TGF-b2 induction regulates invasiveness of Theileria-transformed leukocytes and disease susceptibility

Theileria parasites invade and transform bovine leukocytes causing either East Coast fever (T. parva), or tropical theileriosis (T. annulata). Susceptible animals usually die within weeks of infection, but indigenous infected cattle show markedly reduced pathology, suggesting that host genetic factors may cause disease susceptibility. Attenuated live vaccines are widely used to control tropical theileriosis and attenuation is associated with reduced invasiveness of infected macrophages in vitro. Disease pathogenesis is therefore linked to aggressive invasiveness, rather than uncontrolled proliferation of Theileria-infected leukocytes. We show that the invasive potential of Theileria-transformed leukocytes involves TGF-b signalling. Attenuated live vaccine lines express reduced TGF-b2 and their invasiveness can be rescued with exogenous TGF-b. Importantly, infected macrophages from disease susceptible Holstein-Friesian (HF) cows express more TGF-b2 and traverse Matrigel with great efficiency compared to those from disease-resistant Sahiwal cattle. Thus, TGF-b2 levels correlate with disease susceptibility. Using fluorescence and time-lapse video microscopy we show that Theileria-infected, disease-susceptible HF macrophages exhibit increased actin dynamics in their lamellipodia and podosomal adhesion structures and develop more membrane blebs. TGF-b2-associated invasiveness in HF macrophages has a transcription-independent element that relies on cytoskeleton remodelling via activation of Rho kinase (ROCK). We propose that a TGF-b autocrine loop confers an amoeboid-like motility on Theileria-infected leukocytes, which combines with MMP-dependent motility to drive invasiveness and virulence.

Theileria parva-transformed T cells show enhanced resistance to Fas/Fas ligand-induced apoptosis

Lymphocyte homeostasis is regulated by mechanisms that control lymphocyte proliferation and apoptosis. Activation-induced cell death is mediated by the expression of death ligands and receptors, which, when triggered, activate an apoptotic cascade. Bovine T cells transformed by the intracellular parasite Theileria parva proliferate in an uncontrolled manner and undergo clonal expansion. They constitutively express the death receptor Fas and its ligand, FasL but do not undergo apoptosis. Upon elimination of the parasite from the host cell by treatment with a theilericidal drug, cells become increasingly sensitive to Fas/FasL-induced apoptosis. In normal T cells, the sensitivity to death receptor killing is regulated by specific inhibitor proteins. We found that anti-apoptotic proteins such as cellular (c)-FLIP, which functions as a catalytically inactive form of caspase-8, and X-chromosome-linked inhibitor of apoptosis protein (IAP) as well as c-IAP, which can block downstream executioner caspases, are constitutively expressed in T. parva-transformed T cells. Expression of these proteins is rapidly down-regulated upon parasite elimination. Antiapoptotic proteins of the Bcl-2 family such as Bcl-2 and Bcl-x(L) are also expressed but, in contrast to c-FLIP, c-IAP, and X-chromosome-linked IAP, do not appear to be tightly regulated by the presence of the parasite. Finally, we show that, in contrast to the situation in tumor cells, the phosphoinositide 3-kinase/Akt pathway is not essential for c-FLIP expression. Our findings indicate that by inducing the expression of antiapoptotic proteins, T. parva allows the host cell to escape destruction by homeostatic mechanisms that would normally be activated to limit the continuous expansion of a T cell population.

Eosinophilic esophagitis in adults--no clinical relevance of wheat and rye sensitizations

BACKGROUND: Eosinophilic esophagitis (EE) is often associated with concomitant atopic diseases. In children with EE in whom food allergens have been identified as causative factors, elemental and elimination diets result in an improvement or resolution of symptoms. Most adult EE patients are sensitized to aeroallergens, which cross-react with plant-derived food allergens, most commonly to grass pollen and cereals. AIMS OF THE STUDY: To investigate the clinical relevance of the sensitization to wheat and rye, and the efficacy of an allergen-specific elimination diet in adult EE patients. METHODS: Six patients (five men, one women) with permanently active EE sensitized to grass pollen and the cereals wheat and rye underwent a double-blind placebo-controlled food challenge and were kept on an elimination diet avoiding wheat and rye for 6 weeks. RESULTS: The challenge tests with wheat and rye did not provoke any EE symptoms in all patients. The elimination diet failed in reducing disease activity. Although one patient noticed an improvement of symptoms, endoscopic and histopathologic findings remained unchanged. CONCLUSIONS: In adult EE patients, sensitization to wheat and rye does not seem causative for EE. Elimination diet is not a reliable and efficient therapeutic measure in EE patients sensitized to wheat and rye. Low specific immunoglobulin-E levels to wheat and rye may be a consequence of the underlying grass pollen allergy.

The nuclear factor-kappaB and p53 pathways function independently in primary cells and transformed fibroblasts responding to genotoxic damage

With nuclear factor-kappaB (NF-kappaB) and p53 functions generally having disparate outcomes for cell survival and cell division, understanding how these pathways are coordinated following a common activation signal such as DNA damage has important implications for cancer therapy. Conflicting reports concerning NF-kappaB and p53 interplay in different cell line models prompted a reexamination of this issue using mouse primary thymocytes and embryonic fibroblasts, plus fibroblasts transformed by E1A12S. Here, we report that following the treatment of these cells with a range of stress stimuli, p53 and NF-kappaB were found to regulate cell cycling and survival independently.