Application of a recombinant novel trypsin from Trichinella spiralis for serodiagnosis of trichinellosis

BACKGROUND

The excretory/secretory (ES) antigen of Trichinella spiralis muscle larvae (ML) is currently the most widely used diagnostic antigen to detect T. spiralis infection. However, this antigen has certain drawbacks, such as a complicated ES antigen preparation process and lower sensitivity during the early phase of infection. The aim of this study was to investigate the features of a novel T. spiralis trypsin (TsTryp) and evaluate its potential diagnostic value for trichinellosis.

METHODS

The TsTryp gene was cloned and recombinant TsTryp (rTsTryp) expressed. Western blotting and an enzyme-linked immunosorbent assay (ELISA) were performed to confirm the antigenicity of rTsTryp. The expression pattern and distribution signature of TsTryp at various life-cycle stages of T. spiralis were analyzed by quantitative PCR, western blotting and the immunofluorescence test. An ELISA with rTsTryp and ML ES antigens was used to detect immunoglobulins G and M (IgG, IgM) in serum samples of infected mice, swine and humans. The seropositive results were further confirmed by western blot with rTsTryp and ML ES antigens.

RESULTS

TsTryp expression was observed in diverse T. spiralis life-cycle phases, with particularly high expression in the early developmental phase (intestinal infectious larvae and adults), with distribution observed mainly at the nematode outer cuticle and stichosome. rTsTryp was identified by T. spiralis-infected mouse sera and anti-rTsTryp sera. Natural TsTryp protease was detected in somatic soluble and ES antigens of the nematode. In mice infected with 200 T. spiralis ML, serum-specific IgG was first detected by rTsTryp-ELISA at 8 days post-infection (dpi), reaching 100% positivity at 12 dpi, and first detected by ES-ELISA at 10 dpi, reaching 100% positivity at 14 dpi. Specific IgG was detected by rTsTryp 2 days earlier than by ES antigens. When specific IgG was determined in serum samples from trichinellosis patients, the sensitivity of rTsTryp-ELISA and ES antigens-ELISA was 98.1% (51/52 samples) and 94.2% (49/52 samples), respectively (P = 0.308), but the specificity of rTsTryp was significantly higher than that of ES antigens (98.7% vs. 95.4%; P = 0.030). Additionally, rTsTryp conferred a lower cross-reaction, with only three serum samples in total testing positive from 11 clonorchiasis, 20 cysticercosis and 24 echinococcosis patients (1 sample from each patient group).

CONCLUSIONS

TsTryp was shown to be an early and highly expressed antigen at intestinal T. spiralis stages, indicating that rTsTryp represents a valuable diagnostic antigen for the serodiagnosis of early Trichinella infection.

Characterization of a novel dipeptidyl peptidase 1 of Trichinella spiralis and its participation in larval invasion

The research aimed to describe a new Trichinella spiralis dipeptidyl peptidase 1 (TsDPP1) and investigate its functions in the larval invasion of intestinal epithelial cells (IECs). The gene TsDPP1 was successfully replicated and produced in Escherichia coli BL21 (DE3), showing a strong immune response. TsDPP1 was detected in diverse stages of T. spiralis and showed significant expression in the intestine infective larvae (IIL) and adult worms at 6 days post infection, as confirmed by qPCR and Western blot analysis. The primary localization of TsDPP1 in this parasite was observed in cuticles, stichosomes, and embryos by using the indirect immunofluorescence assay (IIFA). rTsDPP1 exhibited the enzymatic function of natural dipeptidyl peptidase and showed specific binding to IECs, and the binding site was found to be localized on cell membrane. Following transfection with dsRNA-TsDPP1, the expression of TsDPP1 mRNA and protein in muscle larvae (ML) were decreased by approximately 63.52 % and 58.68 %, correspondingly. The activity of TsDPP1 in the ML and IIL treated with dsRNA-TsDPP1 was reduced by 42.98 % and 45.07 %, respectively. The acceleration of larval invasion of IECs was observed with rTsDPP1, while the invasion was suppressed by anti-rTsDPP1 serum. The ability of the larvae treated with dsRNA-TsDPP1 to invade IECs was hindered by 31.23 %. In mice infected with dsRNA-treated ML, the intestinal IIL, and adults experienced a significant decrease in worm burdens and a noticeable reduction in adult female length and fecundity compared to the PBS group. These findings indicated that TsDPP1 significantly impedes the invasion, growth, and reproductive capacity of T. spiralis in intestines, suggesting its potential as a target for anti-Trichinella vaccines.

A novel trypsin of Trichinella spiralis mediates larval invasion of gut epithelium via binding to PAR2 and activating ERK1/2 pathway

BACKGROUND

Proteases secreted by Trichinella spiralis intestinal infective larvae (IIL) play an important role in larval invasion and pathogenesis. However, the mechanism through which proteases mediate larval invasion of intestinal epithelial cells (IECs) remains unclear. A novel T. spiralis trypsin (TsTryp) was identified in IIL excretory/secretory (ES) proteins. It was an early and highly expressed protease at IIL stage, and had the potential as an early diagnostic antigen. The aim of this study was to investigate the biological characteristics of this novel TsTryp, its role in larval invasion of gut epithelium, and the mechanisms involved.

METHODOLOGY/PRINCIPAL FINDING

TsTryp with C-terminal domain was cloned and expressed in Escherichia coli BL21 (DE3), and the rTsTryp had the enzymatic activity of natural trypsin, but it could not directly degrade gut tight junctions (TJs) proteins. qPCR and western blotting showed that TsTryp was highly expressed at the invasive IIL stage. Immunofluorescence assay (IFA), ELISA and Far Western blotting revealed that rTsTryp specifically bound to IECs, and confocal microscopy showed that the binding of rTsTryp with IECs was mainly localized in the cytomembrane. Co-immunoprecipitation (Co-IP) confirmed that rTsTryp bound to protease activated receptors 2 (PAR2) in Caco-2 cells. rTsTryp binding to PAR2 resulted in decreased expression levels of ZO-1 and occludin and increased paracellular permeability in Caco-2 monolayers by activating the extracellular regulated protein kinases 1/2 (ERK1/2) pathway. rTsTryp decreased TJs expression and increased epithelial permeability, which could be abrogated by the PAR2 antagonist AZ3451 and ERK1/2 inhibitor PD98059. rTsTryp facilitated larval invasion of IECs, and anti-rTsTryp antibodies inhibited invasion. Both inhibitors impeded larval invasion and alleviated intestinal inflammation in vitro and in vivo.

CONCLUSIONS

TsTryp binding to PAR2 activated the ERK1/2 pathway, decreased the expression of gut TJs proteins, disrupted epithelial integrity and barrier function, and consequently mediated larval invasion of the gut mucosa. Therefore, rTsTryp could be regarded as a potential vaccine target for blocking T. spiralis invasion and infection.

Binding of Trichinella spiralis C-type lectin with syndecan-1 on intestinal epithelial cells mediates larval invasion of intestinal epithelium

C-type lectin (CTL) is a protein that binds to saccharides and plays an important role in parasite adhesion, host cell invasion and immune evasion. Previous studies showed that recombinant T. spiralis C-type lectin (rTsCTL) promotes larval invasion of intestinal epithelium cells (IEC), whereas anti-rTsCTL antibodies inhibits larval invasion. Syndecan-1 (SDC-1) is a member of the heparan sulfate proteoglycan family which is mainly expressed on the surface of IEC and in extracellular matrices where they interact with a plethora of ligands. SDC-1 has a principal role in maintaining cell morphogenesis, establishing cell-cell adhesions, and regulating the gut mucosal barrier. The aim of this study was to investigate whether rTsCTL binds to SDC-1 on IEC, and the binding of rTsCTL with SDC-1 promotes larval invasion and its mechanism. IFA results show that rTsCTL and SDC-1 co-localized on Caco-2 cell membrane. GST pull-down and Co-IP verified the direct interaction between rTsCTL and SDC-1 on Caco-2 cells. qPCR and Western blotting revealed that rTsCTL binding to SDC-1 increased the expression of SDC-1 and claudin-2, and reduced the expression of occludin and claudin-1 in Caco-2 cells incubated with rTsCTL via the STAT3 pathway. β-Xyloside (a syndecan-1 synthesis inhibitor) and Stattic (a STAT3 inhibitor) significantly inhibited rTsCTL binding to syndecan-1 in Caco-2 cells and activation of the STAT3 pathway, abrogated the effects of rTsCTL on the expression of gut tight junctions, and impeded larval invasion. The results demonstrate that binding of rTsCTL to SDC-1 on Caco-2 cells activated the STAT3 pathway, decreased gut tight junction expression, damaged the integrity of the gut epithelial barrier, and mediated T. spiralis invasion of the gut mucosa. TsCTL might be regarded as a candidate vaccine target against T. spiralis invasion and infection.

[HbA1c comparison and diagnostic efficacy analysis of multi center different glycosylated hemoglobin detection systems]

Objective: Compare and analyze the results of the domestic Lanyi AH600 glycated hemoglobin analyzer and other different detection systems to understand the comparability of the detection results of different detectors, and establish the best cut point of Lanyi AH600 determination of haemoglobin A1c (HbA1c) in the diagnosis of diabetes. Methods: Multi center cohort study was adopted. The clinical laboratory departments of 18 medical institutions independently collected test samples from their respective hospitals from March to April 2022, and independently completed comparative analysis of the evaluated instrument (Lanyi AH600) and the reference instrument HbA1c. The reference instruments include four different brands of glycosylated hemoglobin meters, including Arkray, Bio-Rad, DOSOH, and Huizhong. Scatter plot was used to calculate the correlation between the results of different detection systems, and the regression equation was calculated. The consistency analysis between the results of different detection systems was evaluated by Bland Altman method. Consistency judgment principles: (1) When the 95% limits of agreement (95% LoA) of the measurement difference was within 0.4% HbA1c and the measurement score was≥80 points, the comparison consistency was good; (2) When the measurement difference of 95% LoA exceeded 0.4% HbA1c, and the measurement score was≥80 points, the comparison consistency was relatively good; (3) The measurement score was less than 80 points, the comparison consistency was poor. The difference between the results of different detection systems was tested by paired sample T test or Wilcoxon paired sign rank sum test; The best cut-off point of diabetes was analyzed by receiver operating characteristic curve (ROC). Results: The correlation coefficient R² of results between Lanyi AH600 and the reference instrument in 16 hospitals is≥0.99; The Bland Altman consistency analysis showed that the difference of 95% LoA in Nanjing Maternity and Child Health Care Hospital in Jiangsu Province (reference instrument: Arkray HA8180) was -0.486%-0.325%, and the measurement score was 94.6 points (473/500); The difference of 95% LoA in the Tibetan Traditional Medical Hospital of TAR (reference instrument: Bio-Rad Variant II) was -0.727%-0.612%, and the measurement score was 89.8 points; The difference of 95% LoA in the People's Hospital of Chongqing Liang Jiang New Area (reference instrument: Huizhong MQ-2000PT) was -0.231%-0.461%, and the measurement score was 96.6 points; The difference of 95% LoA in the Taihe Hospital of traditional Chinese Medicine in Anhui Province (reference instrument: Huizhong MQ-2000PT) was -0.469%-0.479%, and the measurement score was 91.9 points. The other 14 hospitals, Lanyi AH600, were compared with 4 reference instrument brands, the difference of 95% LoA was less than 0.4% HbA1c, and the scores were all greater than 95 points. The results of paired sample T test or Wilcoxon paired sign rank sum test showed that there was no statistically significant difference between Lanyi AH600 and the reference instrument Arkray HA8180 (Z=1.665,P=0.096), with no statistical difference. The mean difference between the measured values of the two instruments was 0.004%. The comparison data of Lanyi AH600 and the reference instrument of all other institutions had significant differences (all P<0.001), however, it was necessary to consider whether it was within the clinical acceptable range in combination with the results of the Bland-Altman consistency analysis. The ROC curve of HbA1c detected by Lanyi AH600 in 985 patients with diabetes and 3 423 patients with non-diabetes was analyzed, the area under curve (AUC) was 0.877, the standard error was 0.007, and the 95% confidence interval 95%CI was (0.864, 0.891), which was statistically significant (P<0.001). The maximum value of Youden index was 0.634, and the corresponding HbA1c cut point was 6.235%. The sensitivity and specificity of diabetes diagnosis were 76.2% and 87.2%, respectively. Conclusion: Among the hospitals and instruments currently included in this study, among these four hospitals included Nanjing Maternity and Child Health Care Hospital in Jiangsu Province (reference instrument: Arkray HA8180), Tibetan Traditional Medical Hospital of TAR (reference instrument: Bio-Rad Variant Ⅱ), the People's Hospital of Chongqing Liang Jiang New Area (reference instrument: Huizhong MQ-2000PT), and the Taihe Hospital of traditional Chinese Medicine in Anhui Province (reference instrument: Huizhong MQ-2000PT), the comparison between Lanyi AH600 and the reference instruments showed relatively good consistency, while the other 14 hospitals involved four different brands of reference instruments: Arkray, Bio-Rad, DOSOH, and Huizhong, Lanyi AH600 had good consistency with its comparison. The best cut point of the domestic Lanyi AH600 for detecting HbA1c in the diagnosis of diabetes is 6.235%.

Mannose facilitates Trichinella spiralis expulsion from the gut and alleviates inflammation of intestines and muscles in mice

Trichinellosis is a major zoonotic parasitosis which is a vital risk to meat food safety. It is requisite to exploit new strategy to interdict food animal Trichinella infection and to obliterate Trichinella from food animals to ensure meat safety. Mannose is an oligosaccharide that specifically binds to the carbohydrate-recognition domain of C-type lectin; it has many physiological functions including reliving inflammation and regulating immune reaction. The purpose of this study was to investigate the suppressive role of mannose on T. spiralis larval invasion and infection, its effect on intestinal and muscle inflammation, and immune responses after challenge. The results showed that compared to the saline-treated infected mice, the mannose-treated infected mice had less intestinal adult and muscle worm burdens, mild inflammation of intestine and muscle of infected mice. The levels of specific anti-Trichinella IgG (IgG1/IgG2a), IgA and sIgA in mannose-treated infected mice were obviously inferior to saline-treated infected mice (P < 0.01). Furthermore, the levels of two cytokines (IFN-γ and IL-4) in mannose-treated infected mice were also significantly lower than the saline-treated infected mice (P < 0.01). The protective effect of the mannose against Trichinella infection might be not related to specific antibody and cellular immune responses. The above results demonstrated that mannose could be considered as a novel adjuvant therapeutic agent for anti-Trichinella drugs to block larval invasion at early stage of Trichinella infection.

[On detection of chromogranin A, synaptophysin, neuronspecific enolase and progastrin-releasing peptide in small cell lung cancer]

Lung cancer is one of the most common cancer, there is a significant difference between the treatment and prognosis of small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). SCLC tumor cells usually express neuroendocrine tumor (NET) markers, among which there are many studies on chromogranin A (CgA), synaptophysin (Syn), neuronspecific enolase (NSE) and pro-gastrin-releasing peptide (Pro-GRP) with SCLC. The levels of CgA, NSE and pro-GRP were related to the stage of SCLC, which were significantly higher in patients with extensive stage than in patients with limited stage, and their expression was significantly correlated with lower survival rate. Syn as an auxiliary diagnostic index of SCLC is more sensitive than CgA, and has high practical value in the differential diagnosis of SCLC and poorly differentiated squamous cell carcinoma; NSE is the most commonly used tumor marker in SCLC; Pro-GRP has stronger diagnostic advantages than CEA and NSE in distinguishing SCLC from NSCLC. Although these net markers are not specific markers of SCLC, their combined use with each others or combined with CT as an auxiliary diagnostic index may improve the level of differential diagnosis of SCLC, and they have a certain value in the staging of the disease, which is very important for the formulation of SCLC treatment strategy, their detection is conducive to the prevention and control of the disease.

Proteases secreted by Trichinella spiralis intestinal infective larvae damage the junctions of the intestinal epithelial cell monolayer and mediate larval invasion

The intestinal epithelium is the first natural barrier against Trichinella spiralis larval invasion, but the mechanism of larval invasion of the gut epithelium is not fully elucidated. The aim of this study was to investigate whether the excretory/secretory proteins (ESPs) of T. spiralis intestinal infective larvae (IIL) degrade tight junction (TJ) proteins, to assess the main ESP proteases hydrolysing TJ proteins using various enzyme inhibitors and to define the key invasive factors in IIL invasion of the gut epithelium. The results of immunofluorescence, Western blot and Transwell assays showed that serine proteases and cysteine proteases in the ESPs played main roles in hydrolysing occludin, claudin-1 and E-cad and upregulating claudin-2 expression. Challenge infection results showed that IIL expulsion from the gut at 12 hpi was significantly higher in mice which were infected with muscle larvae (ML) treated with a single inhibitor (PMSF, E-64, 1,10-Phe or pepstatin) or various mixtures containing PMSF and E-64 than in mice in the PBS group or the groups treated with an inhibitor mixture not containing PMSF and E-64 (P < 0.0001). At 6 days post-infection, mice which were infected with ML treated with PMSF, E-64, 1,10-Phe or pepstatin exhibited 56.30, 64.91, 26.42 and 31.85% reductions in intestinal adult worms compared to mice in the PBS group (P < 0.0001). The results indicate that serine proteases and cysteine proteases play key roles in T. spiralis IIL invasion, growth and survival in the host and that they may be main candidate target molecules for vaccines against larval invasion and development.

[Comparison and reflection of standardization of public health management system both at home and abroad]

Objective: To better promote the standardization of public health management in China, and provide evidence for the development and improvement of the standardization strategy and management system in public health field in China. Methods: This paper summarizes and analyzes the information about the standardized management mechanism collected from international organizations related with standardization in public health. Results: The standards in public health varied in different management systems of the international organizations, and there were great differences in organization nature, standard types, application, release, organization structure, standard development principles, advantages, transformation, promotion and implementation, and evaluation. Conclusion: China can benefit from the studying of the working mechanism of the international organization related with standardization in public health to facilitate its own standardization in public health.

[Cytocompatibility of angiogenesis-promoting acidified silk protein sponge matrices and its effects on wound healing of full-thickness skin defects in rats]

Objective: To analyze the mechanism of acidified silk protein sponge matrices and methanolized silk protein sponge matrices in promoting wound healing. Methods: The experimental method was conducted. Acidified silk protein sponge matrices with vascularization ability and methanolized silk protein sponge matrices without vascularization ability were prepared by improved freeze-drying method. General observation was performed. Internal morphology was observed with scanning electron microscope. The secondary structure was observed with X-ray diffractometer (XRD) and infrared spectrometer. Compressive modulus was tested by tensile machine. Two 3-week-old male Sprague-Dawley (SD) rats were used to isolate bone marrow mesenchymal stem cells (BMSCs) cultured in above-mentioned two silk protein sponge matrices, the number of cells was counted under laser scanning confocal microscope after 1, 6 days of culture. Four full-thickness skin defect wounds were made on each one of twelve 8-week-old male SD rats, which were divided into methanolized silk group (24 wounds) and acidified silk group (24 wounds) covered with the corresponding silk protein sponge matrices. On post operation day (POD) 3, 7, 10, and 14, general observation was performed and the remaining wound area was recorded. On POD 3, 7, and 14, the wounds and marginal tissue were collected for hematoxylin-eosin staining (HE) staining and Masson staining to observe growth of new tissue and collagen deposition and CD34 immunohistochemical staining to observe vascularization. Sample number of each index of each group at every time point in animal experiment was 6. Data were statistically analyzed with analysis of variance of factorial design, analysis of variance for repeated measurement, independent-samples t test, and Bonferroni correction. Results: Methanolized silk protein sponge matrices and acidified silk protein sponge matrices had the same composition and similar porous structure, with pore size of 300-500 μm. XRD showed that methanolized silk protein sponge matrices showed a significant crystallization peak, while acidified silk protein sponge matrices was mainly composed of amorphous structure. Infrared spectrometer showed that acidified silk protein sponge matrices appeared a strong absorption peak at 1 650 cm(-1), and the methanolized silk protein sponge matrices appeared a strong absorption peak at 1 630 cm(-1). Compressive modulus of methanolized silk protein sponge matrices was (23.8±1.3) kPa, which was significantly higher than (6.1±0.9) kPa of acidified silk protein sponge matrices (t=19.550, P<0.01). After one day of culture, BMSCs successfully adhered to the two kinds of silk protein sponge matrices, and the cells were not spread. After six days of culture, BMSCs were spread on the two kinds of silk protein sponge matrices, and the number of cells on the acidified silk protein sponge matrices increased significantly. On POD 3, the wounds of the 2 groups did not shrink significantly. On POD 7, the wound area in acidified silk group was significantly smaller than that in methanolized silk group, and new epithelium growth occurred at the wound edge. On POD 14, the wounds of acidified silk group basically healed, and the wounds of methanolized silk group were dry and shrinked significantly. Remaining wound area of acidified silk group on POD 3, 7, 10, and 14 were significantly smaller compared with that in methanolized silk group ( t=7.782, 10.620, 3.707, 6.830, P<0.05 or P<0.01). HE staining, Masson staining, and CD34 immunohistochemical staining showed on POD 3, new tissue growing into silk protein sponge matrices of wounds of acidified silk group was more than that in methanolized silk group, the former group secreted a small amount of collagen, collagen formation was not observed in the latter group, the number of vascular endothelial cells migrated into the matrices were more in the former group than the latter group; on POD 7, the area of new tissue covering matrices hole of wounds of acidified silk group was larger than that in methanolized silk group, collagen in the former group was more than that in the latter group and was evenly distributed, the number of blood vessels in the former group was more than that on POD 3, and the new blood vessels in the latter group were scattered; on POD 14, the new tissue in acidified silk group was similar in structure to normal skin tissue and formed a certain thickness, the new tissue in methanolized silk group basically grew into the matrices, the former group had rich collagen deposition, the latter group had scattered collagen, and blood vessels in the former group distributed uniformly and density of blood vessels was significantly higher than that in the latter group ((55.7±6.0) and (34.1±1.0) pieces/mm(2), respectively, t=9.042, P<0.01). Conclusions: Angiogenesis-promoting acidified silk protein sponge matrices have good cytocompatibility, which can facilitate the rapid formation of vascular network in wound area, providing sufficient blood supply to accelerate the tissue regeneration and collagen deposition, thereby promoting wound healing and improving healing quality, these effects are better than methanolized silk protein sponge matrices.

[Progress in research of allergen detection methods]

Allergic diseases have continued to increase year by year causing serious physical and mental injury to patients, families and individuals. This increase has been driven by conventional environmental and nutritional changes but is also created by the continual introduction of food additives into the diet and novel interior decoration materials into the living space. The causes of allergic diseases are complex and diverse, and the medical laboratory often is not be able to identify the allergic trigger; this creates a difficult environment to identify the appropriate clinical treatment for disease prevention and control. Physicians must be able to identify these triggers to help patients avoid the underlying allergenic cause of their disease. This can only be done by actively knowing a patient's medical history, identifying the clinical manifestations of hypersensitivity and utilizing confirmatory testing as an important clinical tool in identifying the allergic source.