Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/1997
Publication Date: N/A
Interpretive Summary: Cryptosporidium parvum is a worldwide pathogen of newborn calves causing severe diarrhea and sometimes death. Knowledge of the ability of newborn calves to mount an immune response is vitally important for the development of any vaccination scheme or other induced immune protection. The present series of experiments elucidated the types of cells and cytokines present and absent at the site of Cryptosporidium infection in young calves. These findings indicate that the cytokine interleukin-12 (IL-12) might play a role in the cascade of activities leading to protection and therefore suggests that the administration of a gene-cloned bovine interleukin-12 could stimulate protection in very young immunologically immature calves.
Technical Abstract: Twenty six experimentally infected calves were monitored daily for oocyst excretion. All began excreting oocysts 3 to 6 days p.i. Most calves (n-23)_ excreted oocysts for 6 to 9 days with a daily range from 4 x 102 to 4.15 x 107 oocysts/g/ of feces. Over half the calves excreted peak numbers of oocysts 6 to 8 days p.i. Diarrhea, observed intermittently beginning as early as day 3 p.i.,lasted 4 to 16 days and varied greatly in severity from calf to calf. In a second study, 9 of 18 calves were orally inoculated with 5 x 106 oocysts between birth and 2 days of age and 9 remained uninfected. Monoclonal antibodies for cell surface markers indicated substantial increases in CD4+ and CD8+ T cells in the intraepithelial lymphocyte (IEL) population of the ilea of infected calves at 7 to 9 days of age. RT-PCR demonstrated increases in mRNA for IL-12 and IFN-y that correlated with increases in both CD4+ and CD8+ IEL cells. Increased mRNA for IL-12 and IFN-y from lamina propria lymphocytes correlated with increased numbers of CD8+ cells. No changes were found in IL-2, IL-4 or IL-10 mRNA levels. However, IL-15 mRNA, possibly from epithelial cells contaminating IELs, was decreased in infected calves and had a negative correlation with increases in CD4+ cells. No differences were detected in mRNA levels for cytokines from lyph node lymphocytes.