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BK polyomavirus (BKPyV) causes premature renal failure in 10% to 30% of kidney transplant recipients (KTRs). Current guidelines recommend screening for new-onset BKPyV-DNAemia/nephropathy and reducing immunosuppression to regain BKPyV-specific immune control. Because BKPyV encompasses 4 major genotype (gt)-encoded serotypes (st1,-2,-3,-4), st-specific antibodies may inform the risk and course of BKPyV-DNAemia/nephropathy. Using BKPyV st-virus-like particle (VLP) enzyme-linked immunosorbent assay, we analyzed plasma from 399 blood donors (BDs) and 428 KTRs (134 KTR-cases with BKPyV-DNAemia, 294 KTR-controls). BDs were anti-BKPyV-VLP immunoglobulin G-seropositive in 85% compared to 93% of KTRs at the timepoint at transplantation (T0) (P < .001). Anti-st1 was predominant in both groups followed by anti-st4, anti-st2, and anti-st3. Antibody levels and quadruple sero-reactivity at T0 were higher in KTR-controls than in KTR-cases (P = .026) or in BDs (P < .001). In KTR-cases, anti-st increased posttransplant (P < .0001) and independently of ongoing or cleared BKPyV-DNAemia. However, anti-st levels were significantly higher at T0 in KTR-cases able to clear at timepoint 6-month posttransplant or timepoint 12-month posttransplant. In 34 KTR-cases with deep genome sequencing, BKPyV-gtI was predominant, and anti-st1 and st1-neutralizing antibodies were significantly lower at T0 than in KTR-controls. Thus, BKPyV st-specific antibody levels at transplantation might reflect gt/st-BKPyV-specific immunity clearing or preventing BKPyV-DNAemia in KTR-cases or KTR-controls, respectively. Accordingly, active or passive immunization may be most efficient pretransplant or early posttransplant., Competing Interests: Declaration of competing interest The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation. Maud Wilhelm is supported in part by a global scholarship from Moderna; Hans H. Hirsch received speaker honoraria from Astellas, Biotest, Eurofins, and Takeda, and consultant honoraria from Allovir, Moderna, and Roche Diagnostics. Authors Caroline A. Hillenbrand, Dorssa Akbar Bani, Océane Follonier, Amandeep Kaur, Fabian H. Weissbach, Marion Wernli, Karoline Leuzinger, Isabelle Binet, Pierre-Yves Bochud, Dela Golshayan, Cédric Hirzel, Oriol Manuel, Nicolas Mueller, Stefan Schaub, Thomas Schachtner, and Christian Van Delden have no conflicts of interest to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

BK polyomavirus (BKPyV) is a double-stranded DNA virus causing nephropathy, hemorrhagic cystitis, and urothelial cancer in transplant patients. The BKPyV-encoded capsid protein Vp1 and large T-antigen (LTag) are key targets of neutralizing antibodies and cytotoxic T-cells, respectively. Our single-center data suggested that variability in Vp1 and LTag may contribute to failing BKPyV-specific immune control and impact vaccine design. We, therefore, analyzed all available entries in GenBank (1516 VP1 ; 742 LTAG ) and explored potential structural effects using computational approaches. BKPyV-genotype (gt)1 was found in 71.18% of entries, followed by BKPyV-gt4 (19.26%), BKPyV-gt2 (8.11%), and BKPyV-gt3 (1.45%), but rates differed according to country and specimen type. Vp1-mutations matched a serotype different than the assigned one or were serotype-independent in 43%, 18% affected more than one amino acid. Notable Vp1-mutations altered antibody-binding domains, interactions with sialic acid receptors, or were predicted to change conformation. LTag-sequences were more conserved, with only 16 mutations detectable in more than one entry and without significant effects on LTag-structure or interaction domains. However, LTag changes were predicted to affect HLA-class I presentation of immunodominant 9mers to cytotoxic T-cells. These global data strengthen single center observations and specifically our earlier findings revealing mutant 9mer epitopes conferring immune escape from HLA-I cytotoxic T cells. We conclude that variability of BKPyV-Vp1 and LTag may have important implications for diagnostic assays assessing BKPyV-specific immune control and for vaccine design., Importance: Type and rate of amino acid variations in BKPyV may provide important insights into BKPyV diversity in human populations and an important step toward defining determinants of BKPyV-specific immunity needed to protect vulnerable patients from BKPyV diseases. Our analysis of BKPyV sequences obtained from human specimens reveals an unexpectedly high genetic variability for this double-stranded DNA virus that strongly relies on host cell DNA replication machinery with its proof reading and error correction mechanisms. BKPyV variability and immune escape should be taken into account when designing further approaches to antivirals, monoclonal antibodies, and vaccines for patients at risk of BKPyV diseases., Competing Interests: The authors declare no conflict of interest.

Introduction: The particularities of the ocular immune environment and its barrier protection in the context of infection are not well elucidated. The apicomplexan parasite Toxoplasma gondii is one of the pathogens successfully crossing this barrier and establishing chronic infection in retinal cells., Methods: As a first approach, we studied the initial cytokine network in vitro in four human cell lines: Retinal pigmented epithelial (RPE), microglial, astrocytic and Müller cells. Furthermore, we looked at the consequences of retinal infection on the integrity of the outer blood-retina barrier (oBRB). We particularly focused on the roles of type I and type III interferons, (IFN-β and IFN-λ). Especially IFN-λ is known for its significant role in barrier defense. However, its effect on the retinal barrier or T. gondii infection remains unexplored, unlike IFN-γ, which has been extensively studied in this context., Results and Discussion: Here, we show that stimulation with type I and III interferons did not limit parasite proliferation in retinal cells we tested. However, IFN-β and IFN-γ strongly induced inflammatory or cell-attracting cytokine production, whereas IFN-λ1 showed less inflammatory activity. Concomitant T. gondii infection influenced these cytokine patterns, distinctly depending on the parasite strain. Interestingly, all these cells could be stimulated to produce IFN-λ1. Using an in vitro oBRB model based on RPE cells, we observed that interferon stimulation strengthened membrane localization of the tight junction protein ZO-1 and enhanced their barrier function, in a STAT1-independent manner., Conclusion: Together, our model shows how T. gondii infection shapes the retinal cytokine network and barrier function, and demonstrates the role of type I and type III interferons in these processes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Geiller, Greigert, Hillenbrand, Gommenginger, Beal, Brunet, Filisetti, Villard, Denis and Pfaff.)

Background: High-level BK polyomavirus (BKPyV) replication in allogeneic hematopoietic cell transplantation (HCT) predicts failing immune control and BKPyV-associated hemorrhagic cystitis., Methods: To identify molecular markers of BKPyV replication and disease, we scrutinized BKPyV DNA-loads in longitudinal urine and plasma pairs from 20 HCT patients using quantitative nucleic acid testing (QNAT), DNase-I treatment prior to QNAT, next-generation sequencing (NGS), and tested cell-mediated immunity., Results: We found that larger QNAT amplicons led to under-quantification and false-negatives results (P < .001). DNase-I reduced urine and plasma BKPyV-loads by >90% (P < .001), indicating non-encapsidated BKPyV genomes. DNase-resistant urine BKPyV-loads remained infectious in cell culture. BKPyV genome fragmentation of ≤250 bp impaired NGS coverage of genetic variation using 1000-bp and 5000-bp amplicons. Conversely, 250-bp amplicons captured viral minority variants. We identified genotype-specific and genotype-independent changes in capsid Vp1 or T-antigen predicted to escape from antibody neutralization or cytotoxic CD8 T-cells, respectively. Genotype-specific changes in immunodominant 9mers were associated with reduced or absent CD8 T-cell responses. Thus, failure to control BKPyV replication in HCT Patients may involve insufficient genotype-specific cytotoxic CD8 T-cell responses, potentially predictable by low neutralizing antibodies as well as genotype-independent immune escape., Conclusions: Our results provide new insights for patient evaluation and for designing immune protection through neutralizing antibodies, adoptive T-cell therapy, or vaccines., Competing Interests: Potential conflicts of interest. H. H. H. has received speaker honorarium from Gilead, Biotest, and Vera Therapeutics; and served as consultant for Roche, Molecular Partners, Vera Therapeutics, and AiCuris. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed, (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)