Tobias Schlapp

Quantitative Detection of Chlamydia psittaci and C. pecorum by High-Sensitivity Real-Time PCR Reveals High Prevalence of Vaginal Infection in Cattle

ABSTRACT Bovine vaginal cytobrush specimens were analyzed for the presence of Chlamydia spp. by a high-sensitivity, high-specificity quantitative PCR. The 53% prevalence of low-level Chlamydia psittaci and C. pecorum genital infection detected in virgin heifers suggests predominantely extragenital transmission of Chlamydia in cattle and conforms to the high seroprevalence of anti-Chlamydia antibodies.

Identification of Foot-and-Mouth Disease Virus-Specific Linear B-Cell Epitopes To Differentiate between Infected and Vaccinated Cattle

ABSTRACT Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals. For several years, vaccination of animals, which had proven to be successful for the eradication of the disease, has been forbidden in the United States and the European Community because of the difficulty of differentiating between vaccinated and infected animals. In this study, detailed investigations of the bovine humoral immune response against FMD virus (FMDV) were performed with the aim of identifying viral epitopes recognized specifically by sera derived from FMDV-infected animals. The use of overlapping 15-mer synthetic peptides, covering the whole open reading frame of FMDV strain O1K in a peptide enzyme-linked immunosorbent assay, allowed the identification of 12 FMDV strain O1K-specific linear B-cell epitopes. Six of these linear B-cell epitopes, located in the nonstructural proteins, were used in further assays to compare the reactivities of sera from vaccinated and infected cattle. Antibodies recognizing these peptides could be detected only in sera derived from infected cattle. In further experiments, the reactivity of the six peptides with sera from animals infected with different strains of FMDV was tested, and strain-independent infection-specific epitopes were identified. Thus, these results clearly demonstrate the ability of a simple peptide-based assay to discriminate between infected and conventionally FMD-vaccinated animals.

Poxvirus-Induced Immunostimulating Effects on Porcine Leukocytes

ABSTRACT The prophylactic application of inactivated parapox ovis viruses (Baypamun; Bayer AG, Leverkusen, Germany) has been shown to reduce efficiently the outbreak of stress-mediated diseases in different species. However, little is known about the basic mechanism behind this observed stimulatory property. We therefore tested eight inactivated poxvirus strains belonging to three different genera (Orthopoxvirus, Avipoxvirus, andParapoxvirus) for their capacity to activate cells of the porcine innate and specific immune systems in vitro. The results indicated that poxviruses failed to induce increased phagocytosis, oxidative burst, or natural killer cell activity in swine. In contrast, enhanced release of interleukin-2, alpha interferon, and gamma interferon, as well as strong proliferation, could be measured. Flow cytometric analyses and cell sorting experiments identified T-helper cells as the main target responding to inactivated poxviruses: the activated cells had a CD4high CD25+ major histocompatibility complex type II-positive phenotype and were the major source of secreted cytokines. Together, the results demonstrated that all tested poxviruses possessed immunostimulating capacity. These in vitro poxvirus-induced effects may be responsible at least in part for the in vivo immunostimulating capacity of inactivated poxviruses.

Reinfection with Chlamydophila abortus by Uterine and Indirect Cohort Routes Reduces Fertility in Cattle Preexposed to Chlamydophila

ABSTRACT This study investigated the effects of controlled reinfection on fertility of cattle naturally preexposed to Chlamydophila abortus. All animals had high prechallenge levels of immunoglobulin M (IgM), IgG, IgG1, and IgG2 serum antibodies against ruminant C. abortus in a chemiluminescent enzyme-linked immunosorbent assay. Twenty virgin heifers were estrus synchronized with prostaglandin F2, artificially inseminated 2 to 3 days later, and challenged immediately by intrauterine administration of 0, 104, 105, 106, or 108 inclusion-forming units (IFU) of C. abortus. Ten heifers were estrus synchronized, inseminated, and uterine challenged 2 weeks later. These animals were also indirectly exposed to C. abortus infection (cohort challenged) by contact with their previously challenged cohorts. Pregnancy was determined by rectal palpation 42 days after insemination. All anti-C. abortus antibody isotypes increased in heifers following uterine challenge with 108 IFU. A total of 11, 83, 50, 66, and 0% of heifers were pregnant after uterine challenge with 0, 104, 105, 106, and 108 IFU of C. abortus, respectively. A total of 50 and 65% of heifers were pregnant with and without cohort challenge, respectively. Uterine inoculum dose and cohort challenge (or, alternatively, a negative pregnancy outcome [infertility]) correlated highly significantly with a rise in postchallenge anti-C. abortus IgM levels over prechallenge levels. Logistic regression modeled fertility, with uterine challenge dose and cohort challenge or prechallenge IgM as predictors (P < 0.05). The models predict that the uterine C. abortus inoculum causing infertility is 8.5-fold higher for heifers without cohort exposure and 17-fold higher for heifers with high IgM levels than for heifers with cohort exposure or with low IgM levels.

Evidence for a parapox ovis virus‐associated superantigen

As shown in a number of species, susceptibility to infectious diseases can be efficiently reduced following application of inactivated parapox ovis viruses (iPPOV). However, the basic mechanism for this stimulating capacity of iPPOV remains unclear. When analyzed, the interaction of iPPOV with porcine peripheral blood mononuclear cells was seen to involve T helper cells as the main target cell population responding to iPPOV. These cells displayed a strong proliferation, and were the major source for the observed increased levels of IL‐2. Activation of the T helper cells was MHC class II dependent, but not MHC class II restricted: cellular processing of iPPOV was not required for presentation by autologous, allogeneic or xenogeneic MHC class II molecules. Furthermore, CD3 and CD4 molecules were involved in the stimulation, indicating a receptor‐mediated activation of T helper cells. The results demonstrated typical characteristics of a superantigen‐induced response providing evidence for a viral component within PPOV functioning as superantigen(s) in swine.