Quantitative evaluation of adalimumab and anti-adalimumab antibodies in sera using a surface plasmon resonance biosensor.

OBJECTIVES: Monitoring of therapeutic antibody adalimumab (ADL) and of anti-adalimumab antibodies (AAA) in autoimmune diseases' patient sera has achieved increased attention since several studies showed a correlation between AAA levels and treatment failure. We evaluated a new surface plasmon resonance (SPR)-based method that, with slight changes in the analysis condition and in the ligand immobilized on the chip surface, allows to monitor both AAA and ADL. This new label-free method does not require sample pretreatments, and it is fully automated, only requiring the preparation of the chip, which can be used for multiple analysis, and the preparation of the sample sets. DESIGN & METHODS: Sera from ADL-treated patients (n = 47) and controls (n = 13) were included in this study. Quantitative analysis of AAA and ADL were performed separately using a new SPR-biosensor, and a commercially available ELISA kit. Agreement was defined by overall, positive and negative agreement. Wilson Score was used to calculate confidence intervals (CI) on binomial probability and Spearman's rho and Bland-Altman test were used to assess correlations. RESULTS: ; ELISA and SPR-based assay were able to identify circulating AAA in ADL-treated patients, with the percentage of positivity varying among the methods, with an overall agreement of 79%. AAA were detected in 18 (38%) out of the 47 treated patients by the ELISA whereas SPR-based assay detected 10 (21%) out of 47 samples. CONCLUSIONS: Real-time label free SPR-based protocol for both AAA and ADL quantification has been set-up. Although quantitative differences were observed when compared with ELISA, the agreement among methodologies was high, particularly for ADL quantification within the therapeutic window of the drug.

The B-cells paradigm in Systemic Sclerosis: an update on pathophysiology and B-cell targeted therapies.

Systemic sclerosis is considered a rare autoimmune disease in which there are alterations of both the innate and adaptive immune response resulting in the production of autoantibodies. Abnormalities of the immune system compromise the normal function of blood vessels leading to a vasculopathy manifested by Raynaud's phenomenon, an early sign of systemic sclerosis. As a consequence of this reactive picture, the disease can evolve leading to tissue fibrosis. Several systemic sclerosis-specific autoantibodies are currently known and are associated with specific clinical manifestations and prognosis. Although the pathogenetic role of these autoantibodies is still unclear, their production by B cells and plasma cells suggests the importance of these cells in the development of systemic sclerosis. This review narratively examines B cell dysfunctions and their role in the pathogenesis of systemic sclerosis and discusses B cell-targeted therapies currently used or potentially useful for the management of end-organ complications.

Effect of antimetabolite regimen on cellular and humoral immune response to SARS-COV-2 vaccination in solid organ transplant recipients.

OBJECTIVE: Novel mRNA-based vaccines have been proven to be powerful tools in combating the global pandemic caused by SARS-CoV-2 protecting individuals, especially the immunocompromised, from COVID-19. Still, it remains largely unknown how solid organ transplant and different immunosuppressive medications affect development of vaccine-induced immunity. METHODS: In this work, we monitored humoral and cellular memory responses after mRNA SARS-CoV-2 two-doses and booster doses vaccination in cystic fibrosis lung transplanted patients (CFT) and compared them with both cystic fibrosis patients without lung transplant (CF) and with kidney transplant recipients (KT). In particular, we investigated the effects of immunosuppressive regimens on immune memory to SARS-CoV-2 after mRNA SARS-CoV-2 vaccine in transplanted patients. RESULTS: Our results showed that immunocompromised transplanted patients displayed a weak cellular and humoral memory to SARS-CoV-2 mRNA vaccination. In addition, obtained data clearly demonstrate that immunosuppressive therapy regimen including antimetabolites, further reduces patients' ability to respond to vaccination at both humoral and cell-mediated level. Notably, patient treated with antimetabolites showed a lower humoral and cellular response also after a booster dose vaccination. CONCLUSION: These results, even if obtained on a small patient's cohort, question whether immunocompromised patients need interventions to improve vaccine SARS-CoV-2 mRNA vaccine response such as additional jab or modulation of immunosuppressive therapy.

HPLC and flow cytometry combined approach for HbF analysis in fetomaternal haemorrhage evaluation.

Introduction: Recently, a flow cytometric (FC) based test has been developed for detection of circulating fetal cells to replace the less accurate and reproducible Kleihauer-Betke test.FC test is easier to perform, it can distinguish the origin of fetal cells, but it is expensive and available in highly specialized laboratories. We evaluated the introduction of high-performance liquid chromatography (HPLC) approach as initial screening to identify patients who need an additional FC test to better discriminate the nature of haemoglobin-F (HbF) positive cells. Methods: Blood samples from 130 pregnant women suspected to have fetomaternal haemorrhage were analysed with HPLC and FC methods. The cut-off for HbF HPLC concentration was calculated. Statistical analyses for the evaluation of HPLC as a screening method were performed. The positivity cut-off of HbF to be used as decision-making value to continue the investigation was calculated. Results: An excellent agreement (R2 > 0.90) was observed between the percentage of HbF obtained by HPLC and the percentage of fetal cells detected by FC. Results obtained from each assay were compared to define the HPLC threshold below which it is not necessary to continue the investigations, confirming the maternal nature of the HbF positive cells detected. Our study demonstrated that a cut-off of 1.0 % HbF obtained by HPLC was associated with the lowest rate of false negative results in our patient cohort. Conclusions: This study provides a new FMH investigation approach that possibly leads to a reduction in times and costs of the analysis.

Utility of bronchoalveolar lavage for COVID-19: a perspective from the Dragon consortium.

Diagnosing COVID-19 and treating its complications remains a challenge. This review reflects the perspective of some of the Dragon (IMI 2-call 21, #101005122) research consortium collaborators on the utility of bronchoalveolar lavage (BAL) in COVID-19. BAL has been proposed as a potentially useful diagnostic tool to increase COVID-19 diagnosis sensitivity. In both critically ill and non-critically ill COVID-19 patients, BAL has a relevant role in detecting other infections or supporting alternative diagnoses and can change management decisions in up to two-thirds of patients. BAL is used to guide steroid and immunosuppressive treatment and to narrow or discontinue antibiotic treatment, reducing the use of unnecessary broad antibiotics. Moreover, cellular analysis and novel multi-omics techniques on BAL are of critical importance for understanding the microenvironment and interaction between epithelial cells and immunity, revealing novel potential prognostic and therapeutic targets. The BAL technique has been described as safe for both patients and healthcare workers in more than a thousand procedures reported to date in the literature. Based on these preliminary studies, we recognize that BAL is a feasible procedure in COVID-19 known or suspected cases, useful to properly guide patient management, and has great potential for research.

Disseminated nocardiosis and anti-GM-CSF antibodies.

Infections that are unusually severe or caused by opportunistic pathogens are a hallmark of primary immunodeficiency (PID). Anti-cytokine autoantibodies (ACA) are an emerging cause of acquired immunodeficiency mimicking PID. Nocardia spp. are Gram-positive bacteria generally inducing disseminated infections in immunocompromised patients, but seldom also occurring in apparently immunocompetent hosts. Anti-GM-CSF autoantibodies are associated with autoimmune pulmonary alveolar proteinosis (PAP). In those patients, an increased incidence of disseminated nocardiosis and cryptococcosis has been observed. It is unclear whether the PAP or the autoantibodies predispose to the infection. We report an apparently immunocompetent woman presenting with disseminated nocardiosis without any evidence of PAP. Clinical data and radiological images were retrospectively collected. Lymphocyte populations were analyzed by flow cytometry. Anti-GM-CSF autoantibodies were measured by ELISA. A 55-year-old otherwise healthy woman presented with cerebral and pulmonary abscesses. Personal and familial history of infections or autoimmunity were negative. After extensive examinations, a final diagnosis of disseminated nocardiosis was made. Immunologic investigations including neutrophilic function and IFN-γ/IL-12 circuitry failed to identify a PID. Whole-exome sequencing did not find pathogenic variants associated with immunodeficiency. Serum anti-GM-CSF autoantibodies were positive. There were no clinical or instrumental signs of PAP. Trimethoprim-sulfamethoxazole and imipenem were administered, with progressive improvement and recovery of the infectious complication. We identified anti-GM-CSF autoantibodies as the cause of disseminated nocardiosis in a previously healthy and apparently immunocompetent adult. This case emphasizes the importance of including ACA in the differential diagnosis of PID, especially in previously healthy adults. Importantly, anti-GM-CSF autoantibodies can present with disseminated nocardiosis without PAP.

Optimization of the diagnosis and characterization of gibberellin-regulated protein sensitization: An Italian cohort study.

BACKGROUND: Pru p 7 was the first gibberellin-regulated protein (GRP) to be identified as a food allergen as the basis of a pollen food allergy syndrome. OBJECTIVE: To clinically and biologically characterize a group of patients with suspected allergy to Pru p 7 to optimize the diagnostic workup of GRP sensitization. METHODS: Allergy to Pru p 7 was suspected in the presence of a systemic allergic reaction to plant food, positive skin prick test results for cypress pollen and lipid-transfer protein-enriched peach extract, and absence of Pru p 3-specific immunoglobulin E. Controls were patients with food allergies, patients sensitized to Pru p 3, and patients with cypress allergy without food allergy. Diagnostic workup included skin tests, basophil activation test, Western blot, and single and multiplex assays. RESULTS: In total, 23 patients and 14 controls were enrolled. The most implicated food was peach (91.3%). Approximately 70% of patients reacted to multiple foods. Mueller 4 reactions were 8.7%. In 26.1% of cases, a cofactor triggered the reaction. The basophil activation test results were positive for rPru p 7 in 87% of the patients. Specific immunoglobulin E to Pru p 7 was detected in 95.7% by singleplex and in 73.9% by multiplex assays in patients with suspected allergies; 73.9% of them also reacted to cypress pollen GRP (Cup s 7) in Western blot analysis. CONCLUSION: Patients with Pru p 7-Cup s 7 allergy in our cohort confirm a mild-to-severe clinical syndrome characterized by pollen and food allergy. The diagnosis may benefit from the proposed selection criteria that can be used as preliminary steps to further characterize the cross-reactive GRP sensitization.

Effect of age and treatment on predictive value of measurable residual disease: implications for clinical management of adult patients with acute myeloid leukemia.

Measurable residual disease (MRD) is a powerful predictor of outcome in acute myeloid leukemia. In the early phases of treatment, MRD refines initial disease risk stratification and is used for the allocation to allogeneic transplant. Despite its well-established role, a relatively high fraction of patients eventually relapses albeit achieving MRDneg status. The aim of this work was to assess specifically the influence of baseline features and treatment intensity on the predictive value of an MRDneg status, particularly focusing on MRD2, measured after two consecutive chemotherapy cycles. Among baseline features, younger MRD2neg patients (<55 years) had a significantly longer disease-free survival (median not reached) compared to their older counterparts (median 25.0 months, P=0.013, hazard ratio=2.08). Treatment intensity, specifically the delivery of a high dose of cytarabine in induction or first consolidation, apparently had a pejorative effect on the outcome of MRD2neg patients compared to standard dose (P=0.048, hazard ratio=1.80), a finding also confirmed by the analysis of data extracted from the literature. The combination of age and treatment intensity allowed us to identify categories of patients, among those who reached a MRD2neg status, characterized by significantly different disease-free survival rate. Our data showed that variables such as age and intensity of treatment administered can influence the predictive value of MRD in patients with acute myeloid leukemia. In addition to underscoring the need for further improvement of MRD analysis, these findings call for a reasoned application of MRD data, as currently available, to modulate consolidation therapy on adequately estimated relapse rates.

T lymphocytes-related cell network in the pathogenesis of juvenile idiopathic arthritis: a key point for personalized treatment.

PURPOSE OF REVIEW: Juvenile idiopathic arthritis (JIA) is a heterogeneous group of arthritis of unknown origin occurring in children under 16 years of age and persisting for at least 6 weeks. Given that JIA is an inflammatory disorder, treatment strategies, including also biologicals, are focused on suppressing excessive inflammation. The finding that different patients display different responses to biological drugs supports the concept that different pathogenic mechanisms can exist in JIA, with specific cellular and molecular mechanisms driving inflammation in each patient. The aim of this review is to highlight the most recent advances in understanding the role of immune cells in JIA pathogenesis. RECENT FINDINGS: This review encompasses the role of the different cell subsets involved in sustaining inflammation in JIA, with a particular emphasis on T cells, as they orchestrate both innate and adaptive auto-reactive immunity in affected joints. SUMMARY: The characterization of the cellular and molecular pathways supporting inflammation will be crucial to design novel therapeutic approaches in the context of personalized medicine.

Bendamustine impairs humoral but not cellular immunity to SARS-CoV-2 vaccination in rituximab-treated B-cell lymphoma-affected patients.

Background: Patients with B-cell lymphoma are a fragile category of subjects, particularly exposed to infections and characterized by an impaired vaccination response due to the disease itself and, even more, to the chemotherapy regimen. For this reason, extensive knowledge of the immune response status of these subjects is of fundamental importance to obtain possible indications for a tailored immunization strategy. Methods: We enrolled two cohorts of patients with B-cell lymphoma under rituximab treatment or 3-24 months after treatment. In all patients, we evaluated both humoral and cellular immunological memory toward SARS-CoV-2, after standard vaccination and upon one booster dose. Results: We observed no Spike-specific IgG production in patients (n = 25) under anti-CD20 treatment, whereas patients (n = 16) vaccinated after the completion of chemotherapy showed a higher humoral response. Evaluating SARS-CoV-2-specific T-cell response, we found that patients in both cohorts had developed robust cellular immunity after vaccination. Of the 21 patients (51%) that experienced a breakthrough SARS-CoV-2 infection, only six patients developed severe disease. Interestingly, these six patients had all been treated with rituximab plus bendamustine. Notably, we observed that Spike-specific IgG levels in patients treated with rituximab plus bendamustine were absent or lower compared with those in patients treated with rituximab plus other chemotherapy, whereas Spike-specific T-cell response was not different based on chemotherapy regiment. Discussion: Our results show that, in patients with B-cell lymphoma under rituximab therapy, anti-SARS-CoV-2 mRNA vaccination induces a weak or absent humoral response but a consistent T-cell response. In addition, chemotherapy regimens with bendamustine further reduce patients' ability to mount a Spike-specific humoral response even after a long time period from chemotherapy discontinuation. These results provide evidence that different chemotherapeutics display different immunosuppressive properties that could be taken in to account in the choice of the right drug regimen for the right patient. Moreover, they question whether immunocompromised patients, particularly those treated with bendamustine, need interventions to improve vaccine-induced immune response.

Polyploid tubular cells initiate a TGF-ß1 controlled loop that sustains polyploidization and fibrosis after acute kidney injury.

Polyploidization of tubular cells (TC) is triggered by acute kidney injury (AKI) to allow survival in the early phase after AKI, but in the long run promotes fibrosis and AKI-chronic kidney disease (CKD) transition. The molecular mechanism governing the link between polyploid TC and kidney fibrosis remains to be clarified. In this study, we demonstrate that immediately after AKI, expression of cell cycle markers mostly identifies a population of DNA-damaged polyploid TC. Using transgenic mouse models and single-cell RNA sequencing we show that, unlike diploid TC, polyploid TC accumulate DNA damage and survive, eventually resting in the G1 phase of the cell cycle. In vivo and in vitro single-cell RNA sequencing along with sorting of polyploid TC shows that these cells acquire a profibrotic phenotype culminating in transforming growth factor (TGF)-ß1 expression and that TGF-ß1 directly promotes polyploidization. This demonstrates that TC polyploidization is a self-sustained mechanism. Interactome analysis by single-cell RNA sequencing revealed that TGF-ß1 signaling fosters a reciprocal activation loop among polyploid TC, macrophages, and fibroblasts to sustain kidney fibrosis and promote CKD progression. Collectively, this study contributes to the ongoing revision of the paradigm of kidney tubule response to AKI, supporting the existence of a tubulointerstitial cross talk mediated by TGF-ß1 signaling produced by polyploid TC following DNA damage.NEW & NOTEWORTHY Polyploidization in tubular epithelial cells has been neglected until recently. Here, we showed that polyploidization is a self-sustained mechanism that plays an important role during chronic kidney disease development, proving the existence of a cross talk between infiltrating cells and polyploid tubular cells. This study contributes to the ongoing revision of kidney adaptation to injury, posing polyploid tubular cells at the center of the process.

APP and Bace1: Differential effect of cholesterol enrichment on processing and plasma membrane mobility.

High cholesterol levels are a risk factor for the development of Alzheimer's disease. Experiments investigating the influence of cholesterol on the proteolytic processing of the amyloid precursor protein (APP) by the ß-secretase Bace1 and on their proximity in cells have led to conflicting results. By using a fluorescence bioassay coupled with flow cytometry we found a direct correlation between the increase in membrane cholesterol amount and the degree of APP shedding in living human neuroblastoma cells. Analogue results were obtained for cells overexpressing an APP mutant that cannot be processed by α-secretase, highlighting the major influence of cholesterol enrichment on the cleavage of APP carried out by Bace1. By contrast, the cholesterol content was not correlated with changes in membrane dynamics of APP and Bace1 analyzed with single molecule tracking, indicating that the effect of cholesterol enrichment on APP processing by Bace1 is uncoupled from changes in their lateral diffusion.

Clonally expanded PD-1-expressing T cells are enriched in synovial fluid of juvenile idiopathic arthritis patients.

Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic condition in childhood. The disease etiology remains largely unknown; however, a key role in JIA pathogenesis is surely mediated by T cells. T-lymphocytes activity is controlled via signals, known as immune checkpoints. Delivering an inhibitory signal or blocking a stimulatory signal to achieve immune suppression is critical in autoimmune diseases. However, the role of immune checkpoints in chronic inflammation and autoimmunity must still be deciphered. In this study, we investigated at the single-cell level the feature of T cells in JIA chronic inflammation, both at the transcriptome level via single-cell RNA sequencing and at the protein level by flow cytometry. We found that despite the heterogeneity in the composition of synovial CD4+ and CD8+ T cells, those characterized by PD-1 expression were clonally expanded tissue-resident memory (Trm)-like cells and displayed the highest proinflammatory capacity, suggesting their active contribution in sustaining chronic inflammation in situ. Our data support the concept that novel therapeutic strategies targeting PD-1 may be effective in the treatment of JIA. With this approach, it may become possible to target overactive T cells regardless of their cytokine production profile.

Musculin does not modulate the disease course of Experimental Autoimmune Encephalomyelitis and DSS colitis.

Previous evidences show that Musculin (Msc), a repressor member of basic helix-loop-helix transcription factors, is responsible in vitro for the low responsiveness of human Th17 cells to the growth factor IL-2, providing an explanation for Th17 cells rarity in inflammatory tissue. However, how and to what extent Musculin gene can regulate the immune response in vivo in an inflammatory context is still unknown. Here, exploiting two animal models of inflammatory diseases, the Experimental Autoimmune Encephalomyelitis (EAE) and the dextran sodium sulfate (DSS)-induced colitis, we evaluated the effect of Musculin gene knock-out on clinical course, performing also a deep immune phenotypical analysis on T cells compartment and an extended microbiota analysis in colitis-sick mice. We found that, at least during the early phase, Musculin gene has a very marginal role in modulating both the diseases. Indeed, the clinical course and the histological analysis showed no differences between wild type and Msc knock-out mice, whereas immune system appeared to give rise to a regulatory milieu in lymph nodes of EAE mice and in the spleen of DSS colitis-sick mice. Moreover, in the microbiota analysis, we found irrelevant differences between wild type and Musculin knock-out colitis-sick mice, with a similar bacterial strains' frequency and diversity after the DSS treatment. This work strengthened the idea of a negligible Msc gene involvement in these models.

Effectiveness of tocilizumab in hospitalized moderate-to-severe COVID-19 patients: a real-life study.

BACKGROUND: To assess the clinical effectiveness of Tocilizumab (TCZ) in moderate-to-severe hospitalized COVID-19 patients and factors associated with clinical response. METHODS: Five hundred eight inpatients with moderate-to-severe SARS-CoV-2 infection were enrolled. TCZ effect in addition to standard medical therapy was evaluated in terms of death during hospital stay. Unadjusted and adjusted risk of mortality for TCZ treated patients versus TCZ untreated ones was estimated using robust Cox regression model. We considered the combination of TCZ and ICU as time-dependent exposure and created a model using duplication method to assess the TCZ effect in very severe COVID-19 patients. RESULTS: TCZ reduced death during hospital stay in the unadjusted model (HR 0.54, 95%CI 0.33-0.88) and also in the adjusted model, although with loss of statistical significance (HR 0.72, 0.43-1.20). Better effectiveness was observed in patients with low SpO2/FiO2 ratio (HR 0.35, 0.21-0.61 vs. 1.61, 0.54-4.82, P<0.05), and, without statistical significance, in patients with high CRP (HR 0.51, 0.30-0.87 vs. 0.41, 0.12-1.37, P=NS) and high IL-6 (HR 0.49, 0.29-0.82 vs. 1.00, 0.28-3.55, P=NS). TCZ was effective in patients not admitted to ICU, both in the unadjusted (HR 0.33, 0.14-0.74) and in the adjusted (HR 0.39, 0.17-0.91) model but no benefit was observed in critical ICU-admitted patients both in the unadjusted (HR 0.66, 0.37-1.15) and in the adjusted model (HR 0.95, 0.54-1.68). CONCLUSIONS: Our real-life study suggests clinical efficacy of TCZ in moderate-to-severe COVID-19 patients but not in end-stage disease. Thus, to enhance TCZ effectiveness, patients should be selected before grave compromise of clinical conditions.

Disease correlates and clinical relevance of hereditary α-tryptasemia in patients with systemic mastocytosis.

BACKGROUND: Systemic mastocytosis (SM) encompasses a heterogeneous group of clonal disorders characterized by abnormal expansion of mast cells (MCs). Beyond KIT and other genes recurrently mutated in myeloid neoplasms, several genetic variants have been described as predisposing to the development of the disease and influencing its clinical phenotype. Increased copy number variants of the TPSAB1 gene were identified as a cause of nonclonal elevated tryptasemia and defined as hereditary α-tryptasemia (HαT). Moreover, HαT is enriched in patients with SM, where it can affect the incidence of mediator-related symptoms. OBJECTIVE: In a multicenter data set of 444 patients with MC disorders, we aimed to investigate the clinical correlates of germline TPSAB1 copy number gains. METHODS: Droplet digital PCR was performed in all cases to ascertain the presence of HαT. Clinical history along with blood values and bone marrow examination were analyzed. RESULTS: We confirmed a higher incidence of HαT+ cases (n = 59, 13.3%) in patients diagnosed with mastocytosis with respect to the general population (approximately 5%). HαT+ patients were characterized by a lower MC-associated disease burden and higher levels of tryptase. Several disease variables were coherent with this pattern, from bone marrow MC infiltration to MC-related histopathologic traits, which also accounted for a significantly higher incidence of clonal MC activation syndrome in HαT+ (10.2%) compared to HαT- (3.4%, P = .029) patients. We also confirmed that HαT+ carriers had a significantly higher frequency of anaphylaxis, without relevant differences for other clinical manifestations. CONCLUSION: These findings on a large patient series support and extend previous data, and suggest that knowledge of HαT status may be useful for personalized management of patients with SM.

Fourth Dose of mRNA COVID-19 Vaccine Transiently Reactivates Spike-Specific Immunological Memory in People Living with HIV (PLWH).

Background: People Living With HIV (PLWH), with advanced disease, lower CD4+ T cell counts or an unsuppressed HIV viral load can have a suboptimal vaccine response. For this reason, in the current COVID-19 pandemic, they represent a prioritized population for the SARS-CoV-2 fourth (or second booster) vaccine dose. This work aims to investigate the effects of a second booster on the reactivation of the spike-specific humoral and cell-mediated immune responses in PLWH. Methods: A total of eight PLWH, who received a fourth dose of the original mRNA vaccines were enrolled. They were evaluated before and then 7 days, 1 month and 2 months after the injection. The humoral response was assessed via a chemiluminescent immunoassay. Immunophenotyping and the functional evaluation of the SARS-CoV-2-specific cellular immune responses were performed via flow cytometry. Results: Anti-spike IgG levels were above the cut-off value for all subjects at all timepoints. The spike-specific CD4+ T cell response was reactivated one week after the fourth vaccine dose, and on average declined at two months post-vaccination. A similar trend was observed for the spike-specific B cells. A low percentage of spike-specific CD4+ T cells was activated by the B.1.1.529 BA.1 Omicron-spike mutated peptides, and the majority of these cells were reactive to the conserved portions of the spike protein. Similarly, the majority of the spike-specific memory B cells were able to bind both Wuhan and Omicron-spike entire protein. Conclusions: Spike-specific adaptive immune responses are transiently reactivated in PLWH following the fourth mRNA vaccine dose. The breadth of the immune responses to the mutated spike protein provides insight on the possible cross-reactivity for the SARS-CoV-2 variants of concern (VOCs).