Detection of naturally acquired, strain-transcending antibodies against rosetting Plasmodium falciparum strains in humans.

Strain-transcending antibodies against virulence-associated subsets of P. falciparum-infected erythrocyte surface antigens could protect children from severe malaria. However, the evidence supporting the existence of such antibodies is incomplete and inconsistent. One subset of surface antigens associated with severe malaria, rosette-mediating Plasmodium falciparum Erythrocyte Membrane Protein one (PfEMP1) variants, cause infected erythrocytes to bind to uninfected erythrocytes to form clusters of cells (rosettes) that contribute to microvascular obstruction and pathology. Here, we tested plasma from 80 individuals living in malaria-endemic regions for IgG recognition of the surface of four P. falciparum rosetting strains using flow cytometry. Broadly reactive plasma samples were then used in antibody elution experiments in which intact IgG was eluted from the surface of infected erythrocytes and transferred to heterologous rosetting strains to look for strain-transcending antibodies. We found that seroprevalence (percentage of positive plasma samples) against allopatric rosetting strains was high in adults (63%-93%) but lower in children (13%-48%). Strain-transcending antibodies were present in nine out of eleven eluted antibody experiments, with six of these recognizing multiple heterologous rosetting parasite strains. One eluate had rosette-disrupting activity against heterologous strains, suggesting PfEMP1 as the likely target of the strain-transcending antibodies. Naturally acquired strain-transcending antibodies to rosetting P. falciparum strains in humans have not been directly demonstrated previously. Their existence suggests that such antibodies could play a role in clinical protection and raises the possibility that conserved epitopes recognized by strain-transcending antibodies could be targeted therapeutically by monoclonal antibodies or vaccines.

HCMV Infection Reduces Nidogen-1 Expression, Contributing to Impaired Neural Rosette Development in Brain Organoids.

Human cytomegalovirus (HCMV) is a leading cause of birth defects in humans. These birth defects include microcephaly, sensorineural hearing loss, vision loss, and cognitive impairment. The process by which the developing fetus incurs these neurological defects is poorly understood. To elucidate some of these mechanisms, we have utilized HCMV-infected induced pluripotent stem cells (iPSCs) to generate in vitro brain organoids, modeling the first trimester of fetal brain development. Early during culturing, brain organoids generate neural rosettes. These structures are believed to model neural tube formation. Rosette formation was analyzed in HCMV-infected and mock-infected brain organoids at 17, 24, and 31 days postinfection. Histological analysis revealed fewer neural rosettes in HCMV-infected compared to mock-infected organoids. HCMV-infected organoid rosettes incurred multiple structural deficits, including increased lumen area, decreased ventricular zone depth, and decreased cell count. Immunofluorescent (IF) analysis found that nidogen-1 (NID1) protein expression in the basement membrane surrounding neural rosettes was greatly reduced by virus infection. IF analysis also identified a similar downregulation of laminin in basement membranes of HCMV-infected organoid rosettes. Knockdown of NID1 alone in brain organoids impaired their development, leading to the production of rosettes with increased lumen area, decreased structural integrity, and reduced laminin localization in the basement membrane, paralleling observations in HCMV-infected organoids. Our data strongly suggest that HCMV-induced downregulation of NID1 impairs neural rosette formation and integrity, likely contributing to many of HCMV's most severe birth defects. IMPORTANCE HCMV infection in pregnant women continues to be the leading cause of virus-induced neurologic birth defects. The mechanism through which congenital HCMV (cCMV) infection induces pathological changes to the developing fetal central nervous system (CNS) remains unclear. Our lab previously reproduced identified clinical defects in HCMV-infected infants using a three dimensional (3D) brain organoid model. In this new study, we have striven to discover very early HCMV-induced changes in developing brain organoids. We investigated the development of neural tube-like structures, neural rosettes. HCMV-infected rosettes displayed multiple structural abnormalities and cell loss. HCMV-infected rosettes displayed reduced expression of the key basement membrane protein, NID1. We previously found NID1 to be specifically targeted in HCMV-infected fibroblasts and endothelial cells. Brain organoids generated from NID1 knockdown iPSCs recapitulated the structural defects observed in HCMV-infected rosettes. Findings in this study revealed HCMV infection induced early and dramatic structural changes in 3D brain organoids. We believe our results suggest a major role for infection-induced NID1 downregulation in HCMV-induced CNS birth defects.

SRGP-1/srGAP and AFD-1/afadin stabilize HMP-1/⍺-catenin at rosettes to seal internalization sites following gastrulation in C. elegans.

A hallmark of gastrulation is the establishment of germ layers by internalization of cells initially on the exterior. In C. elegans the end of gastrulation is marked by the closure of the ventral cleft, a structure formed as cells internalize during gastrulation, and the subsequent rearrangement of adjacent neuroblasts that remain on the surface. We found that a nonsense allele of srgp-1/srGAP leads to 10-15% cleft closure failure. Deletion of the SRGP-1/srGAP C-terminal domain led to a comparable rate of cleft closure failure, whereas deletion of the N-terminal F-BAR region resulted in milder defects. Loss of the SRGP-1/srGAP C-terminus or F-BAR domain results in defects in rosette formation and defective clustering of HMP-1/⍺-catenin in surface cells during cleft closure. A mutant form of HMP-1/⍺-catenin with an open M domain can suppress cleft closure defects in srgp-1 mutant backgrounds, suggesting that this mutation acts as a gain-of-function allele. Since SRGP-1 binding to HMP-1/⍺-catenin is not favored in this case, we sought another HMP-1 interactor that might be recruited when HMP-1/⍺-catenin is constitutively open. A good candidate is AFD-1/afadin, which genetically interacts with cadherin-based adhesion later during embryonic elongation. AFD-1/afadin is prominently expressed at the vertex of neuroblast rosettes in wildtype, and depletion of AFD-1/afadin increases cleft closure defects in srgp-1/srGAP and hmp-1R551/554A/⍺-catenin backgrounds. We propose that SRGP-1/srGAP promotes nascent junction formation in rosettes; as junctions mature and sustain higher levels of tension, the M domain of HMP-1/⍺-catenin opens, allowing maturing junctions to transition from recruitment of SRGP-1/srGAP to AFD-1/afadin. Our work identifies new roles for ⍺-catenin interactors during a process crucial to metazoan development.

Rosette formation by Plasmodium vivax gametocytes favors the infection in Anopheles aquasalis.

Plasmodium vivax is a public health problem and the most common type of malaria outside sub-Saharan Africa. The capacity of cytoadhesion, rosetting, and liver latent phase development could impact treatment and disease control. Although the ability to P. vivax gametocyte develop rosetting is known, it is not yet clear which role it plays during the infection and transmission process to the mosquito. Here, we used ex vivo approaches for evaluate the rosetting P. vivax gametocytes capacity and we have investigated the effect of this adhesive phenotype on the infection process in the vector Anopheles aquasalis mosquito. Rosette assays were performed in 107 isolates, and we have observed an elevated frequency of cytoadhesive phenomena (77,6%). The isolates with more than 10% of rosettes have presented a higher infection rate in Anopheles aquasalis (p=0.0252). Moreover, we found a positive correlation between the frequency of parasites in rosetting with the infection rate (p=0.0017) and intensity (p=0.0387) in the mosquito. The disruption of P. vivax rosette formation through mechanical rupture assay confirmed the previously findings, since the paired comparison showed that isolates with disrupted rosettes have a lower infection rate (p<0.0001) and intensity (p=0.0003) compared to the control group (no disruption). Herein we have demonstrated for the first time a potential effect of the rosette phenomenon on the infection process in the mosquito vector An. aquasalis, favoring its capacity and intensity of infection, thus allowing the perpetuation of the parasite cycle life.

Role of intra-operative squash cytology in rosette-forming glioneuronal tumor of the fourth ventricle: a case report.

Rosette-forming glioneuronal tumor (RGNT) of the 4th ventricle is a newly described WHO grade I brain tumor included in recent WHO classification of CNS tumors. It is a biphasic tumor thought to originate from pluripotent progenitor cells of subependymal plate. Intra-operative diagnosis plays an important role, as complete surgical excision is the treatment of choice. We are reporting a case of RGNT in a 19 years-old young male emphasizing the intra-operative pathological pointers and their role in accurate diagnosis for the suitable surgical intervention.

Diffuse Large B-Cell Lymphoma with pseudo Rosettes, A Rare Entity: Case Report with Literature Review.

Background: Rosette formation is an unusual finding in malignant lymphomas. We report a case of a diffuse large B-cell lymphoma (DLBCL) with abundant rosette formation histologically mimicking non lymphoid tumors. Case presentation: A sixty-five-year-old female presented with a complaint of swelling on left side axillary region since a period of six months with no history of fever, fatigue or weight loss or other similar swellings elsewhere. No relevant personal and family history relatable to the present complaint. Subsequent clinical and radiological investigations revealed isolated left axillary lymphadenopathy. The lymph node on further biopsy showed a particular morphology of pseudorosette formation masquerading a metastatic rosette forming malignancies. Subsequent histopathological and immunohistochemical investigations revealed a rare morphological variant of diffuse large B cell lymphoma. The fluorodeoxyglucose positron emission tomography scan showed multiple discreet supra-diphramatic (left lower cervical and left axillary lymph nodes) metabolically active lymph nodes. Conclusion: Diffuse large B cell lymphoma with rosette formation is a rare entity which can mimic other tumors with rosette formation in a metastatic node. Knowledge on the rosette forming lymphoma entity is thus essential for diagnosis and treatment plan. To the best of our knowledge this case report is the sixth known documented case of a diffuse large B cell lymphoma with rosette in literature.

Association between Serum Erythrocyte Immune Function Indexes and Blue Light Treatment or the Severity of PJON.

BACKGROUND: The association between serum erythrocyte immune function indexes and blue light treatment effect and severity in child patients with pathological jaundice was testified. METHODS: One hundred and seven children with pathological jaundice and 69 children with physiological jaundice were enrolled to analyze the association between erythrocyte immune function indexes and blue light treatment or disease progression. RESULTS: The area under the ROC curve (AUC) of red blood cell immune complex rosettes (RBC-ICR) and red blood cell C3b receptor rosette (RBC-C3bR) in diagnosing pathological jaundice and assessing the efficacy of blue light therapy overweighed 0.8. Meanwhile, the RBC-ICR values of the child patients were positively correlated with the severity of the disease, and the RBC-C3bR and red blood cell immune affinity receptor (FEER) values were negatively correlated with them (p < 0.05). CONCLUSIONS: The erythrocyte immune function indexes of child patients with pathological jaundice were relevant to the disease severity, and was provided with diagnostic value for pathological jaundice or assessed value for the efficacy of blue light therapy.

Evolving perspectives on rosetting in malaria.

The ability of the intraerythrocytic Plasmodium spp. to form spontaneous rosettes with uninfected red blood cells (URBCs) has been observed in the medically important malaria parasites. Since the discovery of rosettes in the late 1980s, different formation mechanisms and pathobiological roles have been postulated for rosetting; most of which have focused on Plasmodium falciparum. Recent breakthroughs, including new data from Plasmodium vivax, have highlighted the multifaceted roles of rosetting in the immunopathobiology and the development of drug resistance in human malaria. Here, we provide new perspectives on the formation and the role of rosetting in malaria rheopathobiology.

Measuring Rosetting Inhibition in Plasmodium falciparum Parasites Using a Flow Cytometry-Based Assay.

Rosetting is the ability of Plasmodium falciparum-infected erythrocytes (IEs) to bind to host receptors on the surface of uninfected erythrocytes (uE) leading to the formation of a cluster of cells with a central IE surrounded by uE. It is a hallmark event during the pathogenesis of P. falciparum malaria, the most severe species causing malaria, which affects mostly young children in Africa. There are no current treatments effectively targeting and disrupting parasite rosette formation. Here, we detail a high-throughput, flow cytometry based assay that allows testing and identification of potential rosetting-inhibitory compounds that could be used in combination with anti-plasmodial drugs to reduce malaria morbidity and mortality.

Chromodomain Protein Interacts with H3K9me3 and Controls RBC Rosette Formation by Regulating the Expression of a Subset of RIFINs in the Malaria Parasite.

Plasmodium falciparum expresses clonally variant proteins on the surface of infected erythrocytes to evade the host immune system. The clonally variant multigene families include var, rifin, and stevor, which express Erythrocyte Membrane Protein 1 (EMP1), Repetitive Interspersed Families of polypeptides (RIFINs), and Sub-telomeric Variable Open Reading frame (STEVOR) proteins, respectively. The rifins are the largest multigene family and are essentially involved in the RBC rosetting, the hallmark of severe malaria. The molecular regulators that control the RIFINs expression in Plasmodium spp. have not been reported so far. This study reports a chromodomain-containing protein (PfCDP) that binds to H3K9me3 modification on P. falciparum chromatin. Conditional deletion of the chromodomain (CD) gene in P. falciparum using an inducible DiCre-LoxP system leads to selective up-regulation of a subset of virulence genes, including rifins, a few var, and stevor genes. Further, we show that PfCDP conditional knockout (PfΔCDP) promotes RBC rosette formation. This study provides the first evidence of an epigenetic regulator mediated control on a subset of RIFINs expression and RBC rosetting by P. falciparum.

Platelet Satellitism in a Patient with Bronchial Asthma.

Platelet satellitism is uncommon phenomenon characterized by formation of platelet rosette around polymorphonuclear leucocytes in blood smear prepared from Ethylenediaminetetraacetic acid anticoagulated blood. This phenomenon may cause reporting of spurious thrombocytopenia unless proper examination of blood smears. Here we describe a case of platelet satellitism in a 29 year old female which has been incidentally found on evaluation of eosinophilia in a bronchial asthma patient.

Plasmodium falciparum rosetting protects schizonts against artemisinin.

BACKGROUND: Artemisinin (ART) resistance in Plasmodium falciparum is thought to occur during the early stage of the parasite's erythrocytic cycle. Here, we identify a novel factor associated with the late stage parasite development that contributes to ART resistance. METHODS: Rosetting rates of clinical isolates pre- and post- brief (one hour) exposure to artesunate (AS, an ART derivative) were evaluated. The effects of AS-mediated rosetting on the post-AS-exposed parasite's replication and survival, as well as the extent of protection by AS-mediated rosetting on different parasite stages were investigated. The rosetting ligands, mechanisms, and gene mutations involved were studied. FINDINGS: Brief AS exposure stimulated rosetting, with AS-resistant isolates forming more rosettes in a more rapid manner. AS-mediated rosetting enabled infected erythrocytes (IRBC) to withstand AS exposure for several hours and protected the IRBC from phagocytosis. When their rosetting ability was blocked experimentally, the post-AS exposure survival advantage by the AS-resistant parasites was abrogated. Deletions in two genes coding for PfEMP1 exon 2 (PF3D7_0200300 and PF3D7_0223300) were found to be associated with AS-mediated rosetting, and these mutations were significantly selected through time in the parasite population under study, along with the K13 mutations, a molecular marker of ART-resistance. INTERPRETATION: Rapid ART parasite clearance is driven by the direct oxidative damages on IRBC by ART and the phagocytic destruction of the damaged IRBC. Rosetting serves as a rapid 'buying time' strategy that allows more parasites to complete schizont maturation, reinvasion and subsequent development into the intrinsically less ART-susceptible ring stage. FUNDING: A*STAR, NMRC-OF-YIRG, HRC e-ASIA, Wellcome.

Red blood cell blood group A antigen level affects the ability of heparin and PfEMP1 antibodies to disrupt Plasmodium falciparum rosettes.

BACKGROUND: The histo-blood group ABO system has been associated with adverse outcomes in COVID-19, thromboembolic diseases and Plasmodium falciparum malaria. An integral part of the severe malaria pathogenesis is rosetting, the adherence of parasite infected red blood cells (RBCs) to uninfected RBCs. Rosetting is influenced by the host's ABO blood group (Bg) and rosettes formed in BgA have previously been shown to be more resilient to disruption by heparin and shield the parasite derived surface antigens from antibodies. However, data on rosetting in weak BgA subgroups is scarce and based on investigations of relatively few donors. METHODS: An improved high-throughput flow cytometric assay was employed to investigate rosetting characteristics in an extensive panel of RBC donor samples of all four major ABO Bgs, as well as low BgA expressing samples. RESULTS: All non-O Bgs shield the parasite surface antigens from strain-specific antibodies towards P. falciparum erythrocyte membrane protein 1 (PfEMP1). A positive correlation between A-antigen levels on RBCs and rosette tightness was observed, protecting the rosettes from heparin- and antibody-mediated disruption. CONCLUSIONS: These results provide new insights into how the ABO Bg system affects the disease outcome and cautions against interpreting the results from the heterogeneous BgA phenotype as a single group in epidemiological and experimental studies.

Rosette-Forming Glioneuronal Tumor in the Pineal Region: A Series of 6 Cases and Literature Review.

Resected lesions from the pineal region are rare specimens encountered by surgical pathologists, and their heterogeneity can pose significant diagnostic challenges. Here, we reviewed 221 pineal region lesions resected at New York-Presbyterian Hospital/Columbia University Irving Medical Center from 1994 to 2019 and found the most common entities to be pineal parenchymal tumors (25.3%), glial neoplasms (18.6%), and germ cell tumors (17.6%) in this predominantly adult cohort of patients. Six cases of a rare midline entity usually found exclusively in the fourth ventricle, the rosette-forming glioneuronal tumor, were identified. These tumors exhibit biphasic morphology, with a component resembling pilocytic astrocytoma admixed with variable numbers of small cells forming compact rosettes and perivascular pseudorosettes. Targeted sequencing revealed a 100% co-occurrence of novel and previously described genetic alterations in the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) signaling pathways, suggesting a synergistic role in tumor formation. The most common recurrent mutation, PIK3CA H1047R, was identified in tumor cells forming rosettes and perivascular pseudorosettes. A review of the literature revealed 16 additional cases of rosette-forming glioneuronal tumors in the pineal region. Although rare, this distinctive low-grade tumor warrants consideration in the differential diagnosis of pineal region lesions.

Dissemination Patterns and Short-Term Management of Multifocal Rosette-Forming Glioneuronal Tumors.

BACKGROUND: Multifocal rosette-forming glioneuronal tumors (RGNTs) are challenging to manage. Gross total resection is often impossible, and data on adjunctive therapies are limited. We reviewed cases of multifocal RGNTs in the literature with special focus on dissemination patterns and management. METHODS: A literature review was conducted using PubMed and the key words "(multifocal OR multicentric OR satellite OR dissemination) AND glioneuronal." RESULTS: There were 21 cases of multifocal RGNTs identified. Follow-up was available in 18 cases at a median of 17 months. Progression-free survival and overall survival at 1 year were 84% and 94%, respectively. Of all cases, 43% had cerebrospinal fluid (CSF) dissemination, 48% had intraparenchymal spread, and 10% had both. The presence of CSF dissemination led to palliative care and/or death in 20% of cases (n = 2). None of the cases with intraparenchymal spread progressed. Radiotherapy was used in 50% of cases with CSF dissemination, chemotherapy was used in 20%, and CSF shunting was used in 36%. No tumors with intraparenchymal spread required adjunctive therapy or shunting. CONCLUSIONS: RGNTs with CSF dissemination are more likely to behave aggressively, and early adjunctive therapies should be discussed with patients. Tumors with intraparenchymal spread grow slowly, and maximal safe resection followed by observation is likely sufficient in the short term. Long-term behavior of multifocal RGNTs is still unclear.

Rosettes integrity protects Plasmodium vivax of being phagocytized.

Plasmodium vivax is the most prevalent cause of malaria outside of Africa. P. vivax biology and pathogenesis are still poorly understood. The role of one highly occurring phenotype in particular where infected reticulocytes cytoadhere to noninfected normocytes, forming rosettes, remains unknown. Here, using a range of ex vivo approaches, we showed that P. vivax rosetting rates were enhanced by plasma of infected patients and that total immunoglobulin M levels correlated with rosetting frequency. Moreover, rosetting rates were also correlated with parasitemia, IL-6 and IL-10 levels in infected patients. Transcriptomic analysis of peripheral leukocytes from P. vivax-infected patients with low or moderated rosetting rates identified differentially expressed genes related to human host phagocytosis pathway. In addition, phagocytosis assay showed that rosetting parasites were less phagocyted. Collectively, these results showed that rosette formation plays a role in host immune response by hampering leukocyte phagocytosis. Thus, these findings suggest that rosetting could be an effective P. vivax immune evasion strategy.