• Parasites, Hosts and Diseases
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• v.25 no.2
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• pp.188-194
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• 1987

The development of antibody titers and crossreaction between Sarcocystis and Toxoplasma were investigated by means of IF A test and ELISA in pigs experimentally infected with $1.5{\times}10^6$ S. suicanis sporocysts and 10,000 T. gondii oocysts, respectively. The intact and soluble Sarcocystis antigens were prepared from the bradyzoites harvested by peptic digestion of infected pork. The intact and soluble Toxoplasma antigens were prepared from the tachyzoites in mouse peritoneal cavity. IgG antibodies in pigs infected with Sarcocystis and Toxoplasma, respectively were detected first at 2 weeks post infection on both IF A test and ELISA. The antibody titer to Toxoplasma reached its maximum at 6 weeks post infection and decreased thereafter. The antibody titer to Sarcocystis reached its maximum terminally. The cross-reaction titer in pigs infected with Toxoplasma against Sarcocystis antigen was up to 1 : 16 in IFA test and up to 1 : 32 in ELISA. The titer in control group was below 1 : 4 in both reactions.

• Clinical and Experimental Pediatrics
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• v.48 no.5
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• pp.506-511
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• 2005

Purpose : Streptococcus pneumoniae serotype 6B and 6A are important pathogens in pneumococcal infections. It is commonly assumed that the 6B vaccines elicit antibodies cross-reacting with the 6A serotype and the cross-reactive antibodies protect against infections of 6A. To examine this assumption, we measured the opsonophagocytic capacity to serotype 6A and 6B in adults. Methods : Twenty-four adults were immunized with pneumococcal PS vaccine that contains 6B PS. Their preimmune and postimmune sera were studied for the capacity to opsonize 6B and 6A serotypes with opsonophagocytic killing assay. Results : Opsonization titers to 6B were significantly higher than those to 6A in preimmune and postimmune sera. Because significant increasesof opsonization titers were observed in adults with polysaccharide vaccines for 6A(cross-reactive) serotype as well as for 6B(vaccine) serotype, 6B PS in vaccine elicited cross-protective antibodies to 6A, but not in all cases. One adult did not have detectable levels of opsonization titers to 6A after immunization. Conclusion : Although 6B PS in pneumococcal PS vaccine elicits antibodies cross-reacting with 6A serotype in some adults, it may not occur always. This study should be extended to other age groups such as children and elderly people. The presence of the cross-protection should be directly determined in clinical trials of the pneumococcal vaccines as well as during the postlicensure monitoring surveys by serotyping the clinical isolates of pneumococci.