Passive immunization against somatostatin increases resistance to Eimeria vermiformis infection in susceptible mice

The effect of in vivo immunoneutralization of somatostatin (SRIF) on Eimeria vermiformis intestinal infection was studied in resistant (BALB/c), and susceptible (C57BL/6) mouse strains. An anti-SRIF monoclonal antibody (MAb-SRIF) was used to passively immunize the mice by intraperitoneal injection. The animals were subsequently orally infected with oocysts of E. vermiformis. Individual fecal samples were collected daily for 21 days to monitor the kinetics of oocyst shedding. The fecal oocyst shedding was significantly higher in the C57BL/6 strain than in the BALB/c strain (P < 0.01). Passive immunization with MAb-SRIF in the C57BL/6 mice significantly reduced the number of oocysts in feces (P < 0.05), when compared to the infected non-immunized mice of the same strain. Infected BALB/c mice showed no difference in oocyst shedding in response to the passive immunoneutralization with MAb-SRIF. In conclusion, passive immunization with MAb-SRIF increased resistance to E. vermiformis-infection in the susceptible C57BL/6 mice, but not in the resistant BALB/c mice. This suggests that SRIF modulates gut immune function in parasitic infection.