Immunomodulatory effect of Hypoderma lineatum antigens: in vitro effect on bovine lymphocyte proliferation and cytokine production

This study examines the immunomodulatory effect of a crude larval extract (CLE), obtained from first stage larvae (L1) of H. lineatum , and the purified fractions hypodermin A (HyA), HyB and HyC. Proliferative responses of peripheral blood mononuclear cells (PBMC) from uninfested and previously infested cattle and the production of the cytokines IL-10, IL-4 and IFN-γ, in response to concanavalin A (Con A), were determined. The stimulation index of peripheral blood mononuclear cells from uninfested cattle was significantly lower than that from infested animals with the different antigens assayed. The HyA was the antigen that most inhibited the proliferative response, followed by the HyB, the HyC and the CLE. This hypodermin provoked an increase of IFN-γ and a suppression of IL-10 production that would support a Th1-like cytokine response. The HyB reduced the production of IL-10 stimulated by the Con A in cultures from infested animals. The HyC did not modulate the production of cytokines. Finally, the CLE induced a marked suppression in the production of the different cytokines in cultures from naïve and previously sensitized animals. Our results indicate that Hypoderma larval secretions are comprised of different components (hypodermins) that individually induce distinct but partially overlapping modulatory responses.     

Humoral immune responses of Hereford cattle vaccinated with midgut antigens of the cattle tick, Boophilus microplus

Vaccination of cattle with midgut membrane (GM) antigen derived from the cattle tick, Boophilus microplus, infected with the adjuvant Quil A, resulted in significant increases in total immunoglobulins, mainly in the IgG1 and IgG2 fractions of the serum. Analysis of the anti-GM antibody levels of vaccinated cattle showed that the levels of IgG, IgG1 and complement-fixing antibodies were significantly correlated to protection against infestation with cattle ticks. Anti-GM antibodies of the IgG2 and IgM isotype were not correlated to protection against infestation with cattle ticks. Anti-GM antibodies fixed complement (C') in the presence of GM, larval membrane antigen and live, midgut cells, but not in the presence of live, larval cells. Anti-GM antibodies were able to fix C' equally well in the presence of GM antigen and live, midgut cells. None of the antigens tested activated the alternate pathway of complement under the conditions tested. Levels of anti-GM IgG1 antibodies were used to develop a regression model for predicting levels of protection against infestation with cattle ticks in vaccinated cattle.     

Galanin-like immunoreactive endocrine cells in bovine pancreas

Pancreata of fetal, neonatal and adult cattle were studied immunohistochemically for galanin. The results revealed galanin-like immunoreactivity both in the endocrine cells and in the neural elements. The galanin-like immunoreactive endocrine cells (Gal-LIEC) were confined to the large islets, and were not observed in the islets of Langerhans and exocrine pancreas. They were first detected at the third prenatal month. Their developmental profile showed an increase from fetal to early neonatal stage with a subsequent decrease towards adulthood. The considerable number of Gal-LIEC from late prepartum to early postpartum stage may imply functional significance of galanin during the perinatal development of cattle. Coexistence of galanin and insulin was also observed which may suggest autocrine interaction between the 2 hormones.     

Accumulation of L-type Bovine Prions in Peripheral Nerve Tissues

We recently reported the intraspecies transmission of L-type atypical bovine spongiform encephalopathy (BSE). To clarify the peripheral pathogenesis of L-type BSE, we studied prion distribution in nerve and lymphoid tissues obtained from experimentally challenged cattle. As with classical BSE prions, L-type BSE prions accumulated in central and peripheral nerve tissues.     

四川省2001年耕牛血吸虫感染现状分析

目的 了解耕牛在四川省血吸虫病传播和防治中的作用。方法 普查全省流行村耕牛存栏情况，按20％流行村比例抽样调查耕牛感染情况。结果 耕牛是四川省血吸虫病传播的主要污染源，IPC为87．70％；耕牛养殖量与人群感染呈正比，养殖越多，感染越重；养牛户人群感染率明显高于无牛户，有病牛的家庭人群感染率是其它家庭的4～70倍。结论 加强耕牛血吸虫病防治是当前山丘型血吸虫病流行区的主要任务。     

A rapid colorimetric assay for measuring low concentrations of haemoglobin in large numbers of bovine plasma samples

The aim of this study was to develop a microplate colorimetric assay that could measure low levels (<2mg/mL) of haemoglobin in bovine plasma as a result of haemolytic trauma. The method presented uses the pseudo-peroxidase activity of haemoglobin to catalyse a redox reaction between tetramethylbenzidine (TMB) and hydrogen peroxide in an acidic environment. There is a good linear relationship (r ²=0.999) between the optical density of the reaction product and haemoglobin concentration. The assay is highly repeatable (F=1.219, P=0.303) with an intra- and inter-assay variation ranging from 2.3% to 3.9% and 5.8% to 11.3% respectively for three control samples containing high, medium and low levels of haemoglobin. In conclusion, the method described in this paper provides an accurate, precise measurement of low concentrations of haemoglobin in bovine plasma that enables correction for haemolysis.     

Outcome of Three Commercial Serum ELISAs and Faecal Detection of Mycobacterium avium subsp. paratuberculosis in Consecutive Samples from a Cattle Herd with Low Prevalence of Paratuberculosis (Johne’s Disease)

Paratuberculosis (Johne’s disease) in ruminants is caused by Mycobacterium avium subsp. paratuberculosis (MAP). Owing to the lack of accurate laboratory tests, diagnosis is challenging in subclinically infected cattle. To evaluate the long‐term performance of serum ELISAs for the detection of paratuberculosis in a dairy herd with low MAP‐prevalence, three investigations of all the cows and the consecutive testing of 33 cows suspected to be infected with MAP and 30 cows classified as MAP free were performed over a period of 22 months. Blood samples were tested by three commercial serum ELISAs, MAP shedding was detected by bacteriological culture and polymerase chain reaction (PCR). The ELISA results varied in a wide range in the herd investigations with 1.2% to 18.8% positive samples, the faecal samples were positive for MAP between 1.8% and 4.9% in the three herd investigations. Over the study period, ELISA‐positive serum samples varied between 0.0% and 69.7% in MAP‐suspicious and 0.0% and 17.6% in MAP‐unsuspicious cows with a poor correlation between ELISAs and faecal shedding. The correlation coefficient of the optical density values of the three ELISAs varied between 0.348 and 0.61. Evidence of cow specific variations of residuals was found in all linear models. The linear mixed models showed relevant contribution of cow specific variation in explanation of the residual variances. They also showed significant effects of the explanatory ELISA, the group (MAP‐suspicious or MAP‐unsuspicious) and the time of sampling. It can be concluded that the choice of the laboratory test significantly influences the outcome of the testing for MAP and that none of the three ELISAs can be thoroughly recommended as single test for the early diagnosis of paratuberculosis in cattle. Test results should always be interpreted with caution to avoid erroneous decisions and the disappointment of those engaged in the abatement of paratuberculosis.