Early host responses to cattle gastro-intestinal parasite Ostertagia ostertagi

Abstract Ostertagia ostertagi is a gastrointestinal parasite of cattle that has a huge economic impact on the US cattle industry. With the rise in drug resistance among nematodes, vaccination is advanced as the most cost-effective alternative; however, nematode vaccines have met with lackluster results thus far. Thus, understanding host-parasite interactions is a critical step for controlling parasite transmission. Reports show that a primary O. ostertagi infection in cattle does not elicit the classic Th2 (anti-inflammatory) paradigm suggesting that an overall mixed response (mixture of Th1, Th2 and other types of Th) may dominate in the absence of a protective response. Little is known about the host innate immune pathways to which O. ostertagi is subjected. This research investigates the early onset of host immune response during the infection by determining the; 1) kinetic responses of immune mediated genes within peripheral blood mononuclear cells using quantitative (q) real time (RT) PCR; and 2) influence of O. ostertagi excretory secretory molecules on host innate immune cells i.e., macrophages, by in-vitro cell activation assays followed by qRT-PCR and immune-cytochemistry. Results show that upon progression of the disease, gene expression of a subset of Toll-like receptor genes increased, indicating active involvement of different cellular immune responses. Additionally, morphological changes in macrophages coupled with transcriptional changes in TNFα and TGFβ supported classical signs of cell activation. These results demonstrate early initiation of host immune responses during a parasitic infection and help further elucidate the complex and intimate relationship between O. ostertagi and its bovine host.