Immunohistochemistry: Forging the links between immunology and pathology

Evaluation of species-specific polyclonal antibodies to detect and differentiate between Neospora caninum and Toxoplasma gondii

Neosporosis and toxoplasmosis are major causes of abortion in livestock worldwide, leading to substantial economic losses. Detection tools are fundamental to the diagnosis and management of those diseases. Current immunohistochemistry (IHC) tests, using sera raised against whole parasite lysates, have not been able to distinguish between Toxoplasma gondii and Neospora caninum. We used T. gondii and N. caninum recombinant proteins, expressed in Escherichia coli and purified using insoluble conditions, to produce specific polyclonal rabbit antisera. We aimed to develop species-specific sera that could be used in IHC on formalin-fixed, paraffin-embedded (FFPE) tissue sections to improve the diagnosis of ruminant abortions caused by protozoa. Two polyclonal rabbit sera, raised against recombinant proteins, anti-Neospora-rNcSRS2 and anti-Toxoplasma-rTgSRS2, had specificity for the parasite they were raised against. We tested the specificity for each polyclonal serum using FFPE tissue sections known to be infected with T. gondii and N. caninum. The anti-Neospora-rNcSRS2 serum labeled specifically only N. caninum-infected tissue blocks, and the anti-Toxoplasma-rTgSRS2 serum was specific to only T. gondii-infected tissues. Moreover, tissues from 52 cattle and 19 sheep previously diagnosed by lesion profiles were tested using IHC with our polyclonal sera and PCR. The overall agreement between IHC and PCR was 90.1% for both polyclonal anti-rNcSRS2 and anti-rTgSRS2 sera. The polyclonal antisera were specific and allowed visual confirmation of protozoan parasites by IHC, but they were not as sensitive as PCR testing.

Biocompatibility of three different root canal sealers, experimental study

OBJECTIVES

This study was assessed the biocompatibility of three different root canal sealers (Well-Root St, GuttaFlow Bioseal, and AH-Plus) following implantation in rat subcutaneous tissues, using histopathological immunohistochemical analysis.

METHODS

Four groups of eighty-four male rats each underwent subcutaneous dorsal implantation of a polyethylene tube, either empty or filled. Tissues were collected, fixed, and processed for histological analysis after 7, 15, and 30 d. Slides were photographed and digitally processed to identify lymphocytes and macrophages using Cluster of differentiation 3 (CD3) and cluster of differentiation 68 (CD68) markers, respectively. P was set at 0.05, when lymphocyte and macrophage infiltration was compared between groups and observation times using one-way analysis of variance (ANOVA).

RESULTS

Histopathological analysis of all groups revealed an inflammatory reaction followed by the emergence of a fibrous capsule after 7 days. After 30 days, the thickness of the fibrous capsule and the inflammatory response subsided. CD3 staining for immunohistochemical analysis revealed that the AH-Plus group had the highest mean percentage of lymphocyte infiltration at 7 and 15 days, followed by the Well-Root St, GuttaFlow Bioseal, and Control groups. After 30 days, no discernible difference was observed between the groups in terms of the mean percentage of lymphocyte infiltration. After 7, 15, and 30 days, there was a significant difference in the mean percentage of macrophage infiltration across the groups, as demonstrated by CD68 staining. After 7, 15, and 30 days, the AH-Plus group had the highest mean percentage of macrophage infiltration, followed by the Well-Root St. and GuttaFlow Bioseal groups, while the control group had the lowest mean percentage.

CONCLUSION

All observational periods showed minimal inflammatory reactions to GuttaFlow Bioseal. After subcutaneous tissue implantation in a rat model, the initial inflammatory reactions to Well-Root St and AH-Plus had abated by day 30, and all tested sealers had outstanding biocompatibility.

Localization and distribution of goose astrovirus 2 antigens in different tissues at different times

Goose astrovirus 2 (GAstV-2) causes visceral gout in goslings and has resulted in significant economic losses in the goose industry of China since its outbreak in 2017. To further investigate the distribution and localization of GAstV-2 in different tissues at different times, a monoclonal antibody (mAb)-based immunohistochemical (IHC) assay was developed to detect GAstV-2. A total of 80 1-day-old healthy goslings were inoculated with GAstV-2 via the oral (n = 40) and intramuscular routes (n = 40). GAstV-2 in the tissues of interest was detected using the established IHC assay. The results showed that positive signals were detected in most tissues at 1 day post-infection (dpi). Viral antigens were mainly distributed in the cytoplasm, and the staining intensity was higher in the renal tubular epithelial cells than in other cells. Taken together, our data demonstrated that GAstV-2 has a broad tissue tropism and primarily targets the kidneys. These results are likely to provide a scientific basis for further elucidation of the pathogenesis of GAstV-2.

Assessing CB1 Expression in the Brain by Immunohistochemical Methods: Light, Confocal, and Electron Microscopy

Conventional techniques to reveal the neuroanatomical distribution of type 1 cannabinoid receptor (CB₁) in the brain, at the cellular and subcellular level, are mainly represented by light, confocal, and electron microscopy. By using immunoperoxidase and immunofluorescence methods, it is possible to reveal CB₁ distribution and localization in the brain and its changes under pathological conditions. Moreover, by using electron microscopy, we can define the ultrastructural localization at the level of subcellular structures and organelles. Here, we describe immunoperoxidase, immunofluorescence, and electron microscopy protocols used to get information about CB₁ spatial distribution and localization in the brain. Preparation of reagents, resin embedding, preparation for an endogenous activity-blocking step, and background counterstaining and revelation of CB₁ by using specific labeled secondary antibodies will be presented. The methods here discussed are highly sensitive and specific multistep processes, where each step is critical to finally obtain an optimum signal.

The Role of Pathology in the Diagnosis of Swine Respiratory Disease

The definition “porcine respiratory disease complex” (PRDC) is used to indicate the current approach for presenting respiratory pathology in modern pig farming. PRDC includes pneumonias with variable pictures, mixed with both aerogenous and hematogenous forms with variable etiology, often multimicrobial, and influenced by environmental and management factors. The notion that many etiological agents of swine respiratory pathology are ubiquitous in the airways is commonly understood; however, their isolation or identification is not always associable with the current pathology. In this complex context, lung lesions registered at slaughterhouse or during necropsy, and supplemented by histological investigations, must be considered as powerful tools for assigning a prominent role to etiologic agents. In recent years, the goal of colocalizing causative agents with the lesions they produce has been frequently applied, and valid examples in routine diagnostics are those that indicate pulmonary involvement during porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) infections.

Electrical Detection of Innate Immune Cells

Accurately classifying the innate immune players is essential to comprehensively and quantitatively evaluate the interactions between the innate and the adaptive immune systems. In addition, accurate classification enables the development of models to predict behavior and to improve prospects for therapeutic manipulation of inflammatory diseases and cancer. Rapid development in technologies that provide an accurate definition of the type of cell in action, allows the field of innate immunity to the lead in therapy developments. This article presents a novel immunophenotyping technique using electrical characterization to differentiate between the two most important cell types of the innate immune system: dendritic cells (DCs) and macrophages (MACs). The electrical characterization is based on capacitance measurements, which is a reliable marker for cell surface area and hence cell size. We differentiated THP-1 cells into DCs and MACs in vitro and conducted electrical measurements on the three cell types. The results showed average capacitance readings of 0.83 µF, 0.93 µF, and 1.01 µF for THP-1, DCs, and MACs, respectively. This corresponds to increasing cell size since capacitance is directly proportional to area. The results were verified with image processing. Image processing was used for verification because unlike conventional techniques, especially flow cytometry, it avoids cross referencing and by-passes the limitation of a lack of specificity of markers used to detect the different cell types.

Immunohistochemistry to Study YAP in Human Tissue Samples

Immunohistochemistry (IHC) analysis of YAP in human tissue samples represents an important means to analyze overall expression levels and subcellular localization of YAP in specimen of interest. As transcriptional coactivator, alterations of YAP levels in the cellular nucleus allow important predictions for YAP activity and transcriptional state of target genes. In the following report, IHC procedures optimized for the detection of YAP in tissue slides of FFPE material are provided. Of note, de-paraffinization and heat-induced antigen retrieval are strictly necessary for successful YAP IHC staining. Further, immunostaining using a labelled polymer-HRP system combined with diaminobenzidine (DAB), as signal-amplifying chromogen, allows strong staining results with minimal unspecific background signal.

Monoclonal Antibodies Against Porcine sIgA and Their Use in Immunohistochemistry

Secretory IgA (sIgA) is known as the predominant immunoglobulin in the mucosal system. It prevents pathogens from invading an animal's body through mucosa, making homeostasis. However, few studies examining the secretion of sIgA in mucosal-associated tissues of porcines based on immunohistochemistry methods have been done. In this study, BALB/c mice were immunized with porcine sIgA and the splenocytes were then fused with myeloma cells. Finally, three hybridoma cell lines secreting monoclonal antibody (MAb) against porcine sIgA were obtained. All three MAbs had no cross-reaction with porcine IgG confirmed by Western blot analysis. Furthermore, lungs, tracheas, and intestines were collected from healthy porcines to prepare tissue slices, followed by incubation with the MAb produced in this study. The results showed that sIgA existing in respiratory and digestive systems could be detected by this newly produced MAb. These generated MAbs against porcine sIgA might have a potential use in mucosal research of porcines.

An experimental study of the pathogenicity of a duck hepatitis A virus genotype C isolate in specific pathogen free ducklings

Duck hepatitis A virus genotype C (DHAV-C), recognized recently, is one of the pathogens causing fatal duck viral hepatitis in ducklings, especially in Asia. To demonstrate the pathogenesis of the DHAV-C isolate, 3-day-old specific pathogen free ducklings were inoculated subcutaneously with a DHAV-C isolate and the clinical signs were observed. Virus distribution, histological and apoptotic morphological changes of various tissues were examined at different times post inoculation. The serial, characteristic changes included haemorrhage and swelling of the liver. Apoptotic cells and virus antigen staining were found in all of the tissues examined. Where more virus antigen staining was detected, there were more severe histopathological and apoptotic changes. The amount of virus antigen and the histological and apoptotic morphological changes agreed with each other and became increasingly severe with length of time after infection. Apoptotic cells were ubiquitously distributed, especially among lymphocytes, macrophages and monocytes in immune organs such as the bursa of Fabricius, thymus and spleen, and in liver, kidney and cerebral cells. Necrosis was also observed within 72 h post inoculation in all organs examined, except the cerebrum, and was characterized by cell swelling and collapsed plasma membrane. These results suggest that the recent outbreak of disease caused by DHAV-C virus is pantropic, causing apoptosis and necrosis of different organs. The apoptosis and necrosis caused by the DHAV-C field strain in this study is associated with pathogenesis and DHAV-C-induced lesions.

Immunofluorescence detection and localization of B[a]P and TCDD in earthworm tissues

An immunohistochemical method using antibodies against polycyclic aromatic hydrocarbons (PAHs) and dioxins was developed on frozen tissue sections of the earthworm Eisenia andrei exposed to environmentally relevant concentrations of benzo[a]pyrene (B[a]P) (0.1, 10, 50 ppm) and 2,3,7,8-tetrachloro-dibenzo-para-dioxin (TCDD) (0.01, 0.1, 2 ppb) in spiked standard soils. The concentrations of B[a]P and TCDD in E. andrei exposed to the same conditions were also measured using analytical chemical procedures. The results demonstrated that tissues of worms exposed to even minimal amount of B[a]P and TCDD reacted positively and specifically to anti-PAHs and -dioxins antibody. Immunofluorescence revealed a much more intense staining for the gut compared to the body wall; moreover, positively immunoreactive amoeboid coelomocytes were also observed, i.e. cells in which we have previously demonstrated the occurrence of genotoxic damage. The double immunolabelling with antibodies against B[a]P/TCDD and the lysosomal enzyme cathepsin D demonstrated the lysosomal accumulation of the organic xenobiotic compounds, in particular in the cells of the chloragogenous tissue as well as in coelomocytes, involved into detoxification and protection of animals against toxic chemicals. The method described is timesaving, not expensive and easily applicable.

Validation of an immunohistochemical assay for bovine cysticercosis, with comparison to a standard histological method

The larval stage (syn Cysticercus bovis) of the human tapeworm Taenia saginata causes cysticercosis in cattle, which has both aesthetic and food safety implications to consumers of beef. A monoclonal antibody-based immunohistochemical (IHC) assay developed to improve postmortem diagnosis of this parasite and a standard histological method were assessed to determine their fitness for intended use. Sections from 169 known-positive specimens of T. saginata from experimentally or naturally infected cattle, and from 30 known-negative specimens and lesions of various etiologies from non-infected cattle, were tested. The IHC assay identified significantly more known positive bovine cysticerci than the histological method (91.7% and 38.5%, respectively). Positive IHC staining occurred on sections from other cestode species, but should not affect the diagnostic specificity of this assay for bovine cysticercosis, due to the different host and/or tissue preferences amongst these parasites. Use of the IHC assay should improve the reliability of diagnosing lesions caused by degenerated cysticerci, facilitating more effective and efficient control of bovine cysticercosis.

Expression and immunohistochemical distribution of duck plague virus glycoprotein gE in infected ducks

To determine the distribution of duck plague virus (DPV) gE protein in paraformaldehyde-fixed, paraffin-embedded tissues of experimentally DPV-infected ducks, an indirect immunoperoxidase assay was established to detect glycoprotein E (gE) protein for the first time. The rabbit anti-His-gE serum, raised against the recombinant His-gE fusion protein expressed in Escherichia coli BL21 (DE3), was prepared and purified. Western blotting and indirect immunofluorescence analysis showed that the anti-His-gE serum had a high level of reactivity and specificity and could be used as the first antibody for further experiments to study the distribution of DPV gE protein in DPV-infected tissues. A number of DPV gE proteins were distributed in the bursa of Fabricius, thymus, spleen, liver, esophagus, duodenum, jejunum, ileum, and kidney of DPV-infected ducks and a few DPV gE were distributed in the Harders glands, myocardium, cerebrum, and lung, whereas the gE was not seen in the skin, muscle, and pancreas. Moreover, DPV gE was expressed abundantly in the cytoplasm of lymphocytes, reticulum cells, macrophages, epithelial cells, and hepatocytes. The present study may be useful not only for describing the characteristics of gE expression and distribution in infected ducks but also for understanding the pathogenesis of DPV.

Development and application of an indirect immunohistochemical method for the detection of duck plague virus vaccine antigens in paraffin sections and localization in the vaccinated duckling tissues

The objective of the present study was to develop and apply a streptavidin-alkaline phosphatase labeling system of indirect immunohistochemistry (SP-IHC) to detect antigenic distribution and localization regularity of duck plague virus (DPV) vaccine antigens in paraformaldehyde-fixed paraffin-embedded tissues of experimentally vaccinated ducklings. Male New Zealand rabbits were immunized with purified DPV antigens, which were engaged by a combination of differential centrifugation and sucrose-density gradient ultracentrifugation. The rabbit anti-DPV polyclonal antibodies were purified and used as the primary antibodies. Forty-eight 28-d-old DPV-free Pekin ducklings were subcutaneously inoculated with attenuated DPV vaccine in the immunization group and sterile PBS in the control group. The tissues were collected at sequential time points between 4 h and 18 wk postvaccination (PV) and were prepared for SP-IHC observation. The presence of DPV-specific antigens was first observed in the liver and spleen at 12 h PV; in the bursa of Fabricius, thymus, Harderian gland, esophagus, and intestinal tract at 1 d PV; and in the heart, lung, kidney, pancreas, and brain at 3 d PV. The positive staining reaction could be detected in the vaccinated duckling tissues until 18 wk PV, and no positive staining cells could be observed in the controls. The highest levels of positive staining reaction were found in the liver, spleen, bursa of Fabricius, thymus, and intestinal tract, whereas a few DPV vaccine antigens were distributed in the heart, pancreas, and esophagus. The target cells had a ubiquitous distribution, especially in the mucosal epithelial cells, lamina propria cells, macrophages, hepatocytes, and lymphocytes, which served as the principal sites for antigen localization. These findings demonstrated that SP-IHC was a reliable method for detecting antigenic distribution and localization regularity of DPV vaccine antigens in routine paraffin sections. The present study may be useful for describing proliferation and distribution regularity of DPV vaccine in the vaccinated duckling tissues and enhance further studies and clinical application of attenuated DPV vaccine.

Immunohistochemistry as an important tool in biomarkers detection and clinical practice

The immunohistochemistry technique is used in the search for cell or tissue antigens that range from amino acids and proteins to infectious agents and specific cellular populations. The technique comprises two phases: (1) slides preparation and stages involved for the reaction; (2) interpretation and quantification of the obtained expression. Immunohistochemistry is an important tool for scientific research and also a complementary technique for the elucidation of differential diagnoses which are not determinable by conventional analysis with hematoxylin and eosin. In the last couple of decades there has been an exponential increase in publications on immunohistochemistry and immunocytochemistry techniques. This review covers the immunohistochemistry technique; its history, applications, importance, limitations, difficulties, problems and some aspects related to results interpretation and quantification. Future developments on the immunohistochemistry technique and its expression quantification should not be disseminated in two languages—that of the pathologist and another of clinician or surgeon. The scientific, diagnostic and prognostic applications of this methodology must be explored in a bid to benefit of patient. In order to achieve this goal a collaboration and pooling of knowledge from both of these valuable medical areas is vital

Aspectos clínicos e patológicos em bovinos afetados por raiva com especial referência ao mapeamento do antígeno rábico por imuno-histoquímica

Este estudo retrospectivo incluiu achados clínicos e patológicos de 15 bovinos afetados por raiva. Em treze dos quinze casos, raiva foi confirmada por imunofluorescência direta. Bovinos entre 4 meses e 8 anos foram afetados. O curso clínico variou de três a sete dias. A forma paralítica foi a mais frequente e incluiu incoordenação, paresia e paralisia dos membros pélvicos, decúbito, movimentos de pedalagem e morte. Os principais achados histopatológicos foram meningoencefalite linfoplasmocitária associada com corpúsculos de Negri em 86,6% dos casos. Todos os casos foram positivos na imuno-histoquímica para raiva, cujas reações foram mais evidentes no tronco encefálico, incluindo bulbo, ponte e mesencéfalo, além de gânglio trigêmeo. A imuno-histoquímica demonstrou o vírus da raiva em axônios, dendritos e pericário de neurônios, como agregados de grânulos ou em formações arredondadas associadas com números variáveis de corpúsculos de inclusão virais nos neurônios. Houve também marcação nos neurônios de Purkinje e de seus processos na camada molecular, nos núcleos do tronco encefálico e camada profunda do córtex telencefálico. A imuno-histoquímica pode ser importante ferramenta diagnóstica no diagnóstico da raiva, especialmente em situações nas quais não é possível manter refrigeração adequada das amostras e em casos com meningoencefalite não-supurativa e ausência de corpúsculos de inclusão.

Immunohistochemical detection and localization of new type gosling viral enteritis virus in paraformaldehyde-fixed paraffin-embedded tissue

To determine the distribution and localization of new type gosling viral enteritis virus (NGVEV) in paraformaldehyde-fixed paraffin-embedded tissues of experimentally infected goslings, for the first time, an immunohistochemical (IHC) staining method was reported. Anti-NGVEV polyclonal serum was obtained from the rabbits immunized with purified NGVEV antigen, which was extracted by caprylic-ammonium sulphate method and purified through High-Q columns anion exchange chromatography. Three-day-old NGVEV-free goslings were orally inoculated with NGVEV-CN strain suspension as infection group and phosphate buffered saline solution (PBS) as control group, respectively. The tissues were collected at sequential time points between 0.5 and 720h post inoculation (PI), and prepared for IHC staining and ultra-structural observation. The positive immunoreactivity could be readily detected in the lymphoid and gastrointestinal organs of infected goslings as early as 48 h PI, in the liver, kidney, pancreas and myocardium from 72 h, and in the cerebrum and cerebellum from 96 h, while it was hardly detected in the respiratory organs at any time. The positive staining reaction could be detected in NGVEV-infected goslings until 600 h PI, and no positive staining cell could be observed in the controls. The highest levels of viral antigen were found in the bursa of Fabricius (BF), thymus, proventriculus, gizzard and intestine tract, moreover, the liver, kidney, spleen, myocardium and pancreas were intensively and widely stained. The target cells had a ubiquitous distribution, especially included the epithelial cells, endothelial cells, superficial and crypt mucosal cells, glandular cells, fibrocytes, macrophages and lymphocytes, which served as the principal sites for antigen localization. The ultra-structural observation by transmission electron microscope (TEM) further indicated that NGVEV particles could be widely detected in the lymphoid and digestive organs of infected goslings from 72 h PI onwards. This work may be useful not only for offering a possibility of routine diagnosis of NGVE, but also for better understanding of the pathogenesis of the disease.