Case-control study on feed risk factors for BSE cases born after the feed ban in France.

In France, after the ban on meat and bone meal (MBM) in cattle feeding in June 1990, cases of Bovine Spongiform Encephalopathy (BSE) have continued to be detected in bovines born after that ban (called BAB cases). A case-control study was therefore carried out to determine the way these cases were contaminated. A multivariate conditional model was built adjusting for the production type of the animals and taking into account the herd size. The results confirmed that feeding cattle with proprietary concentrates was at risk for BSE, with an adjusted odds ratio of 6.8 (2.5; 18.7) for the consumption of less or three different proprietary concentrates and 17.6 (5.7; 54.8) for more than three, when comparing with no consumption of proprietary concentrates, considering feeding of bovines before the age of two. The results suggest that cross-contaminations by MBM in bovine concentrates have occurred after 1990. To a lesser extent, on-farm cross-contaminations, i.e. consumption by cattle of feedstuffs initially dedicated to other animals and which could legally contain MBM, have probably also existed, since the presence on farms of poultry fed purchased feed involved an increased risk of BSE with an odds ratio of 1.8 (1.1; 3.0). The use of milk replacers, which often incorporates animal fats, was also at risk with an odds ratio of 1.8 (1.0; 3.1).

Estimating the trend of the French BSE epidemic over six birth cohorts through the analysis of abattoir screening in 2001 and 2002.

A bovine spongiform encephalopathy (BSE) testing programme at the abattoir started in 2001 in France. A total of 5 281 293 bovines were tested in 2001 and 2002; 87 were found positive in 2001--37 per million (95% CI 30-46)--, whereas only 71 in 2002--24 per million (95% CI 19-30). Logistic regression models were run to compare the prevalence of BSE on successive birth cohorts, using a pair-wise method of controlling for age at testing; the prevalence on the first one, determined on animals slaughtered in 2001, was compared to the prevalence on the following one determined on animals slaughtered in 2002. Five models were performed in order to compare the birth cohorts preceding and following the months of June 1993 (i.e. July 92-June 93 birth cohort compared to July 93-June 94 birth cohort) (8.5 years old cattle), June 1994 (7.5 years old cattle), June 1995 (6.5 years old cattle), June 1996 (5.5 years old cattle) and June 1997 (4.5 years old cattle). The models were adjusted for the production type of cattle and the test used. The results showed a significant increase (OR = 2.31, 95% CI 1.08-4.9) of the BSE prevalence between the July 93-June 94 and July 94-June 95 cohorts, and then a significant decrease over the next two birth cohorts; the July 95-June 96 birth cohort was significantly less affected than the July 94-June 95 one (OR = 0.46, 95% CI 0.27-0.78), and the July 96-June 97 birth cohort was significantly less affected than the July 95-June 96 one (OR = 0.17, 95% CI 0.07-0.37). The increase in BSE prevalence between the July 93-June 94 and July 94-June 95 cohorts was in agreement with modelling studies, but needs to be confronted to the data on fallen stock at the national level. The decrease in BSE prevalence on the birth cohorts born after June 1995 was in agreement with the findings on the fallen stock in the western part of France and matches the implementation of the removal of specified risk materials (SRM) and dead animals from the processing of meat and bone meal (MBM) since June 1996.

The porcine trophoblastic interferon-gamma, secreted by a polarized epithelium, has specific structural and biochemical properties.

At the time of implantation in the maternal uterus, the trophectoderm of the pig blastocyst is the source of a massive secretion of interferon-gamma (IFN-gamma), together with lesser amounts of IFN-delta, a unique species of type I IFN. This trophoblastic IFN-gamma (TrIFN-gamma) is an unprecedented example of IFN-gamma being produced spontaneously by an epithelium. We therefore studied some of its structural and biochemical properties, by comparison with pig IFN-gamma from other sources, either natural LeIFN-gamma (from adult leucocytes), or recombinant. Biologically active TrIFN-gamma is a dimeric molecule, of which monomers are mainly composed of a truncated polypeptide chain with two glycotypes, unlike LeIFN-gamma which is formed of at least two polypeptide chains and four glycotypes. TrIFN-gamma collected in the uterus lumen was enzymatically deglycosylated and analysed by mass spectrometry (MALDI-TOF). The data revealed that the more abundant polypeptide has a mass of 14.74 kDa, corresponding to a C-terminal cleavage of 17 residues from the expected 143-residue long mature sequence. A minor polypeptide, with a mass of 12.63 kDa, corresponds to a C-terminal truncation of 36 amino acids. MALDI-TOF analysis of tryptic peptides from the glycosylated molecule(s) identifies a single branched carbohydrate motif, with six N-acetylgalactosamines, and no sialic acid. The only glycan microheterogeneity seems to reside in the number of l-fucose residues (one to three). The lack of the C-terminal cluster of basic residues, and the presence of nonsialylated glycans, result in a very low net charge of TrIFN-gamma molecule. However, the 17-residue truncation does not affect the antiproliferative activity of TrIFN-gamma on different cells, among which is a porcine uterine epithelial cell line. It is suggested that these specific properties might confer on TrIFN-gamma a particular ability to invade the uterine mucosa and exert biological functions beyond the endometrial epithelium.

Trophoblastic interferon-gamma: current knowledge and possible role(s) in early pig pregnancy.

In the pig as in ruminant species, the implantation of the elongated conceptus - the embryo with its associated membranes - onto the maternal uterus is accompanied by an intense secretion of interferon (IFN), which culminates at day 15 of development. It has been shown that in fact the pig trophectoderm - the polarized epithelium which lines the conceptus - simultaneously secretes two types of interferons: IFN-gamma (IFN-gamma), which is the more abundant species, is produced in very substantial amounts. Another IFN is also secreted, which happens to be a novel type I IFN, now named IFN-delta. It was previously shown that the uterus is the most probable target of the pig trophoblastic IFNs, since no autocrine effect was found on the trophoblast. It has also been shown that, unlike for the ruminant species, the pig trophoblastic IFNs do not play an apparent role in the so-called maternal recognition of pregnancy. We have focused this review on IFN-gamma, because first, it is the major species secreted and secondly, IFN-gamma has various regulatory effects on different tissues, including lymphoid cells. We particularly address the question of the possible role of trophoblastic IFN-gamma in early pregnancy, in the light of the known biological functions of human and mouse IFN-gamma.

Cellular prion protein status in sheep: tissue-specific biochemical signatures.

Expression of the cellular prion protein PrP(C) is sine qua none for the development of transmissible spongiform encephalopathy and thus for the accumulation of the illness-associated conformer PrP(Sc). Therefore, the tissue distribution of PrP(C) at the protein level in both quantitative and qualitative terms was investigated. PrP(C) was quantified using a two-site enzyme immunometric assay which was calibrated with purified ovine recombinant prion protein (rPrP). The most PrP(C)-rich tissue was the brain, followed by the lungs, skeletal muscle, heart, uterus, thymus and tongue, which contained between 20- and 50-fold less PrP(C) than the brain. The PrP(C) content of these tissues seems to be comparable between sheep. Other organs, however, showed different, but low, levels of the protein depending on the animal examined. This was also the case for tissues from the gastrointestinal tract. The tissue containing the lowest concentration of PrP(C) was shown to be the liver, where PrP(C) was found to be between 564- and 16000-fold less abundant than in the brain. PrP(C) was concentrated from crude cellular extracts by immunoprecipitation using several monoclonal and polyclonal anti-ovine PrP antibodies. Interestingly, it was observed that the isoform profile of PrP(C) was tissue-specific. The most atypical electrophoretic profile of PrP(C) was found in the skeletal muscle, where two polypeptides of 32 and 35 kDa were detected.