Search Results (9)

Modern instant messaging systems require end-to-end (E2E) security guarantees while operating over server-mediated infrastructures that cannot be fully trusted. At the same time, the impending transition to post-quantum cryptography raises nontrivial challenges for the design of secure messaging protocols that preserve these guarantees. In this work, we present the design of a post-quantum end-to-end secure protocol for instant messaging applications under an untrusted relay model. The proposed construction relies on lattice-based primitives standardized by NIST, namely ML-KEM for key establishment and ML-DSA for authentication, and follows a Double-KEM pattern combined with explicit context binding to derive an E2E session key known only to the communicating clients. The server acts solely as an authenticated relay and never gains access to plaintext messages or session keys. In addition to the protocol design, we complement the protocol description with an automated symbolic verification using ProVerif, establishing injective mutual authentication and session-key secrecy under a Dolev–Yao adversary model. Finally, we characterize the computational cost of different authentication and verification policies and evaluate the performance of the handshake on heterogeneous cloud-based architectures. The results provide practical insight into the feasibility of deploying post-quantum end-to-end secure protocols within existing instant messaging infrastructures. Full article

Background/Objectives: While standard Luminex single antigen bead (SAB) detects total IgG antibodies, qualitative differences among IgG subclasses may influence their immunologic risk. In particular, complement fixing ability, assessed via C1q binding, is linked to poor transplant outcomes. This study aimed to evaluate the relationship between IgG subclasses and C1q-binding activity in HLA antibodies and to define clinically relevant subclass-specific mean fluorescence intensity (MFI) thresholds for predicting complement binding. Methods: We analyzed 4189 HLA IgG bead reactions from sera of 37 kidney transplant recipients using SAB assays for total IgG, IgG1-4 subclasses, and C1q-binding. IgG subclasses were assessed using a modified SAB assay with subclass-specific monoclonal secondary antibodies. Results: IgG reactivity (MFI ≥ 1000) was observed in 15.3% of beads (639/4189), with 31.0% (198/639) also positive for C1q binding. IgG⁺C1q⁺ beads exhibited significantly higher MFIs compared with IgG⁺C1q⁻ beads. IgG1 showed positive correlations with both total IgG (r_s = 0.5439, p < 0.0001) and C1q MFIs (r_s = 0.4042, p < 0.0001), with the strongest correlations at HLA-DQ. Among subclass-positive beads, IgG1 predominated and was strongly associated with C1q binding, whereas isolated IgG2 or IgG4 positivity was rarely C1q-binding. ROC analysis identified an IgG1 MFI threshold of >837 to predict C1q positivity with 73.2% sensitivity and 92.3% specificity, while the cutoff for total IgG MFI was >7881 with 85.4% sensitivity and 88.9% specificity. At the patient level, IgG1-positive immunodominant DSAs were more frequent in antibody-mediated rejection than in non-rejection biopsies Conclusions: IgG1 predominates among complement-fixing antibodies and correlates strongly with total IgG and C1q binding. Quantitative IgG subclass assessment, especially IgG1, may serve as a useful predictor of complement activation. Full article

Donor-specific anti-HLA antibodies (DSAs) bind to donor vascular endothelial cells and mediate allograft rejection (AMR), but a clinical challenge for which targeted therapeutic options remain limited. We used a multiplexed single-antigen bead (SAB) assay to detect anti-human leukocyte antigen (HLA) antibodies. Based on the antigens which patient’s antibodies aganist to, we developed bivalent HLA-Fc fusion proteins composed of HLA-derived antigenic domains and human IgG1-Fc effector regions (rA24-Fc and rB13-Fc). Specific binding and functional activity of the HLA-Fc proteins were further validated by flow cytometry, ELISA, complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) assays. Our findings demonstrate that the fusion proteins rA24-Fc and rB13-Fc significantly reduced HLA-specific antibody reactivity in vitro. Notably, rA24-Fc and rB13-Fc selectively bound to B-cell hybridomas (e.g., mouse W6/32 cells) expressing membrane immunoglobulins (BCR) which bound to the most HLA class I antigens. Importantly, rA24-Fc and rB13-Fc elicited antigen-specific, Fc-dependent elimination of the specific B-cell hybridomas. This study highlights HLA-Fc fusion proteins as a promising therapeutic strategy for the antigen-specific suppression of depletion of alloreactive B cells through dual cytotoxic mechanisms. This precision targeted to BCR of B cells approach is used to apply to the treatment of antibody-mediated rejection. Full article

Antibodies directed against donor-specific human leukocyte antigens (HLAs) can be detected de novo after heart transplantation and play a key role in long-term survival. De novo donor-specific antibodies (dnDSAs) have been associated with cardiac allograft vasculopathy, antibody-mediated rejection, and mortality. Advances in detection methods and international guideline recommendations have encouraged the adoption of screening protocols among heart transplant units. However, there is still a lack of consensus about the correct course of action after dnDSA detection. Treatment is usually started when antibody-mediated rejection is present; however, some dnDSAs appear years before graft failure is detected, and at this point, damage may be irreversible. In particular, class II, anti-HLA-DQ, complement binding, and persistent dnDSAs have been associated with worse outcomes. Growing evidence points towards a more aggressive management of dnDSA. For that purpose, better diagnostic tools are needed in order to identify subclinical graft injury. Cardiac magnetic resonance, strain techniques, or coronary physiology parameters could provide valuable information to identify patients at risk. Treatment of dnDSA usually involves plasmapheresis, intravenous immunoglobulin, immunoadsorption, and ritxumab, but the benefit of these therapies is still controversial. Future efforts should focus on establishing effective treatment protocols in order to improve long-term survival of heart transplant recipients. Full article

Complement activation by HLA antibodies is a key component of immune-mediated graft injury. We examined the clinical outcomes of kidney transplant recipients with complement-fixing de novo donor-specific antibodies (dnDSA) who were followed in our center. The C1q-binding ability was retrospectively assessed in 69 patients with dnDSA and mean fluorescence intensity (MFI) values > 2000 out of the 1325 kidney transplant recipients who were screened for DSA between 2015 and 2019. Luminex IgG single antigen beads (SAB)and C1q-SAB assays (One Lambda) were used. C1q-binding dnDSA was identified in 32/69 (46.4%) of the patients. Significantly higher MFI values were observed in C1q-positive DSA (18,978 versus 5840, p < 0.001). Renal graft biopsies were performed in 43 of the kidney transplant recipients (62.3%) with allograft dysfunction. Antibody-mediated rejection (ABMR) was detected in 29/43 (67.4%) of the patients. The incidence of ABMR was similar among patients with C1q-binding and non-C1q-binding DSA (51.7% vs. 48.3%, p = 0.523). Graft loss occurred in 30/69 (43.5%) of the patients at a median time of 82.5 months (IQR 45–135) from DSA detection. C1q-binding DSA was present in more patients who experienced graft loss (53.1% vs. 35.1%, p = 0.152). Higher MFI values and inferior clinical outcomes occurred in most of the kidney transplant recipients with C1q-binding dnDSA. Full article

Background: Antibody-mediated rejection (AMR) is one of the most important challenges in the context of renal transplantation, because the binding of de novo donor-specific antibodies (dnDSA) to the kidney graft triggers the activation of the complement, which in turn leads to loss of transplant. In this context, the objective of this study was to evaluate the association between complement-fixing dnDSA antibodies and graft loss as well as the possible association between non-complement-fixing antibodies and transplanted organ survival in kidney transplant recipients. Methods: Our study included a cohort of 245 transplant patients over a 5-year period at Virgen de las Nieves University Hospital (HUVN) in Granada, Spain. Results: dnDSA was observed in 26 patients. Of these patients, 17 had non-complement-fixing dnDSA and 9 had complement-fixing dnDSA. Conclusions: Our study demonstrated a significant association between the frequency of rejection and renal graft loss and the presence of C1q-binding dnDSA. Our results show the importance of the individualization of dnDSA, classifying them according to their ability to activate the complement, and suggest that the detection of complement-binding capacity by dnDSA could be used as a prognostic marker to predict AMR outcome and graft survival in kidney transplant patients who develop dnDSA. Full article

Introduction: De novo anti-HLA donor specific antibodies (DSA) have been inconsistently associated with cardiac allograft vasculopathy (CAV) and long-term mortality. We tested whether C3d-binding de novo DSA were associated with CAV or long-term-survival. Methods: We included 282 consecutive patients without preformed DSA on coronary angiography between 2010 and 2012. Angiographies were classified according to CAV ISHLT grading. The primary outcome was a composite criterion of severe CAV or mortality. As the impact of de novo antibodies should be assessed only after appearance, we used a Cox regression with time-dependent covariables. Results: Of the 282 patients, 51(18%) developed de novo DSA during follow-up, 29 patients had DSA with C3d-binding ability (DSA+C3d+), and 22 were without C3d-binding ability (DSA+C3d-). Compared with patients without DSA, DSA+C3d+ patients had an increased risk for the primary outcome of severe CAV or mortality (adjusted HR = 4.31 (2.40–7.74) p < 0.001) and long-term mortality (adjusted HR = 3.48 (1.97–6.15) p < 0.001) whereas DSA+C3d- did not (adjusted HR = 1.04 (0.43–2.47) p = 0.937 for primary outcome and HR = 1.08 (0.45–2.61) p = 0.866 for mortality). Conclusion: According to this large monocentric study in heart transplant patients, donor specific antibodies were associated with worse clinical outcome when binding complement. DSA and their complement-binding ability should thus be screened for to optimize heart transplant patient follow-up. Full article

Visceral hemangiosarcoma (HSA) is one of the more frequent cancers in dogs and has a high metastatic rate and poor prognosis, as clinical signs only become apparent in advanced stages of tumor development. In order to improve early and differential diagnostic capabilities and hence, prognosis for dogs with HSA, two types of biomarker are needed: a point-of-care diagnostic biomarker and a prognostic biomarker—preferentially based on samples obtained with minimally invasive methods. In this study, we applied a lectin magnetic bead array-coupled tandem mass spectrometry (LeMBA-MS/MS) workflow through discovery and validation phases to discover serum glycoprotein biomarker candidates for canine HSA. By this approach, we found that Datura stramonium (DSA), wheat germ agglutinin (WGA), Sambucus nigra (SNA), and Pisum sativum (PSA) lectins captured the highest number of validated candidate glycoproteins. Secondly, we independently validated serum LeMBA-MS/MS results by demonstrating the in situ relationship of lectin-binding with tumor cells. Using lectin-histochemistry and immunohistochemistry (IHC) for key proteins on tissues with HSA and semi-quantitation of the signals, we demonstrate that a combination of DSA histochemistry and IHC for complement C7 greatly increases the prospect of a more specific diagnosis of canine HSA. Full article

C3d-binding assays have been introduced as methods for the prediction of the presence of complement-binding functional antibodies; however, the prognostic value of C3d-positive preformed donor-specific antibodies (pDSAs) has not been fully evaluated. In this study, we performed a retrospective investigation of the association of pDSAs and their C3d-binding capacity with one-year clinical outcomes. pDSAs were defined as donor-specific antibodies (DSAs) that were produced before kidney transplants (KTs) (pre-pDSAs) or within the first four weeks after KTs, owing to rebound immune response (post-pDSAs). Of 455 adult KT recipients, pre-pDSAs and post-pDSAs were found in 56 (12.3%) and 56 (12.3%) recipients, respectively, and C3d-positive post-pDSAs were found in 13 recipients (2.9%) in total. Approximately half of the C3d-negative pre-pDSAs (37/73, 50.7%) disappeared after transplantation; however, all C3d-positive pre-pDSAs (8/8, 100%) persisted after transplantation despite desensitization (p = 0.008). C3d-positive pDSAs were significantly associated with a higher incidence and risk of AMR (p < 0.001, OR 94.467–188.934). Identification of the C3d-binding activity of pDSAs before and early after KT is important for predicting the persistence of pDSAs and the risk of AMR induced by the presence of pDSAs. Full article