Scalable, Micro-Neutralization Assay for Qualitative Assessment of SARS-CoV-2 (COVID-19) Virus-Neutralizing Antibodies in Human Clinical Samples

As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic was expanding, it was clear that effective testing for the presence of neutralizing antibodies in the blood of convalescent patients would be critical for development of plasma-based therapeutic approaches. To address the need for a high-quality neutralization assay against SARS-CoV-2, a previously established fluorescence reduction neutralization assay (FRNA) against Middle East respiratory syndrome coronavirus (MERS-CoV) was modified and optimized. The SARS-CoV-2 FRNA provides a quantitative assessment of a large number of infected cells through use of a high-content imaging system. Because of this approach, and the fact that it does not involve subjective interpretation, this assay is more efficient and more accurate than other neutralization assays. In addition, the ability to set robust acceptance criteria for individual plates and specific test wells provided further rigor to this assay. Such agile adaptability avails use with multiple virus variants. By February 2021, the SARS-CoV-2 FRNA had been used to screen over 5,000 samples, including acute and convalescent plasma or serum samples and therapeutic antibody treatments, for SARS-CoV-2 neutralizing titers.

Clinical, laboratory, and temporal predictors of neutralizing antibodies against SARS-CoV-2 among COVID-19 convalescent plasma donor candidates

BACKGROUNDSARS-CoV-2-specific antibodies may protect from reinfection and disease, providing rationale for administration of plasma containing SARS-CoV-2-neutralizing antibodies (nAbs) as a treatment for COVID-19. Clinical factors and laboratory assays to streamline plasma donor selection, and the durability of nAb responses, are incompletely understood.METHODSPotential convalescent plasma donors with virologically documented SARS-CoV-2 infection were tested for serum IgG against SARS-CoV-2 spike protein S1 domain and against nucleoprotein (NP), and for nAb.RESULTSAmong 250 consecutive persons, including 27 (11%) requiring hospitalization, who were studied a median of 67 days since symptom onset, 97% were seropositive on 1 or more assays. Sixty percent of donors had nAb titers ≥1:80. Correlates of higher nAb titers included older age (adjusted OR [AOR] 1.03 per year of age, 95% CI 1.00-1.06), male sex (AOR 2.08, 95% CI 1.13-3.82), fever during illness (AOR 2.73, 95% CI 1.25-5.97), and disease severity represented by hospitalization (AOR 6.59, 95% CI 1.32-32.96). Receiver operating characteristic analyses of anti-S1 and anti-NP antibody results yielded cutoffs that corresponded well with nAb titers, with the anti-S1 assay being slightly more predictive. nAb titers declined in 37 of 41 paired specimens collected a median of 98 days (range 77-120) apart (P < 0.001). Seven individuals (2.8%) were persistently seronegative and lacked T cell responses.CONCLUSIONnAb titers correlated with COVID-19 severity, age, and sex. SARS-CoV-2 IgG results can serve as useful surrogates for nAb testing. Functional nAb levels declined, and a small proportion of convalescent individuals lacked adaptive immune responses.FUNDINGThe project was supported by the Frederick National Laboratory for Cancer Research with support from the NIAID under contract number 75N91019D00024, and was supported by the Fred Hutchinson Joel Meyers Endowment, Fast-Grants, a New Investigator award from the American Society for Transplantation and Cellular Therapy, and NIH contracts 75N93019C0063, 75N91019D00024, and HHSN272201800013C, and NIH grants T32-AI118690, T32-AI007044, K08-AI119142, and K23-AI140918.

[Iliac mucosa changes in late periods after total colectomy in patients with syndromes of gastro-intestinal polyposis]

We studied follow-up iliac mucosa biopsies from 11 patients with juvenile polyposis and 4 patients with familial adenomatous polyposis who had undergone total colectomy with mucosal proctoectomy with creation of straight ileoanal anastomosis. The biopsies that have been taken from the posterior wall of the terminal ileum show incomplete and focal neocolonic transformation of iliac mucosa. Nevertheless, in most cases iliac mucosa preserved its architectural and histochemical characteristics. Chronic inflammation in iliac mucosa is not typical for patients with polyposis.

[Morphological characteristics of gastrointestinal lesions in patients after total colectomy for colon polyposis]

11 patients with juvenile polyposis and 4 patients with familial adenomatous polyposis after total colectomy entered the study. Long-term follow-up with endoscopic examination and multiple biopsies in these patients showed high probability of polyps in preserved regions of the gastrointestinal tract. Therefore, regular prophylactic endoscopy, morphological examinations and biopsies of endoscopically normal mucous membrane are justified. Such policy is recommended especially for patients with familial adenomatous polyposis.

[Conformational changes of the platelet membrane glycoprotein IIb-IIIa complex stimulated by a monoclonal antibody to the N-terminal segment of glycoprotein IIIa]

During platelet activation, the glycoprotein (GP) complex IIb-IIIa (alpha 11b beta 3-integrin) changes its conformation, resulting in binding of adhesive proteins of RGD containing an amino acid sequence as well as in expression of new ligand-induced binding sites (LIBS) on the GPIIb-IIIa molecule. Like its F(ab)-fragments, the monoclonal antibody CRC54, whose epitope is located in the N-terminal part of the GPIIIa molecule, binds to no more than 10% of GPIIb-IIIa on the resting platelet surface. However, the binding of CRC54 increases considerably during activation of platelets by thrombin, platelet adhesion on plastic, GPIIb-IIIa interaction with RGDS-peptide as well as during dissociation of the complex in the presence of EDTA. These finding suggest that CRC54 is specifically directed against the LIBS epitope on the GPIIIa molecule. This epitope differs from those of other known conformation-dependent antibodies against GPIIb-IIIa (LIBS1, LIBS6, PMI-1, pl55 and p180), since those antibodies did not block the CRC54 binding to GPIIb-IIIa on the surface of adhering platelets. Unlike whole platelets, the binding of GPIIb-IIIa from lysates of platelets treated with Triton X-100 with immobilized CRC54 did not depend on the presence of the RGDS peptide. Under these conditions another anti-LIBS-antibody, p180 specifically directed against GPIIb, preserved its ability to discriminate the RGDS-occupied and resting conformations of GPIIb-IIIA. CRC54 and its F(ab) fragments induced platelet aggregation in both platelet-enriched plasma and in suspensions of washed platelets. CRC54 also stimulated the binding to platelets of GPIIb-IIIa ligand fibrinogen, labelled with 125I as well as adhesion of 51Cr-labelled platelets to immobilized ligands-fibrinogen and fibronectin. The CRC54-dependent aggregation was fully blocked by RGDS-peptide and antibody CRC64 inhibiting the GPIIb-IIIa binding to the ligands. However, the platelet activation inhibitor, prostaglandin EI, and the mixture of metabolic inhibitors, deoxyglucose-sodium azide, only party inhibited the CRC54-dependent aggregation. Incubation of platelets with CRC54 induced the binding to platelets of the anti-GPIIb LIBS antibody p180 and of the anti-GPIIb-IIIa activation-dependent antibody p155. The binding of GPIIb-IIIa from lysates of CRC54-treated platelets with immobilized p180 and p155 was also several times as high as that of GPIIb-IIIa from control platelet lysates. The data obtained indicate that the GPIIb-IIIa transition to the active state and its interaction with ligands induces conformational changes in the N-terminal part of GPIIIa and that the CRC54 binding to the N-terminal part of GPIIIa stimulates conformational changes in GPIIb-IIIa, complex interaction with ligands and platelet aggregation.

[Anoplasty for anorectal anomalies in children]

The work analyses the causes of insufficient air-tightness of the anal canal in the postoperative period (in children operated on for anorectal developmental anomalies), which leads to anal incontinence. The authors suggest a method for anoplasty based on: (1) performance of sphincteroplasty with consideration for the function of three muscles forming the external sphincter of the anal canal; (2) formation from the musculo-serous coat of the intestine subjected to the pull-through procedure a soft elastic pad lining the canal on the inside; (3) creating conditions for adherence of the mucous coat of the intestine to the walls of the neoanal canal. Manometric, CT, and ultrasonic special methods of examination showed that with the use of the suggested method the obturative pressure in the neoanal canal increases, "prolapse" of the mucosa of the operated on intestine is prevented, the accumulative and evacuative functions of the rectum are improved. The causes and errors which led to poor results (2 cases) are analysed. In the remaining 42 cases the results were good and satisfactory.

[Computed tomography of the pelvis in pediatric proctology]

The article shows the wide possibilities of computed tomography (CT) diagnosis of the topography of muscles forming the external sphincter of the anus (ESA) in patients with developmental anorectal anomalies and in trauma and rupture of the perineum. It is shown that in anorectal anomalies with fistulas opening into the urinary system the puborectal muscular sling is "drawn up" ventrally in relation to the external sphincter elements lying closer to the surface. Analysis of the results of CT examination of the pelvic floor in 16 children with anorectal anomalies showed that the degree of development of the sphincter muscles does not always correspond to the level of atresia. For instance, the mass of the ESA muscles is manifested more in some forms of cloacal atresia than in "tubular" stenoses of the rectum (anorectal stenosis--Curravino-triad component) (G. Curravino, 1981). CT examination of children with this complex of caudal anomalies allowed the authors to reveal a fourth constant component: dysplasia of the pelvic floor and a specific developmental anomaly of the anal sphincter. CT is the method of choice in the examination of children with this pathological condition because it makes it possible to recognise the presence of presacral masses. The use of CT in traumas and ruptures of the perineum allows the depth and extension of ruptures of the ESA muscles to be authentically determined.

[The surgical treatment of diffuse polyposis coli in children]

Results of surgical treatment of patients with diffuse polyposis of the colon (a juvenile form) are analyzed. During 1979-1990 20 ileoanal and 8 ileorectal anastomoses were performed with demucosation of the rectum. The operative intervention is performed by an original method without temporary creation of ileostoma. Long-term results of treatment allow recommendations of these operations for use in pediatric practice.

[Treatment of children with diffuse polyposis of the colon]

In 1971-1990 the authors treated 41 children 3 to 15 years of age with diffuse familial polyposis of the colon (juvenile form). Forty-four operations were carried out (3 patients underwent the second operation. The authors conducted several variants of colon resection with due account for the sites of greatest accumulation of the polyps--resection of the sigmoid colon, hemicolectomy, combined resection. Progressive growth of polyps was encountered in the remaining areas in the late-term periods. In view of this, the authors recommend total colectomy with the creation of an ileorectal or ileoanal anastomosis as the method of choice. The article describes an original operative method suggested by the authors. Twenty-eight similar operations were performed with good results.

[Elimination of a stable residual pleural cavity with an antibacterial fibrin filling]

A simple, effective and safe method is proposed to liquidate a persistent residual pleural cavity by a biological filling prepared ex tempore from a solution of fibrinogen with antibacterial drugs. The method was used in 24 patients after pleura empyema. The method of filling is described as well as the conditions for a successful use of the new means of liquidation of the residual pleural cavity and prevention of recurrent pleura empyemas.

[Current trends and problems in surgery for Hirschsprung's disease in children]

The authors discuss the results of 211 operations for Hirschsprung's disease with special reference to the optimal terms for surgery, questions of medical policy and remote results. The remote results were studied in 102 patients. Excellent results were obtained in 63% of cases, good--in 28% and in 9% the results were satisfactory. The authors make special accent on residual functional disorders and necessary rehabilitation measures till full recovery of the patient.