Faculty Bibliography

Objective: To examine antibody and T-cell responses to mRNAplatform COVID-19 vaccines in Ocrelizumab-treated MS patients over a 12-month period. Introduction: B-cell depletion with Ocrelizumab attenuates humoral responses to vaccines. The kinetics of humoral and cellular immune responses to COVID-19 vaccines in B-cell depleted MS patients has not been reported.
Method(s): VIOLA (NCT04843774) is an open-label, observational study enrolling 60 MS patients on Ocrelizumab from NYU and Rocky Mountain at the University of Colorado MS Centers. First vaccine dose occurred >=2 weeks after ocrelizumab infusion; second-dose >=8 weeks before the next infusion. Antibody responses to SARS-COV-2 spike proteins were assessed with Elecsys Anti-SARS-CoV-2 (Roche Diagnostics) and multiplex bead-based immunoassays. T-cell responses to SARS-CoV-2 Spike protein were assessed with IFNgamma ELISpot (Invitrogen) and TruCulture (Myriad RBM) and high-dimensional immunophenotyping. Samples are collected pre-vaccination and at 4, 12, 24, and 48-weeks post-vaccination.
Result(s): As of 7/15/2021, 52 subjects have been enrolled (39.7+/-10.0 years; 73% female; 47% non-white), of whom 47 were fully vaccinated (85% Pfizer, 15% Moderna). Anti-spike RBD antibody (Elecsys Anti-SARS-CoV-2) were available for pre- and post-vaccine timepoints for 15 patients. Pre-vaccine, 1/15 (7%) patients had detectable titers, while at 4-weeks postvaccine, 10/15 (66%) patients had detectible titers (mean for positives: 1189 U/ml; 5 patients had positive titers <25 U/ml). T-cell activation based on induced IFNgamma secretion (TruCulture) at baseline and 4-week post-vaccine timepoints were available for 13 patients, of whom 12 (92%) were increased (mean pre-vaccine: 24 pg/ml; mean post-vaccine: 366 pg/ml, two-tailed t-test, p=0.0032).
Conclusion(s): This prospective study of humoral and cellular immune responses to COVID-19 vaccines in Ocrelizumab-treated patients will generate data to help guide management of MS patients on anti-CD20 therapies. Early results suggest that 4-weeks post-vaccination nearly all Ocrelizumab-treated MS patients develop T-cell immunity and two-thirds showed evidence of humoral response. Additional 4-week and 12-week post-vaccination data will be presented

Objective: To compare humoral and T-cell responses to COVID- 19 vaccines in 400 MS patients who were on Ocrelizumab ('OCR') v. other disease-modifying therapies ('non-OCR') at the time of vaccination. Introduction: Peripheral B-cell depletion with anti-CD20 therapies attenuates humoral responses to vaccines. Whether immune responses to COVID-19 vaccines differ between B-cell depleted and non-B cell depleted MS patients is not known.
Method(s): Consecutive MS patients from NYU MS Care Center were invited to participate if they completed COVID-19 vaccination >=6 weeks previously. Immune testing included anti-spike RBD antibody (Elecsys Anti-SARS-CoV-2) (Roche Diagnostics); multiplex bead-based immunoassays of antibody-responses to SARS-COV-2 spike proteins; T-cell responses to SARS-CoV-2 Spike protein using IFNgamma enzyme-linked immune-absorbent spot (Invitrogen) and TruCulture (Myriad RBM) assays; high dimensional immunophenotyping; and live virus immunofluorescencebased microneutralization assay.
Result(s): As of 7/15/2021, 105 MS subjects were enrolled (mean age: 40.5 years; 76% female; 41% non-white; 38% on OCR; 12% with prior COVID-19 infection). 95% were fully vaccinated with mRNA vaccines (Pfizer/Moderna); 5% - with adenovirus-based vaccine (Johnson&Johnson). Median time from sample collection to last vaccine was 79 days. Positive Elecsys Anti-SARS-CoV-2 Ab titers post-vaccine were detected in 11/37 (30%) in OCR (mean level: 702 U/mL among seropositives) and 54/54 (100%) patients in non-OCR (mean level: 2310 U/mL; p<0.0001). Positive response by multiplex assay (threshold of 'positive' defined as 2 SD below the mean for the non-OCR) were detected in 10/27 (37%) OCR and 29/31 (94%) non-OCR (p<0.00001). T-cell activation based on induced IFNgamma secretion (TruCulture) was detected in 20/25 (80%) OCR and 16/19 (84%) non-OCR patients (p=0.71).
Conclusion(s): Preliminary results suggest robust T-cell immune response to SARS-CoV2 vaccines in approximately 80% of both OCR and non-OCR MS patients. Antibody responses were markedly attenuated in OCR compared to non-OCR group. Updated results will be presented

Maintenance of immune homeostasis involves a synergistic relationship between the host and the microbiome. Canonical interferon (IFN) signaling controls responses to acute microbial infection, through engagement of the STAT1 transcription factor. However, the contribution of tonic levels of IFN to immune homeostasis in the absence of acute infection remains largely unexplored. We report that STAT1 KO mice spontaneously developed an inflammatory disease marked by myeloid hyperplasia and splenic accumulation of hematopoietic stem cells. Moreover, these animals developed inflammatory bowel disease. Profiling gut bacteria revealed a profound dysbiosis in the absence of tonic IFN signaling, which triggered expansion of T_H17 cells and loss of splenic T_reg cells. Reduction of bacterial load by antibiotic treatment averted the T_H17 bias and blocking IL17 signaling prevented myeloid expansion and splenic stem cell accumulation. Thus, tonic IFNs regulate gut microbial ecology, which is crucial for maintaining physiologic immune homeostasis and preventing inflammation.

Antibodies to double-stranded DNA (dsDNA) are prevalent in systemic lupus erythematosus (SLE), particularly in patients with lupus nephritis, yet the nature and regulation of antigenic cell-free DNA (cfDNA) are poorly understood. Null mutations in the secreted DNase DNASE1L3 cause human monogenic SLE with anti-dsDNA autoreactivity. We report that >50% of sporadic SLE patients with nephritis manifested reduced DNASE1L3 activity in circulation, which was associated with neutralizing autoantibodies to DNASE1L3. These patients had normal total plasma cfDNA levels but showed accumulation of cfDNA in circulating microparticles. Microparticle-associated cfDNA contained a higher fraction of longer polynucleosomal cfDNA fragments, which bound autoantibodies with higher affinity than mononucleosomal fragments. Autoantibodies to DNASE1L3-sensitive antigens on microparticles were prevalent in SLE nephritis patients and correlated with the accumulation of cfDNA in microparticles and with disease severity. DNASE1L3-sensitive antigens included DNA-associated proteins such as HMGB1. Our results reveal autoantibody-mediated impairment of DNASE1L3 activity as a common nongenetic mechanism facilitating anti-dsDNA autoreactivity in patients with severe sporadic SLE.

The report from El-Gabalawy and coworkers represents an important chapter in their studies of rheumatoid arthritis (RA) in a unique First Nation (FN) patient cohort and their at-risk first-degree relatives (FDR)(1). These members of the Cree and Chippewa tribes in rural Manitoba Canada share racial/ethnic (and presumed genetic) features distinct from other RA cohorts. Here, the investigators show that during the preclinical phase, when patients were asymptomatic, these FN FDR express serum RA disease-associated anti-citrullinated protein antibodies (ACPA), anti-carbamylated protein antibodies and rheumatoid factors (RFs).

Staphylococcus aureus, a common cause of serious and often fatal infections, is well-armed with secreted factors that disarm host immune defenses. Highly expressed in vivo during infection, Staphylococcal protein A (SpA) is reported to also contribute to nasal colonization that can be a prelude to invasive infection. Co-evolution with the host immune system has provided SpA with an Fc-antibody binding site, and a Fab-binding site responsible for non-immune superantigen interactions via germline-encoded surfaces expressed on many human BCRs. We wondered whether the recurrent exposures to S. aureus commonly experienced by adults, result in the accumulation of memory B-cell responses to other determinants on SpA. We therefore isolated SpA-specific class-switched memory B cells, and characterized their encoding VH : VL antibody genes. In SpA-reactive memory B cells, we confirmed a striking bias in usage for VH genes, which retain the surface that mediates the SpA-superantigen interaction. We postulate these interactions reflect co-evolution of the host immune system and SpA, which during infection results in immune recruitment of an extraordinarily high prevalence of B cells in the repertoire that subverts the augmentation of protective defenses. Herein, we provide the first evidence that human memory responses are supplemented by B-cell clones, and circulating-antibodies, that bind to SpA determinants independent of the non-immune Fc- and Fab-binding sites. In parallel, we demonstrate that healthy individuals, and patients recovering from S. aureus infection, both have circulating antibodies with these conventional binding specificities. These findings rationalize the potential utility of incorporating specially engineered SpA proteins into a protective vaccine.

Staphylococcus aureus infection is a major public health threat in part due to the spread of antibiotic resistance and repeated failures to develop a protective vaccine. Infection is associated with production of virulence factors that include exotoxins that attack host barriers and cellular defenses, such as the leukocidin (Luk) family of bicomponent pore-forming toxins. To investigate the structural basis of antibody-mediated functional inactivation of Luk toxins, we generated a panel of murine monoclonal antibodies (MAbs) that neutralize host cell killing by the γ-hemolysin HlgCB. By biopanning these MAbs against a phage-display library of random Luk peptide fragments, we identified a small subregion within the rim domain of HlgC as the epitope for all the MAbs. Within the native holotoxin, this subregion folds into a conserved β-hairpin structure, with exposed key residues, His252 and Tyr253, required for antibody binding. On the basis of the phage-display results and molecular modeling, a 15-amino-acid synthetic peptide representing the minimal epitope on HlgC (HlgC241-255) was designed, and preincubation with this peptide blocked antibody-mediated HIgCB neutralization. Immunization of mice with HlgC241-255 or the homologous LukS246-260 subregion peptide elicited serum antibodies that specifically recognized the native holotoxin subunits. Furthermore, serum IgG from patients who were convalescent for invasive S. aureus infection showed neutralization of HlgCB toxin activity ex vivo, which recognized the immunodominant HlgC241-255 peptide and was dependent on His252 and Tyr253 residues. We have thus validated an efficient, rapid, and scalable experimental workflow for identification of immunodominant and immunogenic leukotoxin-neutralizing B-cell epitopes that can be exploited for new S. aureus-protective vaccines and immunotherapies.

Unbiased identification of individual, immunogenic B-cell epitopes in major antigens of a pathogen remains a technology challenge for vaccine discovery. We therefore developed a platform for rapid phage display screening of deep recombinant libraries consisting of as little as a single major pathogen antigen. Using the bi-component pore-forming leukocidin (Luks) exotoxins of the major pathogen Staphylococcus aureus (Sa) as a prototype, we randomly fragmented and separately ligated the Hemolysin gamma A (HlgA) and LukS genes into a custom-built, phage-display system, termed pComb-Opti8. Deep sequence analysis of barcoded amplimers of the HlgA and LukS gene fragment libraries demonstrated that biopannng against a cross-reactive anti-Luk mAb recovered convergent molecular clones with short overlapping homologous sequences. We thereby identified an 11-amino acid sequence that is highly conserved in four Luk toxin subunits, and is ubiquitous in representation within Sa clinical isolates. The isolated 11-amino acid peptide probe was predicted to retain the native 3D-conformation seen within the Luk holotoxin. Indeed, this peptide was recognized by the selecting anti-Luk mAb, and using mutated peptides we showed that a particular amino acid side-chain was essential for these interactions. Furthermore, murine immunization with this peptide elicited IgG-responses that were highly reactive with both the autologous synthetic peptide and the full-length Luk toxin homologues. Thus, using a gene fragment, phage-display based pipeline, we have identified and validated immunogenic B-cell epitopes that are cross-reactive between members of the pore-forming leukocidin family. This approach could be harnessed to identify novel epitopes for a much needed Sa-protective subunit vaccine.