the second generation meronts,each forming 2～4 merozoites,one or many type II merozoites localized in the same parasitophorous vacuole,and the size was 5～10μm by 2.5～5.0μm .The third completed maturation at 4～6d p.i, the shape of meront was spherical or ovid,including 2～12 nucleus,the size was 5～10 by3.5～7.5μm ,each forming 2～12 crescent merozoites.occasionally we seen type III merozoites attached to a residual body. The size of type III merozoites was 4.75 ～8 μm by 1.25～1.5μm.Mature sexual stages were most prominet at 5～6d after infection.Developmental stages were localized within the epithelial cells of villi and crypts of small intestine.No developmental stages localized within the large intestine.DPI120h,we found occysts in the fecal.The prepatent period was 5d and discharge of oocysts continued for 7d. Sporulation of oocysts occurred in 26h at 28℃. Marked histopaological changes including desquamation and necrosis of intestinal epithelium,submucosal edema,infiltration of inflammatory cells and villous atrophy presented during the periods of late merogony, gamogony and oocyst shedding, but most pronounced in the ileum and the regions adjacent to it.The infected piglets showed severe diarrhoea with necrotic epithelium, anorexia, emaciation and even deaths.The oocysts of I.suis were purified by discontinous sucrose gradients,then treated by filtration and centrifugation ,freeze-thawed and sonicated.Balb/c mice were immunized for...