Analysis of the seroprevalence of bovine paratuberculosis and the application of modified absorbed ELISA to field sample testing in Korea

Paratuberculosis (PTB) is a major disease problem worldwide, and causes major economic losses in the dairy industry. Although PTB has been reported in Korea, no studies have been conducted to determine its prevalence and no program has been developed to control the disease. In this study, the sera of beef (n = 1,056) and dairy cattle (n = 1,105) from all provinces in Korea were tested to determine the prevalence of PTB using two different ELISA: an 'in house' modified absorbed ELISA (P-ELISA) based on sonicated antigen from Mycobacterium avium subsp. paratuberculosis ATCC 19698, and a commercial ELISA (C-ELISA). Receiver operating characteristic analysis was used to determine the cutoff point for P-ELISA. Based on C-ELISA results, the area under the curve for P-ELISA was 0.913 (95% CI, 0.883 to 0.943). Using a cutoff point of 0.100, P-ELISA showed a sensitivity of 62.0% and a specificity of 93.7%. The kappa value and the percent agreement between the two ELISAs were 0.322 and 92.5%, respectively. Both ELISAs showed a significant correlation between age and seropositivity (p < 0.01). According to C-ELISA, 71 of 2,161 sera (3.3%, 95 CI, 2.6% to 4.1%) were test-positive. The national true prevalence of PTB was estimated to be 7.1%. The findings suggest that a control program should be implemented to limit the spread of this disease, and that P-ELISA could be used as a screening test that produces results similar to C-ELISA.

Cloning a new allele form of bovine TNF-alpha

Although little is known on the function of gammadelta T lymphocytes, there is increasing evidence that gammadelta T lymphocytes are early responders and modulators of immune responses against pathogens and cytokines such as IL-2, IL-7, IL-15 and TNF-alpha. To study the role TNF-alpha on gammadelta T lymphocytes, we cloned bovine TNF-alpha. Sequence analysis revealed that a new allele form of bovine TNF-alpha was cloned which has 3 additional nucleotide sequences as well as 3 nucleotide substitutions compared with previously reported bovine TNF-alpha. Further studies are needed to document the functional significance of a new allele form of TNF-alpha in cattle.