Detection and localization of Mycoplasma hyopneumoniae DNA in lungs from naturally infected pigs by in situ hybridization using a digoxigenin-labeled probe

The rapid diagnosis of Mycoplasma pneumonia using in situ hybridization on clinical samples

The microbiological etiology of seasonal upper respiratory illnesses in the United States is dominated by viruses, including influenza A, B, respiratory syncytial virus, and SARS-CoV2. Mycoplasma pneumonia, treatable with antibiotics, can also cause upper respiratory symptoms and is typically associated with about 15 % of cases. There is no clinical or radiologic finding diagnostic of Mycoplasma pneumonia infection and PCR-based testing is not routinely used in the clinical setting. Further, the bacteria grows slowly in culture and the diagnostic IgM response will take days after the onset of infection. Thus, a rapid diagnostic test for Mycobacterium pneumonia infection is needed. This study documented two cases of Mycoplasma pneumonia infection of the upper respiratory system using in situ hybridization in a series of over 20 patients who were being tested for SARS-CoV2 infection. The respiratory secretions were placed on a glass slide, fixed in 10 % buffered formalin, and then tested using a Mycoplasma pneumonia probe. The high bacterial number associated with acute infection allowed for straightforward detection by in situ hybridization in a few hours. Antibiotic therapy led to rapid resolution of the symptoms. This highlights the ability of standard in situ hybridization as a rapid diagnostic test for Mycoplasma pneumonia in the clinical setting.

Macrophage Identification In Situ

Understanding the processes of inflammation and tissue regeneration after injury is of great importance. For a long time, macrophages have been known to play a central role during different stages of inflammation and tissue regeneration. However, the molecular and cellular mechanisms by which they exert their effects are as yet mostly unknown. While in vitro macrophages have been characterized, recent progress in macrophage biology studies revealed that macrophages in vivo exhibited distinctive features. Actually, the precise characterization of the macrophages in vivo is essential to develop new healing treatments and can be approached via in situ analyses. Nowadays, the characterization of macrophages in situ has improved significantly using antigen surface markers and cytokine secretion identification resulting in specific patterns. This review aims for a comprehensive overview of different tools used for in situ macrophage identification, reporter genes, immunolabeling and in situ hybridization, discussing their advantages and limitations.

Experimental reproduction of porcine respiratory disease complex in pigs inoculated porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae and followed by inoculation with porcine circovirus type 2

The aim of this study was to reproduce severe pneumonic lesions, similar to those during naturally-occurring porcine respiratory disease complex, in pigs dually inoculated with porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae at 6 weeks of age, followed by inoculation with porcine circovirus type 2 at two weeks after. Time and sequence of infection with three pathogens mirror Asian field conditions. Microscopically, interstitial pneumonia and peribronchiolar lymphoid hyperplasia are considered the most characteristic lung lesions in infected pigs. The results of the present study demonstrate that inoculation of pigs with these three pathogens can lead to severe interstitial pneumonia with peribronchial or peribronchiolar lymphoid hyperplasia and fibrosis.

IL-12p40 gene expression in lung and hilar lymph nodes of MPS-resistant pigs

Mycoplasma pneumonia of swine (MPS) is caused by Mycoplasma hyopneumoniae (M.hp) and is a common chronic respiratory disease of pigs. Recently, a genetically selected variant of the Landrace pig (Miyagino L2) has a lower incidence of pulmonary MPS lesions. We investigated the pathological and immunological characteristics of MPS resistance in these pigs (n = 24) by comparing with the normal landrace pig (control: n = 24). The pathological MPS lung lesion score in MPS-selected landrace pigs was significantly lower than in the control. The gene expression of interleukin (IL)-12p40, which acts as a chemoattractant and a component of the bioactive cytokines IL-12 and IL-23, was significantly higher at the hilar lymph nodes, lung, and spleen in MPS-selected landrace pigs than in control landrace pigs, and these were negatively correlated with the macroscopic MPS lung lesion score. In summary, we demonstrate that resistance against MPS in Miyagino L2 pigs is associated with IL-12p40 up-regulation, in comparison with normal landrace pigs without the MPS vaccine. In addition, a comparative study of macroscopic MPS lung lesions and IL-12p40 gene expression in lung and hilar lymph nodes may lead to beneficial selection traits for the genetic selection for MPS resistance in pigs.

Immunohistochemical and Ultrastructural Studies of Mycoplasma hyopneumoniae Strain in Naturally Infected Pigs in Nigeria

Enzootic pneumonia caused by hyopneumoniae (MHYO) remains a serious concern to the swine industry in many countries including Nigeria. MHYO strains isolated from pigs from different countries and geographical locations are known to vary in pathogenicity. There is a paucity of information on the pathogenicity of the MHYO strain affecting pigs in Nigeria. This study investigated the pathogenicity of the MHYO strain in naturally infected pigs using immunohisto-chemistry and electron microscopy. Two hundred and sixty four lungs of slaughtered pigs were randomly collected from abattoirs at Abeokuta, Ibadan and Lagos, in Southwest Nigeria. A sub-sample of 104 pneumonic and 20 apparently normal lungs was selected, processed for routine histopathological examination and immunohistochemistry, while 3 lung tissues samples were selected for ultrastructural studies. The most significant microscopic changes observed were suppurative broncho-interstitial pneumonia associated with varying degrees of lymphoid hyperplasia of the bronchus-associated lymphoid tissue (BALT) and thickened alveolar septa due to cellular infiltration consisting predominantly of neutrophils and a few mononuclear cells. Immunohistochemically, MHYO antigen was detected in 86/104 (82.69 %) of MHYO-infected lung tissues and typically exhibited a granular brown reaction on the bronchial and bronchiolar epithelial lining, mononuclear cells in the BALT and luminal cellular exudates within the airways. Transmission electron microscopy revealed numerous Mycoplasma organisms in the lumina of the airways, in between degenerated cilia, while a few Mycoplasmas were located within the alveoli. It was concluded that the MHYO strain detected in this study was pathogenic to pigs and capable of inducing pneumonia, and therefore implicated in the pathogenesis.

Identification and Genomic Analysis of a Pathogenic Strain of Mycoplasma hyopneumoniae (TB1) Isolated from Tibetan Pigs

The present study aims to identify the species and strains of Mycoplasma hyopneumoniae isolated from Tibetan pigs (Mh TB1) at the genetic level for understanding the basis of its pathogenicity. Mh TB1 was isolated from the consolidated lungs of Tibetan pigs by liquid culture and agar plate colony method. Polymerase chain reaction (PCR) amplification of the 16S recombinant DNA (rDNA) conservative sequence and a species-specific gene (P36) of Mh provided species confirmation. PCR products were imaged on gels and shotgun sequencing was performed. DNA sequences were compared for assessing genetic similarity between Mh TB1 and Mh reference strains in the GenBank database. The isolated strains were >98% similar to the Mh reference strains. Genomic analysis revealed significant sequence conservation between Mh TB1 and the reference strains; however, differential genes were more prevalent in Mh TB1 than in other reported strains. Therefore, we concluded that Mh is a major pathogen of Tibetan pigs that cause enzootic pneumonia. The Mh TB1 strain harbors more genes and specific virulence factors, consistent with its plateau-related adaptability to hypoxia and virulence. Differential gene analysis revealed gene variations in the inclement plateau environment, enriched gene pool, and plateau adaptability of the Mh TB1 strain, which will be important for vaccine development.

Chronologic Localization ofMycoplasma hyopneumoniaein Experimentally Infected Pigs

The chronologic localization of Mycoplasma hyopneumoniae was examined by in situ hybridization in experimentally infected pigs for a period of 35 days after intratracheal inoculation. M. hyopneumoniae DNA was detected in bronchial and bronchiolar epithelial cells from infected pigs at 7, 14, 21, and 28 days postinoculation (DPI) and in alveolar and interstitial macrophages and type I pneumocytes from infected pigs at 14, 21, 28, and 35 DPI. Strong hybridization signals for M. hyopneumoniae were detected mainly at the luminal surface of bronchial and bronchiolar lining epithelial cells. When a hybridization signal was detected at the luminal surface of bronchial and bronchiolar lining epithelial cells, a given bronchus or bronchiole also exhibited peribronchiolar lymphoid cuffing. These observations suggested that the presence of M. hyopneumoniae in different tissues could be due to a difference in the duration of the infection.

Increased fucosyl glycoconjugate by Mycoplasma hyopneumoniae enhances adherences of Pasteurella multocida type A in the ciliated epithelial cells of the respiratory tract

BACKGROUND

The objective of this study was to elucidate the pathogenic mechanisms of how Mycoplasma hyopneumoniae enhances secondary Pasteurella multocida type A infection which leads to porcine enzootic pneumonia in infected pigs. Sixteen pigs were experimentally infected with M. hyopneumoniae and then euthanized at 7, 14, 21 and 28 days post inoculation. In situ hybridization for M. hyopneumoniae DNA and Ulex europaeus agglutinin-I (UEA-I) lectin histochemistry for fucosyl glycoconjugate, was performed in serial lung sections to determine alteration of fucosyl glycoconjugate in M. hyopneumoniae-infected bronchial and bronchiolar epithelium. Bacterial overlay assay was performed to determine the affinity of P. multocida type A with L-fucose.

RESULTS

The luminal surface of bronchial and bronchiolar epithelial cells that were stained with UEA-I always showed hybridization signals for M. hyopneumoniae but it was negative in the unaffected parts of the lung from M. hyopneumoniae-infected pigs and in lung from negative control pigs. Colocalization of M. hyopneumoniae and UEA-I was especially prominent in the luminal surface of bronchial and bronchiolar epithelial cells in serial section of lung. The mean number of M. hyopneumoniae-positive cells correlated with the mean number of UEA-I-positive cells in lungs from infected pigs throughout the experiment. All eight P. multocida type A isolates from naturally occurring enzootic pneumonia, bound strongly at levels of 2 μg and 5 μg of L-fucose.

CONCLUSIONS

The results of the present study demonstrate that M. hyopneumoniae increases the L-fucose composition to enhance adherence of P. multocida type A to the bronchial and bronchiolar epithelial cells.

A new single-dose bivalent vaccine of porcine circovirus type 2 and Mycoplasma hyopneumoniae elicits protective immunity and improves growth performance under field conditions

The efficacy of the new single-dose bivalent vaccine of porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae was evaluated under field conditions for registration as recommended by the Republic of Korea's Animal, Plant & Fisheries Quarantine & Inspection Agency. Three farms were selected based on their history of co-infection with PCV2 and M. hyopneumoniae. On each farm, a total of 80 3-week-old pigs were randomly allocated to one of two treatment groups: (i) vaccinated (n=40) and (ii) unvaccinated (n=40) animals at 3 weeks of age. Protection by the bivalent vaccine helped increase the market weight by 6.2 kg/pig (106.2 kg in vaccinated group vs. 100 kg in unvaccinated group; P<0.05) and decreased mortality rate by 13.4% (0.8% in unvaccinated group vs. 14.2% in unvaccinated group; P<0.05). Vaccinated animals induced PCV2-specific neutralizing antibodies (NA) and interferon-γ secreting cells (IFN-γ-SC), and M. hyopneumoniae-specific IFN-γ-SC. Vaccinated animals displayed a reduced PCV2 load in the blood and M. hyopneumoniae load in nasal swabs compared to unvaccinated animals. Vaccination of pigs against PCV2 and M. hyopneumoniae effectively reduced the lung and lymphoid lesion scores compared to unvaccinated animals in all 3 farms. The new bivalent vaccine is very efficacious in controlling PCV2 and M. hyopneumoniae infection based on clinical, immunological, virological, and pathological evaluations under field conditions.

Interaction of porcine circovirus type 2 and Mycoplasma hyopneumoniae vaccines on dually infected pigs

The objective of this study was to determine the effects of porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae vaccinations on disease severity in an experimental PCV2-M. hyopneumoniae dual challenge model. Vaccine effectiveness was evaluated using microbiological (PCV2 viremia and M. hyopneumoniae nasal shedding), immunological (neutralizing antibodies and interferon-γ-secreting cells), and pathological (gross lung lesions, histopathologic pulmonary and lymphoid lesions, and the presence of PCV2 antigen and M. hyopneumoniae DNA within the lesions) evaluations. Although M. hyopneumoniae potentiates the severity of PCV2-associated lesions and lesion-associated PCV2 antigen in dually challenged pigs, vaccination against M. hyopneumoniae alone did not reduce PCV2 viremia, PCV2-induced lesions, or PCV2 antigen in dually challenged pigs. In addition, vaccination against PCV2 did not reduce the nasal shedding of M. hyopneumoniae, the M. hyopneumoniae-induced pulmonary lesions or the lesion-associated M. hyopneumoniae DNA in dually challenged pigs. Dual challenge with PCV2 and M. hyopneumoniae did not interfere with the induction of active immunity induced by a previous single vaccination for either PCV2 or M. hyopneumoniae. The results of this study demonstrated that (i) vaccination against M. hyopneumoniae alone did not decrease the potentiation of PCV2-induced lesions by M. hyopneumoniae and (ii) vaccination against PCV2 alone decreased the potentiation of PCV2-induced lesions by M. hyopneumoniae in dually challenged pigs.

Mycoplasma genitalium and cancer: a brief review

Approximately, 15-20% of all cancers worldwide are caused by infectious agents. Understanding the role of infectious agents on cancer development might be useful for developing new approaches to its prevention. Mycoplasma genitalium is a clinically important sexually transmitted pathogen that has been associated with several human diseases. There have been a few studies suggestive of probable roles of Mycoplasma genitalium in cancer development, including prostate and ovarian cancers and lymphomas, but the role of this microorganism like other Mycoplasma species in neoplasia is still conjectural. Considering the prevalence of Mycoplasma genitalium infections and also the emergence of resistant strains, Mycoplasma genitalium needs more attention in the infectious agent cancer-causing research area.

In situ hybridization for the detection of Mycoplasma bovis in paraffin-embedded lung tissue from experimentally infected calves

Mycoplasma bovis DNA was detected in lung tissue of experimentally infected calves by in situ hybridization (ISH) with a nonradioactive, digoxigenin-labeled DNA probe. The 171-base pair DNA probe targeting part of the gene of the major immunodominant variable surface protein A, which is conserved among all vsp genes, was generated by polymerase chain reaction. Four calves between 57 and 63 days old were inoculated intratracheally with 30 ml of a suspension of M. bovis strain 1067 containing 7 x 10(4) colony forming units per milliliter. Two calves inoculated with 30 ml of sterile medium served as control animals. The calves were euthanized and then examined 21 days after inoculation. The ISH method developed in the current study was suitable for the detection of M. bovis DNA in formalin-fixed, paraffin-embedded lung tissue and may be a valuable tool for diagnostic purposes and for further investigating the pathogenesis of M. bovis infection.

Identification of interleukin-1, tumor necrosis factor-alpha, and interleukin-6 expression in lungs from pigs naturally infected with Mycoplasma hyopneumoniae by in situ hybridization

The detection and distribution of interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha) and IL-6 were studied, by in situ hybridization with a non-radioactive digoxigenin-labeled probe, in formalin-fixed, paraffin-embedded lung tissue from 10 pigs naturally infected with Mycoplasma hyopneumoniae. The morphology of host cells was preserved despite the relatively high temperature required during the incubation procedure. Examination of three serial sections from each of the 10 lung samples showed that the three cytokines closely resembled each other in respect of cellular distribution. Three inflammatory cytokines are expressed in response to M. hyopneumoniae infection, with IL-6 localized primarily to peribronchiolar lymphoid hyperplastic tissues, and both IL-1 and TNF-alpha expressed in alveolar macrophages. Although statistically non-significant, IL-1 (r=0.5744, p=0.0883) showed potentially important correlation with histopatholgical lesions. No other potentially clinically important correlations (r>0.30) were observed between any of the other cytokines (TNF-alpha; r=0.2045, p=0.5603 and IL-6; r=-0.06607, p=0.8651) and histopathological lesion score. The results suggest that inflammatory cytokines are associated with the development of pneumonia in M. hyopneumoniae infection and may contribute to disease severity.

Current perspectives on the diagnosis and epidemiology of Mycoplasma hyopneumoniae infection

Mycoplasma hyopneumoniae is the principal aetiological agent of enzootic pneumonia (EP), a chronic respiratory disease that affects mainly finishing pigs. Although major efforts to control M. hyopneumoniae infection and its detrimental effects have been made, significant economic losses in pig production worldwide due to EP continue. M. hyopneumoniae is typically introduced into pig herds by the purchase of subclinically infected animals or, less frequently, through airborne transmission over short distances. Once in the herd, M. hyopneumoniae may be transmitted by direct contact from infected sows to their offspring or between pen mates.

The ‘gold standard’ technique used to diagnose M. hyopneumoniae infection, bacteriological culture, is laborious and is seldom used routinely. Enzyme-linked immunosorbent assay and polymerase chain reaction detection methods, in addition to post-mortem inspection in the form of abattoir surveillance or field necropsy, are the techniques most frequently used to investigate the potential involvement of M. hyopneumoniae in porcine respiratory disease. Such techniques have been used to monitor the incidence of M. hyopneumoniae infection in herds both clinically and subclinically affected by EP, in vaccinated and non-vaccinated herds and under different production and management conditions. Differences in the clinical course of EP at farm level and in the efficacy of M. hyopneumoniae vaccination suggest that the transmission and virulence characteristics of different field isolates of M. hyopneumoniae may vary. This paper reviews the current state of knowledge of the epidemiology of M. hyopneumoniae infection including its transmission, infection and seroconversion dynamics and also compares the various epidemiological tools used to monitor EP.

Diagnosis ofMycoplasma hyopneumoniae

Mycoplasma hyopneumoniae, the cause of enzootic pneumonia, remains an important pathogen in the swine industry. This small, complex organism colonizes the ciliated cells of the respiratory tract, resulting in little exposure to the immune system. Confirming the presence ofM. hyopneumoniae, as well as identifying its role in respiratory disease and pneumonia, remains challenging to the veterinary profession. While culture of the organism remains the gold standard for identification, the use of serology, the polymerase chain reaction and various assays to detect the presence ofM. hyopneumoniaein tissue is common in diagnostic laboratories. Because of the roleM. hyopneumoniaeplays in increasing the severity of pneumonia associated with concurrent bacterial and viral infections, understanding the pathogenesis and diagnostic assays available is critical for developing effective intervention strategies to control respiratory disease on a herd basis.

Expression of inflammatory cytokines in pigs experimentally infected with Mycoplasma hyopneumoniae

The expression of interleukin-1 (IL-1), tumour necrosis factor-alpha (TNF-alpha) and IL-6 were studied over a period of 35 days in the lungs of pigs experimentally infected with Mycoplasma hyopneumoniae, by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), morphometric analysis and in-situ hybridization. Fifteen colostrum-deprived pigs aged 14 days were inoculated intranasally with M. hyopneumoniae. IL-1, TNF-alpha and IL-6 were detected by RT-PCR in the lungs of the infected pigs from 7 days post-inoculation (dpi) onwards, but not in the uninfected control pigs. Concurrent expression of all three cytokines was always observed, in association with lung lesions. Inflammatory cytokine-positive cells were detected in the lungs at 7 dpi, their number increasing at 21dpi, and decreasing thereafter. The results suggest that such cytokines play a role in mediating and regulating inflammation in M. hyopneumoniae infection.

Diagnóstico da pneumonia enzoótica suína pela técnica da imunoperoxidase

Avaliou-se a técnica da imunoperoxidase como método auxiliar para a detecção de Mycoplasma hyopneumoniae em suínos naturalmente infectados. Foram colhidos 80 fragmentos de pulmões de 40 animais provenientes de granjas consideradas negativas e 40 de granjas com diagnóstico positivo de pneumonia enzoótica. Com a utilização de soro policlonal específico (IgG de coelho anti- M. hyopneumoniae) observou-se correlação positiva de 77% entre os diagnósticos microscópicos e imunoistoquímicos, enquanto que a correlação entre os diagnósticos macroscópico e imunoistoquímico foi de 49%. Nas granjas consideradas negativas observou-se presença de discreta imunorreação em 22,5% dos casos, o que poderia indicar a existência de reação cruzada com outros microrganismos. Nas granjas com diagnóstico positivo para pneumonia enzoótica a técnica da peroxidase-anti-peroxidase (PAP) revelou diferentes graus de intensidade, variando de fraca imunomarcação até espesso depósito amarronzado no epitélio ou na luz das vias aéreas, ou ainda no interior de macrófagos, com relação direta entre a intensidade das lesões e da imunorreação. A técnica imunoistoquímica possui sensibilidade de 95% e especificidade de 77,5%, podendo ser recomendada como ferramenta auxiliar, rápida e de baixo custo para o diagnóstico de pneumonia enzoótica suína em laboratórios de rotina em histopatologia.

Detection of nuclear factor-kappaB and inducible nitric oxide synthase in the lungs of pigs naturally infected with Actinobacillus pleuropneumoniae

Activated nuclear factor-kappaB (NF-kappaB) and inducible nitric oxide synthase (iNOS) were detected immunohistochemically in pleuropneumonic lungs from 20 pigs naturally infected with Actinobacillus pleuropneumoniae. NF-kappaB was detected mainly in nuclei of inflammatory cells, confirming its activation. Intense immunolabelling for NF-kappaB and iNOS was seen within the lung lesions, but labelling was minimal in unaffected portions of the lung of infected pigs and in normal lung from uninfected (control) pigs. Examination of serial sections from the 20 infected lung samples demonstrated a close association between NF-kappaB and iNOS. This suggests that NF-kappaB plays a key role in triggering the activation of iNOS in porcine pleuropneumonia.

Association of porcine circovirus 2 with porcine respiratory disease complex

A retrospective study was performed on natural cases of porcine respiratory disease complex (PRDC) to determine the association and prevalence of PRDC with porcine circovirus 2 (PCV2) and other co-existing pathogens in Korea. Histologically, alveolar septa were markedly thickened by infiltrates of mononuclear cells. Moderate to marked multifocal peribronchial and peribronchiolar fibrosis were present and often extended into the airway lamina propria. Among the 105 pigs with PRDC, 85 were positive for PCV2, 66 were positive for porcine reproductive and respiratory syndrome virus (PRRSV), 60 were positive for porcine parvovirus (PPV), and 14 were positive for swine influenza virus (SIV). There were 80 co-infections and 25 single infections. A co-infection of PCV2 with another additional bacterial pathogen is frequently diagnosed in PRDC. The combination of PCV2 and Pasteurella multocida (38 cases) was most prevalent followed by PCV2 and Mycoplasma hyopneumoniae (33 cases). The consistent presence of PCV2, but lower prevalence of other viral and bacterial pathogens in all pigs examined with PRDC, has led us to speculate that PCV2 plays an important role in PRDC.

A morphologic and immunohistochemical study of the bronchus-associated lymphoid tissue of pigs naturally infected with Mycoplasma hyopneumoniae

Porcine enzootic pneumonia (PEN), caused by Mycoplasma hyopneumoniae (Mh), has been described in pigs in all geographic areas. The disease is characterized by high morbidity and low mortality rates in intensive swine production systems. A morphologic and immunohistochemical study was done to determine the cellular populations present in lung parenchyma of infected pigs, with special attention to the bronchus-associated lymphoid tissue (BALT). Polyclonal and monoclonal antibodies were used for the detection of antigens of Mh, T lymphocytes (CD3+, CD4+, and CD8+), IgG+ or IgA+ lymphocytes, and cells containing lysozyme, S-100 protein, major histocompatibility complex class II antigen or myeloid-histiocyte antigen. Findings in lung tissues associated with Mh infection were catarrhal bronchointerstitial pneumonia, with infiltration of inflammatory cells in the lamina propria of bronchi and bronchioles and alveolar septa. Hyperplasia of mononuclear cells in the BALT areas was the most significant histologic change. The BALT showed a high morphologic and cellular organization. Macrophages and B lymphocytes were the main cellular components of germinal centers. T lymphocytes were primarily located in perifollicular areas of the BALT, lamina propria and within the airway epithelium, and plasma cells containing IgG or IgA at the periphery of the BALT, in the lamina propria of bronchi and bronchioles, in alveolar septa, and around bronchial submucosal glands. The hyperplastic BALT in PEN cases consisted of macrophages, dendritic cells, T and B lymphocytes, and IgG+ and IgA+ plasma cells. CD4+ cells predominated over CD8+ cells. Local humoral immunity appears to play an important role in the infection.

Evidence of nitric oxide synthase 2 activity in swine naturally infected with Actinobacillus pleuropneumoniae

Evidence of nitric oxide synthase (NOS) 2 activity was determined by formation of nitrotyrosine (a reaction product of peroxynitrite) and by activation of poly(ADP-ribose) synthetase (PARS) in NOS2-expressed pleuropneumonic lungs from 20 pigs naturally infected with Actinobacillus pleuropneumoniae using immunohistochemistry. Intense immunostaining for nitrotyrosine residue was seen within the lung lesions from A. pleuropneumoniae-infected pigs, but it was minimal in the unaffected parts of the lung from A. pleuropneumoniae-infected pigs and in the normal lung from control pigs. Staining was especially strong in neutrophils and macrophages in the periphery of the lesions and within the alveolar spaces. There was close cell-to-cell correlation when serial sections were examined by immunohistochemistry for NOS2 and nitrotyrosine in each of the 20 lung samples. Expression of PARS was always present within inflammatory lesions but was minimal in the unaffected lung of A. pleuropneumoniae-infected pigs. Macrophages in alveolar spaces frequently exhibited strong staining for PARS. Colocalization of nitrotyrosine and PARS antigen was especially prominent in macrophages in the periphery of lesions. NOS2 expression in pleuropneumonic areas associated with protein nitrosation and PARS suggests that NOS2 is functionally active during infections caused by A. pleuropneumoniae.

Localization of classical swine fever virus from chronically infected pigs by in situ hybridization and immunohistochemistry

Classical swine fever (CSF) virus (CSFV) nucleic acid and antigen were detected in 15 pigs with naturally occurring chronic CSF by in situ hybridization and immunohistochemistry. The most consistent and prominent microscopic lesions were perivascular mononuclear cell infiltration and gliosis in the central nervous system of pigs with chronic CSF. Positive cells typically exhibited a dark brown (in situ hybridization) or red (immunohistochemistry) reaction product in the cytoplasm without background staining. A positive signal for both in situ hybridization and immunohistochemistry was detected in mononuclear cells and lymphocytes of lymphoid tissues. Viral nucleic acid was detected in some tissue sections in the absence of viral antigen. The in situ hybridization technique developed in this study was useful for the detection of CSFV RNA in tissues taken from chronically infected pigs and may be a valuable technique for studying the pathogenesis of chronic CSFV infection.

Expression of cyclooxygenase-2 in swine naturally infected with Actinobacillus pleuropneumoniae

Cyclooxygenase-2 (COX-2) was detected and localized in 15 pigs with naturally occurring pleuropneumonia using a 437-base pair digoxigenin-labeled cDNA probe in an in situ hybridization protocol. Histopathologic changes in the acute stage were characterized by coagulative necrosis of lung parenchyma, hemorrhage, vascular thrombosis, edema, fibrin deposition, and infiltration of lung parenchyma by neutrophils and alveolar macrophages in nine pigs. In chronic lesions, a thick layer of granulation tissue surrounded foci of pulmonary necrosis in six pigs. All 15 pigs infected with Actinobacillus pleuropneumoniae, confirmed by bacterial isolation, had distinct positive hybridization signals for COX-2 in bronchial, bronchiolar epithelial cells, alveolar macrophages, neutrophils, and type I pneumocytes. COX-2 expression was detected primarily in neutrophils from pigs with acute lesions and primarily in alveolar macrophages from pigs with chronic lesions. The results suggest that a prostanoid product of COX-2 is an important component of the inflammatory response to acute and chronic A. pleuropneumoniae infection.

Immunohistochemical detection of cyclooxygenase-2 in lungs of pigs naturally infected with Actinobacillus pleuropneumoniae

Cyclooxygenase-2 (COX-2) protein was detected immunohistochemically in formalin-fixed, paraffin wax-embedded lung tissues from 15 pigs with naturally occurring pleuropneumonia caused by Actinobacillus pleuropneumoniae. Positive cells typically exhibited a red reaction product without background staining. Alveolar macrophages, neutrophils, and bronchial and bronchiolar epithelial cells had positive immunohistochemical signals. Immunoreactivity of COX-2 protein was intense in the clustered leucocytes with streaming nuclear chromatin that are a characteristic histological feature of porcine pleuropneumonia. COX-2 protein was always associated with macrophages and neutrophils in pleuropneumonic lung lesions but was minimal in non-lesional lung of A. pleuropneumoniae -infected pigs and in normal lung from control pigs. The results suggest that COX-2 plays a role in pathophysiological processes during A. pleuropneumoniae infection.

Immunohistochemical detection and distribution of inducible nitric oxide synthase in pigs naturally infected with Actinobacillus pleuropneumoniae

Inducible nitric oxide synthase (iNOS) protein was detected immunohistochemically in formalin-fixed, paraffin wax-embedded lung tissues from 10 natural cases of porcine pleuropneumonia. Positive cells typically exhibited a red reaction product without background staining. Labelling of iNOS protein was intense in "oat cells", the clustered leucocytes with streaming nuclear chromatin that are a characteristic histological feature of porcine pleuropneumonia. Macrophages and neutrophils within alveolar spaces but not within blood vessels consistently showed iNOS labelling, but such labelling was minimal in non-lesional lung of Actinobacillus pleuropneumoniae -infected pigs and in normal lung from control pigs. The results suggest that iNOS plays a role in pathophysiological processes during A. pleuropneumoniae infection.

Expression of nitric oxide synthase 2 and tumor necrosis factor alpha in swine naturally infected with Actinobacillus pleuropneumoniae

Nitric oxide synthase 2 (NOS2) and tumor necrosis factor alpha (TNF-alpha) were detected and localized in 15 pigs with naturally occurring pleuropneumonia by use of in situ hybridization with a nonradioactive digoxigenin-labeled cDNA probe. Two cDNA probes 491 and 219 base pairs for NOS2 and TNF-alpha, respectively, were generated by reverse transcription polymerase chain reaction. All 15 pigs infected with Actinobacillus pleuropneumoniae had distinct positive hybridization signals for NOS2 and TNF-alpha. Strong hybridization signals for both NOS2 and TNF-alpha were evident in degenerate alveolar leukocytes bordering zones of coagulative necrosis and in alveolar spaces. NOS2 nucleic acids were detected in neutrophils and macrophages. In situ hybridization of serial sections of lung tissue revealed numerous cells positive for NOS2 and TNF-alpha, suggesting that NOS2 and TNF-alpha expression may play a role in the pathophysiology of pleuropneumonia.

Expression of the apxIV gene in pigs naturally infected with Actinobacillus pleuropneumoniae

The apxIV gene was detected, by in-situ hybridization with a non-radioactive digoxigenin-labelled probe, in formalin-fixed, paraffin wax-embedded samples of lung tissue from 10 pigs naturally infected with Actinobacillus pleuropneumoniae. A 442 base pair DNA probe of the apxIV gene from A. pleuropneumoniae serotype 2 was generated by the polymerase chain reaction. All 10 pigs infected with A. pleuropneumoniae serotypes 2, 5, 6, or an untypable strain showed a distinct, positive signal in the degenerate alveolar leucocytes in alveolar spaces, and in the dense zone of degenerated cells in granulation tissue surrounding the necrotic areas. Thus, the study demonstrated the presence of the apxIV gene in pleuropneumonic lesions caused by A. pleuropneumoniae.

Detection and localization of ApxI, -II and -III genes of Actinobacillus pleuropneumoniae in natural porcine pleuropneumonia in natural porcine pleuropneumonia by in situ hybridization

In situ hybridization techniques that employed a nonradioactive digoxigenin-labeled probe were used to detect and localize ApxI, II and III genes in tissue sections of pneumonic lung naturally infected with Actinobacillus pleuropneumoniae. In pigs infected with either serotype 2 or 6, a hybridization signal for apxIICA, apxIIICA, apxIBD, and apxIIIBD was detected, and in pigs infected with serotype 5, a hybridization signal for apxICA, apxIICA, and apxIBD was detected in the pneumonic lesions. A hybridization signal for apxIICA and apxIBD was detected in pigs infected with serotype 7. A strong hybridization signal for apx genes was seen in streaming degenerate alveolar leukocytes bordering zones of coagulative necrosis. Simultaneous detection of hybridization signals for the apxCA and apxBD genes provided scientific evidence that the expression of the apx genes could be potential indicators of the production of corresponding Apx toxins. This study demonstrates the expression of ApxI, II, and III genes in pneumonic lesions caused by A. pleuropneumoniae.

In-situ hybridization for the detection of inflammatory cytokines (IL-1, TNF-alpha and IL-6) in pigs naturally infected with Actinobacillus pleuropneumoniae

The detection and distribution of interleukin-1 (IL-1), tumour necrosis factor-alpha (TNF-alpha) and IL-6 were studied, by in-situ hybridization with a non-radioactive digoxigenin-labelled probe, in formalin-fixed paraffin wax- embedded lung tissue from 10 pigs naturally infected with Actinobacillus pleuropneumoniae. A strong hybridization signal for IL-1, TNF-alpha and IL-6 was detected in "streaming" degenerate alveolar leucocytes (the so-called "oat cells") bordering zones of coagulative necrosis, and a less intense signal was seen in the dense zone of degenerate cells in granulation tissue surrounding the necrotic areas. IL-1 expression was also prominent in scattered endothelial cells bordering zones of coagulative necrosis. Simultaneous expression of all three cytokines was always associated with pleuropneumonic lung lesions. Expression of inflammatory cytokines was minimal in non-lesional lung tissue of the infected pigs and in normal lung from control pigs. The results suggest that these cytokines play a crucial role in mediating and regulating inflammation through cells of several types in A. pleuropneumoniae infection. 1999 Harcourt Publishers Ltd.