Background: The effect of pre-weaning concentrate supplementation on peripheral distribution of leukocytes, functional activity of neutrophils, acute phase protein response, metabolic and behavioural response, and performance of abruptly weaned and housed beef calves was investigated. Calves were grazed with their dams until the end of the grazing season when they were weaned and housed (day (d) 0) in a concrete slatted floor shed, and offered grass silage ad libitum plus supplementary concentrates. Twenty-six days prior to weaning and housing, 20 singled suckled, pure-bred Simmental male (non-castrated), (n = 10, m) and female (n = 10, f) calves were assigned to one of two treatments (i) concentrate supplement (CS: n = 10 (5 m and 5 f), mean age (s.d.) 201 (12.8) d, mean weight (s.d.) 258 (20.2) kg) or (ii) no concentrate supplement (controls) (NCS: n = 10, (5 m and 5 f), mean age (s.d.) 201 (13.4) d, mean weight (s.d.) 257 (19.6) kg) pre-weaning. Results: There was a treatment × sampling time interaction (P < 0.05) for percentage CD4⁺ and WC1⁺ (γδ T cells) lymphocytes and concentration of plasma globulin. On d 2, percentage CD4⁺ lymphocytes decreased (P < 0.001) in both treatments. Subsequently on d 7, percentage of CD4⁺ lymphocytes increased (P < 0.01) in CS compared with d 0, whereas percentage of CD4⁺ lymphocytes in NCS did not differ (P > 0.05) from d 0. On d 2, WC1⁺ lymphocytes decreased (P < 0.05) in both treatments but the decrease was greater (P < 0.05) in NCS than CS. Subsequently, percentages did not differ (P > 0.05) from pre-weaning baseline. On d 2, the increase in concentration of globulin was greater (P < 0.05) in CS compared with NCS, and subsequently there was no difference between treatments. Pre-weaning ADG was 1.07 (s.e.m.) (0.26) kg and 0.99 (s.e.m.) (0.26) kg for CS and NCS, respectively. Post-weaning, CS calves spent more time lying compared with NCS calves. Conclusions: Calves supplemented with concentrate prior to weaning had a lesser reduction in WC1⁺ lymphocytes, increased percentage CD4⁺ lymphocytes and concentration of total protein, and spent more time lying post-weaning, compared with non-supplemented calves.

Gliotoxin, and other related molecules, are encoded by multi-gene clusters and biosynthesized by fungi using non-ribosomal biosynthetic mechanisms. Almost universally described in terms of its toxicity towards mammalian cells, gliotoxin has come to be considered as a component of the virulence arsenal of Aspergillus fumigatus. Here we show that deletion of a single gene, gliT, in the gliotoxin biosynthetic cluster of two A. fumigatus strains, rendered the organism highly sensitive to exogenous gliotoxin and completely disrupted gliotoxin secretion. Addition of glutathione to both A. fumigatus ΔgliT strains relieved gliotoxin inhibition. Moreover, expression of gliT appears to be independently regulated compared to all other cluster components and is up-regulated by exogenous gliotoxin presence, at both the transcript and protein level. Upon gliotoxin exposure, gliT is also expressed in A. fumigatus ΔgliZ, which cannot express any other genes in the gliotoxin biosynthetic cluster, indicating that gliT is primarily responsible for protecting this strain against exogenous gliotoxin. GliT exhibits a gliotoxin reductase activity up to 9 µM gliotoxin and appears to prevent irreversible depletion of intracellular glutathione stores by reduction of the oxidized form of gliotoxin. Cross-species resistance to exogenous gliotoxin is acquired by A. nidulans and Saccharomyces cerevisiae, respectively, when transformed with gliT. We hypothesise that the primary role of gliotoxin may be as an antioxidant and that in addition to GliT functionality, gliotoxin secretion may be a component of an auto-protective mechanism, deployed by A. fumigatus to protect itself against this potent biomolecule. The pathogenic fungus Aspergillus fumigatus causes disease in immunocompromised individuals such as cancer patients. The fungus makes a small molecule called gliotoxin which helps A. fumigatus bypass the immune system in ill people, and cause disease. Although a small molecule, gliotoxin biosynthesis is enabled by a complex series of enzymes, one of which is called GliT, in A. fumigatus. Amazingly, nobody has really considered that gliotoxin might be toxic to A. fumigatus itself. Here we show that absence of GliT makes A. fumigatus highly sensitive to added gliotoxin and inhibits fungal growth, both of which can be reversed by restoring GliT. Neither can the fungus make or release its own gliotoxin when GliT is missing. We also show that gliotoxin sensitivity can be totally overcome by adding glutathione, which is an important anti-oxidant within cells. We demonstrate that gliotoxin addition increases the production of GliT, and that GliT breaks the disulphide bond in gliotoxin which may be a step in the pathway for gliotoxin protection or release from A. fumigatus. We conclude that gliotoxin may mainly be involved in protecting A. fumigatus against oxidative stress and that it is an accidental toxin.

Increased recognition of parvovirus B19 (B19), an erythrovirus, as a significant human pathogen that causes fetal loss and severe disease in immunocompromised patients has resulted in intensive efforts to understand the pathogenesis of B19-related disease, to improve diagnostic strategy that is deployed to detect B19 infection and blood-product contamination and, finally, to elucidate the nature of the cellular immune response that is elicited by the virus in diverse patient cohorts. It is becoming clear that at least three related erythrovirus strains (B19, A6/K71 and V9) are circulating in the general population and that viral entry into target cells is mediated by an expanding range of cellular receptors, including P antigen and β-integrins. Persistent infection by B19 is emerging as a contributory factor in autoimmune disease, a hypothesis that is constrained by the detection of B19 in the skin of apparently healthy individuals. B19 infection during pregnancy may account for thousands of incidences of fetal loss per annum in Europe, North America and beyond, yet there is currently only minimal screening of pregnant women to assess serological status, and thereby risk of infection, upon becoming pregnant. Whilst major advances in diagnosis of B19 infection have taken place, including standardization of serological and DNA-based detection methodologies, blood donations that are targeted at high-risk groups are only beginning to be screened for B19 IgG and DNA as a means of minimizing exposure of at-risk patients to the virus. It is now firmly established that a Th1-mediated cellular immune response is mounted in immunocompetent individuals, a finding that should contribute to the development of an effective vaccine to prevent B19 infection in selected high-risk groups, including sickle-cell anaemics.

The secretion and activation of the major cathepsin L1 cysteine protease involved in the virulence of the helminth pathogen Fasciola hepatica was investigated. Only the fully processed and active mature enzyme can be detected in medium in which adult F. hepatica are cultured. However, immunocytochemical studies revealed that the inactive procathepsin L1 is packaged in secretory vesicles of epithelial cells that line the parasite gut. These observations suggest that processing and activation of procathepsin L1 occurs following secretion from these cells into the acidic gut lumen. Expression of the 37-kDa procathepsin L1 in Pichia pastoris showed that an intermolecular processing event within a conserved GXNXFXD motif in the propeptide generates an active 30-kDa intermediate form. Further activation of the enzyme was initiated by decreasing the pH to 5.0 and involved the progressive processing of the 37 and 30-kDa forms to other intermediates and finally to a fully mature 24.5 kDa cathepsin L with an additional 1 or 2 amino acids. An active site mutant procathepsin L, constructed by replacing the Cys²⁶ with Gly²⁶, failed to autoprocess. However, [Gly²⁶]procathepsin L was processed by exogenous wild-type cathepsin L to a mature enzyme plus 10 amino acids attached to the N terminus. This exogenous processing occurred without the formation of a 30-kDa intermediate form. The results indicate that activation of procathepsin L1 by removal of the propeptide can occur by different pathways, and that this takes place within the parasite gut where the protease functions in food digestion and from where it is liberated as an active enzyme for additional extracorporeal roles.