Analysis of coexisting pathogens in nasopharyngeal swabs from COVID-19.

Background: The impact of COVID-19 on the world is still ongoing, and it is currently under regular management. Although most infected people have flu-like symptoms and can cure themselves, coexisting pathogens in COVID-19 patients should not be taken lightly. The present study sought to investigate the coexisting pathogens in SARS-CoV-2 infected patients and identify the variety and abundance of dangerous microbes to guide treatment strategies with a better understanding of the untested factors. Methods: We extracted total DNA and RNA in COVID-19 patient specimens from nasopharyngeal swabs to construct a metagenomic library and utilize Next Generation Sequencing (NGS) to discover chief bacteria, fungi, and viruses in the body of patients. High-throughput sequencing data from Illumina Hiseq 4000 were analyzed using Krona taxonomic methodology for species diversity. Results: We studied 56 samples to detect SARS-CoV-2 and other pathogens and analyzed the species diversity and community composition of these samples after sequencing. Our results showed some threatening pathogens such as Mycoplasma pneumoniae, Klebsiella pneumoniae, Streptococcus pneumoniae, and some previously reported pathogens. SARS-CoV-2 combined with bacterial infection is more common. The results of heat map analysis showed that the abundance of bacteria was mostly more than 1000 and that of viruses was generally less than 500. The pathogens most likely to cause SARS-CoV-2 coinfection or superinfection include Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Klebsiella pneumoniae, and Human gammaherpesvirus 4. Conclusions: The current coinfection and superinfection status is not optimistic. Bacteria are the major threat group that increases the risk of complications and death in COVID-19 patients and attention should be paid to the use and control of antibiotics. Our study investigated the main types of respiratory pathogens prone to coexisting or superinfection in COVID-19 patients, which is valuable for identifying and treating SARS-CoV-2.

Ultrasound assessment of the elbow joint in infants and toddlers and its clinical significance.

BACKGROUND: Ultrasound can be used for the diagnosis of elbow injuries in infants and toddlers. However, ultrasound is highly operator-dependent and accurate ultrasound examinations require a complete understanding of the complex anatomy of the elbow joint. PURPOSE: To report the normal ultrasound anatomy of the elbow, particularly of the humeroulnar joint, in infants and toddlers. MATERIAL AND METHOD: Thirty subjects aged <3 years with no history of elbow injuries underwent ultrasound examinations of the elbow joint from six directions: (i) lateral to the humeroradial joint; (ii) anterior to the humeroradial joint; (iii) posterior to the humeroradial joint; (iv) medial to the humeroulnar joint; (v) anterior to the humeroulnar joint; and (vi) posterior to the humeroulnar joint. RESULTS: The appearance of the humeroradial joint observed from three directions was similar and resembled a pair of double fists ("double-breast sign"). The appearance of the humeroulnar joint observed from three directions was different, which is related to the irregular morphology of the medial sides of the humerus and ulna. Anteroposteriorly, the coronoid and olecranon epiphyses and coronoid fossa appear anteriorly and the olecranon and trochlear epiphyses and olecranon fossa appear posteriorly, resembling a "check-mark sign". The medial epicondyle, cubital tunnel and distal humerus appear together ("double-hump sign"). The "anterior hump" is the medial epicondyle and is always higher than the "posterior hump", which is the bony protrusion on the articular surface of the distal humerus. The ultrasound signal of cortical bone in the metaphysis of the distal humerus is continuous with that of the epiphysis of the medial epicondyle. CONCLUSION: Ultrasound is useful for the diagnosis of elbow injuries in infants and toddlers.

Induction and maintenance of T-dependent or T-independent xenotolerance by nonprimarily-vascularized skin or thymus grafts.

BACKGROUND: The success of clinical xenotransplantation will depend on induction of xenotolerance. We have previously shown that combined xenothymus and vascularized xenoheart transplantation under the coverage of a tolerizing regimen (TR) can induce and maintain full xenotolerance. Here, induction/maintenance of xenotolerance using nonprimarily-vascularized thymus and/or skin grafts was investigated. MATERIALS AND METHODS: Hamster skin or thymus or combined skin and thymus transplantation was performed in nude rat recipients with or without administering a TR (NK cell depletion, day -14; xenoantigen infusion, day -14; Leflunomide, day -14 through +14). Xenotolerance was confirmed by subsequent transplantation of a vascularized hamster heart, measurement of xenoantibody formation, or mixed lymphocyte reaction (MLR). RESULTS: Skin grafts were as effective as vascularized heart grafts to induce/maintain T-independent xenotolerance. Even without TR and despite being rejected themselves, xenoskin grafts lead to progressively developing xenononreactivity. Xenothymus transplantation induced xenotolerance in the T-dependent but not in the T-independent immune compartment, leading to rejection of subsequently transplanted hamster hearts by T-independent mechanisms (production of IgM but not IgG xenoantibodies (Xabs), presence of antihamster MLR nonresponsiveness). Combined skin and thymus xenotransplantation sensitized the T-cell compartment, leading to hyperacute rejection of subsequently transplanted hamster hearts. This was not the case when the skin grafts were transplanted late (2 months) after the thymus grafts. CONCLUSIONS: Xenogeneic skin and xenogeneic thymus grafts have opposite xenotolerance inducing capacities in the T-independent as compared to the T-dependent immune compartment. Thymus grafts induce and maintain T-dependent but not T-independent xenotolerance. Skin grafts alone induce T-independent xenotolerance but sensitize the T-cell compartment when transplanted concomitantly with thymus grafts.

Effects of a short course of leflunomide on T-independent B-lymphocyte xenoreactivity and on susceptibility of xenografts to acute or chronic rejection.

BACKGROUND: Leflunomide is a novel immunosuppressive agent with promising activity for xenotransplantation. It is not clear yet which mechanisms of action of leflunomide are responsible for that. METHODS: In a hamster-to-C57BL/6 nude mouse heart transplantation model, a 2-week course of leflunomide was used after transplantation or for pretreating donors. Nontolerant B lymphocytes were transferred to recipients after transplantation of first or second xenogeneic heart grafts that were transplanted with or without leflunomide treatment. RESULTS: Hamster xenogeneic hearts transplanted into athymic C57BL/6 nude mice receiving leflunomide did not induce immunoglobulin (Ig) M xenoantibodies (XAb) and survived without signs of chronic rejection. Second xenogeneic hearts transplanted 4 weeks after withdrawal of leflunomide survived without induction of XAb but developed chronic vascular lesions. After injection of naive B lymphocytes at 6 weeks after grafting a first or second hamster heart, only in the latter case were XAb induced. These were deposited in, and provoked acute rejection of, only the second grafts. Pretreatment of donors with leflunomide decreased the ex vivo xenoantibody deposition on the xenogeneic heart endothelia. CONCLUSIONS: A short posttransplant course of leflunomide induces T-independent B-lymphocyte xenotolerance. Leflunomide treatment also influences xenoantigen expression, as nontolerant B lymphocytes provoke IgM XAb formation and rejection of only second xenografts (transplanted without leflunomide) and not of first xenografts (transplanted with leflunomide treatment). The ex vivo experiments that show that XAb deposition is decreased in leflunomide-pretreated xenografts further confirm this. The latter may also explain the resistance of first and not second xenografts against chronic rejection.

Pulmonary toxicity of polyvinyl chloride particles after repeated intratracheal instillations in rats. Elevated CD4/CD8 lymphocyte ratio in bronchoalveolar lavage.

Occupational exposure to polyvinyl chloride (PVC) particles has been associated with interstitial lung disease. Our previous study showed that a single intratracheal instillation of emulsion PVC particles, with or without residual additives, induces acute but transient alveolitis in a dose-dependent manner in rats. The aim of the present study was to investigate the pulmonary response after the administration of the same PVC particles (PVC-E3 and PVC-W3) given in the same cumulative doses (10 and 50 mg/kg BW), but fractionated as seven intratracheal instillations (7 x 1.4 and 7 x 7.1 mg/kg BW) in the course of 3 weeks (day 0 to day 21). Pulmonary response was characterized by analysis of lung weight, bronchoalveolar lavage (BAL) fluid for lactate dehydrogenase (LDH), total protein, and cell cytology, and a microscopic evaluation of lung tissue. BAL T lymphocyte phenotypes (CD3 + CD4 +, CD3 + CD8+) were analyzed by flow cytometry. On day 28, lung weights, BAL-LDH, cell numbers in BAL, and CD4/CD8 ratios in BAL T lymphocytes were higher in rats that had received the high dose of PVC-E3 or PVC-W3 than in rats that had received the low dose of PVC particles and control rats. On day 90, the pulmonary response had partially regressed towards control values, but there were still microscopically evident lesions in the lungs and greater CD4/CD8 ratio in the high dose groups. There were significant positive correlations between the CD4/CD8 ratio and a histopathology score of the lung (r = 0.36, P = 0.038 on day 28, and r = 0.46, P = 0.006 on day 90). In conclusion, repeated intratracheal instillations of PVC particles yielded similar results as single instillations. The examined PVC particles have the potential of inducing a limited and transient acute inflammatory reaction in the lung, and possibly a more persistent alteration of pulmonary T lymphocyte subsets towards a high CD4/CD8 ratio.

Pathogenesis of autoimmunity after xenogeneic thymus transplantation.

Thymus transplantation is a promising strategy to induce xenotolerance, but may also induce an autoimmune syndrome (AIS). The pathogenesis of this AIS was explored using nude rats as recipients. Thymus grafts consisted of fetal hamster thymic tissue with or without mixing with fetal rat tissue such as thymus, thyroid, salivary gland, and heart. All hamster thymus recipients died of AIS within 2-3 mo. In most recipients of xenothymus mixed with rat tissues such as thymus, thyroid, and salivary gland, but not heart, AIS was prevented, indicating an insufficient presence of rat epithelial cell Ags within the xenothymus. AIS could be transferred to control nude rats by whole splenocytes or by splenocyte subpopulations such as CD3(+), CD3(-), and B lymphocytes, but not by non-T, non-B cells from AIS animals. This transfer could be suppressed by cotransferring either CD4(+) or CD8(+) lymphocytes from euthymic rats, but not by splenocytes from recipients of syngeneic or xenogeneic thymus mixed with rat tissue, indicating a defective generation of regulatory lymphocytes. As for CD4(+) regulatory cells this defect was probably qualitative, because the percentages of CD4(+)CD25(+) or CD4(+)CD45RC(low) populations were normal after xenothymus transplantation. As for the CD8(+) regulatory cells, the defect was quantitative, as CD8(+) cell levels always remained low. The latter was related to the nonvascularized nature of thymus grafts. In conclusion, AIS after xenothymus transplantation in nude rats is due to a combination of insufficient intrathymic presence of host-type epithelial cell Ags and a defective generation of regulatory T lymphocytes.