The predominant usage of VH4-34 and V3-21 and reports of stereotyped CDR3s suggest a shared antigenic target of B-cell receptors (BCR) from mantle cell lymphomas (MCL). To identify the target antigens of MCL-BCRs, BCRs from 21 patients and seven MCL cell lines were recombinantly expressed and used for antigen screening. The BCRs from 8/21 patients and 2/7 MCL cell lines reacted specifically with the autoantigen low-density lipoprotein receptor-related protein-associated protein 1 (LRPAP1). High-titered and light chain-restricted anti-LRPAP1 serum antibodies were found in MCL patients, but not in controls. LRPAP1 induced proliferation by BCR pathway activation, while an LRPAP1-ETA' toxin-conjugate specifically killed MCL cells with LRPAP1-specific BCRs. Our results suggest a role of LRPAP1 in lymphomagenesis and maintenance of a considerable proportion of MCL cases by chronic autoantigenic stimulation, likely evolving from a chronic autoreactive B-cell response. Importantly, LRPAP1 can be used for a novel therapeutic approach that targets MCL with LRPAP1-reactive BCRs with high specificity.

STRUCTURED ABSTRACTINTRODUCTIONHyperinflammation is frequently observed in patients with severe COVID-19. Inadequate and defective IFN type I responses against SARS-CoV-2, caused by autoantibodies in a proportion of patients, lead to severe courses. In addition, hyperactive responses of the humoral immune system have been described so far.RATIONALEIn the current study we investigated a possible role of neutralizing autoantibodies against anti-inflammatory mediators. Plasma from patients with severe and critical COVID-19 was screened by ELISA for antibodies against PGRN, IL-10, IL-18BP, IL-22BP and IL-1-RA. Autoantibodies were characterized and the antigens were analyzed for immunogenic alterations.RESULTSPGRN-autoantibodies were detected with high titers in 11 of 30 (36.7%), and IL-1-RA-autoantibodies in 14 of 30 (46.7%) patients of a discovery cohort with severe to critical COVID-19. In a validation cohort of 41 patients with critical COVID-19 high-titered PGRN-Abs were detected in 12 (29.3%) and IL-1-RA-Abs in 19 of 41 patients (46.2%). PGRN-Abs and IL-1-RA-Abs belonged to IgM and several IgG subclasses. In separate cohorts with non-critical COVID-19, PGRN-Abs and IL-1-RA-Abs were detected significantly less frequently and at low titers. Neither PGRN-nor IL-1-RA-Abs were found in 40 healthy controls vaccinated against SARS-CoV-2. PGRN-Abs were not cross-reactive against SARS-CoV-2 structural proteins or against IL-1-RA. Plasma levels of both free PGRN and IL-1-RA were significantly decreased in autoantibody-positive patients compared to Ab-negative and non-COVID controls. Functionally, PGRN-Abs from patients reduced PGRN-dependent inhibition of TNF-α signaling in vitro. The pSer81 hyperphosphorylated PGRN isoform was exclusively detected in patients with high-titer PGRN-Abs; likewise, a yet unidentified hyperphosphorylated IL-1-RA isoform was only found in patients with high-titer IL-1-RA-Abs. No autoantibodies against IL-10, IL-18BP or IL-22BP were found.CONCLUSIONTo conclude, neutralizing autoantibodies to IL-1-RA and PGRN occur in a significant proportion of patients with critical COVID-19, with a concomitant decrease in circulating PGRN and IL-1-RA, which is indicative of a misdirected, proinflammatory autoimmune response. The break of self-tolerance is likely caused by atypical isoforms of both antigens due to hyperphosphorylation. It remains to be determined whether these secondary modifications are induced by the SARS-CoV-2-infection itself, or are preexisting and predispose for a critical course.

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Background: Community service nurses placed in the Western Cape Government public health facilities render essential healthcare to underserved populations. Anecdotal evidence from operational nurse managers indicated concerns that community service nurses may lack competence in basic required nursing competencies.Objectives: To investigate operational nurse managers’ perceptions of the competence of community service nurses in public health facilities in the Western Cape.Method: A quantitative survey was conducted with an all-inclusive sample of 297 operational nurse managers in the Western Cape. A self-administered questionnaire with 65 questions with a 4-point rating scale was used to rate perceived competence of community service nurses across the South African Nursing Council (SANC) competencies. Descriptive and inferential statistics were calculated per competency domain.Results: The survey (response rate: 59%) showed that the operational nurse managers perceived the community service nurses to be competent in the clinical patient care domain and mostly either developing proficiency or proficient in the SANC competencies of legal framework and ethical practice, interprofessional relationships, leadership, quality management and management competency domains.Conclusion: Community service nurses were found to be competent in the clinical patient care, possibly because of the integration of theory and practice focus of work-integrated learning in the programme. Education and practice supportive strategies for community service nurses should be developed to support the successful transition from students to community service nurses, especially around the development of research and critical thinking skills.

Introduction: Burkitt lymphoma represents the most aggressive neoplasm of mature sIg+ B cells. Besides the characterisitc translocation of the MYC gene with an immunoglobulin heavy or light chain gene locus, activating mutations in the TCF3 gene and inactivating mutations in the ID3 gene represent the key events in the pathogenesis of Burkitt lymphoma. These TCF3/ID3 mutations result in tonic and antigen-independent B cell receptor (BCR) pathway activation. Additionally, chronic BCR activation by antigens might play a role in Burkitt lymphoma pathogenesis and we set out to identify such potential target antigens of BCRs of Burkitt lymphoma. Methods: BCRs were expressed as recombinant Fabs in TG1 E.coli based on corresponding pairs of functional variable region heavy and light chain genes, which had been amplified from isolated genomic DNA of snap-frozen sporadic Burkitt lymphoma specimens. Additionally, natural Fabs and recombinant Fabs were produced of 8 established Burkitt lymphoma cell lines by Papain digestion and BCR expression cloning. The purified pooled Fabs were screened for reactivities against non-modified and differently posttranslationally modified human protein macroarrays. Reactivities were verified by ELISA with coated N-terminally FLAG-tagged candidate antigens, each separately for the posttranslationally modified and non-modified isoforms. Recombinant Fabs derived of mantle cell lymphoma, diffuse large B cell lymphoma and primary central nervous system lymphoma served as controls. Moreover the functional effects on proliferation and BCR pathway activation after addition of the identified target antigens to Burkitt lymphoma cell lines with and without reactive BCRs were analyzed by proliferation assays and western blots. Finally, mutation status, methylation status and expression level of identified target antigens were analyzed in ICGC MMML-Seq lymphoma databases for differences in Burkitt lymphoma versus distinct lymphoma entities. Results: The Burkitt lymphoma derived Fabs were tested on posttranslationally modified protein arrays. The BCR of CA46 line showed specific reactivity against sumoylated Bystin, the Fab of the BL41 line reacted specifically against acetylated HSP40. Recombinant Fabs of diffuse large B cell lymphoma, primary central nervous system lymphoma and mantle cell lymphoma did neither bind sumoylated Bystin nor acetylated HSP40. Addition of the posttranslationally modified cognate antigens to respective Burkitt lymphoma cell line with the reactive BCR induced proliferaton. The analysis of the ICGC MMML-Seq lymphoma databases (representing different cohorts) showed a higher expression of Bystin in Burkitt lymphoma compared to other aggressive B-cell lymphomas. However, the mutation and methylation status of Bystin and HSP40 in the ICGC MMML-seq cohort did not provide any direct indication of the origin of their immunogenic post-translational modifications. Conclusions: A subgroup of sporadic Burkitt lymphoma has autoreactive BCRs with specific affinity against posttranslationally modified self antigens, demonstrating a new aspect in the pathogenesis of Burkitt lymphoma. Specific secondary modifications, as sumolytation of Bystin or acetylation of HSP40 appear to evoke the immunogenicity. Future studies will focus on the functional consequences of the antigen/BCR interaction on Burkitt cells. Furthermore, the causes of these posttranslationally modified neoantigens will be investigated in more detail. Disclosures Stilgenbauer: Mundipharma: Consultancy, Honoraria, Other: travel support, Research Funding; Pharmacyclics: Consultancy, Honoraria, Other: travel support, Research Funding; Celgene: Consultancy, Honoraria, Other: travel support, Research Funding; Roche: Consultancy, Honoraria, Other: travel support, Research Funding; Genetech: Consultancy, Honoraria, Other: travel support, Research Funding; Amgen: Consultancy, Honoraria, Other: travel support, Research Funding; AbbVie: Consultancy, Honoraria, Other: travel support, Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding; GlaxoSmithKline: Consultancy, Honoraria, Other: travel support, Research Funding; Janssen: Consultancy, Honoraria, Other: travel support, Research Funding; Gilead: Consultancy, Honoraria, Other: travel support, Research Funding.