Th2-related cytokines are associated with Fasciola gigantica infection and evasion in the natural host, swamp buffalo.

The infection of ruminants by Fasciola spp. always induces a non-protective Th2-type immune response. However, little is known about changes in the local and systemic immune environment during F. gigantica migration in buffalo. In this study, native swamp buffaloes were each infected with 500 viable F. gigantica metacercariae. Mesenteric lymph node (MLN), hepatic lymph node (HLN), spleen, and serum samples were collected from control and infected buffaloes at 3, 10, 28, 42, 70, and 98 days post-infection (DPI). The mRNA expression levels of the Th1- and Th2-related cytokines IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p40, IFN-γ, TNF-α, and CD4 were measured during different infection stages in the MLNs, spleens, and HLNs using quantitative real-time PCR (qRT-PCR). Levels of the specific anti-ESP isotype antibodies IgG, IgG1, and IgG2 were used to reflect changes in humoral immunity. The results of this study indicated that swamp buffaloes were susceptible to F. gigantica infection, and that susceptibility to this infection was closely related to the cytokine environment associated with the Th2-type immune response. The MLNs showed a mixed Th1- and Th2-type immune response during the acute infection stages, after which the production of these cytokines returned to normal. Cytokine expression in the HLNs also expressed a mixed Th1- and Th2-type immune response during the early infection stages. When the infection became chronic, the typical Th2 immune response was induced in the HLNs. At the acute infection stages, the spleen exhibited a Th2 immune response. Nevertheless, cytokines associated with the Th1 and Th2 immune responses were upregulated at 98 DPI. In addition, the total IgG and IgG1 of the parasite-specific antibodies increased. This suggested that the Th2-related cytokines and IgG1 induced by F. gigantica infection might mediate successful F. gigantica infection in the natural host, swamp buffalo.

[Establishment of Duplex PCR for Identifying Metagonimus yokogawai and Haplorchis taichui].

OBJECTIVE: To develop a duplex PCR method for identifying Metagonimus yokogawai and Haplorchis taichui. METHODS: ITS1 sequences of M. yokogawai and H. taichui, as well as those of their homologous species were obtained from GenBank, and two sets of specific primer pairs for M. yokogawai and H. taichui were designed accordingly using Primer Premier 5.0 software. PCR reaction system and conditions were optimized. The established duplex PCR method was applied in a pool of M. yokogawai, H. taichui, and 17 related species to examine its specificity. Sensitivity was evaluated through serial dilutions of plasmids containing their specific sequences. Finally, the duplex PCR was applied to identify M. yokogawai and H. taichui among trematodes collected from the viscera of 47 cats and 40 dogs to test its practicality. RESULTS: The duplex PCR method amplified target sequences of M. yokogawai and H. taichui, generating 648 bp and 279 bp products, respectively. No cross reaction was found with the following 17 related species: Haplorchis pumilio, Clonorchis sinensis, Pharyngostomum cordatum, the metacercaria of Metorchis sp. and Exorchis sp., Echinochasmus liliputanus, Echinochasmus perfoliatus, Echinostoma friedi, Hypoderaeum conoideum, Holostephanus sp., Diplodiscus sp., Anisakis sp., Metorchis orientais, Paragonimus westermani, Watsonius watsoni, Notocotylus sp. and Hysterothylacium sp, indicating a high specificity of this method. The detection limits for DNAs of M. yokogawai and H. taichui were 1.49 x 10(-1) pg and 1.14 x 10(-1) pg, suggesting a good sensitivity for this method. Further, the duplex PCR successfully identified M. yokogawai and H. taichui from cat and dog viscera, with no cross amplification of other trematodes. CONCLUSION: The duplex PCR is effective in identifying Metagonimus yokogawai and Haplorchis taichui.