We here show that anergic T cells are active mediators of T cell suppression. In co-culture experiments, we found that anergic T cells, derived from established rat T cell clones and rendered anergic via T cell presentation of the specific antigen (Ag), were active inhibitors of T cell responses. Anergic T cells inhibited not only the responses of T cells with the same Ag specificity as the anergic T cells, but were also capable of efficiently inhibiting polyclonal T cell responses directed to other epitopes. This suppression required close cell-cell contact between antigen-presenting cells (APC), anergic T cells and responder T cells, and only occurred when the epitope recognized by the anergic T cell was present. The suppression was not caused by passive competition for ligands on the APC surface, IL-2 consumption, or cytolysis, and was not mediated by soluble factors derived from anergic T cells that were stimulated with their specific Ag. When responder T cells were added 24 h after co-culturing anergic cells in the presence of Ag and APC, T cell responses were still suppressed, indicating that the suppressive effect was persistently present. However, anergic T cells were not able to suppress responder T cells that had already received a full activation signal. We propose that suppression by anergic T cells is mediated via the APC, either through modulation of the T cell-activating capacity of the APC (APC/T cell interaction), or by inhibition of T cells recognizing their ligand in close proximity on the same APC (T/T cell interaction).

The genetic stability of selected epidemiologically linked strains of Campylobacter jejuni during outbreak situations was investigated by using subtyping techniques. Strains isolated from geographically related chicken flock outbreaks in 1998 and from a human outbreak in 1981 were investigated. There was little similarity in the strains obtained from the different chicken flock outbreaks; however, the strains from each of three chicken outbreaks, including strains isolated from various environments, were identical as determined by fla typing, amplified fragment length polymorphism (AFLP) analysis, and pulsed-field gel electrophoresis, which confirmed the genetic stability of these strains during the short time courses of chicken flock outbreaks. The human outbreak samples were compared with strain 81116, which originated from the same outbreak but has since undergone innumerable laboratory passages. Two main AFLP profiles were recognized from this outbreak, which confirmed the serotyping results obtained at the time of the outbreak. The major type isolated from this outbreak (serotype P6:L6) was exemplified by strain 81116. Despite the long existence of strain 81116 as a laboratory strain, the AFLP profile of this strain was identical to the profiles of all the other historical P6:L6 strains from the outbreak, indicating that the genotype has remained stable for almost 20 years. Interestingly, the AFLP profiles of the P6:L6 group of strains from the human outbreak and the strains from one of the recent chicken outbreaks were also identical. This similarity suggests that some clones of C. jejuni remain genetically stable in completely different environments over long periods of time and considerable geographical distances.

Veterinarians play an important role in the reduction of antimicrobial use in farm animals. This study aims to quantify opinions of veterinarians from the Netherlands and Flanders regarding antimicrobial use and resistance issues in farm animals. An online survey was sent out to 678 and 1100 farm animal veterinarians in Flanders and the Netherlands, of which 174 and 437 were returned respectively. Suboptimal climate conditions were regarded as the most important cause for high antimicrobial use in farm animals. Flemish veterinarians also regarded insufficient biosecurity measures and farmers' mentality as important determinants, while the Dutch respondents ranked insufficient immunity of young animals and economic considerations of farmers as major causes. The majority of Dutch respondents (63.8 per cent) supported the existing national policy, which aimed to halve veterinary antimicrobial use, while the Flemish (32.9 per cent) were less supportive of such a policy. Improvements in housing and climate conditions, biosecurity measures and strict control of specific infectious diseases were seen as important and promising measures to reduce antimicrobial use. To reduce antimicrobial use in farm animals, some shared approaches might be applicable in both countries. However, cultural, political and societal differences between Flanders and the Netherlands require differentiated approaches to reduce veterinary antimicrobial use.

T cell responses to heat shock proteins (HSP) have disease suppressive activities through production of anti-inflammatory cytokines in patients and in models of inflammatory diseases. There is evidence that the anti-inflammatory activity of HSP-specific T cells depends on their recognition of endogenous HSP epitopes as expressed by stressed cells at sites of inflammation. Previously, we have demonstrated that such T cells can be induced by conserved sequences of microbial HSP. Now we propose that drug induced up-regulation of endogenous HSP can contribute to anti-inflammatory T cell regulation.

Objective. To prevent and treat experimental arthritis via nasal administration of an altered peptide ligand (APL) from the major arthritogenic epitope in adjuvant-induced arthritis (AIA) and to explore the mechanisms involved.Methods. Peptides were administered nasally before and after induction of arthritis. Splenocytes and lymph node cells draining both the site of inflammation and the site of tolerance induction were used for cell transfer and were studied for antigen-specific T cell characteristics. In addition, attempts were made to stop T cell tolerance in vitro, using anticytokine antibodies.Results. Nasal administration of a modulatory APL of the heat-shock protein 60 (Hsp60) 180-188 T cell epitope, alanine 183, had a suppressive effect in AIA that far exceeded that of the wild-type epitope. In addition to its effectiveness in preventing AIA, alanine 183 may be effective in the treatment of ongoing AIA.The protective effect of alanine 183 can be passively transferred using activated splenocytes. Nasal administration of alanine 183 did not lead to detectable T cell proliferation or interleukin-2 (IL-2) production in mandibular lymph node cells, while transforming growth factor ␤ (TGF␤), IL-10, and IL-4 were readily produced. Likewise, after nasally induced tolerance, followed by induction of arthritis, inguinal lymph node cells produced IL-4, TGF␤, and IL-10. After neutralizing in vitro the individual cytokines with anticytokine antibodies, only blocking of IL-10 production led to reversal of tolerance, at the site of tolerance induction and the site of inflammation.Conclusion. Nasal administration of an APL of Hsp60 180-188 induces highly effective protection against AIA through generation of regulatory cells that produce IL-4, TGF␤, and IL-10, whereas the induced tolerance is driven mainly by production of IL-10.

Intestinal colonization and shedding of pathogenic bacteria in animal feces is an important factor in both human food safety and animal health. The effect of broiler feed additives flavophospholipol (FPL; Flavomycin, bambermycins) and salinomycin sodium (SAL; Sacox) given singly on the excretion of Salmonella enteritidis, Campylobacter jejuni, and Clostridium perfringens was studied following controlled infection. The incidence of shedding (number of birds with positive fecal cultures) and the degree of shedding (cfu per gram of feces in positive birds) were measured to determine the influence of these two common feed additive antibiotics on shedding rates of potential pathogens. A total of 216 Ross broiler chickens, housed in battery cages, were fed either an unmedicated feed (controls), feed containing FPL, or feed containing SAL. Feed treatment groups were subdivided into three bacterial challenge groups of 24 chicks, each receiving only one of the pathogens. Bacterial challenge was administered orally on Days 11 and 12 for Salmonella and Campylobacter and on Days 2 and 3 for Clostridium. Fecal samples were collected weekly up to 6 wk of age and cultured for presence of the target organism. The shedding rate was determined by decimal dilutions of the fecal samples. Feeding FPL resulted in a reduced (P < or = 0.05) degree and incidence of Salmonella and Clostridium shedding at 6 wk. Feeding SAL reduced (P < or = 0.05) the incidence of Salmonella shedding at 6 wk. Neither feed additive affected the incidence nor the degree of Campylobacter shedding. The results of this study indicate that these feed additives may reduce the incidence of these potential human and animal pathogens in preslaughter broilers.

This study reports an identification of the major processing products of an exogenous protein antigen, viz, sperm-whale myoglobin, as obtained after cell-free processing with partially purified macrophage endosomes. It is demonstrated that such a system yields fragments that are indistinguishable by high performance liquid chromatography analysis from those generated after uptake of myoglobin inside live macrophages. The concerted action of the endosomal proteases cathepsin D and cathepsin B can account for nearly all cleavages observed. Cathepsin D appears to be mainly responsible for the initial cleavage of myoglobin, while cathepsin B catalyzes the C-terminal trimming of initially released fragments. The fragments released by cathepsin D contain most, if not all, major epitopes for murine myoglobin-specific helper T cells. Interestingly, each known T cell epitope of myoglobin is located at the very N terminus of a different myoglobin fragment released upon processing. In order to explain this correspondence, noted also in several other protein antigens, a structural relationship is proposed between antigen processing by cathepsin D and antigen recognition by major histocompatibility complex (MHC) class II products. As is demonstrated here, this relationship may be used as a predictive tool for the identification of MHC-binding sequences as well as of T cell epitopes in their naturally occurring form.

SummarySalmonellosis is a public health concern in both the developed and developing countries. Although the majority of human non‐typhoidal Salmonella enterica (NTS) cases are the result of foodborne infections or person‐to‐person transmission, NTS infections may also be acquired by environmental and occupational exposure to animals. While a considerable number of studies have investigated the presence of NTS in farm animals and meat/carcasses, very few studies have investigated the risk of NTS colonization in humans as a result of direct animal exposure. We investigated asymptomatic NTS colonization in 204 backyard chicken farms, 204 farmers and 306 matched individuals not exposed to chicken farming, in southern Vietnam. Pooled chicken faeces, collected using boot or handheld swabs on backyard chicken farms, and rectal swabs from human participants were tested. NTS colonization prevalence was 45.6%, 4.4% and 2.6% for chicken farms, farmers and unexposed individuals, respectively. Our study observed a higher prevalence of NTS colonization among chicken farmers (4.4%) compared with age‐, sex‐ and location‐ matched rural and urban individuals not exposed to chickens (2.9% and 2.0%). A total of 164 chicken NTS strains and 17 human NTS strains were isolated, and 28 serovars were identified. Salmonella Weltevreden was the predominant serovar in both chickens and humans. NTS isolates showed resistance (20–40%) against tetracycline, chloramphenicol, sulfamethoxazole‐trimethoprim and ampicillin. Our study reflects the epidemiology of NTS colonization in chickens and humans in the Mekong delta of Vietnam and emphasizes the need of larger, preferably longitudinal studies to study the transmission dynamics of NTS between and within animal and human host populations.