PubMed Health⌕ Search

Biomedical subjects

B Poutrel

Publications and source records attributed to B Poutrel.

At least 19 recordsLinked to original sources
PubMed2001

Immunopotentiation of Staphylococcus aureus type 5 capsular polysaccharide co-entrapped in liposomes with alpha-toxin.

Immunopotentiation of Staphylococcus aureus type 5 capsular polysaccharide (CP5) by use of liposomes as an alternative to protein-polysaccharide conjugates was investigated. Mice were immunized twice with cationic liposomes containing CP5 alone or CP5 co-entrapped with alpha-toxin or heat-detoxified alpha-toxin. Immunogenicity of these different antigens was compared with CP5-alpha-toxin conjugates. Antibodies against CP5 were elicited in mice immunized with conjugates or liposomes containing co-entrapped CP5 and alpha-toxin. Liposomes containing CP5 alone or co-entrapped CP5 and alpha-toxoid failed to induce antibodies against CP5. All the preparations entailed an antibody response against alpha-toxin and highest antibody and neutralizing activity titers were obtained with liposomes. These results show that liposomes can be used to immunopotentiate CP5, however, a co-incorporated protein able to insert lipids bilayers is probably required.

Adjuvants, Immunologic↗
PubMed2001

Cell subpopulations and cytokine expression in cow milk in response to chronic Staphylococcus aureus infection.

Staphylococcus aureus is a major pathogen in bovine intramammary infections of subclinical and chronic nature. Persistent infection with S. aureus has been postulated to be associated with an impaired immune response. This study was designed to define changes in peripheral blood and milk cell subpopulations during chronic S. aureus infection. The expression of specific antigens on the surface of lymphocytes and neutrophils was studied by flow cytometry. Cytokines and cytokine transcripts elaborated by the milk-derived cells were also investigated, using ELISA and reverse transcription polymerase chain reaction, respectively. The results indicated that cell subpopulations in blood from infected cows were not modified. In contrast, changes occurred in infected milk: neutrophils were the main cell population, but they were not in a highly activated state; the CD8+ T-lymphocytes were mainly recruited compared with the CD4+ T-lymphocytes, suggesting that CD8+ T-lymphocytes play an important role in chronic S. aureus infection. Also, the proportion of the B-lymphocytes among the total lymphocyte population was increased, suggesting that a humoral response developed, and no change was observed in the gammadelta subset. No cytokine mRNA was found in milk cells from uninfected mammary glands. In contrast, interleukin (IL)-1alpha, IL-1beta, IL-6 and tumor necrosis factor alpha pro-inflammatory cytokine and IL-10 and IL-12 regulatory cytokine mRNA were synthesized in cells derived from infected mammary glands, whereas no IL-2 nor IL-4 mRNA were found. Therefore, cells present in milk during chronic S. aureus infection were activated, but did not reveal any polarization of the immune response.

Animals↗
PubMed2001

Characterization of Staphylococcus aureus strains isolated from cystic fibrosis patients by conventional and molecular typing.

The phenotypic and genotypic characteristics of Staphylococcus aureus strains isolated from respiratory tract of cystic fibrosis (CF) patients were investigated. Slime production, cell-surface hydrophobicity, type of capsular polysaccharide, profile of heteroresistance to methicillin and Sma I restriction profiles were evaluated. S. aureus CF strains have been shown to be heterogeneous in respect to several important features. All of them were slime producing with variation in colony morphology. High or moderate cell-surface hydrophobicity (CSH) was found for, respectively, 16.2% and 83.8% strains. Thirty strains were resistant to methicillin, 60% of them showed heteroresitance and 40% were homoresistant. It was found that 59.6% of strains produced capsular polysaccharides (CP) of 5 or 8 type. Among CP5/CP8 strains, CP8 was the predominant type (81.1%). Typing of 62 CF strains by macrorestriction analysis of chromosomal DNA revealed several major types, differing in their SmaI profiles with a similarity coefficient lower than 0.4. Some of the strains isolated from the same patient at different times of hospitalization, as well as strains isolated at the same time from the relatives, were identical in their PFGE pattern.

Adolescent↗
PubMed2000

Cells and cytokines in inflammatory secretions of bovine mammary gland.

In response to invading bacteria, the mammary gland is protected by a variety of defence mechanisms, which can be separated into two distinct categories: innate immunity and specific immunity. Milk somatic cells consist of several cell types, including neutrophils, macrophages, lymphocytes and a smaller percentage of epithelial cells. In the healthy lactating mammary gland, macrophages are the predominant cell type whereas neutrophils are the major cell population during early inflammation. Following a bacteria invasion, neutrophil recruitment is elicited by inflammatory mediators that are produced in the infected gland by cells, possibly macrophages, activated by bacteria phagocytosis or responding to bacterial toxins or metabolites. Several cytokines, including interleukin- (IL-) 1 beta, IL-6, IL-8, tumour necrosis factor- (TNF-) alpha and interferon- (IFN-) gamma are known to be important to elicit the acute phase response and allow the accumulation of leukocytes at the site of infection. In addition to their role in early non-specific defences, macrophages also play a key role in the specific immune system, as antigen processing and presenting cells for the T cells. Few lymphocytes are found in milk of healthy glands where the predominant phenotype is CD8+ T cells. During the inflammatory reaction, T cells are recruited in milk and CD4+ cells become the predominant phenotype. The understanding of the specific and nonspecific immune mechanisms involved in the mammary gland defence against invading bacteria may lead to the development of new vaccines and to the use of cytokines to design immunomodulatory strategies for the control of bovine mastitis.

Animals↗
PubMed2000

Kinetics of cells and cytokines during immune-mediated inflammation in the mammary gland of cows systemically immunized with Staphylococcus aureus alpha-toxin.

OBJECTIVE: To examine changes in inflammatory mediators, lymphocyte subpopulations and neutrophil activation that occur during an immune-mediated recruitment of neutrophils in the mammary gland. SUBJECTS: 11 clinically healthy cows. TREATMENT: 5 cows received 2 subcutaneous injections of 30 microg of alpha-toxin of Staphylococcus aureus, two months apart. Three months after the last immunization, 5 microg of alpha-toxin were injected, via the teat end, in one randomly selected quarter of the 5 immunized cows and of the 6 unimmunized cows (control group). METHODS: Blood and milk samples were collected at several times during 4 days post-challenge. Blood and milk cells were purified to be stained with specific mAbs and analysed by flow cytometry, or to be used for cytokine RT-PCR. Bovine serum albumin, haptoglobin, cytokines and C5a were also analysed in milk or plasma samples using radial immunodiffusion assay or ELISA. RESULTS: Large amounts of cells (> 1 million/ml of milk) were recruited in the quarters of the immunized cows, whereas no recruitment occurred in the control group. In blood of immunized animals, haptoglobin was present and expression of surface adhesion molecules on neutrophils was modified whereas no change was observed concerning the lymphocyte subpopulations. On milk-derived neutrophils, the expression of CD11b and CD18 was upregulated compared to blood, in contrast to CD62L that was downregulated. The CD8+ cells were recruited as soon as 12 h post-challenge, in contrast to the CD4+ cells, 96 h post-challenge. No IL-1beta, TNF-alpha, IL-8 and C5a were detected using ELISA. mRNA of IL-1alpha, IL-1beta, IL-6, TNF-alpha, IL-8 and IL-12 were found in almost all the samples. CONCLUSIONS: The immunization triggered an early and massive neutrophil recruitment from the blood into the milk compartment as well as the recruitment of a cytotoxic/suppressor lyphocyte population during the early acute phase response. These results could help to devise new vaccinal strategies to fight against staphylococcal mastitis.

Animals↗
PubMed2000

Differential induction of complement fragment C5a and inflammatory cytokines during intramammary infections with Escherichia coli and Staphylococcus aureus.

The prompt recruitment of neutrophils to the site of infection is essential for the defense of the bovine mammary gland against invading pathogens and is determinant for the outcome of the infection. Escherichia coli is known to induce clinical mastitis, characterized by an intense neutrophil recruitment leading to the eradication of the bacteria, whereas Staphylococcus aureus induces subclinical mastitis accompanied by a moderate neutrophil recruitment and the establishment of chronic mastitis. To elicit the neutrophil recruitment into the udder, inflammatory mediators must be produced after recognition of the invading pathogen. To our knowledge, those mediators have never been studied during S. aureus mastitis, although understanding of the neutrophil recruitment mechanisms could allow a better understanding of the differences in the pathogeneses elicited by E. coli and S. aureus. Therefore, we studied, at several time points, the accumulation of neutrophils and the presence of the chemoattractant complement fragment C5a and of the cytokines interleukin-1beta (IL-1beta), tumor necrosis factor alpha, and IL-8 in milk after inoculation of E. coli or S. aureus in lactating bovine udders. The low levels of C5a and the absence of cytokines in milk from S. aureus-infected cows, compared to the high levels found in milk from E. coli-infected animals, mirror the differences in the severities of the two inflammatory reactions. The cytokine deficit in milk after S. aureus inoculation in the lactating bovine mammary gland could contribute to the establishment of chronic mastitis. This result could help in the design of preventive or curative strategies against chronic mastitis.

Animals↗
PubMed2000

Phagocytosis and killing of Staphylococcus aureus by bovine neutrophils after priming by tumor necrosis factor-alpha and the des-arginine derivative of C5a.

OBJECTIVES: To evaluate effects of proinflammatory mediators on phagocytosis and killing of Staphylococcus aureus, the oxidative burst (OB), and expression of receptors for opsonins by bovine neutrophils. SAMPLE POPULATION: Neutrophils from 10 cattle. PROCEDURE: Neutrophils were primed with recombinant bovine tumor necrosis factor-alpha (TNF-alpha) or the des-arginine derivative of bovine C5a (C5a(desArg)) and mixed with S aureus. Phagocytosis and OB were measured by use of flow cytometry. Rate of phagocytosis and intracellular killing were evaluated. Expression of receptors for immunoglobulins and the C3bi fragment of complement were estimated by use of flow cytometry. RESULTS: Priming of neutrophils by TNF-alpha improved phagocytosis of S aureus with a concentration-dependent effect. Phagocytosis of preopsonized washed bacteria was increased by activation of neutrophils with C5a(desArg). Phagocytosis was optimal when neutrophils primed with TNF-alpha were activated with C5a(desArg). The OB of phagocytizing neutrophils was highest when TNF-alpha and C5a(desArg) were used in combination. Bactericidal activity of neutrophils was stimulated by priming with TNF-alpha or C5a(desArg). Binding of bovine IgM or IgG2 to bovine neutrophils was not stimulated byTNF-alpha, C5a(desArg), or both, and aggregated IgG1 did not bind to neutrophils regardless of their activation state. Both TNF-alpha and C5a(desArg) increased expression of beta2 integrins (CD18), with the highest expression when they were used in combination. CONCLUSIONS AND CLINICAL RELEVANCE: The mediators TNF-alpha and C5a(desArg) stimulated phagocytic killing by neutrophils and potentiated each other when used at suboptimal concentrations. Bovine neutrophils have enhanced bactericidal activities at inflammatory sites when TNF-alpha, C5a(desArg), or both are produced locally.

Animals↗
PubMed2000

Use of bovine primary mammary epithelial cells for the comparison of adherence and invasion ability of Staphylococcus aureus strains.

Adherence and invasion of epithelial cells are thought to play a role in the pathogenesis of Staphylococcus aureus mastitis. A cell culture model with primary mammary epithelial cells originating from the secretory tissue from the bovine udder was used to study adherence and invasion of S. aureus. The cells were characterized with antibodies against several cell markers that had been validated on histologic cryostat sections of bovine mammary tissue. All cells stained positively with the anticytokeratin antibodies, which are restricted to epithelial cells. The cell cultures contained a small number of alpha-smooth-muscle-actin positive cells (< 1%), probably myoepithelial cells. The use of bovine primary mammary epithelial cells and bovine S. aureus isolates, which were cultured in milk serum, results in a system similar to in vivo. Strain differences for adherence and invasion of S. aureus strains cultured in milk serum were studied. In addition, the correlation between adherence and invasion was evaluated. The number of adhered and invaded bacteria was strain dependent. The percentage of adherence after 5 min of incubation was correlated to the percentage of adherence after 3 h of incubation (r = 0.94; Pearson's correlation test). Fourteen of the 20 strains were able to invade epithelial cells. The percentage of invasion was correlated to the percentage of adherence after 5 min and to the percentage adherence after 3 h (r = 0.95 and 0.90, respectively; Pearson's correlation test). Results indicate that strain differences of adherence and invasion exist for S. aureus and that the invasion is a post adherence event.

Animals↗
PubMed2000

Generation of complement fragment C5a in milk is variable among cows.

The appearance of chemotactic fragments of complement at sites of infection is an important component of innate immunity. The contribution of C5a, the most biologically active complement fragment, to the recruitment of phagocytes in milk is not well defined, in particular the amount of C5a that is released in normal milk before inflammation. The generation of C5a in normal milk upon activation of complement by invading bacteria depends on the amount of available C5 and on the activity of the C3/C5-convertase of the alternative pathway. Concentrations of C5 were measured in one fore and one rear uninfected quarter of 19 Holstein cows. Values were consistent within cows, but widely dispersed among cows (0.19 to 1.94% blood concentration). C5 concentrations in milk were loosely related to concentrations in blood. By comparison, the range of milk concentrations of C3 (1.4 to 4.4%, mean 2.46 +/- 0.63% of blood concentration) was narrower. Two groups of six cows with high milk concentrations of C5 (cows H5: mean = 1.31%) and six cows with low milk concentrations of C5 (cow L5: mean = 0.21%) were constituted for further analysis of complement activation. There was a positive correlation between concentrations in milk of BSA and C5, but not between concentrations of BSA and C3. The activities of the C3- and C5-convertases were assessed through the deposition on complement-activating bacteria (Streptococcus agalactiae) of C3 and C5 fragments, respectively. The deposition of C3 was 1.7-fold higher, and the deposition of C5 was 2.75-fold higher in milk from H5 cows than in milk of L5 cows. Higher concentrations of C5 and better functioning of C5-convertase were mirrored by a much higher concentration of C5a in milk from H5 cows (12.30 ng/ml) than in milk of L5 cows (0.76 ng/ml) after activation of complement with zymosan. These results indicate that cows differed widely in their capacity to generate C5a in milk before inflammation, and that milk C5 concentrations were a primary limiting factor for C5a generation. Cows with the lowest milk concentrations of C5 are likely unable to use the complement system for the initial recruitment of leukocytes.

Animals↗
PubMed2000

Location of Staphylococcus aureus within the experimentally infected bovine udder and the expression of capsular polysaccharide type 5 in situ.

The objective of this study was to locate Staphylococcus aureus in the bovine udder and to investigate the expression of capsular polysaccharide type 5 (CP5) in situ in both the early and chronic stages of experimental intramammary S. aureus infections. Bovine udder tissue was obtained in early and chronic stages of intramammary infection; i.e., 24 to 96 h and 122 d after experimental intramammary infection with S. aureus Newbould 305. The presence and location of S. aureus was investigated by Gram staining of tissue sections. The expression of CP5 by S. aureus in situ was investigated by immunochemical staining of tissue sections with specific antibodies against CP5. Both in the early and chronic stages of infection, S. aureus was located within the lumen of alveoli or lactiferous ducts, in association with the epithelium, and within phagocytic cells. The staphylococci were mainly observed in clusters and often in the presence of polymorphonuclear neutrophils. Expression of CP5 by S. aureus was observed both in the early and chronic stages of infection. In general, CP5-positive S. aureus were located in alveoli and in association with the mammary epithelium. In the chronic infection, CP5-positive S. aureus were also located deep in the interstitial tissue. These results indicate that--both in early and chronic stages of experimental S. aureus mastitis--colonization of the mammary epithelia and invasion into the interstitial tissue occurs and that CP5 is expressed by S. aureus Newbould 305 in situ. The invasion of S. aureus in the interstitial tissue and the expression of CP5 probably help the bacteria to withstand the host defense mechanisms.

Animals↗
PubMed1998

Effect of extreme walking conditions for dairy cows on milk yield, chemical composition, and somatic cell count.

Thirty-two cows (16 Montbeliardes and 16 Tarentaises) in midlactation were used in an experiment utilizing a 2 x 2 factorial arrangement of treatments. Throughout the trial, cows received first-cutting cocksfoot hay for ad libitum intake supplemented with a fixed amount of concentrate that was individually adapted to the milk yield of each cow. During a 23-d experimental period, one group of cows walked 9.6 km/d; the other group of cows remained in the barn. Cows that walked daily ate less hay (-1.3 and -2.1 kg/d of dry matter for Tarentaise and Montbeliarde cows, respectively) and yielded less milk (-1.7 and -2.5 kg/d for Tarentaise and Montbeliarde cows, respectively) than did cows that did not walk daily. A residual effect of walking on milk yield was observed during the 10 d following the experimental period. For both breeds, fat content and, to a lesser extent, protein content were higher (+6.4 and +1.0 g/kg, respectively) for cows that walked. Somatic cell count was also higher for cows that walked (+115,000 cells/ml). This difference was more marked in cows that were initially infected by a minor or major pathogen (+185,000 cells/ml) than in uninfected cows (+47,000 cells/ml) and on the 1st d of walking when walking was linked to increases in pH, bovine serum albumin, and immunoglobulin G1 contents of milk (+0.08 unit, +0.16 g/L, and +0.19 g/L, respectively). Throughout the experimental period, walking induced a rise in body temperature (+1 degree C) and in plasma nonesterified fatty acids (+0.63 mM/L). On the 1st d of walking, plasma glucose, lactic acid, and cortisol contents were significantly higher for cows that walked (+0.25 g/L, +0.64 g/L, and +28.8 ng/ml, respectively).

Animals↗
PubMed1997

Differentiation of human and animal strains of Streptococcus dysgalactiae by pulsed-field gel electrophoresis.

The genetic diversity among 54 human isolates and 33 animal isolates belonging to the species Streptococcus dysgalactiae (20 alpha-haemolytic Streptococcus dysgalactiae, 23 Streptococcus equisimilis, 43 group G streptococci and one group L streptococcus) was evaluated by macrorestriction analysis of chromosomal DNA with SmaI and resolution by pulsed-field gel electrophoresis. This technique revealed a high degree of intraspecies polymorphism, leading to the differentiation of 80 distinct banding patterns, and identified the presence of two major clusters, one containing isolates of human origin and the other isolates of animal origin. These results suggest than human and animal isolates of S.dysgalactiae are genetically distinct, and support the recent proposal of the subspecies S. dysgalactiae subsp. equisimilis for human isolates. The heterogeneity revealed within isolates from the same host type indicates that pulsed-field gel electrophoresis is a powerful epidemiological tool for studying S. dysgalactiae infections.

Animals↗
PubMed1997

Heterogeneity of cell-associated CP5 expression on Staphylococcus aureus strains demonstrated by flow cytometry.

It was reported previously that two capsular polysaccharides, types 5 and 8 (CP5 and CP8), account for 70 to 80% of Staphylococcus aureus strains isolated from human and animal sources. The capsular material has been shown to play a part in virulence and in resistance to phagocytosis. With a view to investigating the role that CP plays in pathogenicity or protection, relative measurement of cell-associated CP is desirable. Flow cytometry, which permits the analysis of individual bacteria, was used to that end. Thirty isolates expressing CP5, of human (n = 7) and animal (cow, n = 11; goat, n = 3; swine, n = 3; hen, n = 3; and rabbit, n = 3) origin, were cultivated on either brain heart infusion agar (BHI) or modified medium 110 (mod 110) agar. Staphylococci were incubated with a mouse anti-CP5 monoclonal antibody (an immunoglobulin M, which does not react with staphylococcal protein A) and then stained with a fluorescein-labeled anti-murine antibody. The bacteria were washed, sonicated, and analyzed by flow cytometry. Except for three isolates, the expression of cell-bound CP5 was higher when bacteria were cultivated on mod 110 than when they were cultivated on BHI. We found a wide intraisolate phenotypic heterogeneity in surface-exposed CP5 in many strains, which appeared as mixtures of stained and unstained bacteria. Four main patterns could be distinguished on the basis of the distribution of the fluorescence of individual bacteria within the strain population as a function of growth medium. Great variations in both percentages of stained bacteria and fluorescence intensity were recorded among strains regardless of their origin. Flow cytometry analysis provided information on both the relative amounts and the distribution patterns of the surface expression of CP. This information is potentially useful for the evaluation of the part played by the capsule in the interaction of bacteria with host cells or for the study of the activities of antibodies to this target antigen, such as opsonization or prevention of adherence.

Animals↗
PubMed1997

Serological diagnosis of bovine, caprine, and ovine mastitis caused by Listeria monocytogenes by using an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay for detecting Listeria monocytogenes antibodies in bovine (n = 35), caprine (n = 27), and ovine (n = 30) milk samples was evaluated by comparison with bacteriological examination. Microtiter plates were coated with proteins obtained from culture supernatant, and antibodies were revealed with a monoclonal antibody able to react with the immunoglobulins belonging to the three animal species. The arithmetic mean optical density (OD) of milk samples infected with L. monocytogenes was above that of uninfected milk samples or milk samples infected with pathogens others than L. monocytogenes. With an OD threshold of 0.2 for goat and ewe milk samples, the sensitivity and specificity of the test were 100 and 88%, respectively. The choice of a different OD threshold (0.5) for cows allowed the discrimination of all of the infected cows and yielded no false positives, and both sensitivity and specificity were 100%.

Animals↗
PubMed1997

Control of intramammary infections in goats: impact on somatic cell counts.

Udder-half infections were recorded throughout a lactation for 1,060 goats belonging to eight commercial herds. Bacteriological examination from aseptic milk samples and somatic cell counts (SCC) determined by Fossomatic cell counting were performed at the beginning, the middle, and the end of lactation. Coagulase-negative staphylococci (CNS) were the prevalent microorganisms isolated. Geometric means of SCC for uninfected halves or halves infected by CNS or major pathogens were 272 x 10(3) cells/mL, 932,000 x 10(3) cells/mL and 2,443,000 x 10(3) cells/mL, respectively. Two field trials were carried out for evaluation of effectiveness of systematic treatment at drying-off (1 syringe by half) by a combination of penicillin, nafcillin, and dihydrostreptomycin labeled for bovines. In the first trial, all goats (n = 217) of two herds were treated immediately after the last milking, and two herds (n = 196) were used as untreated controls. In the second trial, 215 goats were treated at drying-off. There were no untreated controls. Dry period cures were determined by bacteriological examination of udder-half milk samples collected aseptically at drying-off and 2 wk after parturition. Impact of treatment on SCC was determined from composite milk samples collected monthly after kidding. At parturition, in the first trial, 40 of 202 (19.8%) udder halves were spontaneously cured in the control group vs 169 of 217 (77.9%) in the treatment group. In the second trial, 141 out of 215 treated halves were cured. During the first 75 d in lactation, geometric mean SCC was significantly lower for treated goats than for control goats. After 75 d, SCC for treated and control goats were similar. These data suggest that other methods are required to prevent new intramammary infections throughout the lactation in order to keep a low SCC in goat milk. To determine whether this could be accomplished through teat dipping, half of the goats in five commercial herds were dipped (n = 294) after morning and evening milkings through the lactation (10 mo) with a teat dip product containing nisin. Undipped goats (n = 292) served as a control group. No difference was found for SCC in milk between the dipped and undipped groups. It was concluded that systematic treatment of goats at drying-off is an efficient method for the cure of subclinical mastitis and control of SCC at the beginning of the following lactation and that effectiveness of postmilking teat disinfection remains to be demonstrated.

Animals↗
PubMed1997

Immune recruitment and bactericidal activity of neutrophils in milk of cows vaccinated with staphylococcal alpha-toxin.

The ability of Staphylococcus aureus alpha-toxin to recruit neutrophils in the milk of vaccinated cows and the bactericidal efficiency of these neutrophils were evaluated. Six lactating Holstein cows that were free of intramammary infection received systemic immunization by subcutaneous injection of Freund's incomplete adjuvant with alpha-toxin (n = 2), alpha-toxin mixed with type 5 capsular polysaccharide (n = 2), or a conjugate of these two antigens (n = 2). Controls (n = 4) and vaccinated cows (n = 6) received intramammary infusions of alpha-toxin. No increase in somatic cell count was recorded in quarter milk samples from unimmunized cows; however, 10 micrograms of alpha-toxin induced a local inflammatory reaction in vaccinated cows that was characterized by early and massive cellular recruitment into the mammary gland. More than 90% of the recruited cells were neutrophils. The speed and magnitude of the cellular recruitment were dose-dependent; the threshold dose was 0.6 microgram. Milk samples showed significant bactericidal activity against the type 5 S. aureus strain, regardless of the vaccine used, and showed a decrease in bacterial count of about 2 log10 from the initial inoculum. The best efficiency was recorded during the early phase of cellular recruitment with concomitant activation of blood-derived neutrophils. This study demonstrates that a bacterial virulence factor, alpha-toxin, is able to induce immune recruitment of neutrophils for efficient bactericidal activity in milk when cows are immunized with alpha-toxin that is used either as a nonconjugate vaccinate or as a carrier protein in a conjugate vaccine. The study also suggests that neutrophils that are recruited from blood are activated during inflammation in response to specific antigens.

Animals↗
PubMed1996

Bovine mastitis caused by Listeria monocytogenes: kinetics of antibody responses in serum and milk after experimental infection.

The kinetics of antibodies in serum and milk directed against proteins from Listeria monocytogenes were studied using 4 lactating cows after infection was experimentally induced in the udder with four strains of serotypes 4b or 1/2a. Antibodies (IgG and IgA) in samples of composite quarter milk and serum of the cow were measured by indirect ELISA. Microtiter plates were coated with proteins obtained from the culture supernatant of L. monocytogenes 4b. After challenge, an IgG response in serum and milk to listerial infections in the udder occurred for all cows, although the response varied among cows. In sera, the IgG titers reached a peak at 9 to 13 wk after challenge and remained elevated until 21 to 33 wk after challenge. In milk, the IgG titer increased significantly 3 wk after the challenge for all cows. A weak and nonpersistent increase in IgA antibodies also occurred. These results indicate that IMI by L. monocytogenes induced an increase of antibodies in milk, which could be detected with an ELISA test using our antigenic preparation. Therefore, this antigenic preparation could be used for the evaluation of a new method of diagnosis for bovine mastitis caused by L. monocytogenes.

Animals↗