Immunotherapy: ALLOGENEIC UMBILICAL CORD BLOOD REGULATORY T CELLS DECREASE INFLAMMATION AND PRESERVE ANTI-TUMOR ACTIVITY OF CAR T CELLS

Background & Aim: With larger accessibility and increased number of patients being treated with CART cell therapy, real-world toxicity continues to remain a significant challenge to its widespread adoption. We have previously shown that allogeneic umbilical cord blood derived (UCB) regulatory T cells (Tregs) can resolve uncontrolled inflammation and can treat acute and immune mediated lung injury in a xenogenic model as well as in patients suffering from COVID-19 acute respiratory distress syndrome. The unique properties of UCB Tregs including: i) lack of plasticity when exposed to inflammatory micro-environments;ii) no requirement for HLA matching;iii) long shelf life of cryopreserved Tregs;and iv) immediate product availability for on demand treatment, makes them an attractive source for treating acute inflammatory syndromes. Therefore, we hypothesized that add-on therapy with UCB derived Tregs may resolve uncontrolled inflammation responsible for CART cell therapy associated toxicity. Methods, Results & Conclusion(s): UCB Tregs were added in 1:1 ratio to CART cells, where no interference in their ability to kill CD19+ Raji cells, was detected at different ratios : 8:1 (80.4% vs. 81.5%);4:1 (62.0% vs. 66.2%);2:1 (50.1% vs. 54.7%);1:1 (35.4% vs. 44.1%) (Fig 1A). In a xenogenic B cell lymphoma model, multiple injections of Tregs were administered after CART injection (Fig 1B), which did not impact distribution of CD8+ T effector cells (Fig 1C) or CART cells cells (Fig 1D) in different organs. No decline in the CAR T levels was observed in the Tregs recipients (Fig 1E). Specifically, no difference in tumor burden was detected between the two arms (Fig 2A). No tumor was detected in CART+Tregs in liver (Fig 2B) or bone marrow (Fig 2C). A corresponding decrease in multiple inflammatory cytokines in peripheral blood was observed in CART+Tregs when compared to CART alone (Fig 2D). Here we show "proof of concept" for add-on therapy with Tregs to mitigate hyper-inflammatory state induced by CART cells without interference in their on-target anti-tumor activity. The timing of Tregs administration after CART cells have had sufficient time for forming synapse with tumor cells allows for preservation of their anti-tumor cytotoxicity, such that the infused Tregs home to the areas of tissue damage to bind to the resident antigen presenting cells which in turn collaborate with Tregs to resolve inflammation. Such differential distribution of cells allow for a Treg "cooling blanket" and lays ground for clinical study. [Figure presented]Copyright © 2023 International Society for Cell & Gene Therapy

Teclistamab in combination with daratumumab and lenalidomide in multiple myeloma (MajesTEC-2 study)

Introduction: Combination of daratumumab (Dara) and lenalidomide (Len) may enhance the function of teclistamab (Tec), potentially resulting in improved antimyeloma activity in a broader population. We present initial safety and efficacy data of Tec-Dara- Len combination in patients with multiple myeloma (MM) in a phase 1b study (MajesTEC-2;NCT04722146). Method(s): Eligible patients who received 1-3 prior lines of therapy (LOT), including a proteasome inhibitor and immune-modulatory drug, were given weekly doses of Tec (0.72-or- 1.5 mg/kg with step-up dosing) + Dara 1800 mg + Len 25 mg. Responses per International Myeloma Working Group criteria, adverse events (Aes) per CTCAE v5.0, and for cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) per ASTCT guidelines, were assessed. Result(s): 32 patients received Tec-Dara- Len (0.72 mg/kg, n = 13;1.5 mg/kg, n = 19). At data cut-off (11 July 2022), median follow-up (range) was 5.78 months (1.0-10.4) and median treatment duration was 4.98 months (0.10-10.35). Median age was 62 years (38-75);87.5% were male. Median prior LOT was 2 (1-3), 18.8% were refractory to Dara and 28.1% refractory to Len. CRS was most frequent AE (81.3% [n = 26], all grade 1/2), 95% occurred during cycle1. Median time to onset was 2 days (1-8), median duration was 2 days (1-22). No ICANS were reported. Frequent Aes (>=25.0% across both dose levels) were neutropenia (75.0% [n = 24];grade 3/4: 68.8% [n = 22]), fatigue (43.8% [n = 14];grade 3/4: 6.3% [n = 2]), diarrhoea (37.5% [n = 12];all grade 1/2), insomnia (31.3% [n = 10];grade 3/4: 3.1% [n = 1]), cough (28.1% [n = 9];all grade 1/2), hypophosphatemia (25.0% [n = 8];all grade 1/2), and pyrexia (25% [n = 8];grade 3/4: 6.3% [n = 2]). Febrile neutropenia frequency was 12.5% (n = 4). Infections occurred in 24 patients (75.0%;grade 3/4: 28.1% [n = 9]). Most common were upper respiratory infection (21.9% [n = 7]), COVID-19 (21.9% [n = 7]), and pneumonia (21.9% [n = 7]). Three (9.4%) had COVID-19 pneumonia. One (3.1%) discontinued due to COVID-19 infection and this patient subsequently died of this infection. Overall response rate (ORR, median follow-up) was 13/13 (8.61 months) at 0.72 mg/kg and 13/16 evaluable patients (less mature at 4.17 months) at 1.5 mg/kg. 12 patients attained very good/better partial response at 0.72 mg/kg dose, and response was not mature for 1.5 mg/kg group. Median time to first response was 1.0 month (0.7-2.0). Preliminary pharmacokinetic concentrations of Tec-Dara- Len were similar as seen with Tec monotherapy. Tec-Dara- Len- treatment led to proinflammatory cytokine production and T-cell activation. Conclusion(s): The combination of Tec-Dara- Len has no new safety signals beyond those seen with Tec or Dara-Len individually. Promising ORR supports the potential for this combination to have enhanced early disease control through the addition of Tec. These data warrant further investigation.

IDDF2023-ABS-0045 Spatiotemporal immune landscape of Mas-driven pro-inflammatory microenvironment with hyperactivated glycolysis in acetaminophen-induced liver injury

IDDF2023-ABS-0045 Figure 1 IDDF2023-ABS-0045 Figure 2 IDDF2023-ABS-0045 Figure 3 IDDF2023-ABS-0045 Figure 4

Coronavac inactivated vaccine triggers durable, cross-reactive Fc-mediated phagocytosis activities.

Although humoral responses elicited by infection or vaccine lost the ability to prevent transmission against Omicron, vaccine-induced antibodies may still contribute to disease attenuation through Fc-mediated effector functions. However, Fc effector function elicited by CoronaVac, as the most widely supplied inactivated vaccine globally, has not been characterized. For the first time, our study depicted Fc-mediated phagocytosis activity induced by CoronaVac, including antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent neutrophil phagocytosis (ADNP) activities, and further compared with that from convalescent individuals and CoronaVac recipients with subsequent breakthrough infections. We showed that 2-dose of CoronaVac effectively induced both ADCP and ADNP, but was substantially lower compared to infection, whereas the booster dose further augmented ADCP and ADNP responses, and remained detectable for 52 weeks. Among CoronaVac recipients, ADCP and ADNP responses also demonstrated cross-reactivity against Omicron subvariants, and breakthrough infection could enhance the phagocytic response. Meanwhile, serum samples from vaccinees, convalescent individuals with wildtype infection, BA.2 and BA.5 breakthrough infection demonstrated differential cross-reactive ADCP and ADNP responses against Omicron subvariants, suggesting the different subvariants of spike antigen exposure might alter the cross-reactivity of Fc effector function. Further, ADCP and ADNP responses were strongly correlated with Spike-specific IgG responses and neutralizing activities, indicating coordinated neutralization activity, ADCP and ADNP responses triggered by CoronaVac. Of note, the ADCP and ADNP responses were more durable and cross-reactive than corresponding Spike-specific IgG titers and neutralizing activities. Our study has important implications for optimal boosting vaccine strategies that may induce potent and broad Fc-mediated phagocytic activities.

A Dual-Approach Strategy to Optimize the Safety and Efficacy of Anti-Zika Virus Monoclonal Antibody Therapeutics.

Antibody-dependent enhancement of infection (ADE) is clinically relevant to Dengue virus (DENV) infection and poses a major risk to the application of monoclonal antibody (mAb)-based therapeutics against related flaviviruses such as the Zika virus (ZIKV). Here, we tested a two-tier approach for selecting non-cross-reactive mAbs combined with modulating Fc glycosylation as a strategy to doubly secure the elimination of ADE while preserving Fc effector functions. To this end, we selected a ZIKV-specific mAb (ZV54) and generated three ZV54 variants using Chinese hamster ovary cells and wild-type (WT) and glycoengineered ΔXF Nicotiana benthamiana plants as production hosts (ZV54CHO, ZV54WT, and ZV54ΔXF). The three ZV54 variants shared an identical polypeptide backbone, but each exhibited a distinct Fc N-glycosylation profile. All three ZV54 variants showed similar neutralization potency against ZIKV but no ADE activity for DENV infection, validating the importance of selecting the virus/serotype-specific mAbs for avoiding ADE by related flaviviruses. For ZIKV infection, however, ZV54CHO and ZV54ΔXF showed significant ADE activity while ZV54WT completely forwent ADE, suggesting that Fc glycan modulation may yield mAb glycoforms that abrogate ADE even for homologous viruses. In contrast to the current strategies for Fc mutations that abrogate all effector functions along with ADE, our approach allowed the preservation of effector functions as all ZV54 glycovariants retained antibody-dependent cellular cytotoxicity (ADCC) against the ZIKV-infected cells. Furthermore, the ADE-free ZV54WT demonstrated in vivo efficacy in a ZIKV-infection mouse model. Collectively, our study provides further support for the hypothesis that antibody-viral surface antigen and Fc-mediated host cell interactions are both prerequisites for ADE, and that a dual-approach strategy, as shown herein, contributes to the development of highly safe and efficacious anti-ZIKV mAb therapeutics. Our findings may be impactful to other ADE-prone viruses, including SARS-CoV-2.

Die Kämpfe únd schláchten-the struggles and battles of innate-like effector T lymphocytes with microbes.

The large majority of lymphocytes belong to the adaptive immune system, which are made up of B2 B cells and the αß T cells; these are the effectors in an adaptive immune response. A multitudinous group of lymphoid lineage cells does not fit the conventional lymphocyte paradigm; it is the unconventional lymphocytes. Unconventional lymphocytes-here called innate/innate-like lymphocytes, include those that express rearranged antigen receptor genes and those that do not. Even though the innate/innate-like lymphocytes express rearranged, adaptive antigen-specific receptors, they behave like innate immune cells, which allows them to integrate sensory signals from the innate immune system and relay that umwelt to downstream innate and adaptive effector responses. Here, we review natural killer T cells and mucosal-associated invariant T cells-two prototypic innate-like T lymphocytes, which sense their local environment and relay that umwelt to downstream innate and adaptive effector cells to actuate an appropriate host response that confers immunity to infectious agents.

Advancements in CRISPR-Based Biosensing for Next-Gen Point of Care Diagnostic Application.

With the move of molecular tests from diagnostic labs to on-site testing becoming more common, there is a sudden rise in demand for nucleic acid-based diagnostic tools that are selective, sensitive, flexible to terrain changes, and cost-effective to assist in point-of-care systems for large-scale screening and to be used in remote locations in cases of outbreaks and pandemics. CRISPR-based biosensors comprise a promising new approach to nucleic acid detection, which uses Cas effector proteins (Cas9, Cas12, and Cas13) as extremely specialized identification components that may be used in conjunction with a variety of readout approaches (such as fluorescence, colorimetry, potentiometry, lateral flow assay, etc.) for onsite analysis. In this review, we cover some technical aspects of integrating the CRISPR Cas system with traditional biosensing readout methods and amplification technologies such as polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and recombinase polymerase amplification (RPA) and continue to elaborate on the prospects of the developed biosensor in the detection of some major viral and bacterial diseases. Within the scope of this article, we also discuss the recent COVID pandemic and the numerous CRISPR biosensors that have undergone development since its advent. Finally, we discuss some challenges and future prospects of CRISPR Cas systems in point-of-care testing.

Post-translational modifications: Host defence mechanism, pathogenic weapon, and emerged target of anti-infective drugs

Post-translational modifications are changes introduced to proteins after their translation. They are the means to generate molecular diversity, expand protein function, control catalytic activity and trigger quick responses to a wide range of stimuli. Moreover, they regulate numerous biological processes, including pathogen invasion and host defence mechanisms. It is well established that bacteria and viruses utilize post-translational modifications on their own or their host's proteins to advance their pathogenicity. Doing so, they evade immune responses, target signaling pathways and manipulate host cytoskeleton to achieve survival, replication and propagation. Many bacterial species secrete virulence factors into the host and mediate hostpathogen interactions by inducing post-translational modifications that subvert fundamental cellular processes. Viral pathogens also utilize post translational modifications in order to overcome the host defence mechanisms and hijack its cellular machinery for their replication and propagation. For example, many coronavirus proteins are modified to achieve host invasion, evasion of immune responses and utilization of the host translational machinery. PTMs are also considered potential targets for the development of novel therapeutics from natural products with antibiotic properties, like lasso peptides and lantibiotics. The last decade, significant progress was made in understanding the mechanisms that govern PTMs and mediate regulation of protein structure and function. This urges the identification of relevant molecular targets, the design of specific drugs and the discovery of PTM-based medicine. Therefore, PTMs emerge as a highly promising field for the investigation and discovery of new therapeutics for many infectious diseases.Copyright © 2021 Bentham Science Publishers.

Galectin-9 promotes natural killer cells activity via interaction with CD44.

Natural killer (NK) cells are a potent innate source of cytokines and cytoplasmic granules. Their effector functions are tightly synchronized by the balance between the stimulatory and inhibitory receptors. Here, we quantified the proportion of NK cells and the surface presence of Galectin-9 (Gal-9) from the bone marrow, blood, liver, spleen, and lungs of adult and neonatal mice. We also examined the effector functions of Gal-9+NK cells compared with their Gal-9- counterparts. Our results revealed that Gal-9+NK cells are more abundant in tissues, in particular, in the liver than in the blood and bone marrow. We found Gal-9 presence was associated with enhanced cytotoxic effector molecules granzyme B (GzmB) and perforin expression. Likewise, Gal-9 expressing NK cells displayed greater IFN-γ and TNF-α expression than their negative counterparts under hemostatic circumstances. Notably, the expansion of Gal-9+NK cells in the spleen of mice infected with E. coli implies that Gal-9+NK cells may provide a protective role against infection. Similarly, we found the expansion of Gal-9+NK cells in the spleen and tumor tissues of melanoma B16-F10 mice. Mechanistically, our results revealed the interaction of Gal-9 with CD44 as noted by their co-expression/co-localization. Subsequently, this interaction resulted in enhanced expression of Phospho-LCK, ERK, Akt, MAPK, and mTOR in NK cells. Moreover, we found Gal-9+NK cells exhibited an activated phenotype as evidenced by increased CD69, CD25, and Sca-1 but reduced KLRG1 expression. Likewise, we found Gal-9 preferentially interacts with CD44high in human NK cells. Despite this interaction, we noted a dichotomy in terms of effector functions in NK cells from COVID-19 patients. We observed that the presence of Gal-9 on NK cells resulted in a greater IFN-γ expression without any changes in cytolytic molecule expression in these patients. These observations suggest differences in Gal-9+NK cell effector functions between mice and humans that should be considered in different physiological and pathological conditions. Therefore, our results highlight the important role of Gal-9 via CD44 in NK cell activation, which suggests Gal-9 is a potential new avenue for the development of therapeutic approaches to modulate NK cell effector functions.

Fc-mediated pan-sarbecovirus protection after alphavirus vector vaccination.

Group 2B ß-coronaviruses (sarbecoviruses) have caused regional and global epidemics in modern history. Here, we evaluate the mechanisms of cross-sarbecovirus protective immunity, currently less clear yet important for pan-sarbecovirus vaccine development, using a panel of alphavirus-vectored vaccines covering bat to human strains. While vaccination does not prevent virus replication, it protects against lethal heterologous disease outcomes in both severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and clade 2 bat sarbecovirus challenge models. The spike vaccines tested primarily elicit a highly S1-specific homologous neutralizing antibody response with no detectable cross-virus neutralization. Rather, non-neutralizing antibody functions, mechanistically linked to FcgR4 and spike S2, mediate cross-protection in wild-type mice. Protection is lost in FcR knockout mice, further supporting a model for non-neutralizing, protective antibodies. These data highlight the importance of FcR-mediated cross-protective immune responses in universal pan-sarbecovirus vaccine designs.

Effector memory T cell subset CD45RA−CCR7−CD27−CD28− EM3 increases in direct proportion to the disease severity of COVID-19

COVID-19, which emerged in December 2019 and continues to wreak havoc, has led to the death of many people around the world. In this study, we aimed to uncover the variables underlying the exacerbation of the disease by considering the changes in T cell subsets in adults and juveniles with different disease severity of COVID-19. Peripheral blood samples of 193 patients (128 adults and 65 juveniles) diagnosed with COVID-19 were evaluated in a flow cytometer, and a broad T cell profile was revealed by examining T cell subsets in terms of exhaustion and senescence. We found remarkable differences in the effector memory (EM;CD45RA−CCR7−) cell subsets of severe pneumonia cases. The frequencies of EM2 CD4+ T, EM3 CD4+ T, EM3 CD8+ T, EM2 DN T and EM3 DN T cells were found to increase in severe pneumonia cases. Consistently, these cells were found in juveniles and uncomplicated adults in similar or lower proportions to healthy controls. The findings of our study provide a view of the T cell profile that may underlie differences in the course of COVID-19 cases in juveniles and adults and may provide new insights into the development of effective treatment strategies. © 2022 The Scandinavian Foundation for Immunology.

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

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Acquisition of T6SS Effector TseL Contributes to the Emerging of Novel Epidemic Strains of Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen with multiple strategies to interact with other microbes and host cells, gaining fitness in complicated infection sites. The contact-dependent type VI secretion system (T6SS) is one critical secretion apparatus involved in both interbacterial competition and pathogenesis. To date, only limited numbers of T6SS-effectors have been clearly characterized in P. aeruginosa laboratory strains, and the importance of T6SS diversity in the evolution of clinical P. aeruginosa remains unclear. Recently, we characterized a P. aeruginosa clinical strain LYSZa7 from a COVID-19 patient, which adopted complex genetic adaptations toward chronic infections. Bioinformatic analysis has revealed a putative type VI secretion system (T6SS) dependent lipase effector in LYSZa7, which is a homologue of TseL in Vibrio cholerae and is widely distributed in pathogens. We experimentally validated that this TseL homologue belongs to the Tle2, a subfamily of T6SS-lipase effectors; thereby, we name this effector TseL (TseLPA in this work). Further, we showed the lipase-dependent bacterial toxicity of TseLPA, which primarily targets bacterial periplasm. The toxicity of TseLPA can be neutralized by two immunity proteins, TsiP1 and TsiP2, which are encoded upstream of tseL. In addition, we proved this TseLPA contributes to bacterial pathogenesis by promoting bacterial internalization into host cells. Our study suggests that clinical bacterial strains employ a diversified group of T6SS effectors for interbacterial competition and might contribute to emerging of new epidemic clonal lineages. IMPORTANCE Pseudomonas aeruginosa is one predominant pathogen that causes hospital-acquired infections and is one of the commonest coinfecting bacteria in immunocompromised patients and chronic wounds. This bacterium harbors a diverse accessory genome with a high frequency of gene recombination, rendering its population highly heterogeneous. Numerous Pa lineages coexist in the biofilm, where successful epidemic clonal lineage or strain-specific type commonly acquires genes to increase its fitness over the other organisms. Current studies of Pa genomic diversity commonly focused on antibiotic resistant genes and novel phages, overlooking the contribution of type VI secretion system (T6SS). We characterized a Pa clinical strain LYSZa7 from a COVID-19 patient, which adopted complex genetic adaptations toward chronic infections. We report, in this study, a novel T6SS-lipase effector that is broadly distributed in Pa clinical isolates and other predominant pathogens. The study suggests that hospital transmission may raise the emergence of new epidemic clonal lineages with specified T6SS effectors.

Pre-existing immunity modulates responses to mRNA boosters.

mRNA vaccines are effective in preventing severe COVID-19, but breakthrough infections, emerging variants, and waning immunity warrant the use of boosters. Although mRNA boosters are being implemented, the extent to which pre-existing immunity influences the efficacy of boosters remains unclear. In a cohort of individuals primed with the mRNA-1273 or BNT162b2 vaccines, we report that lower antibody levels before boost are associated with higher fold-increase in antibody levels after boost, suggesting that pre-existing antibody modulates the immunogenicity of mRNA vaccines. Our studies in mice show that pre-existing antibodies accelerate the clearance of vaccine antigen via Fc-dependent mechanisms, limiting the amount of antigen available to prime B cell responses after mRNA boosters. These data demonstrate a "tug of war" between pre-existing antibody responses and de novo B cell responses following mRNA vaccination, and they suggest that transient downmodulation of antibody effector function may improve the efficacy of mRNA boosters.

Complete genome sequence of the Pogostemon cablin bacterial wilt pathogen Ralstonia solanacearum strain SY1.

BACKGROUND: Ralstonia solanacearum causes bacterial wilt of Pogostemon cablin which is an important aromatic herb and also the main materials of COVID-19 therapeutic traditional drugs. However, we are lacking the information on the genomic sequences of R. solanacearum isolated from P. cablin. OBJECTIVE: The acquisition and analysis of this whole-genome sequence of the P. cablin bacterial wilt pathogen. METHODS: An R. solanacearum strain, named SY1, was isolated from infected P. cablin plants, and the complete genome sequence was sequenced and analyzed. RESULTS: The SY1 strain contains a 3.70-Mb chromosome and a 2.18-Mb megaplasmid, with GC contents of 67.57% and 67.41%, respectively. A total of 3308 predicted genes were located on the chromosome and 1657 genes were located in the megaplasmid. SY1 strain has 273 unique genes compared with five representative R. solanacearum strains, and these genes were enriched in the plant-pathogen interaction pathway. SY1 possessed a higher syntenic relationship with phylotype I strains, and the arsenal of type III effectors predicted in SY1 were also more closely related to those of phylotype I strains. SY1 contained 14 and 5 genomic islands in its chromosome and megaplasmid, respectively, and two prophage sequences in its chromosome. In addition, 215 and 130 genes were annotated as carbohydrate-active enzymes and antibiotic resistance genes, respectively. CONCLUSION: This is the first genome-scale assembly and annotation for R. solanacearum which isolated from infected P. cablin plants. The arsenal of virulence and antibiotic resistance may as the determinants in SY1 for infection of P. cablin plants.

Heterogeneity in IgG-CD16 signaling in infectious disease outcomes.

In this review, we discuss how IgG antibodies can modulate inflammatory signaling during viral infections with a focus on CD16a-mediated functions. We describe the structural heterogeneity of IgG antibody ligands, including subclass and glycosylation that impact binding by and downstream activity of CD16a, as well as the heterogeneity of CD16a itself, including allele and expression density. While inflammation is a mechanism required for immune homeostasis and resolution of acute infections, we focus here on two infectious diseases that are driven by pathogenic inflammatory responses during infection. Specifically, we review and discuss the evolving body of literature showing that afucosylated IgG immune complex signaling through CD16a contributes to the overwhelming inflammatory response that is central to the pathogenesis of severe forms of dengue disease and coronavirus disease 2019 (COVID-19).

Effector memory T cell subset CD45RA−CCR7−CD27−CD28− EM3 increases in direct proportion to the disease severity of COVID‐19

COVID‐19, which emerged in December 2019 and continues to wreak havoc, has led to the death of many people around the world. In this study, we aimed to uncover the variables underlying the exacerbation of the disease by considering the changes in T cell subsets in adults and juveniles with different disease severity of COVID‐19. Peripheral blood samples of 193 patients (128 adults and 65 juveniles) diagnosed with COVID‐19 were evaluated in a flow cytometer, and a broad T cell profile was revealed by examining T cell subsets in terms of exhaustion and senescence. We found remarkable differences in the effector memory (EM;CD45RA−CCR7−) cell subsets of severe pneumonia cases. The frequencies of EM2 CD4+ T, EM3 CD4+ T, EM3 CD8+ T, EM2 DN T and EM3 DN T cells were found to increase in severe pneumonia cases. Consistently, these cells were found in juveniles and uncomplicated adults in similar or lower proportions to healthy controls. The findings of our study provide a view of the T cell profile that may underlie differences in the course of COVID‐19 cases in juveniles and adults and may provide new insights into the development of effective treatment strategies.

Antibody-dependent cellular cytotoxicity against SARS-CoV-2 Omicron sub-lineages is reduced in convalescent sera regardless of infecting variant.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.4 and BA.5 variants caused major waves of infections. Here, we assess the sensitivity of BA.4 to binding, neutralization, and antibody-dependent cellular cytotoxicity (ADCC) potential, measured by FcγRIIIa signaling, in convalescent donors infected with four previous variants of SARS-CoV-2, as well as in post-vaccination breakthrough infections (BTIs) caused by Delta or BA.1. We confirm that BA.4 shows high-level neutralization resistance regardless of the infecting variant. However, BTIs retain activity against BA.4, albeit at reduced titers. BA.4 sensitivity to ADCC is reduced compared with other variants but with smaller fold losses compared with neutralization and similar patterns of cross-reactivity. Overall, the high neutralization resistance of BA.4, even to antibodies from BA.1 infection, provides an immunological mechanism for the rapid spread of BA.4 immediately after a BA.1-dominated wave. Furthermore, although ADCC potential against BA.4 is reduced, residual activity may contribute to observed protection from severe disease.

The Fc-effector function of COVID-19 convalescent plasma contributes to SARS-CoV-2 treatment efficacy in mice.

COVID-19 convalescent plasmas (CCPs) are chosen for plasma therapy based on neutralizing titers and anti-Spike immunoglobulin levels. However, CCP characteristics that promote SARS-CoV-2 control are complex and incompletely defined. Using an in vivo imaging approach, we demonstrate that CCPs with low neutralizing (ID50 ≤ 1:250), but moderate to high Fc-effector activity, in contrast to those with poor Fc function, delay mortality and/or improve survival of SARS-CoV-2-challenged K18-hACE2 mice. The impact of innate immune cells on CCP efficacy depended on their residual neutralizing activity. Fractionation of a selected CCP revealed that IgG and Ig(M + A) were required during therapy, but the IgG fraction alone sufficed during prophylaxis. Finally, despite reduced neutralization, ancestral SARS-CoV-2-elicited CCPs significantly delayed Delta and Beta-induced mortality suggesting that Fc-effector functions contribute to immunity against VOCs. Thus, Fc activity of CCPs provide a second line of defense when neutralization is compromised and can serve as an important criterion for CCP selection.

Nucleocapsid-specific antibody function is associated with therapeutic benefits from COVID-19 convalescent plasma therapy.

Coronavirus disease 2019 (COVID-19) convalescent plasma (CCP), a passive polyclonal antibody therapeutic agent, has had mixed clinical results. Although antibody neutralization is the predominant approach to benchmarking CCP efficacy, CCP may also influence the evolution of the endogenous antibody response. Using systems serology to comprehensively profile severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) functional antibodies of hospitalized people with COVID-19 enrolled in a randomized controlled trial of CCP (ClinicalTrials.gov: NCT04397757), we find that the clinical benefits of CCP are associated with a shift toward reduced inflammatory Spike (S) responses and enhanced nucleocapsid (N) humoral responses. We find that CCP has the greatest clinical benefit in participants with low pre-existing anti-SARS-CoV-2 antibody function and that CCP-induced immunomodulatory Fc glycan profiles and N immunodominant profiles persist for at least 2 months. We highlight a potential mechanism of action of CCP associated with durable immunomodulation, outline optimal patient characteristics for CCP treatment, and provide guidance for development of a different class of COVID-19 hyperinflammation-targeting antibody therapeutic agents.