Thymic hypoplasia in Japanese black calves with stillbirth/perinatal weak calf syndrome

Dynamics of the thymic transcriptome at stages of acute thymic involution in Japanese Black calves with a poor prognosis

Transcriptome analysis was performed on the thymus of Japanese Black calves that were necropsied due to poor prognosis, to characterize changes associated with acute thymic involution. Gene expression profiles obtained by DNA microarray analysis of eight calf thymuses were classified into three patterns that correlated with the histopathological stage of acute thymic involution. Using principal component analysis, the first principal component of the global gene expression levels in the calf thymus was associated with the stage of acute thymic involution, suggesting that histopathological changes greatly influence the gene expression profile. Gene ontology enrichment analysis revealed that genes related to cell proliferation, wound healing, and inflammatory responses were the main contributors to the first principal component. Real-time RT-PCR showed that the thymus had lower expression of PCNA, KIFC1, and HES6, and higher expression of SYNPO2, PDGFRB, and TWIST1 during acute thymic involution. Immunohistochemistry demonstrated a decrease in the rate of Ki67-positive cells in the thymic cortex during the late stage of acute thymic involution. The rate of cleaved caspase-1-positive cells increased in the thymic cortex at an earlier stage than the increase in the rate of cleaved caspase-3-positive cells. Vimentin, which was almost absent in the non-involuted thymic cortex, appeared in the thymic cortex during acute thymic involution. These results suggest that in farmed calves with a poor prognosis, inflammatory responses and impaired thymocyte proliferation are primarily involved in acute thymic involution.

Insufficiency of CD205-positive cortical thymic epithelial cells in immature Japanese Black cattle with severe thymic abnormalities and poor prognosis

To investigate the involvement of thymic function in the development of diseases with poor prognosis in calves, this study conducted a survey for the assessment of thymus cell composition in immature Japanese Black cattle with poor prognosis. Histopathological evaluation of 47 cattle showed signs of acute thymic involution in most cases. Less than half of the cases had a cortex predominant over the medulla in the thymic parenchyma, and a quarter of the cases indicated severe histological condition with an unclear boundary between the cortex and medulla. Correlation analysis revealed a close relationship between the corresponding stages of acute involution, cortical occupancy, and the expression of CD4, CD8B, and CD205. When cases were grouped by cortical occupancy, the expression of CD4 and CD8B expression was lower in the severe group with less than 25 % cortical occupancy, and the expression of CD205 was lower in the group with an unclear cortical-medullary boundary. Meanwhile, there was no difference in the expressions of IL7, CD80, FEZF2, and FOXN1 according to cortical occupancy. Immunohistochemistry has shown that cytokeratin-positive thymic epithelial cells are more densely populated in the severe thymus. UEA-I-binding medullary thymic epithelial cells were also present, but CD205-positive cortical thymic epithelial cells were rare in severe thymus. Moreover, there were significantly fewer Ki-67-positive cells in cattle with severe thymus. Therefore, these results indicate that thymic histological abnormalities frequently occur in immature cattle with a poor prognosis, and the presence of CD205-positive cortical thymic epithelial cells is associated with the severity of the abnormalities.

Studies on the immune status of calves with chronic inflammation and thymus atrophy

The thymus is a primary lymphoid organ where the primary T cell repertoire is generated. Thymus atrophy is induced by various conditions, including infectious diseases, glucocorticoid treatment, and poor breeding management. Cattle with thymus atrophy tend to exhibit weak calf syndrome, a condition in which approximately half of neonates die shortly after birth. Calves with thymus atrophy that survive the first month typically contract chronic inflammatory diseases. In this study, we analyzed the populations of the peripheral blood mononuclear cells and thymocytes in calves with thymus atrophy. In addition, we evaluated polarization of master gene and cytokine mRNA expression in peripheral blood CD4⁺ cells in the calves. The population of CD4⁺CD8⁺ cells in thymus of the calves with thymus atrophy was lower than that of control calves. IL10 mRNA expression in peripheral blood CD4⁺ cells of calves with thymus atrophy was significantly lower than that of control calves. TBX21 mRNA expression in peripheral CD4⁺ cells of thymus atrophy calves was tended to be higher than that of the control group. In addition, FOXP3 mRNA expression in peripheral CD4⁺ cells of the thymus atrophy calves was tended to be lower than that of the control calves. Thymus atrophy calves exhibited chronic inflammatory disease leading, in severe situations, to conditions such as pneumonia with caseous necrosis. These severe inflammatory responses likely are due to decreases in IL10 mRNA expression, impairing control of macrophages, one of the main cell fractions of natural immunity.

Role of Infection and Immunity in Bovine Perinatal Mortality: Part 2. Fetomaternal Response to Infection and Novel Diagnostic Perspectives

Simple Summary

Bovine perinatal mortality (death of the fetus or calf before, during, or within 48 h of calving at full term (≥260 days) may be caused by noninfectious and infectious causes. Although infectious causes of fetal mortality are diagnosed less frequently, infection in utero may also compromise the development of the fetus without causing death. This review presents fetomaternal responses to infection and the changes which can be observed in such cases. Response to infection, especially the concentration of immunoglobulins and some acute-phase proteins, may be used for diagnostic purposes. Some changes in internal organs may also be used as an indicator of infection in utero. However, in all cases (except pathogen-specific antibody response) non-pathogen-specific responses do not aid in pathogen-specific diagnosis of the cause of calf death. But, nonspecific markers of in utero infection may allow us to assign the cause of fetal mortality to infection and thus increase our overall diagnosis rate, particularly in cases of the “unexplained stillbirth”.

Abstract

Bovine perinatal mortality due to infection may result either from the direct effects of intrauterine infection and/or the fetal response to such infection, leading to the fetal inflammatory response syndrome (FIRS). Both intrauterine infection and FIRS, which causes multi-organ damage and involution of immune organs, compromise fetal survivability, sometimes fatally. Organ injury associated with FIRS may, in addition to causing fetal mortality, irreversibly compromise extrauterine adaptation of the neonate, a recognized problem in human fetuses. Diagnosis of intrauterine infection and of FIRS requires related, but independent analytical approaches. In addition to detection of pathogens, the immune and inflammatory responses of the bovine fetus may be utilized to diagnose intrauterine infection. This can be done by detection of specific changes in internal organs and the measurement of antibodies and/or elements of the acute phase reaction. Currently our ability to diagnose FIRS in bovine fetuses and neonates is limited to research studies. This review focuses on both the fetomaternal response to infection and diagnostic methods which rely on the response of the fetus to infection and inflammatory changes, as well other methods which may improve diagnosis of intrauterine infection in cases of bovine perinatal mortality.

IARS mutation causes prenatal death in Japanese Black cattle

Isoleucyl-tRNA synthetase (IARS) c.235G > C (p.V79L) is a causative mutation for a recessive disease called IARS disorder in Japanese black cattle. The disease is involved in weak calf syndrome and is characterized by low birth weight, weakness and poor suckling. The gestation period is often slightly extended, implying that intrauterine growth is retarded. In a previous analysis of 2597 artificial insemination (AI) procedures, we suggested that the IARS mutation might contribute toward an increase in the incidence of prenatal death. In this study, we extended this analysis to better clarify the association between the IARS mutation and prenatal death. The IARS genotypes of 92 animals resulting from crosses between carrier (G/C) × G/C were 27 normal (G/G), 55 G/C and 10 affected animals (C/C) (expected numbers: 23, 46 and 23, respectively). Compared to the expected numbers, there were significantly fewer affected animals in this population (P < 0.05), suggesting that more than half of the affected embryos died prenatally. When the number of AI procedures examined was increased to 11 580, the frequency of re-insemination after G/C × G/C insemination was significantly higher at 61-140 days (P < 0.001). The findings suggested that the homozygous IARS mutation not only causes calf death, but also embryonic or fetal death.

Surveillance of diarrhea-causing pathogens in dairy and beef cows in Yamagata Prefecture, Japan from 2002 to 2011

The economic consequences of bovine diarrhea are serious. Few long‐term epidemiological data are available concerning the causative pathogens of bovine diarrhea in Japan. From 2002 to 2011, surveillance of enteric pathogens was performed in cows of various breed and age from 302 farms in which diarrhea had occurred in Yamagata Prefecture, Japan. Differences between dairy and beef cows in the number of cases of diarrhea and rates of infection by Salmonella spp. and Eimeria spp. were found. Clinical symptoms (duration of epidemic, hematochezia and complications) caused by bovine rotavirus infection were milder than those caused by bovine coronavirus infection.

Intranuclear coccidiosis caused by Cyclospora spp. in calves

Intranuclear coccidiosis in 3 calves is described. Two calves with no genetic relationship were kept in the same pen, and the third calf was on another farm. The animals suffered from watery diarrhea or severe emaciation. Histologic examination showed epithelial desquamation (cases 1 and 2) or atrophy (case 3) of the jejunal villi. Coccidial meronts or merozoites were present in the nuclei of the majority of villus epithelial cells. There were rare intranuclear macrogametocytes, macrogametes, microgametocytes, microgametes, and oocysts in cases 1 and 2, but these were more easily observed in case 3. Parasite 18S ribosomal RNA sequences from case 1 showed 99.5% sequence identity with Cyclospora sp. Guangzhou 1, which has been found in fecal samples of cattle from China. In addition to the molecular results in one of the cases, the fact that the microgametocytes and oocysts were noticeably smaller in size than those of Eimeria alabamensis in all cases indicates the close association between Cyclospora and the 3 cases described herein.

Mapping and exome sequencing identifies a mutation in the IARS gene as the cause of hereditary perinatal weak calf syndrome

We identified an IARS (isoleucyl-tRNA synthetase) c.235G>C (p.Val79Leu) substitution as the causative mutation for neonatal weakness with intrauterine growth retardation (perinatal weak calf syndrome). In Japanese Black cattle, the syndrome was frequently found in calves sired by Bull A. Hence, we employed homozygosity mapping and linkage analysis. In order to identify the perinatal weak calf syndrome locus in a 4.04-Mb region of BTA 8, we analysed a paternal half-sibling family with a BovineSNP50 BeadChip and microsatellites. In this critical region, we performed exome sequencing to identify a causative mutation. Three variants were detected as possible candidates for causative mutations that were predicted to disrupt the protein function, including a G>C (p.Val79Leu) mutation in IARS c.235. The IARS c.235G>C mutation was not a homozygous risk allele in the 36 healthy offspring of Bull A. Moreover, the IARS Val79 residue and its flanking regions were evolutionarily and highly conserved. The IARS mutant (Leu79) had decreased aminoacylation activity. Additionally, the homozygous mutation was not found in any of 1526 healthy cattle. Therefore, we concluded that the IARS c.235G>C mutation was the cause of hereditary perinatal weak calf syndrome.

Ultrasonographic evaluation of thymus in Holstein calves and Heifers and its diagnostic application

This study was performed to evaluate the cross section of the thymus in 46 clinically healthy Holstein calves and heifers from birth to 100 weeks of age and 8 age-matched affected animals with chronic bronchopneumonia by ultrasonography. The cross sectional area of the thymus increased in healthy calves and heifers from birth to 31 weeks of age, peaked around 35 weeks of age, and then decreased until 100 weeks after birth. A positive correlation (r = 0.74, P < 0.05) was found between the area in cross section and the weight of the whole thymus in calves and heifers with chronic bronchopneumonia. The cross- sectional areas of the thymus were significantly (P < 0.05) lowered in animals with chronic bronchopneumonia. The cross sections of thymus in clinically healthy calves at 2 weeks of age and heifers at 34 weeks and 87 weeks of age were hypoechoic, moderately hyperechoic and hyperechoic, respectively. The observation of thymus by ultrasonography seems to be an effective tool for estimating the size of the thymus objectively in Holstein calves and heifers from birth to 100 weeks of age. The results of this study prove the approach to be useful and applicable to monitor the growth of thymus in Holstein calves and heifers and their association with chronic pneumonia.

Comparison of the peripheral blood leukocyte population between Japanese Black and Holstein calves

Japanese black (JB) calves have greater susceptibility to infectious diseases compared to Holstein (Hol) calves. In order to clarify the differences in cellular immune status between JB and Hol calves, the leukocyte population and lymphocyte proliferative ability were analyzed. In total 200 healthy calves, 1 day to 14 weeks of age, were examined: 105 JB and 95 Hol calves. Lower numbers in peripheral blood and percentage in peripheral blood mononuclear cells of CD3(+)TcR1-N12(+) T cells and major histocompatibility complex class-II(+)CD14(-) B cells were observed in the JB compared to the Hol. The percentage of TcR1-N12(+)CD25(+) T cell in the JB was significantly lower than that of the Hol at 4-6, and 8-10 weeks. Interleukin (IL)-2 sensitivity in the JB was lower than that in the Hol, and significant differences were observed in age groups of 6-8 weeks and 10-14 weeks. These findings indicated that the lower numbers of γδ T cells and B cells in the JB compared to the Hol might be associated with the specificity of the immune systems in JB calves.

Relationship between diarrhea and peripheral leukocyte population in neonatal Japanese black calves

Neonatal Japanese Black (JB) calves show a high incidence of diarrhea. The objective of this study was to analyze the immune cell populations of neonatal JB calves in detail and examine its correlation with the incidence of diarrhea immediately after birth. Understanding the immune cell populations is helpful in clinics in order to determine the condition of the immune system for prevention of diseases. Blood samples were obtained from JB calves on the day of birth. The peripheral leukocyte populations were analyzed separately for calves that had diarrhea within 2 weeks after birth (diarrhea group; n = 26) and for calves without diarrhea (control group; n = 74). The numbers of the peripheral blood CD3(+)TcR1-N12(+) and CD8(+) T cells were significantly lower in the diarrhea group compared with the control group. These findings suggest that the congenital lower peripheral γδ and CD8(+) T cells results in a high risk of diarrhea in neonatal JB calves.