AUTHOR=Meng Zhen , Zhai Lele , Guo Yanfeng , Zheng Mengwei , Li Liang , Wen Chongli , Zhang Weiyu , Di Wenda 

TITLE=Secondary infection of Fasciola gigantica in buffaloes shows a similar pattern of serum cytokine secretion as in primary infection

JOURNAL=Frontiers in Veterinary Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1109947

DOI=10.3389/fvets.2023.1109947

ISSN=2297-1769

ABSTRACT=<sec><title>Background</title><p>As a natural host of <italic>Fasciola gigantica</italic>, buffalo is widely infected by <italic>F. gigantica</italic>. Its impact on buffalo production has caused great losses to the husbandry sector, and repeat infection is non-negligible. In buffaloes experimentally infected with <italic>F. gigantica</italic>, primary and secondary infection have yielded the same rate of fluke recovery, indicating a high susceptibility of buffalo to <italic>F. gigantica</italic>, which contributes to the high infection rate. Determining the immunological mechanism of susceptibility will deepen the understanding of the interaction between <italic>F. gigantica</italic> and buffalo. Here, we explored the immune response of buffaloes against primary and secondary <italic>F. gigantica</italic> infection, with a focus on cytokines’ dynamics explored through serum cytokine detection.</p></sec><sec><title>Methods</title><p>Buffaloes were assigned to three groups: group A (noninfected, <italic>n</italic> = 4), group B (primary infection, <italic>n</italic> = 3), and group C (secondary infection, <italic>n</italic> = 3). Group B was infected via oral gavage with 250 viable <italic>F. gigantica</italic> metacercariae, and group C was infected twice with 250 metacercariae at an interval of 4 weeks. The second infection of group C was performed simultaneously with that of group B. Whole blood samples were collected pre-infection (0 weeks) and at 1–6, 10, and 12  weeks after that. The serum levels of seven cytokines (IFN-γ, IL-4, IL-5, IL-10, IL-13, TGF-β, and IL-17) were simultaneously determined using ELISA and further analyzed.</p></sec><sec><title>Results</title><p>In the present study, no significant changes in Th1-type cytokines production were detected in early infection, both in primary and secondary infections, while the Th2-type response was strongly induced. A comparison of primary and secondary infection showed no significant difference in the cytokine secretion, which may indicate that the re-infection at 4 weeks after primary infection could not induce a robust adaptive immune response. The full extent of interaction between buffalo and <italic>F. gigantica</italic> in re-infection requires further study.</p></sec>