Humoral immunity to memory antigens and pathogens is maintained in patients with chronic kidney disease

Distinct Neutralising and Complement-Fixing Antibody Responses Can Be Induced to the Same Antigen in Haemodialysis Patients After Immunisation with Different Vaccine Platforms

Background/Objectives: Generalised immune dysfunction in chronic kidney disease, especially in patients requiring haemodialysis (HD), significantly enhances the risk of severe infections. Vaccine-induced immunity is typically reduced in HD populations. The SARS-CoV-2 pandemic provided an opportunity to examine the magnitude and functionality of antibody responses in HD patients to a previously unencountered antigen-Spike (S)-glycoprotein-after vaccination with different vaccine platforms (viral vector (VV); mRNA (mRV)). Methods: We compared the total and functional anti-S antibody responses (cross-variant neutralisation and complement binding) in 187 HD patients and 43 healthy controls 21-28 days after serial immunisation. Results: After 2 doses of the same vaccine, HD patients had anti-S antibody levels and a complement binding capacity comparable to controls. However, 2 doses of mRV induced greater polyfunctional antibody responses than VV (defined by the presence of both complement binding and cross-variant neutralisation activity). Interestingly, an mRV boost after 2 doses of VV significantly enhanced antibody functionality in HD patients without a prior history of SARS-CoV-2 infection. Conclusions: HD patients can generate near-normal, functional antigen-specific antibody responses following serial vaccination to a novel antigen. Encouragingly, exploiting immunological memory by using mRNA vaccines and boosting may improve the success of vaccination strategies in this vulnerable patient population.

Urinary Immune Complexes Reflect Renal Pathology in Lupus Nephritis

BACKGROUND/OBJECTIVES

Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE), involving immune complex deposition in the kidneys. While renal biopsy is the diagnostic gold standard, its invasiveness limits frequent use, driving the need for non-invasive urinary biomarkers to monitor disease progression and response to treatment. This study aimed to identify and validate urinary biomarkers for LN.

METHODS

Data from 10 LN-related omics databases, including urine, PBMCs, and kidney tissue, were analyzed. Differentially expressed proteins (DEPs) and genes (DEGs) were identified, and candidate biomarkers were validated via ELISA in an independent cohort of 87 urine samples.

RESULTS

We identified 78 biomarkers, with 14 overlapping across transcriptomic categories. Novel urinary biomarkers, including SERPING1, SLPI, and CD48, were validated. Urinary CD163, VCAM1, and ALCAM levels showed significant differences between LN and healthy controls, while urinary immune complexes (ICx) demonstrated superior diagnostic performance, with urinary ALCAM-ICx and CCL21-ICx achieving the highest AUC values.

CONCLUSIONS

Our findings highlight the potential of urinary immune complexes and antigens as non-invasive biomarkers for LN. ALCAM, CD163, and SERPING1-ICx, in particular, were found as promising candidates for a urinary biomarker panel to aid in the diagnosis and monitoring of LN.

Platelet aggregation responses to Salmonella Typhimurium are determined by host anti-Salmonella antibody levels

Invasive non-typhoidal Salmonella infections are responsible for >75 000 deaths/year and >500 000 cases/year globally. Seventy-five percent of these cases occur in Sub-Saharan Africa, an increasing number of which are from multi-drug resistant strains. Interactions between bacteria and platelets can lead to thrombus formation, which can be beneficial for control of infection (immunothrombosis), or harmful through uncontrolled inflammation and organ damage (thromboinflammation). It is unknown whether Salmonella Typhimurium can activate human platelets. To assess this, light transmission aggregometry was used to measure platelet activation by two different Salmonella Typhimurium strains in 26 healthy donors in platelet-rich plasma and washed platelets. In platelet-rich plasma, but not in washed platelets, Salmonella Typhimurium activated platelets in a donor- and strain-dependent manner mediated through the low affinity immune receptor FcγRIIA and the feedback agonists, ADP and thromboxane A2. Plasma swap studies between strong and weak responders demonstrated a plasma component was responsible for the variation between donors. Depletion of anti-Salmonella antibodies from plasma abolished Salmonella-induced platelet aggregation responses, and addition of polyclonal anti-Salmonella antibody allowed aggregation in washed platelets. Correlating levels of anti-Salmonella total IgG or the IgG1, IgG2, IgG3 and IgG4 subclasses to platelet responses revealed total IgG levels, rather than levels of individual subclasses, positively correlated with maximum platelet aggregation results, and negatively with lag times. Overall, we show that anti-Salmonella IgG antibodies are responsible for donor variation in platelet aggregation responses to Salmonella and mediate this activity through FcγRIIA.

Latent Cytomegalovirus Infection and Previous Capsular Polysaccharide Vaccination Predict Poor Vaccine Responses in Older Adults, Independent of Chronic Kidney Disease

BACKGROUND

Patients with chronic kidney disease (CKD) are more prone to severe infection. Vaccination is a key strategy to reduce this risk. Some studies suggest vaccine efficacy may be reduced in patients with CKD, despite preserved maintenance of long-term responses to some pathogens and vaccines. Here, we investigated immune responses to 2 vaccines in patients with CKD to identify predictors of immunological responsiveness.

METHODS

Individuals >65 years old, with or without nondialysis CKD (n = 36 and 29, respectively), were vaccinated with a nonadjuvanted seasonal influenza vaccine (T-dependent) and Pneumovax23 (23-valent pneumococcal polysaccharide [PPV23], T-independent). Humoral responses were measured at baseline, day 28, and 6 months. Lymphocyte subset and plasma cell/blast analyses were performed using flow cytometry. Cytomegalovirus (CMV) serotyping was assessed by enzyme-linked immunosorbent assay.

RESULTS

Only modest responsiveness was observed to both vaccines, independent of CKD status (25% adequate response in controls vs. 12%-18% in the CKD group). Unexpectedly, previous immunization with PPV23 (median 10-year interval) and CMV seropositivity were associated with poor PPV23 responsiveness in both study groups (P < .001 and .003, respectively; multivariable linear regression model). Patients with CKD displayed expanded circulating populations of T helper 2 and regulatory T cells, which were unrelated to vaccine responses. Despite fewer circulating B cells, patients with CKD were able to mount a similar day 7 plasma cell/blast response to controls.

CONCLUSION

Patients with nondialysis CKD can respond similarly to vaccines as age- and sex-matched healthy individuals. CKD patients display an immune signature that is independent of vaccine responsiveness. Prior PPV23 immunization and CMV infection may influence responsiveness to vaccination. Clinical Trials Registration. NCT02535052.

Longevity of SARS-CoV-2 immune responses in hemodialysis patients and protection against reinfection

Patients with end stage kidney disease receiving in-center hemodialysis (ICHD) have had high rates of SARS-CoV-2 infection. Following infection, patients receiving ICHD frequently develop circulating antibodies to SARS-CoV-2, even with asymptomatic infection. Here, we investigated the durability and functionality of the immune responses to SARS-CoV-2 infection in patients receiving ICHD. Three hundred and fifty-six such patients were longitudinally screened for SARS-CoV-2 antibodies and underwent routine PCR-testing for symptomatic and asymptomatic infection. Patients were regularly screened for nucleocapsid protein (anti-NP) and receptor binding domain (anti-RBD) antibodies, and those who became seronegative at six months were screened for SARS-CoV-2 specific T-cell responses. One hundred and twenty-nine (36.2%) patients had detectable antibody to anti-NP at time zero, of whom 127 also had detectable anti-RBD. Significantly, at six months, 71/111 (64.0%) and 99/116 (85.3%) remained anti-NP and anti-RBD seropositive, respectively. For patients who retained antibody, both anti-NP and anti-RBD levels were reduced significantly after six months. Eleven patients who were anti-NP seropositive at time zero, had no detectable antibody at six months; of whom eight were found to have SARS-CoV-2 antigen specific T cell responses. Independent of antibody status at six months, patients with baseline positive SARS-CoV-2 serology were significantly less likely to have PCR confirmed infection over the following six months. Thus, patients receiving ICHD mount durable immune responses six months post SARS-CoV-2 infection, with fewer than 3% of patients showing no evidence of humoral or cellular immunity.