engleski

Levamisole modulates the numbers and phagocytic functions of leukocytes in weaned pigs vaccinated with non-enterotoxigenic F4ac+ Escherichia coli

induced by stress in the time of weaning, pigs not only show low resistance to enterotoxigenic Escherichia coli (ETEC) infections but also vaccination can failed. As enhancement of immune activity by levamisole seems to occur in immunocytes whose function is impaired, we assessed in vivo its immunomodulatory activity on the phagocytic functions and numbers of peripheral white blood cells (WBCs) in weaned pigs vaccinated with F4ac^+ non-enterotoxigenic E. coli (non-ETEC). Fifteen commercial crossbred pigs were used and assigned to 3 groups of 5 pigs each. Levamisole-treated vaccinated experimental group 1 was intramuscularly injected with levamisole in immunostimulatory dose of 2.5 mg/kg given daily, in 3 consecutive days, prior to the vaccination. The non-treated vaccinated experimental group 2 received saline solution according to the same schedule. Both groups of the pigs were intragastrically vaccinated on day 0 with F4ac^+ non-ETEC strain. At post-vaccination (p.v.) day 7 all pigs, together with non-treated non-vaccinated controls, were challenge-inoculated orally with F4ac^+ ETEC. Blood was sampled from each piglet before the first administration of levamisole (day &#8211 ; 3), on 3 and 6 p.v. days and at day 6 post-challenge (p.c.) for the assessment of WBC counts and for the in vitro assay of their phagocytic functions. We found significant decrease (P<0.005) in WBC numbers in levamisole-treated vaccinated pigs on day 6 p.c., vs non-treated vaccinated pigs and controls. But compared with day &#8211 ; 3, on 6 p.v. and 6 p.c. days the number of WBCs increased in levamisole-treated vaccinated pigs reaching the physiological values normally observed in blood of pigs. These findings indicate that the drug appeared to restore to normal the number of WBCs. We also found here increased proportion of lymphocytes, and decreased proportion of granulocytes in the levamisole-treated vaccinated pigs and inversive results were obtained in non-treated vaccinated pigs as well as in controls, suggesting that levamisole may influence the proportions of WBCs. Its potential role in preventing stress in weaned pigs following vaccination is discussed. Unexpectedly, the phagocytic functions of levamisole-treated vaccinated pig circulating phagocytes were generally impaired by pretreatment of the pigs with levamisole, casting levamisole as an immunosuppressor.

levamisole; immunomodulation; weaned pigs; vaccination; Escherichia coli; leukocytes

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