POS0254 IMMUNE RESPONSE TO SARS-CoV-2 INFECTION IN PATIENTS WITH RHEUMATIC MUSCULOSKELETAL DISEASES: THE MAINSTREAM STUDY

Background

Rheumatic musculoskeletal diseases (RMD) are pathological conditions characterized by an impaired immunological system that is determinant both in the pathogenesis and in the inadequate response to infections. The use of disease-modifying anti-rheumatic drugs (DMARDs), which include conventional synthetic (cs) or biologic and targeted synthetic (b/ts) DMARDs, contribute to compromise immunological reactivity.

Objectives

To analyze the immune response to SARS-CoV-2 in patients with rheumatoid arthritis (RA) or spondyloarthritis (SpA) receiving treatment with DMARDs and to investigate the effect of the different classes of drugs on humoral and cellular response.

Methods

Patients were tested for anti-SARS-CoV-2 IgG, IgM and IgA antibodies to nucleoprotein (N) and receptor-binding domain (RBD) through ELISA and neutralization assays. Then, we performed a flow cytometry analysis of monocytes, NK cells, B and T lymphocytes from PBMCs of serologically positive patients. We also included a cohort of non-RMD individuals recovered from COVID-19 as a reference group of non-immunosuppressed subjects. A first recruitment occurred in May-June 2020 (T1) and a second recruitment, 3-4 months after (T2), allowed to evaluate the persistence of the antibody response over time and to investigate the cellular immune response to SARS-CoV-2 in RMD patients having resolved the infection.

Results

During T1, 358 patients with RA (n=200) or SpA (n=158) were recruited. Mean age was 52.8, 64% were female. All patients were treated with DMARDs, 299 with b/tsDMARDs and 59 received csDMARDs alone. One third was also receiving corticosteroids (CS). At T2, 36 subjects were recruited. We found a seroprevalence rate of 18.4%, which did not significantly differ between RA and SpA groups, and between patients treated with b/ts-DMARD or csDMARDs, either alone or in combination with CS (Table 1). Antibody levels of RMD patients were lower than non-RMD individuals (Figure 1), with CTLA4-Ig-treated patients having the lowest IgG levels. This difference was less marked in symptomatic RMD patients. 72% of seropositive patients elicited neutralizing sera. Despite an overall decrease in anti-RBD and anti-N titers, more than two-third of patients maintained antibodies titers above positivity threshold at T2. Concerning cellular response, we found that CD8+ T-cells frequency was overall comparable between RMD and non-RMD convalescents, and did not differ in b- or cs-DMARD treated ones. Conversely, CD4+ T-cell frequencies were significantly lower in RMD patients, especially those treated with anti-IL6R and CTLA4-Ig. B-cell subpopulations (class-switched, memory, and IgG+ memory B-cells) had sustained frequencies in anti-TNFα treated patients, while they had a trend of reduction in patients treated with anti-IL6R and CTLA4-Ig.

Table 1.

Anti-RBD seroprevalence

TotalSeropositive, n(%)IgM (n)(%)IgG (n)(%)IgA (n)(%)COVID19 symptomatic772532.51924.71722.11722.1COVID19 asymptomatic2814114.6*238.2*134.6 *269.3*RA20036192311.520102713.5SpA15830191912106.31610.1b/ts-DMARD2995518.43511.72483612cs-DMARD591118.6711.9610.2711.9csDMARD+b/tsDMARD1122623.287.187.198a-TNFa1733721.42514.5169.12112.1a-IL-6R35822.9514.3617.1822.9CTLA4-Ig42511.937.112.447.1

*P value < 0,005

Figure 1.

Magnitude of the anti-RBD and anti-N antibody response

Conclusion

Our data provide a comprehensive picture of the humoral and cellular immune responses to SARS-CoV-2 infection in RMD patients. We showed that DMARDs treatments did not alter a successful antibody response to the virus and did not hamper the antibody neutralizing ability. However, the magnitude of antibody response was slightly reduced compared to non-RMD individuals, especially in patients receiving CTLA4-Ig. We did not observe marked differences in the B- and T-cell populations between RMD patients compared to non-RMD individuals. However, in patients receiving anti-TNFα we found a higher relative abundance of effector adaptive population compared to other bDMARDs.

Acknowledgements

The project was co-financed by Lombardy 2014-2020 Operational Program under the European Regional Development Fund.

Disclosure of Interests

None declared

POS0048 SEROPREVALENCE OF ANTI-SARS-COV-2 ANTIBODIES IN RHEUMATIC PATIENTS TREATED WITH BIOLOGICAL AND TARGETED THERAPY LIVING IN LOMBARDY, ITALY (MAINSTREAM PROJECT)

Background:

Emerging observational data have shown that rheumatic patients seem not to be more susceptible to SARS-CoV-2 infection neither to worse outcomes. However, the true prevalence of COVID19 is still unknown due to the high proportion of subclinical infection. In this scenario, measuring the seroprevalence of SARS-CoV-2 may be crucial to improve the knowledge about the impact of COVID19 in rheumatic patients.

Objectives:

To estimate in a COVID19 high-endemic area (Lombardy, Italy) the prevalence of anti-SARS-CoV-2 antibodies in a large cohort of patients with rheumatoid arthritis (RA) or spondyloarthritis (SpA) treated with biologic (b-) or targeted synthetic (ts-) disease modifying drugs (DMARDs).

Methods:

A seroprevalence cross-sectional study was conducted in the period between 4th May and 16th June 2020, including patients with confirmed RA or SpA treated with b- or tsDMARDs. Patients were tested for anti-SARS-CoV-2 IgG, IgM and IgA antibodies against main viral antigens (nucleoprotein [N], spike 1 [S1], receptor-binding domain [RBD]) using ELISA. These data were compared with those observed in the healthy population in the same period and region. Patients also answered a questionnaire on history of symptoms consistent with COVID19, risk factors and comorbidities. Serological response to RBD was evaluated according to symptom severity (asymptomatic, minor, or major [respiratory and fever >37.5°C] symptoms).

Results:

The study population included 300 patients (62% females, mean age 53 years, 20% over 65 years old) diagnosed with RA (56%), psoriatic arthritis (23%), or ankylosing spondylitis (21%), treated with anti-TNF (57%), abatacept (20%), anti-IL6 (11%), or JAK inhibitors (5%). Four patients (1.3%) referred a prior diagnosis of COVID19 defined by nasopharyngeal swab. Immunoglobulin titers were evaluated resulting in 9%, 13.6%, and 13.3% positive patients for IgG, IgM and IgA, respectively (Table 1), with no significant difference to the healthy population. Among seropositive patients, 55.3% were asymptomatic, 16% had minor and 19.6% major symptoms, 7.1% were hospitalized. No deaths or admission to intensive care units occurred. IgM, IgG and IgA titers to RBD were higher in patients with both minor and major symptoms compared with asymptomatic ones (Figure 1). No differences were found between seronegative and seropositive patients in relation to age, sex, rheumatic diagnosis, and treatments with b- or tsDMARDs. A relative lower risk of seropositivity was observed in patients receiving concomitant methotrexate (RR 0.49, 95% CI 0.25-0.94; p 0.04), while an increased risk was associated with obesity (RR 2.33, 95% CI 1.26-3.79; p 0.019) and presence of at least 2 comorbidities (RR 1.94, 95% CI 1.11-3.15; p 0.037). Corticosteroids use was numerically more frequent in seropositive than seronegative patients (18% vs 14%).

Conclusion:

This study confirms that, even in a cohort of rheumatic patients, the spread of SARS-CoV-2 infection is much greater than that observed by capturing only swab-diagnosed COVID19 cases. The underlying rheumatic disease and ongoing therapy with b/ts-DMARDs do not seem to impact SARS-CoV-2 antibody positivity, which conversely seems to be proportional to the intensity of COVID19 symptoms and less frequent in patients receiving concomitant methotrexate. The project was co-financed by Lombardy Region 2014-2020 Regional Operational Programme under the European Regional Development Fund.

Table 1.

Prevalence of specific anti-SARS-CoV-2 antibodies.

AntibodiesPosivite(n)Seroprevalence (%)(95% CI)IgG279%(6.2 – 12.7)IgG anti-N268.6%(5.9 – 12.3)IgG anti-RBD206.6%(4.3 – 10)IgG anti-S1186%(3.8 – 9.2)IgM4113.6%(10.2 – 18)IgM anti-N3511.6%(8.5 – 15.7)IgM anti-RBD258.3%(5.7 – 12)IgA4013.3%(9.9 – 17.6)IgA anti-N3712.3%(9.0 – 16.5)IgA anti-RBD258.3%(5.7 – 12)IgG+IgM237.6%(5.1 – 11.2)IgG+IgM+IgA227.3%(4.9 – 10.5)IgG+IgA248%(5.4 – 11.6)IgG/IgM/IgA5618.6%(14.6 – 23.4)Figure 1.

Antibody levels (S/Co) against SARS-CoV-2 RBD.

Disclosure of Interests:

None declared.

Gene expression profile in Neisseria meningitidis and Neisseria lactamica upon host-cell contact: from basic research to vaccine development

Differential gene regulation in the human pathogen Neisseria meningitidis group B (MenB) and in Neisseria lactamica, a human commensal species, was studied by whole genome microarray after bacterial interaction with epithelial cells. Host-cell contact induced changes in the expression of 347 and 285 genes in MenB and N. lactamica, respectively. Of these, only 167 were common to MenB and N. lactamica, suggesting that a different subset of genes is activated by pathogens and commensals. Change in gene expression was stable over time in N. lactamica, but short-lived in MenB. A large part (greater than 30%) of the regulated genes encoded proteins with unknown function. Among the known genes, those coding for pili, capsule, protein synthesis, nucleotide synthesis, cell wall metabolism, ATP synthesis, and protein folding were down-regulated in MenB. Transporters for iron, chloride and sulfate, some known virulence factors, GAPDH and the entire pathway of selenocysteine biosynthesis were upregulated. Gene expression profiling indicates that approximately 40% of the regulated genes encode putative surface-associated proteins, suggesting that upon cell contact Neisseria undergoes substantial surface remodeling. This was confirmed by FACS analysis of adhering bacteria using mouse sera against a subset of recombinant proteins. Finally, a few surface-located, adhesion-activated antigens were capable of inducing bactericidal antibodies, indicating that microarray technology can be exploited for the identification of new vaccine candidates.

Combined automated PCR cloning, in vitro transcription/translation and two-dimensional electrophoresis for bacterial proteome analysis

The most popular approach for proteomics analysis is based on the combination of two-dimensional gel electrophoresis and mass spectrometry (MS). Although very effective, the method suffers from a number of limitations, the most serious one being the necessity to have expensive and sophisticated instrumentation requiring handling by skilled personnel. Here we propose an alternative approach which may offer some advantages over the current methods, at least for some specific applications. The method is based on two-dimensional gel separation of radiolabeled synthetic proteins derived from transcription/translation reactions of linear polymerase chain reaction amplified genes. The gel is autoradiographed and this is superimposed on the sample gel whose protein spots have to be identified. Matching between autoradiographs and sample gel spots allows immediate protein identification. The method has been validated identifying six proteins from a membrane protein preparation of Neisseria meningitidis MC58 strain. All proteins were correctly identified as judged by confirmation analysis with MS. The approach is particularly useful when a specific subset of proteins needs to be identified in a complex protein mixture.

Emulsion/solvent evaporation as an alternative technique in pellet preparation

Paracetamol/Eudragit RS, paracetamol/ethylcellulose, and paracetamol/cellulose acetate pellets of different drug/polymer ratios (w/w) were prepared by the dissolution/solvent evaporation technique. These pellets were then characterized by particle size distribution analysis, ultraviolet (UV) spectroscopy, differential thermal analysis, and scanning electron microscopy (SEM). Hard gelatin capsules were filled with each particle size fraction of these pellets, and in vitro dissolution studies were performed to verify the capability of each series of pellets to control drug release. Pellets were spherical, presented a polynucleated microcapsule structure, and under certain experimental conditions, the yield of the preparation process reached very high values. The dissolution studies pointed out the slow paracetamol release from these pellets.

Multi-plasmid DNA vaccination avoids antigenic competition and enhances immunogenicity of a poorly immunogenic plasmid

DNA immunization is a very promising approach to the formulation of multivalent vaccines. However, little information is currently available on the immunogenicity of multi-plasmid formulations. To address this issue, we immunized mice with a combination of four plasmids encoding malarial antigens and we compared antibody responses with those obtained with single-plasmid injections. We found that when four plasmids encoding Plasmodium falciparum circumsporozoite protein, thrombospondin-related anonymous protein, major merozoite surface protein (MSP)1 and Pfs25 are co-injected into mice, Ab responses against each antigen are elicited at levels at least as high as the level obtained with single-plasmid injection. The quality of antibody production, as determined by isotype analysis, was similar when single- and multi-plasmid administrations were compared, indicating the priming of the same cytokine profile for CD4+ T helper cells. The sera from mice immunized with the four-plasmid formulation specifically recognized sporozoites, blood stage schizonts and gametes, indicating that DNA immunization induced antibody responses relevant to the native conformation. Finally and of particular interest, in the case of MSP1, the antibody response appears to be strongly potentiated by the presence of additional plasmids, indicating an adjuvant effect of DNA.

Inhibitory activity of IL-1 receptor antagonist depends on the balance between binding capacity for IL-1 receptor type 1 and IL-1 receptor type II

A series of mutants of human IL-1 receptor antagonist (IL-1ra) has been designed by comparison of IL-1ra and IL-1beta structures in order to increase receptor antagonist capacity. Upon in vitro and in vivo assay of IL-1 antagonism, the IL-1ra mutants DoB 0039 (N91--&gt;R), DoB 0040 (T109--&gt;A) and DoB 0041 (N91/T109--&gt;R/A) could inhibit IL-1beta effects more efficiently than wild-type IL-1ra, with DoB 0041 being the most active. Analysis of the receptor-binding capacity of the IL-1ra mutants showed that all three mutants could inhibit binding of IL-1alpha or IL-1beta to IL-1RI-bearing cells more efficiently than wild-type IL-1ra. Conversely, binding of IL-1beta to IL-1RII-bearing cells could be inhibited by DoB 0041 much less efficiently than by wild-type IL-1ra. It is known that the two types of IL-1 receptors (IL-1RI and IL-1RII) play different roles in the regulation of IL-1 activity, with IL-1RI being solely responsible for cell triggering upon IL-1 binding, whereas IL-1RII acts as a scavenger of IL-1 and can thus be considered as a natural IL-1 inhibitor. Thus, the enhanced inhibitory capacity of DoB 0041 as compared with wild-type IL-1ra is explained in terms of better binding to the activating receptor IL-1RI and poorer interaction with the inhibitory receptor IL-1RII.

Inhibitory activity of IL-1 receptor antagonist depends on the balance between binding capacity for IL-1 receptor type 1 and IL-1 receptor type II

A series of mutants of human IL-1 receptor antagonist (IL-1ra) has been designed by comparison of IL-1ra and IL-1beta structures in order to increase receptor antagonist capacity. Upon in vitro and in vivo assay of IL-1 antagonism, the IL-1ra mutants DoB 0039 (N91-->R), DoB 0040 (T109-->A) and DoB 0041 (N91/T109-->R/A) could inhibit IL-1beta effects more efficiently than wild-type IL-1ra, with DoB 0041 being the most active. Analysis of the receptor-binding capacity of the IL-1ra mutants showed that all three mutants could inhibit binding of IL-1alpha or IL-1beta to IL-1RI-bearing cells more efficiently than wild-type IL-1ra. Conversely, binding of IL-1beta to IL-1RII-bearing cells could be inhibited by DoB 0041 much less efficiently than by wild-type IL-1ra. It is known that the two types of IL-1 receptors (IL-1RI and IL-1RII) play different roles in the regulation of IL-1 activity, with IL-1RI being solely responsible for cell triggering upon IL-1 binding, whereas IL-1RII acts as a scavenger of IL-1 and can thus be considered as a natural IL-1 inhibitor. Thus, the enhanced inhibitory capacity of DoB 0041 as compared with wild-type IL-1ra is explained in terms of better binding to the activating receptor IL-1RI and poorer interaction with the inhibitory receptor IL-1RII.

Topological mapping of the cysteine residues of N-carbamyl-D-amino-acid amidohydrolase and their role in enzymatic activity

The N-carbamyl-D-amino-acid amidohydrolase from Agrobacterium radiobacter NRRL B11291, the enzyme used for the industrial production Of D-amino acids, was cloned, sequenced, and expressed in Escherichia coli. The protein, a dimer constituted by two identical subunits of 34,000 Da with five cysteines each, was susceptible to aggregation under oxidizing conditions and highly sensitive to hydrogen peroxide. To investigate the role of the cysteines in enzyme stability and activity, mutant proteins were constructed by site-directed mutagenesis in which the five residues were substituted by either Ala or Ser. Only the mutant carrying the Cys172 substitution was catalytically inactive, and the other mutants maintained the same specific activity as the wild type enzyme. The crucial role of Cys172 in enzymatic activity was also confirmed by chemical derivatization of the protein with iodoacetate. Furthermore, chemical derivatizations using both acrylamide and Ellman's reagent revealed that (i) none of the five cysteines is engaged in disulfide bridges, (ii) Cys172 is easily accessible to the solvent, (iii) Cys193 and Cys250 appear to be buried in the protein core, and (iv) Cys243 and Cys279 seem to be located within or in proximity of external loops and are derivatized under mild denaturing conditions. These data are discussed in light of the possible mechanisms of enzyme inactivation and catalytic reaction.

Mapping of receptor binding sites on IL-1 beta by reconstruction of IL-1ra-like domains

Upon structure comparison between IL-1 beta and its antagonist IL-1ra, single or multiple residues along the IL-1 beta sequence were replaced with the corresponding amino acids present in the IL-1ra protein, in the attempt to identify sites important for receptor binding and for biologic activity on the two molecules. Ten of fifteen mutant proteins had activity comparable to that of wild-type IL-1 beta in three different biologic assays and in receptor binding, indicating that the introduced changes did not influence the functional structure of the protein. Conversely, three mutants (SMIL-9: 127/263 R/T--&gt;W/Y; SMIL-10: 125/127/263/265 T/R/T/Q--&gt;R/W/Y/E; SMIL-15:222/227 I/E--&gt;S/S) showed an increased binding capacity for IL-1RI, not paralleled by increased agonist activity, indicating that the introduced IL-1ra residues could be involved in the nonagonist IL-1RI binding site. On the other hand, two mutants showed diminished binding capacity with concomitant decrease in biologic activity. Both mutants (SMIL-1, five substitutions in the loop 202-214; and SMIL-3, total replacement of the loop 164-173 with the IL-1ra stretch 52-55) included substitutions of residues allegedly important for agonist binding to IL-1RI. Mutant SMIL-3 showed the most profound reduction in binding capacity for IL-1RI (CDw121a) and a more than 1,000-fold reduced biologic activity both in vitro and in vivo, but it retained full capacity of binding to IL-1RII (CDw121b) and acted as a selective antagonist of IL-1RII. From these results the following conclusions can be drawn. IL-1 beta binds to IL-1RI and to IL-1RII through different sites, and the loop 164-173 appears as one of the areas involved in the selective interaction with IL-1RI. Agonist (IL-1 beta) and nonagonist (IL-1ra) binding to IL-1RI occur through distinct sites, with loops 164-173 and 202-214 of IL-1 beta identified as two of the sites selectively involved in agonist binding to the activating receptor.

Mapping of receptor binding sites on IL-1 beta by reconstruction of IL-1ra-like domains

Upon structure comparison between IL-1 beta and its antagonist IL-1ra, single or multiple residues along the IL-1 beta sequence were replaced with the corresponding amino acids present in the IL-1ra protein, in the attempt to identify sites important for receptor binding and for biologic activity on the two molecules. Ten of fifteen mutant proteins had activity comparable to that of wild-type IL-1 beta in three different biologic assays and in receptor binding, indicating that the introduced changes did not influence the functional structure of the protein. Conversely, three mutants (SMIL-9: 127/263 R/T-->W/Y; SMIL-10: 125/127/263/265 T/R/T/Q-->R/W/Y/E; SMIL-15:222/227 I/E-->S/S) showed an increased binding capacity for IL-1RI, not paralleled by increased agonist activity, indicating that the introduced IL-1ra residues could be involved in the nonagonist IL-1RI binding site. On the other hand, two mutants showed diminished binding capacity with concomitant decrease in biologic activity. Both mutants (SMIL-1, five substitutions in the loop 202-214; and SMIL-3, total replacement of the loop 164-173 with the IL-1ra stretch 52-55) included substitutions of residues allegedly important for agonist binding to IL-1RI. Mutant SMIL-3 showed the most profound reduction in binding capacity for IL-1RI (CDw121a) and a more than 1,000-fold reduced biologic activity both in vitro and in vivo, but it retained full capacity of binding to IL-1RII (CDw121b) and acted as a selective antagonist of IL-1RII. From these results the following conclusions can be drawn. IL-1 beta binds to IL-1RI and to IL-1RII through different sites, and the loop 164-173 appears as one of the areas involved in the selective interaction with IL-1RI. Agonist (IL-1 beta) and nonagonist (IL-1ra) binding to IL-1RI occur through distinct sites, with loops 164-173 and 202-214 of IL-1 beta identified as two of the sites selectively involved in agonist binding to the activating receptor.