Genotypic and phenotypic characterisation of respiratory syncytial virus after nirsevimab breakthrough infections: a large, multicentre, observational, real-world study.

BACKGROUND: Nirsevimab, a long-acting monoclonal antibody, has been approved for the prevention of respiratory syncytial virus (RSV) infection in infants. In France, more than 210 000 single doses were administered in infants younger than 1 year during the 2023-24 season. In this context, the selection and spread of escape variants might be a concern. Here, we aimed to characterise RSV associated with breakthrough infection. METHODS: We did a multicentre, national, observational study in France during the 2023-24 RSV season in RSV-infected infants (aged <1 year) who either received or did not receive a dose of nirsevimab before their first RSV season. We excluded infants with insufficient information about nirsevimab treatment or without parental consent. We used respiratory samples collected in each laboratory for full-length RSV RNA sequencing to analyse changes in the nirsevimab binding site Ø. We tested clinical RSV isolates for neutralisation by nirsevimab. We analysed F candidate substitutions by fusion-inhibition assay. FINDINGS: Of the 695 RSV infected infants, we analysed 545 (78%) full-length RSV genome sequences: 260 (48%) from nirsevimab-treated breakthrough infections (236 [91%] RSV-A and 24 [9%] RSV-B) and 285 (52%) from untreated RSV-infected infants (236 [83%] RSV-A and 49 [17%] RSV-B). Analysis of RSV-A did not reveal any substitution in site Ø known to be associated with resistance to nirsevimab. Two (8%) of 24 RSV-B breakthrough infections had resistance-associated substitutions: F:N208D (dominant resistance-associated substitution) and a newly described F:I64M plus F:K65R combination (minority resistance-associated substitution), both of which induced high levels of resistance in the fusion-inhibition assay. INTERPRETATION: This study is, to the best of our knowledge, the largest genotypic and phenotypic surveillance study of nirsevimab breakthrough infections to date. Nirsevimab breakthrough variants remain very rare despite the drug's widespread use. The detection of resistance-associated substitutions in the RSV-B F protein highlights the importance of active molecular surveillance. FUNDING: ANRS Maladies Infectieuses Emergentes and the French Ministry of Health and Prevention.

Chorionicity and gestational diabetes mellitus in twin pregnancies in relation to placental weight.

BACKGROUND: Gestational diabetes mellitus (GDM) is glucose intolerance first detected during pregnancy. Twin pregnancies have a higher risk of GDM, likely due to increased placental mass and elevated placental lactogen levels. OBJECTIVE: The aims of this study were 1) to assess the impact of chorionicity on the development of GDM in twin pregnancies and 2) to assess a possible association between placenta weight and the development of GDM. METHODS: We conducted a prospective cohort study of all women with twin pregnancies (N = 819) at the department of Obstetrics and Gynecology, Lillebaelt University Hospital, Kolding, Denmark, between January 1, 2007 and April 30, 2019. Information on chronicity was determined at the first visit with ultrasonic imaging, during weeks' gestation 11-13. Oral glucose-tolerance test was performed to diagnose gestational diabetes mellitus. RESULTS: Among 819 twins, 17.8 % were monochorionic twins and 82.2 % were dichorionic twins. There were no statistically significant difference of GDM prevalence between monochorionic twins group 7.4 % and dichorionic twins group 9.8 % (P = 0.42). Placenta's weight in dichorionic twins was larger compared with monochorionic twins. No association was found between the weight of placenta and the prevalence of GDM (P = 0.21), even after adjustment for body mass index, gestational age, and fertility treatment (P = 0.87). CONCLUSIONS: Our study could not find an association between chorionicity, placental weight, and GDM. It is, therefore, possible that twin pregnancies, regardless of chorionicity and placental weight, have the same risk for GDM.

ProACT™ (Uromedica, Plymouth, USA) balloons for male urinary incontinence: A fourteen-year-old cohort.

BACKGROUND: Male urinary incontinence is attributed to SUI consecutive to benign prostate hypertrophy surgery, trauma, neurological diseases, or injury. Medical devices are developed to treat male urinary incontinence among them proACT® balloons. This technique was chosen in our center to achieve continence. Our study aims to evaluate safety and efficacy of proACT® balloons implanted in our center by measuring the rate of efficacy. METHODS: We performed a retrospective and single centre study. A single expert surgeon performed all surgeries. Seventy-one balloons were implanted in 57 male patients between 2007 and 2020. Primary endpoint was the efficacy time lapse of the balloons after surgery. The analysis was performed using Kaplan-Meier method. Factors, which could affect the efficacy of the balloons, were analysed using a Cox regression analysis. RESULTS: In all, 45 balloons successfully cured stress urinary incontinence among the 57 men implanted resulting in a 63.38% success rate. Twenty-six balloons failed to treat stress urinary incontinence and were retrieved out of the 71 implanted. Ten balloons failed to treat urinary stress incontinence without organic cause, 6 balloons deflated, 5 balloons migrated out of the initial implantation site, 2 eroded, and 3 ended up infected. Fifty percent of the balloons were successful for a median time of 95 months. Univariate analysis did not reveal any predictive factor of failure. CONCLUSIONS: Our study showed 50% success rate at 95 months follow-up, therefore allowing a life expectancy of 7.9 years for the balloons. This safe mini-invasive technique ensured stress urinary incontinence in men.

Comparison of two RT-qPCR methods targeting BK polyomavirus microRNAs in kidney transplant recipients.

Background: BK polyomavirus replication leads to progressive tubulointerstitial nephritis and ureteral stenosis, with a considerable risk of subsequent graft failure in kidney transplant recipients. Since specific antiviral therapies are lacking, new tools are required to enhance the biological monitoring of the infection. Viral microRNAs are promising new biomarkers, but the performance of RT-qPCR methods limits the clinical application and the validation of a standard method for quantification. Methods: We compared TaqMan microRNA Assays and TaqMan Advanced miRNA Assays for bkv-miR-B1-3p and bkv-miR-B1-5p quantification in synthetic microRNA templates and in 44 urine samples belonging to 14 consecutive kidney transplant recipients with BK polyomavirus replication from Amiens University Medical Center in a 1-year span. Results: Cycle threshold values were constantly higher with TaqMan Advanced MicroRNA Assays. TaqMan microRNA Assays showed better performance in predicting the good prognosis of BK polyomavirus nephropathy. Conclusion: Overall, TaqMan MicroRNA Assays appeared to be a more sensitive and accurate RT-qPCR method than TaqMan Advanced MicroRNA Assays to quantify bkv-miR-B1-3p and bkv-miR-B1-5p BKPyV miRNAs in patients' urine samples.

Ruxolitinib-induced reactivation of cytomegalovirus and Epstein-Barr virus in graft-versus-host disease.

OBJECTIVES: Steroid-refractory graft-versus-host disease (SR-GVHD) is a challenging complication of allogeneic hematopoietic stem cell transplantation, and leads to high morbidity and mortality rates. The orally administered, selective Janus-associated kinase 1/2 inhibitor ruxolitinib gives overall response rates (ORR) of more than 70 % in acute and chronic SR-GVHD. However, several studies have highlighted an elevated risk of cytomegalovirus (CMV) reactivation in patients with ruxolitinib-treated SR-GVHD. METHODS: We therefore analyzed risk of CMV and Epstein-Barr virus (EBV) primary infection or reactivation in 57 patients with ruxolitinib-treated GVHD, while taking account of the competing risk (CR) of death prior to the first reactivation. RESULTS: Initiation of ruxolitinib treatment was a significant adverse prognostic factor for the CR of first CMV reactivation (hazard ratio (HR)= 1.747, 95 % confidence interval (CI): 1.33-2.92, p < 0.0001) and first EBV reactivation (HR=2.657, 95 % CI: 1.82-3.87, p < 0.0001) during GVHD. In our cohort of ruxolitinib-treated patients, the ORR (48 % and 58 % for acute and chronic GVHD, respectively) and the toxicity profile (haematological adverse events in 29.8 % of the patients) were similar to the literature values. CONCLUSION: Given ruxolitinib's efficacy in SR-GVHD, use of this drug should not be limited by the fear of viral reactivation; however, our present results emphasize the importance of monitoring the viral load.

BK Polyomavirus bkv-miR-B1-5p: A Stable Micro-RNA to Monitor Active Viral Replication after Kidney Transplantation.

BACKGROUND: Bkv-miR-B1-5p is a viral micro-RNA (miRNA) specifically produced during BK polyomavirus (BKPyV) replication. Recent studies have suggested using bkv-miR-B1-5p as a biomarker to monitor viral infection and predict complications in kidney transplant patients. To identify the technical limitations of this miRNA quantification in biological samples, knowledge of its stability and distribution in the extracellular compartment is necessary. Moreover, a proof of concept for using bkv-miR-B1-5p as a biomarker of active replication in chronic infection is still missing in the published literature. METHODS: The stability of bkv-miR-B1-5p was evaluated in samples derived from cell cultures and in urine from BKPyV-infected kidney transplant recipients. The miRNA was quantified in different fractions of the extracellular compartment, including exosomes, and protein binding was evaluated. Finally, we developed an in vitro model for chronic culture of BKPyV clinical isolates to observe changes in the bkv-miR-B1-5p level during persistent infections. RESULTS: Bkv-miR-B1-5p is a stable biomarker in samples from humans and in vitro experiments. Marginally associated with the exosomes, most of the circulating bkv-miR-B1-5p is bound to proteins, especially Ago2, so the miRNA quantification does not require specific exosome isolation. The bkv-miR-B1-5p level is predictable of viral infectivity, which makes it a potential specific biomarker of active BKPyV replication after kidney transplantation.

Pathology Assessments of Multiple Organs in Fatal COVID-19 in Intensive Care Unit vs. Non-intensive Care Unit Patients.

Purpose: The objective of the present study was to provide a detailed histopathological description of fatal coronavirus disease 2019 (COVID 19), and compare the lesions in Intensive Care Unit (ICU) and non-ICU patients. Methods: In this prospective study we included adult patients who died in hospital after presenting with confirmed COVID-19. Multiorgan biopsies were performed. Data generated with light microscopy, transmission electron microscopy (TEM) and RT-PCR assays were reviewed. Results: 20 patients were enrolled in the study and the main pulmonary finding was alveolar damage, which was focal in 11 patients and diffuse in 8 patients. Chronic fibrotic and inflammatory lesions were observed in 18 cases, with acute inflammatory lesions in 12 cases. Diffuse lesions, collapsed alveoli and dystrophic pneumocytes were more frequent in the ICU group (62.5%, vs. 25%; 63%, vs. 55%; 87.5%, vs. 54%). Acute lesions (82%, vs. 37.5%; p = 0.07) with neutrophilic alveolitis (63.6% vs. 0%, respectively; p = 0.01) were observed more frequently in the non-ICU group. Viral RNA was detected in 12 lung biopsies (60%) up to 56 days after disease upset. TEM detected viral particles in the lung and kidney biopsy samples up to 27 days after disease upset. Furthermore, abundant networks of double-membrane vesicles (DMVs, a hallmark of viral replication) were observed in proximal tubular epithelial cells. Conclusion: Lung injury was different in ICU and non-ICU patients. Extrapulmonary damage consisting in kidney and myocardial injury were more frequent in ICU patients. Our TEM experiments provided the first description of SARS-CoV-2-induced DMVs in kidney biopsy samples-a sign of intense viral replication in this organ.

Humoral anti-SARS-CoV-2 immune response after two doses of Comirnaty vaccine in nursing home residents by previous infection status.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is associated with increased morbidity and mortality in older adults. Although the advent of the first vaccines has significantly reduced these rates, data on older adults in clinical trials are scarce. OBJECTIVES: We quantified and compared the humoral response in individuals with vs. without pre-existing seropositivity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in a cohort of 69 patients living in a nursing home and who had received the recommended two doses of the Comirnaty (Pfizer-BioNTech®) vaccine. RESULTS: All 69 patients (100%) tested positive for antibodies against SARS-CoV-2 at 2 months post-vaccination. Residents with a pre-vaccination infection had significantly higher titers of anti-spike 1 IgG than those with no prior infection (median [interquartile range]: 55,726 [14463-78852] vs. 1314 [272-1249] arbitrary units, respectively; p < 0.001). The same result was observed for neutralizing antibodies titers (704 [320-1280] vs. 47 [20-40] respectively; p < 0.001). Between the pre-vaccination and post-vaccination periods, for IgG and neutralizing antibodies, we observed a 49 and 8-fold increase respectively. In comparison to the wild-type Receptor Binding Domain (RBD), the binding capacity of these vaccine sera was significantly decreased on the B.1.351 and P.1 variants RBD but not decreased with respect to the B.1.1.7 RBD. Although all nursing home residents developed a humoral response following Comirnaty vaccine, its intensity appeared to depend on the pre-vaccination serological status. CONCLUSION: Our results raise the question of how many doses of vaccine should be administered in older and how long the protection will be effective.

Impact of pre-graft serology on risk of BKPyV infection post-renal transplantation.

OBJECTIVES: BK polyomavirus-associated nephropathy is a troublesome disease caused by BK polyomavirus (BKPyV) infection in immunocompromised renal graft recipients. There are no effective treatments available, making immunosuppression reduction the only management option. Thus, pre-graft predictive BKPyV replication markers are needed for identification of patients at high risk of viraemia. METHODS: We conducted a retrospective study to assess the correlation between pre-transplantation BKPyV serostatus and post-transplantation incidence of BKPyV infection. Sera from 329 recipients and 222 matched donors were tested for anti-BKPyV antibodies against BKPyV serotypes I and IV by using a virus-like particle-based immunoglobulin G enzyme-linked immunosorbent assay, and BKPyV DNA load was monitored for at least 1 year post-transplantation. RESULTS: Eighty recipients were viruric and 59 recipients were viraemic post-transplantation. In the post-transplantation period, the probability of developing viraemia for serotype I increased from 4.3% for the D-/R+ group to 12.1% for the D+/R+ group, climbing to 37.5% for the D+/R- group (P < 0.05). When calculating recipient mean titres for serotypes I and IV, we observed a clear difference in the proportions of viraemia, decreasing from 50% for mean titres <400 to 13.5% for titres ≥400 (P < 0.001), as well as a higher proportion of presumptive nephropathy (50% versus 23.1%, respectively; P < 0.05). In univariate analysis, this parameter had an odds ratio of 6.41 for the risk of developing post-transplantation BKPyV viraemia (95% confidence interval 3.16-13.07; P < 0.0001). CONCLUSIONS: Determination of both donor and recipient BKPyV seropositivity before transplantation and antibody titre measurements may serve as a predictive tool to manage clinical BKPyV infection by identification of patients at high risk.

From Upper Respiratory Symptoms to Hemophagocytic Lymphohistiocytosis: Case Report of a Human Adenovirus Infection in Haploidentical Hematopoietic Stem Cell Transplant Recipient.

Human adenovirus infection is rare in adult population, except for in immunocompromised individuals. Recipients of allogenic haploidentical hematopoietic stem cell transplantation are reported at high risk for human adenovirus, which is often lethal when it evolves into the disseminated form. Despite existent guidelines, prevention, early diagnosis, and therapeutics remain challenging. Here, we report the case of a fatal evolution of human adenovirus respiratory infection and discuss the actual recommendations to prevent recurrence of this major issue.

Longitudinal Analysis and Comparison of Six Serological Assays up to Eight Months Post-COVID-19 Diagnosis.

BACKGROUND: There is much data available concerning the initiation of the immune response after SARS-CoV-2 infection, but long-term data are scarce. METHODS: We thus longitudinally evaluated and compared the total and neutralizing immune response of 61 patients to SARS-CoV-2 infection up to eight months after diagnosis by RT-PCR using several commercial assays. RESULTS: Among the 208 samples tested, the percentage of seropositivity was comparable between assays up to four months after diagnosis and then tended to be more heterogeneous between assays (p < 0.05). The percentage of patients with a neutralizing titer decreased from 82% before two months postdiagnosis to 57% after six months. This decrease appeared to be more marked for patients under 65 years old and those not requiring hospitalization. The percentage of serology reversion at 6 months was from 11% with the WANTAI total assay to over 39% with the ABBOTT IgG assay. The neutralizing antibody titers decreased in parallel with the decrease of total antibody titers, with important heterogeneity between assays. CONCLUSIONS: In conclusion, serological tests show equivalent sensitivity in the first months after the diagnosis of SARS-CoV-2 infection, but their performance later, postinfection, must be considered when interpreting the results.

BK Polyomavirus Micro-RNAs: Time Course and Clinical Relevance in Kidney Transplant Recipients.

BACKGROUND: Kidney transplant recipients (KTRs) are exposed to a high risk of BK polyomavirus (BKPyV) replication, which in turn may lead to graft loss. Although the microRNAs (miRNAs) bkv-miR-B1-3p and bkv-miR-B1-5p are produced during the viral cycle, their putative value as markers of viral replication has yet to be established. In KTRs, the clinical relevance of the changes over time in BKPyV miRNA levels has not been determined. METHODS: In a retrospective study, we analyzed 186 urine samples and 120 plasma samples collected from 67 KTRs during the first year post-transplantation. Using a reproducible, standardized, quantitative RT-PCR assay, we measured the levels of bkv-miR-B1-3p and bkv-miR-B1-5p (relative to the BKPyV DNA load). RESULTS: Detection of the two miRNAs had low diagnostic value for identifying patients with DNAemia or for predicting DNAuria during follow-up. Seven of the 14 KTRs with a sustained BKPyV infection within the first year post-transplantation showed a progressive reduction in the DNA load and then a rapid disappearance of the miRNAs. DNA and miRNA loads were stable in the other seven KTRs. CONCLUSIONS: After the DNA-based diagnosis of BKPyV infection in KTRs, bkv-miR-B1-3p and bkv-miR-B1-5p levels in the urine might be valuable markers for viral replication monitoring and thus might help physicians to avoid an excessive reduction in the immunosuppressive regimen.

Comparison of nasopharyngeal and saliva swabs for the detection of RNA SARS-CoV-2 during mass screening (SALICOV study).

In the context of a second wave of SARS-CoV-2 transmission, the use of saliva sampling has become an issue of real importance. SARS-CoV-2 RNA screening was performed on nasopharyngeal and saliva swabs collected from 501 individuals from residential homes for the elderly. The saliva samples were collected at the same time as the nasopharyngeal samples. Nasopharyngeal samples yielded positive results for 26 individuals, only two of whom also tested positive with saliva swabs. In this context, saliva collected by swabbing the fluid is not an ideal sample.

Anti-spike, Anti-nucleocapsid and Neutralizing Antibodies in SARS-CoV-2 Inpatients and Asymptomatic Individuals.

A better understanding of the anti-SARS-CoV-2 immune response is necessary to finely evaluate commercial serological assays but also to predict protection against reinfection and to help the development of vaccines. For this reason, we monitored the anti-SARS-CoV-2 antibody response in infected patients. In order to assess the time of seroconversion, we used 151 samples from 30 COVID-19 inpatients and monitored the detection kinetics of anti-S1, anti-S2, anti-RBD and anti-N antibodies with in-house ELISAs. We observed that specific antibodies were detectable in all inpatients 2 weeks post-symptom onset and that the detection of the SARS-CoV-2 Nucleocapsid and RBD was more sensitive than the detection of the S1 or S2 subunits. Using retroviral particles pseudotyped with the spike of the SARS-CoV-2, we also monitored the presence of neutralizing antibodies in these samples as well as 25 samples from asymptomatic individuals that were shown SARS-CoV-2 seropositive using commercial serological tests. Neutralizing antibodies reached a plateau 2 weeks post-symptom onset and then declined in the majority of inpatients but they were undetectable in 56% of asymptomatic patients. Our results indicate that the SARS-CoV-2 does not induce a prolonged neutralizing antibody response. They also suggest that induction of neutralizing antibodies is not the only strategy to adopt for the development of a vaccine. Finally, they imply that anti-SARS-CoV-2 neutralizing antibodies should be titrated to optimize convalescent plasma therapy.

SLC7A11 as a biomarker and therapeutic target in HPV-positive head and neck Squamous Cell Carcinoma.

Ferroptosis, a regulated form of cell necrosis was previously reported to be induced upon pharmacological targeting of the cystine transporter SLC7A11 in Head and neck Squamous Cell Carcinoma (HNSCC). Whether tumors arising in a context of chronic infection with Human Papillomavirus (HPV) are sensitive to ferroptosis is unknown. Using RNAseq data (both whole-tumor and single-cell sequencing) we report that HPV positive (HPV+ve) tumors have lower expression levels of SLC7A11 compared to HPV negative (HPV-ve) HNSCC. We examined in vitro the effect of erastin, a specific blocker of SLC7A11, applied on two HNSCC cell lines with stable expression of HPV16 E6 and E7 oncoproteins. We report a decrease in total GSH levels and an increased sensitivity to erastin-induced ferroptosis in E6-E7 cells. Cell sensitivity to ferroptosis was specificaly related to a defect in cystine transport since we found no difference in ferroptosis induced by the direct inhibition of GPX4, and N-Acetyl Cystein abolished the difference between WT and E6-E7-expressing cells. Our findings point to SLC7A11 as an HPV-related biomarker of potential therapeutic relevance in HNSCC. Targeting cystine import to promote ferroptosis might be a promising strategy against HPV+ve HNSCC. (188 words).

Indoleamine 2,3-Dioxygenase Is Involved in Interferon Gamma's Anti-BKPyV Activity in Renal Cells.

Reactivation of BK polyomavirus (BKPyV) infection is frequently increasing in transplant recipients treated with potent immunosuppressants and highlights the importance of immune system components in controlling viral reactivation. However, the immune response to BKPyV in general and the role of antiviral cytokines in infection control in particular are poorly understood. Here, we investigated the efficacy of interferons (IFN) alpha, lambda and gamma with regard to the BKPyV multiplication in Vero cells. Treatment with IFN-gamma inhibited the expression of the viral protein VP1 in a dose-dependent manner and decreased the expression of early and late viral transcripts. Viral inhibition by IFN-gamma was confirmed in human cells (Caki-1 cells and renal proximal tubular epithelial cells). One of the IFN-stimulated genes most strongly induced by IFN-gamma was the coding for the enzyme indoleamine 2,3 dioxygenase (IDO), which is known to limit viral replication and regulates the host immune system. The antiviral activity induced by IFN-gamma could be reversed by the addition of an IDO inhibitor, indicating that IDO has a specific role in anti-BKPyV activity. A better understanding of the action mechanism of these IFN-gamma-induced antiviral proteins might facilitate the development of novel therapeutic strategies.

Comparison of different serological assays for SARS-CoV-2 in real life.

BACKGROUND: The emergence of the global SARS-CoV-2 pandemic required the rapid and large-scale deployment of PCR and serological tests in different formats. OBJECTIVES: Real-life evaluation of these tests is needed. Using 168 samples from patients hospitalized for COVID-19, non-hospitalized patients but infected with SARS-CoV-2, patients participating in screening campaigns, and samples from patients with a history of other seasonal coronavirus infections, we evaluated the clinical performance of 5 serological assays widely used worldwide (WANTAI®, BIORAD®, EUROIMMUN®, ABBOTT® and LIAISON®). RESULTS: For hospitalized patients, all these assays showed a sensitivity of 100 % from day 9 after the symptoms onset. On the other hand, sensitivity was much lower for patients who did not require hospitalization for COVID-19 confirmed by PCR (from 91.6 % for WANTAI® to 69 % for LIAISON®). These differences do not seem to be due to the antigens chosen by the manufacturers but more to the test formats (IgG detection versus total antibodies). In addition, more than 50 days after a positive PCR for CoV-2-SARS the proportion of positive patients seem to decrease. We did not observe any significant cross-reactions for these techniques with the four other seasonal coronaviruses. CONCLUSION: In conclusion, the evaluation and knowledge of the serological tests used is important and should require an optimized strategy adaptation of the analysis laboratories to best meet patient's expectations in the face of this health crisis.

Dynamic profile for the detection of anti-SARS-CoV-2 antibodies using four immunochromatographic assays.

In order to fight the SARS-CoV-2 pandemic infection, there is a growing need and demand for diagnostic tools that are complementary and different from the RT-PCR currently in use. Multiple serological tests are or will be very soon available but need to be evaluated and validated. We have thus tested 4 immunochromatographic tests for the detection of antibodies to SARS-CoV-2. In addition, we assessed the kinetics of antibody appearance using these assays in 22 patients after they were tested positive by RT-PCR. We observed great heterogeneity in antibody detection post-symptom onset. The median antibody detection time was between 8 and 10 days according to the manufacturers. All the tests showed a sensitivity of 60 to 80% on day 10 and 100% on day 15. In addition, a single cross-reaction was observed with other human coronavirus infections. Thus, immunochromatographic tests for the detection of anti-SARS-CoV-2 antibodies may have their place for the diagnostic panel of COVID-19.

BK Polyomavirus Hijacks Extracellular Vesicles for En Bloc Transmission.

Most people are asymptomatic carriers of the BK polyomavirus (BKPyV), but the mechanisms of persistence and immune evasion remain poorly understood. Furthermore, BKPyV is responsible for nephropathies in kidney transplant recipients. Unfortunately, the sole therapeutic option is to modulate immunosuppression, which increases the risk of transplant rejection. Using iodixanol density gradients, we observed that Vero and renal proximal tubular epithelial infected cells release two populations of infectious particles, one of which cosediments with extracellular vesicles (EVs). Electron microscopy confirmed that a single vesicle could traffic tens of viral particles. In contrast to naked virions, the EV-associated particles (eBKPyVs) were not able to agglutinate red blood cells and did not use cell surface sialylated glycans as an attachment factor, demonstrating that different entry pathways were involved for each type of infectious particle. However, we also observed that naked BKPyV and eBKPyV were equally sensitive to neutralization by the serum of a seropositive patient or commercially available polyvalent immunoglobulin preparations, which occurred at a postattachment step, after endocytosis. In conclusion, our work shows a new mechanism that likely plays a critical role during the primary infection and in the persistence, but also the reactivation, of BKPyV.IMPORTANCE Reactivation of BKPyV is responsible for nephropathies in kidney transplant recipients, which frequently lead to graft loss. The mechanisms of persistence and immune evasion used by this virus remain poorly understood, and a therapeutic option for transplant patients is still lacking. Here, we show that BKPyV can be released into EVs, enabling viral particles to infect cells using an alternative entry pathway. This provides a new view of BKPyV pathogenesis. Even though we did not find any decreased sensitivity to neutralizing antibodies when comparing EV-associated particles and naked virions, our study also raises important questions about developing prevention strategies based on the induction or administration of neutralizing antibodies. Deciphering this new release pathway could enable the identification of therapeutic targets to prevent BKPyV nephropathies. It could also lead to a better understanding of the pathophysiology of other polyomaviruses that are associated with human diseases.