Fc engineered ACE2-Fc is a potent multifunctional agent targeting SARS-CoV2

Joining a function-enhanced Fc-portion of human IgG to the SARS-CoV-2 entry receptor ACE2 produces an antiviral decoy with strain transcending virus neutralizing activity. SARS-CoV-2 neutralization and Fc-effector functions of ACE2-Fc decoy proteins, formatted with or without the ACE2 collectrin domain, were optimized by Fc-modification. The different Fc-modifications resulted in distinct effects on neutralization and effector functions. H429Y, a point mutation outside the binding sites for FcγRs or complement caused non-covalent oligomerization of the ACE2-Fc decoy proteins, abrogated FcγR interaction and enhanced SARS-CoV-2 neutralization. Another Fc mutation, H429F did not improve virus neutralization but resulted in increased C5b-C9 fixation and transformed ACE2-Fc to a potent mediator of complement-dependent cytotoxicity (CDC) against SARS-CoV-2 spike (S) expressing cells. Furthermore, modification of the Fc-glycan enhanced cell activation via FcγRIIIa. These different immune profiles demonstrate the capacity of Fc-based agents to be engineered to optimize different mechanisms of protection for SARS-CoV-2 and potentially other viral pathogens

The Rare Anaphylaxis-Associated FcγRIIa3 Exhibits Distinct Characteristics From the Canonical FcγRIIa1

FcγRIIa is an activating FcγR, unique to humans and non-human primates. It induces antibody-dependent proinflammatory responses and exists predominantly as FcγRIIa1. A unique splice variant, we designated FcγRIIa3, has been reported to be associated with anaphylactic reactions to intravenous immunoglobulins (IVIg) therapy. We aim to define the functional consequences of this FcγRIIa variant associated with adverse responses to IVIg therapy and evaluate the frequency of associated SNPs. FcγRIIa forms from macaque and human PBMCs were investigated for IgG-subclass specificity, biochemistry, membrane localization, and functional activity. Disease-associated SNPs were analyzed by sequencing genomic DNA from 224 individuals with immunodeficiency or autoimmune disease. FcγRIIa3 was identified in macaque and human PBMC. The FcγRIIa3 is distinguished from the canonical FcγRIIa1 by a unique 19-amino acid cytoplasmic insertion and these two FcγRIIa forms responded distinctly to antibody ligation. Whereas FcγRIIa1 was rapidly internalized, FcγRIIa3 was retained longer at the membrane, inducing greater calcium mobilization and cell degranulation. Four FCGR2A SNPs were identified including the previously reported intronic SNP associated with anaphylaxis, but in only 1 of 224 individuals. The unique cytoplasmic element of FcγRIIa3 delays internalization and is associated with enhanced cellular activation. The frequency of the immunodeficiency-associated SNP varies between disease populations but interestingly occurred at a lower frequency than previously reported. None-the-less enhanced FcγRIIa3 function may promote a proinflammatory environment and predispose to pathological inflammatory responses

A point-of-care lateral flow assay for neutralising antibodies against SARS-CoV-2

Background: As vaccines against SARS-CoV-2 are now being rolled out, a better understanding of immunity to the virus, whether from infection, or passive or active immunisation, and the durability of this protection is required. This will benefit from the ability to measure antibody-based protection to SARS-CoV-2, ideally with rapid turnaround and without the need for laboratory-based testing. Methods: We have developed a lateral flow POC test that can measure levels of RBD-ACE2 neutralising antibody (NAb) from whole blood, with a result that can be determined by eye or quantitatively on a small instrument. We compared our lateral flow test with the gold-standard microneutralisation assay, using samples from convalescent and vaccinated donors, as well as immunised macaques. Findings: We show a high correlation between our lateral flow test with conventional neutralisation and that this test is applicable with animal samples. We also show that this assay is readily adaptable to test for protection to newly emerging SARS-CoV-2 variants, including the beta variant which revealed a marked reduction in NAb activity. Lastly, using a cohort of vaccinated humans, we demonstrate that our whole-blood test correlates closely with microneutralisation assay data (specificity 100% and sensitivity 96% at a microneutralisation cutoff of 1:40) and that fingerprick whole blood samples are sufficient for this test. Interpretation: Taken together, the COVID-19 NAb-testTM device described here provides a rapid readout of NAb based protection to SARS-CoV-2 at the point of care

Systems serology detects functionally distinct coronavirus antibody features in children and elderly

The hallmarks of COVID-19 are higher pathogenicity and mortality in the elderly compared to children. Examining baseline SARS-CoV-2 cross-reactive immunological responses, induced by circulating human coronaviruses (hCoVs), is needed to understand such divergent clinical outcomes. Here we show analysis of coronavirus antibody responses of pre-pandemic healthy children (n = 89), adults (n = 98), elderly (n = 57), and COVID-19 patients (n = 50) by systems serology. Moderate levels of cross-reactive, but non-neutralizing, SARS-CoV-2 antibodies are detected in pre-pandemic healthy individuals. SARS-CoV-2 antigen-specific Fcγ receptor binding accurately distinguishes COVID-19 patients from healthy individuals, suggesting that SARS-CoV-2 infection induces qualitative changes to antibody Fc, enhancing Fcγ receptor engagement. Higher cross-reactive SARS-CoV-2 IgA and IgG are observed in healthy elderly, while healthy children display elevated SARS-CoV-2 IgM, suggesting that children have fewer hCoV exposures, resulting in less-experienced but more polyreactive humoral immunity. Age-dependent analysis of COVID-19 patients, confirms elevated class-switched antibodies in elderly, while children have stronger Fc responses which we demonstrate are functionally different. These insights will inform COVID-19 vaccination strategies, improved serological diagnostics and therapeutics

Anti-HIV-1 ADCC antibodies following latency reversal and treatment interruption

There is growing interest in utilizing antibody-dependent cellular cytotoxicity (ADCC) to eliminate infected cells following reactivation from HIV-1 latency. A potential barrier is that HIV-1-specific ADCC antibodies decline in patients on long-term antiretroviral therapy (ART) and may not be sufficient to eliminate reactivated latently infected cells. It is not known whether reactivation from latency with latency-reversing agents (LRAs) could provide sufficient antigenic stimulus to boost HIV-1-specific ADCC. We found that treatment with the LRA panobinostat or a short analytical treatment interruption (ATI), 21 to 59 days, was not sufficient to stimulate an increase in ADCC-competent antibodies, despite viral rebound in all subjects who underwent the short ATI. In contrast, a longer ATI, 2 to 12 months, among subjects enrolled in the Strategies for Management of Antiretroviral Therapy (SMART) trial robustly boosted HIV-1 gp120-specific Fc receptor-binding antibodies and ADCC against HIV-1-infected cells in vitro. These results show that there is a lag between viral recrudescence and the boosting of ADCC antibodies, which has implications for strategies toward eliminating latently infected cells

A Phase 1 Human Immunodeficiency Virus Vaccine Trial for Cross-Profiling the Kinetics of Serum and Mucosal Antibody Responses to CN54gp140 Modulated by Two Homologous Prime-Boost Vaccine Regimens

A key aspect to finding an efficacious human immunodeficiency virus (HIV) vaccine is the optimization of vaccine schedules that can mediate the efficient maturation of protective immune responses. In the present study, we investigated the effect of alternate booster regimens on the immune responses to a candidate HIV-1 clade C CN54gp140 envelope protein, which was coadministered with the TLR4-agonist glucopyranosyl lipid A-aqueous formulation. Twelve study participants received a common three-dose intramuscular priming series followed by a final booster at either 6 or 12 months. The two homologous prime-boost regimens were well tolerated and induced CN54gp140-specific responses that were observed in both the systemic and mucosal compartments. Levels of vaccine-induced IgG-subclass antibodies correlated significantly with Fc gamma R engagement, and both vaccine regimens were associated with strikingly similar patterns in antibody titer and Fc gamma R-binding profiles. In both groups, identical changes in the antigen (Ag)-specific IgG-subclass fingerprint, leading to a decrease in IgG1 and an increase in IgG4 levels, were modulated by booster injections. Here, the dissection of immune profiles further supports the notion that prime-boost strategies are essential for the induction of diverse Ag-specific HIV-1 responses. The results reported here clearly demonstrate that identical responses were effectively and safely induced by both vaccine regimens, indicating that an accelerated 6-month regimen could be employed for the rapid induction of immune responses against CN54gp140 with no apparent impact on the overall quality of the induced immune response. (This study has been registered at http://ClinicalTrials.gov under registration no.NCT01966900.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

Background: The EMPA KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population. Methods: EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110. Findings: Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5–2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62–0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16–1·59), representing a 50% (42–58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1). Interpretation: In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease. Funding: Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council

The immunoglobulin G binding site of complement protein C1q.

The involvement of Clq lysine residues in the binding of human Clq to rabbit IgG was assessed by chemical modification. Modification on of Clq lysyls with acetic anhydride was complicated by the lack of selectivity of the reagent, as loss of Clq functional activity, due to the modification of tyrosine residues, occurred bcfore any effect due to lysyl modification was apparent. Treatment of Clq with trinitrobenzene sulfonate or fluorescein isothiocyanate resulted in loss of binding activity but was also associated with a Clq concentration dependent precipitation of Clq suggesting structural alteration of the protein. N-(iodoacetylaminoethyl) -8 naphthylamine-l-sulphonate was found to be a non-covalent inhibitor of the interaction between Clq and antigen-aggregated IgG. Crosslink ing of human Clq to antigen-aggregated IgG by treatment with dimethyl -3,3'-di thiobispropionimidate (Lysyl-Lysyl crosslinking), 1,5difluoro- 2,4—dinitrobenzene (Lysyl—, Tyrosyl-, Histidyl-) or l-ethyl-S- (Bdimethyl aminopropyl) carbodiimide (Lysyl-Carboxyl) was found to involve the disulfide-linked AB and CC chains of Clq. As the DTBP crosslinking involved linking lysyl groups, the distribution of the lysine residues restricted the possible sites for crosslinking. Possible candidate lysyls in the globular head region of the C chain are limited to four residues flanking the interchain disulfide bond, which are thus likely to be close in space and may constitute a single contiguous contact site for IgG. This region is of high identity between the C and B chains. 1—ethyl-3 -(3-dimethylaminopropyl) carbodiimide (EDC) crosslinking was also determined to involve lysyl groups of Clq. This strengthened the assignment of the proposed lysine residues as points of contact with IgG as the chemistry of carbodiimide crosslinking is a " zero-length" process introducing no additional atoms between the participating sidechain s. This crosslinking method also indicated that iodination of Clq may inactivate the Ig binding activity associated with the C chain into which the 125I-label is incorporated. All three crosslinking methods gave evidence for an altered conformation of Clq bound to antigen-aggregated IgG. Only when C1q bound to immune complexes was treated with crosslinkers was crosslinking within the disulfide-linked AB dimer apparent by the appearance, on Western blotting of non-reduced SDS-PAG E samples, of a more rapidly migrating band with A/ B chain reactivity. Direct identification of the crosslinking sites by proteolysis of the covalent complex formed by DTBP-treatment of Clq and aggregated IgG and purification of the fragment containing crosslinks was unsuccessful. Two anti-Clq monoclonal antibodies, BUS—1 and BUS-2, which inhibited the binding of Clq to antigen aggregated IgG were produced. These mAbs competitively inhibited the binding of each other to Clq and so probably recognised the same or overlapping epitopes. Western blotting analysis showed BUS-1 to have weak reactivity with both the disulfide-linked AB and CC chains, but not with the reduced and alkylated free A, B or C chains. Reduction of the accessible disulfides of 125I—labeled C1q, under non-denaturing conditions, diminished the binding of Clq to immobilized BUS-1. These data were consistent with the BUS—1 epitope being discontinuous and occurring in the homologous regions of both the C and B chains flanking the intrachain disulfides. This interpretation was supportive of the conclusions of the crosslinking study from which it was also proposed these regions of Clq contact IgG. The modification of tyrosine residues of Clq decreased both the IgG-binding activity of the protein and its reactivity with the BUS-1 mAb. This was consistent with the contention that the mAb binds to the Ig recognition site. The loss of both BUS-1 reactivity and IgG binding activity on the cleavage of the accessible cysteines of Clq also indicates some degree of identity between the Ig recognition site and the BUS—1 epitope. A functionally active Fab/c fragment of IgG (i.e. consisting of one antigen-binding Fab and one complement interactive Fc) was produced by the use of cyanocysteine chemistry to achieve cleavage of the heavy chain polypeptide in the hinge region. This fragment is of value as a potential therapeutic agent for the activation of effector functions in situ as it is not subject to antigenic modulation. The physicochemical basis of the enhancement of Clq binding to immune complexes in the presence of polyethylene glycol was shown to be an excluded volume effect. This is of interest as Clq binding activity in the presence polyethylene glycol forms the basis of some assays for circulating immune complexes

Epitope Mapping of Fc gamma RIIa Monoclonal Antibodies

FcγRIIa (CD32) is an IgG receptor which has been shown to be important in autoimmune disease pathology. IV.3, 8.7, and 7.30 are anti-FcγRIIa monoclonal antibodies (mAbs), which block the interaction between FcγRIIa and complex IgG. In this study, the three mAbs were demonstrated to inhibit FcγRIIa function. The determination of the precise epitopes of the IV.3, 8.7, and 7.30 mAbs may become a potential approach for designing inhibitors for FcγRIIa. The epitope of IV.3, 8.7, and 7.30 were determined using chimeric receptors based on the extracellular domains of FcγRIIa and the FcεRI a chain. The epitopes for IV.3 was found to be mapped on amino acid residues 132-137, while 8.7 and 7.30 were on amino acid residues 112-119 and 157-162. Based on the crystal 3D model of FcγRIIa molecule, these amino acid sequences are clustered together forming a contiguous region within the ligand binding site of the receptor