SARS-CoV-2 breakthrough infections elicit potent, broad, and durable neutralizing antibody responses.

Although infections among vaccinated individuals lead to milder COVID-19 symptoms relative to those in unvaccinated subjects, the specificity and durability of antibody responses elicited by breakthrough cases remain unknown. Here, we demonstrate that breakthrough infections induce serum-binding and -neutralizing antibody responses that are markedly more potent, durable, and resilient to spike mutations observed in variants than those in subjects who received only 2 doses of vaccine. However, we show that breakthrough cases, subjects who were vaccinated after infection, and individuals vaccinated three times have serum-neutralizing activity of comparable magnitude and breadth, indicating that an increased number of exposures to SARS-CoV-2 antigen(s) enhance the quality of antibody responses. Neutralization of SARS-CoV was moderate, however, underscoring the importance of developing vaccines eliciting broad sarbecovirus immunity for pandemic preparedness.

Neutralizing immunity in vaccine breakthrough infections from the SARS-CoV-2 Omicron and Delta variants.

Virus-like particle (VLP) and live virus assays were used to investigate neutralizing immunity against Delta and Omicron SARS-CoV-2 variants in 259 samples from 128 vaccinated individuals. Following Delta breakthrough infection, titers against WT rose 57-fold and 3.1-fold compared with uninfected boosted and unboosted individuals, respectively, versus only a 5.8-fold increase and 3.1-fold decrease for Omicron breakthrough infection. Among immunocompetent, unboosted patients, Delta breakthrough infections induced 10.8-fold higher titers against WT compared with Omicron (p = 0.037). Decreased antibody responses in Omicron breakthrough infections relative to Delta were potentially related to a higher proportion of asymptomatic or mild breakthrough infections (55.0% versus 28.6%, respectively), which exhibited 12.3-fold lower titers against WT compared with moderate to severe infections (p = 0.020). Following either Delta or Omicron breakthrough infection, limited variant-specific cross-neutralizing immunity was observed. These results suggest that Omicron breakthrough infections are less immunogenic than Delta, thus providing reduced protection against reinfection or infection from future variants.

SARS-CoV-2-infection- and vaccine-induced antibody responses are long lasting with an initial waning phase followed by a stabilization phase.

It is thought that mRNA-based vaccine-induced immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) wanes quickly, based mostly on short-term studies. Here, we analyzed the kinetics and durability of the humoral responses to SARS-CoV-2 infection and vaccination using >8,000 longitudinal samples collected over a 3-year period in New York City. Upon primary immunization, participants with pre-existing immunity mounted higher antibody responses faster and achieved higher steady-state antibody titers than naive individuals. Antibody kinetics were characterized by two phases: an initial rapid decay, followed by a stabilization phase with very slow decay. Booster vaccination equalized the differences in antibody concentration between participants with and without hybrid immunity, but the peak antibody titers decreased with each successive antigen exposure. Breakthrough infections increased antibodies to similar titers as an additional vaccine dose in naive individuals. Our study provides strong evidence that SARS-CoV-2 antibody responses are long lasting, with initial waning followed by stabilization.

SARS-CoV-2 Omicron BA.1 breakthrough infection drives late remodeling of the memory B cell repertoire in vaccinated individuals.

How infection by a viral variant showing antigenic drift impacts a preformed mature human memory B cell (MBC) repertoire remains an open question. Here, we studied the MBC response up to 6 months after SARS-CoV-2 Omicron BA.1 breakthrough infection in individuals previously vaccinated with three doses of the COVID-19 mRNA vaccine. Longitudinal analysis, using single-cell multi-omics and functional analysis of monoclonal antibodies from RBD-specific MBCs, revealed that a BA.1 breakthrough infection mostly recruited pre-existing cross-reactive MBCs with limited de novo response against BA.1-restricted epitopes. Reorganization of clonal hierarchy and new rounds of germinal center reactions, however, combined to maintain diversity and induce progressive maturation of the MBC repertoire against common Hu-1 and BA.1, but not BA.5-restricted, SARS-CoV-2 Spike RBD epitopes. Such remodeling was further associated with a marked improvement in overall neutralizing breadth and potency. These findings have fundamental implications for the design of future vaccination booster strategies.

SARS-CoV-2 breakthrough infection induces rapid memory and de novo T cell responses.

Although the protective role of neutralizing antibodies against COVID-19 is well established, questions remain about the relative importance of cellular immunity. Using 6 pMHC multimers in a cohort with early and frequent sampling, we define the phenotype and kinetics of recalled and primary T cell responses following Delta or Omicron breakthrough infection in previously vaccinated individuals. Recall of spike-specific CD4+ T cells was rapid, with cellular proliferation and extensive activation evident as early as 1 day post symptom onset. Similarly, spike-specific CD8+ T cells were rapidly activated but showed variable degrees of expansion. The frequency of activated SARS-CoV-2-specific CD8+ T cells at baseline and peak inversely correlated with peak SARS-CoV-2 RNA levels in nasal swabs and accelerated viral clearance. Our study demonstrates that a rapid and extensive recall of memory T cell populations occurs early after breakthrough infection and suggests that CD8+ T cells contribute to the control of viral replication in breakthrough SARS-CoV-2 infections.

The magnitude and timing of recalled immunity after breakthrough infection is shaped by SARS-CoV-2 variants.

Vaccination against SARS-CoV-2 protects from infection and improves clinical outcomes in breakthrough infections, likely reflecting residual vaccine-elicited immunity and recall of immunological memory. Here, we define the early kinetics of spike-specific humoral and cellular immunity after vaccination of seropositive individuals and after Delta or Omicron breakthrough infection in vaccinated individuals. Early longitudinal sampling revealed the timing and magnitude of recall, with the phenotypic activation of B cells preceding an increase in neutralizing antibody titers. While vaccination of seropositive individuals resulted in robust recall of humoral and T cell immunity, recall of vaccine-elicited responses was delayed and variable in magnitude during breakthrough infections and depended on the infecting variant of concern. While the delayed kinetics of immune recall provides a potential mechanism for the lack of early control of viral replication, the recall of antibodies coincided with viral clearance and likely underpins the protective effects of vaccination against severe COVID-19.

Proteomic and Cellular Characterization of Omicron Breakthrough Infections and a Third Homologous or Heterologous Boosting Vaccination in a Longitudinal Cohort.

The understanding of dynamic plasma proteome features in hybrid immunity and breakthrough infection is limited. A deeper understanding of the immune differences between heterologous and homologous immunization could assist in the future establishment of vaccination strategies. In this study, 40 participants who received a third dose of either a homologous BBIBP-CorV or a heterologous ZF2001 protein subunit vaccine following two doses of inactivated coronavirus disease 2019 vaccines and 12 patients with BA2.2 breakthrough infections were enrolled. Serum samples were collected at days 0, 28, and 180 following the boosting vaccination and breakthrough and then analyzed using neutralizing antibody tests and mass spectrometer-based proteomics. Mass cytometry of peripheral blood mononuclear cell samples was also performed in this cohort. The chemokine signaling pathway and humoral response markers (IgG2 and IgG3) associated with infection were found to be upregulated in breakthrough infections compared to vaccination-induced immunity. Elevated expression of IGKV, IGHV, IL-17 signaling, and the phagocytosis pathway, along with lower expression of FGL2, were correlated with higher antibody levels in the boosting vaccination groups. The MAPK signaling pathway and Fc gamma R-mediated phagocytosis were more enriched in the heterologous immunization groups than in the homologous immunization groups. Breakthrough infections can trigger more intensive inflammatory chemokine responses than vaccination. T-cell and innate immune activation have been shown to be closely related to enhanced antibody levels after vaccination and therefore might be potential targets for vaccine adjuvant design.

Triggering photocatalytic performance of La2CoxMn2-xO6 via heat activation.

The La-based perovskite (LaBO3) exhibits excellent optical properties. However, its valence band (VB) potential is not sufficiently positive to reach the oxidation potential required for the cleavage of chemical bonds (such as benzylic C-H), limiting its application in photocatalysis. Herein, we report the unconventional effects of heat activation on the reduction of the dissociation energy of benzylic C-H and aqueous H-O, thereby triggering the photocatalytic activity of La2CoxMn2-xO6 perovskites. Additionally, we demonstrate that photocatalysis is the main contributor to substrate conversion in the selective oxidation of toluene and reduction of CO2. Particularly, La2Co1.5Mn0.5O6 shows excellent performance with a product yield of 550.00 mmol gcat-1 and a toluene conversion of 22,866.67 µmol gcat-1 h-1. To the best of our knowledge, this is the highest reported product yield for the selective oxidation of benzylic C-H bond of toluene. Our findings provide insight into the specific role of heat activation in photocatalysis, which is crucial for breaking and overcoming the VB barrier to realize challenging reactions.

SARS-CoV-2 BA.4/5 infection triggers more cross-reactive FcγRIIIa signaling and neutralization than BA.1, in the context of hybrid immunity.

SARS-CoV-2 variants of concern (VOCs) differentially trigger neutralizing and antibody-dependent cellular cytotoxic (ADCC) antibodies with variable cross-reactivity. Omicron BA.4/5 was approved for inclusion in bivalent vaccination boosters, and therefore the antigenic profile of antibodies elicited by this variant is critical to understand. Here, we investigate the ability of BA.4/5-elicited antibodies following the first documented (primary) infection (n = 13) or breakthrough infection after vaccination (n = 9) to mediate neutralization and FcγRIIIa signaling across multiple SARS-CoV-2 variants including XBB.1.5 and BQ.1. Using a pseudovirus neutralization assay and a FcγRIIIa crosslinking assay to measure ADCC potential, we show that unlike SARS-CoV-2 Omicron BA.1, BA.4/5 infection triggers highly cross-reactive functional antibodies. Cross-reactivity was observed both in the absence of prior vaccination and in breakthrough infections following vaccination. However, BQ.1 and XBB.1.5 neutralization and FcγRIIIa signaling were significantly compromised compared to other VOCs, regardless of prior vaccination status. BA.4/5 triggered FcγRIIIa signaling was significantly more resilient against VOCs (<10-fold decrease in magnitude) compared to neutralization (10- to 100-fold decrease). Overall, this study shows that BA.4/5 triggered antibodies are highly cross-reactive compared to those triggered by other variants. Although this is consistent with enhanced neutralization and FcγRIIIa signaling breadth of BA.4/5 vaccine boosters, the reduced activity against XBB.1.5 supports the need to update vaccines with XBB sublineage immunogens to provide adequate coverage of these highly antibody evasive variants. IMPORTANCE: The continued evolution of SARS-CoV-2 has resulted in a number of variants of concern. Of these, the Omicron sublineage is the most immune evasive. Within Omicron, the BA.4/5 sublineage drove the fifth wave of infection in South Africa prior to becoming the dominant variant globally. As a result this spike sequence was approved as part of a bivalent vaccine booster, and rolled out worldwide. We aimed to understand the cross-reactivity of neutralizing and Fc mediated cytotoxic functions elicited by BA.4/5 infection following infection or breakthrough infection. We find that, in contrast to BA.1 which triggered fairly strain-specific antibodies, BA.4/5 triggered antibodies that are highly cross-reactive for neutralization and antibody-dependent cellular cytotoxicity potential. Despite this cross-reactivity, these antibodies are compromised against highly resistant variants such as XBB.1.5 and BQ.1. This suggests that next-generation vaccines will require XBB sublineage immunogens in order to protect against these evasive variants.

Breakthrough infection and reinfection in patients with mpox.

Recently, patients with Mpox breakthrough infection or reinfection were constantly reported. However, the induction, risk factors, and important clinical symptoms of breakthrough infection and reinfection of Mpox virus (MPXV), as well as the factors affecting the effectiveness of Mpox vaccine are not characterized. Herein, a literature review was preformed to summarize the risk factors and important clinical symptoms of patients with Mpox breakthrough infection or reinfection, as well as the factors affecting the effectiveness of smallpox vaccine against Mpox. Results showed that MSM sexual behavior, condomless sexual behavior, multiple sexual partners, close contact, HIV infection, and the presence of comorbidity are important risk factors for Mpox breakthrough infection and reinfection. Genital ulcers, proctitis, and lymphadenopathy are the important clinical symptoms of Mpox breakthrough infection and reinfection. The effectiveness of emergent vaccination of smallpox vaccine for post-exposure of MPXV is associated with smallpox vaccination history, interval between exposure and vaccination, and history of HIV infection. This review provides a better understanding for the risk factors and important clinical symptoms of Mpox breakthrough infection and reinfection, as well as the formulation of Mpox vaccine vaccination strategies.

Clinical and humoral response after SARS-CoV-2 breakthrough infection in patients receiving immunosuppressant therapy.

BACKGROUND: Despite impaired humoral response in patients treated with immunosuppressants (ISPs), recent studies found similar severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) breakthrough infection compared to controls. One potential explanation is the rapid generation of humoral response on infection, but evidence is lacking. OBJECTIVES: We investigated the longitudinal dynamics of the SARS-CoV-2 antibody repertoire after SARS-CoV-2 delta and omicron breakthrough infection in patients with immune-mediated inflammatory diseases (IMIDs) receiving ISP therapy and controls. METHODS: As a prospective substudy of the national Target-to-B! (T2B!) consortium, we included IMID patients receiving ISPs therapy and controls who reported SARS-CoV-2 breakthrough infection between July 1, 2021, and April 1, 2022. To get an impression of the dynamics of the antibody repertoire, 3 antibody titers of wild-type RBD, wild-type S, and omicron RBD were measured at 4 time points after SARS-CoV-2 breakthrough infection. RESULTS: We included 302 IMID patients receiving ISPs and 178 controls. Antibody titers increased up to 28 days after breakthrough infection in both groups. However, in IMID patients receiving therapy with anti-CD20 and sphingosine-1 phosphate receptor modulators, antibody titers were considerably lower compared to controls. In the anti-TNF group, we observed slightly lower antibody titers in the early stages and a faster decline of antibodies after infection compared to controls. Breakthrough infections were mostly mild, and hospitalization was required in less than 1% of cases. CONCLUSIONS: Most ISPs do not influence the dynamics of the SARS-CoV-2 antibody repertoire and exhibit a rapid recall response with cross-reactive antibody clones toward new virus variants. However, in patients treated with anti-CD20 therapy or sphingosine-1 phosphate receptor modulators, the dynamics were greatly impaired, and to a lesser extent in those who received anti-TNF. Nevertheless, only a few severe breakthrough cases were reported.

Breakthrough Invasive Fungal Infections in Patients With High-Risk Hematological Disorders Receiving Voriconazole and Posaconazole Prophylaxis: A Systematic Review.

BACKGROUND: Primary antifungal prophylaxis with mold-active azoles is used to prevent invasive fungal infections in patients with high-risk hematological disorders; however, breakthrough infections occur, and the reasons for treatment failure are still not fully understood. To help inform clinical decisions, we sought to define microbiological, clinical, and pharmacological characteristics of proven and probable breakthrough invasive fungal infections (bIFIs) in patients with high-risk hematological disorders receiving voriconazole or posaconazole prophylaxis. METHODS: We performed a systematic review of the literature following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search strategy was last conducted on 19 April 2023. RESULTS: We assessed 5293 studies for eligibility, and 300 were selected for data extraction. These studies described 1076 cases of bIFIs occurring under voriconazole (42.5%) or posaconazole (57.5%). The most commonly found pathogens were Aspergillus (40%), Mucorales (20%), Candida (18%), and Fusarium (9%) species. Mucorales were more frequent among voriconazole-emerging cases, whereas Aspergillus and Fusarium were more prevalent among posaconazole-emerging cases. Definitive, putative, or probable antifungal resistance was found in 31% of cases. Therapeutic drug monitoring showed subtherapeutic azole concentration in 32 of 90 (36%) cases. Infection-related mortality was reported in 117 cases and reached 35%. CONCLUSIONS: In our systemic review, the most common bIFIs were aspergillosis, mucormycosis, candidiasis, and fusariosis. Antifungal resistance explains only a minority of cases. Subtherapeutic prophylaxis was frequent but rarely reported. Prospective studies are needed to better understand these infections and to establish optimal management.

Clinical Features and Outcomes of Hospitalized Adult Patients With Breakthrough COVID-19 Infections: A Propensity-Score-Matched Observational Study.

In this study, we aimed to evaluate the impact of vaccination on intensive care unit (ICU) admission and in-hospital mortality among breakthrough coronavirus disease 2019 (COVID-19) infections. A total of 3,351 adult patients hospitalized with COVID-19 in the Memorial Healthcare System (Hollywood, Florida) between June 1 and September 20, 2021, were included; 284 (8.5%) were fully vaccinated. A propensity-score-matched analysis was conducted to compare fully vaccinated patients with unvaccinated controls. Propensity scores were calculated on the basis of variables associated with vaccination status. A 1:1 matching ratio was applied using logistic regression models, ensuring balanced characteristics between the two groups. The matched samples were then subjected to multivariate analysis. Among breakthrough infections, vaccinated patients demonstrated lower incidences of ICU admission (10.3% vs. 16.4%; P = 0.042) and death (12.2% vs. 18.7%; P = 0.041) than the matched controls. Risk-adjusted multivariate analysis demonstrated a significant inverse association between vaccination and ICU admission (odds ratio = 0.52, 95% confidence interval: 0.31, 0.89; P = 0.019) as well as in-hospital mortality (odds ratio = 0.57, 95% confidence interval: 0.34, 0.94; P = 0.027). Vaccinated individuals experiencing breakthrough infections had significantly lower risks of ICU admission and in-hospital mortality. These findings highlight the benefits of COVID-19 vaccines in reducing severe outcomes among patients with breakthrough infections.

Efficacy and safety of tixagevimab-cilgavimab versus SARS-CoV-2 breakthrough infection in the hematological conditions.

BACKGROUND: Managing SARS-CoV-2 infection in frail and immunosuppressed patients still represents an open challenge, but, starting from the phase 3 PROVENT study, prophylaxis with tixagevimab-cilgavimab has improved the approach in this category of patients, guaranteeing a better outcome and inferior mortality. Real-life data in a heterogeneous cohort are few. METHODS: The aim of this study is to evaluate the benefit of prophylaxis with tixagevimab-cilgavimab in a cohort of 202 patients affected by different hematological diseases (lymphoproliferative, myeloproliferative, autoimmune, patients recently receiving a bone marrow transplant), active (with ongoing treatment), or in watch-and-wait strategy, followed in our center, during a median follow-up of 249 (45-325) days. RESULTS: An incidence of 44 breakthrough infections (21.8%) is reported, with no treatment-related adverse effects. Age ≥70 years, ongoing treatment (above all with monoclonal antibodies), baseline lymphoproliferative disorders, and prior virus exposure are identified as risk factors related to subsequent infection (p < 0.05). Moreover, the incidence is higher in low/nonresponse to prior vaccination (p = .002). Patients treated with tixagevimab-cilgavimab had a mild course of the infection and a reduction of the duration compared with preprophylaxis infection (11 vs. 15 days, p < .001). The concurrent treatment with anti-CD20 monoclonal antibodies and B-non-Hodgkin lymphoma still confers a higher duration of infection despite prophylaxis. No deaths attributable to the infection occurred. CONCLUSION: Prophylaxis treatment seems to be a valid and safe strategy, although not preventing breakthrough infection, but the severe complications associated with the infection and the possible delays in administering lifesaving therapies from long positivity.

Correlates of protection and determinants of SARS-CoV-2 breakthrough infections 1 year after third dose vaccination.

BACKGROUND: The emergence of new SARS-CoV-2 variants and the waning of immunity raise concerns about vaccine effectiveness and protection against COVID-19. While antibody response has been shown to correlate with the risk of infection with the original variant and earlier variants of concern, the effectiveness of antibody-mediated protection against Omicron and the factors associated with protection remain uncertain. METHODS: We evaluated antibody responses to SARS-CoV-2 spike (S) and nucleocapsid (N) antigens from Wuhan and variants of concern by Luminex and their role in preventing breakthrough infections 1 year after a third dose of mRNA vaccination, in a cohort of health care workers followed since the pandemic onset in Spain (N = 393). Data were analyzed in relation to COVID-19 history, demographic factors, comorbidities, vaccine doses, brand, and adverse events. RESULTS: Higher levels of anti-S IgG and IgA to Wuhan, Delta, and Omicron were associated with protection against vaccine breakthroughs (IgG against Omicron S antigen HR, 0.06, 95%CI, 0.26-0.01). Previous SARS-CoV-2 infection was positively associated with antibody levels and protection against breakthroughs, and a longer time since last infection was associated with lower protection. In addition, priming with BNT162b2 followed by mRNA-1273 booster was associated with higher antibody responses than homologous mRNA-1273 vaccination. CONCLUSIONS: Data show that IgG and IgA induced by vaccines against the original strain or by hybrid immunization are valid correlates of protection against Omicron BA.1 despite immune escape and support the benefits of heterologous vaccination regimens to enhance antibodies and the prioritization of booster vaccination in individuals without recent infections.

What is quality in long covid care? Lessons from a national quality improvement collaborative and multi-site ethnography.

BACKGROUND: Long covid (post covid-19 condition) is a complex condition with diverse manifestations, uncertain prognosis and wide variation in current approaches to management. There have been calls for formal quality standards to reduce a so-called "postcode lottery" of care. The original aim of this study-to examine the nature of quality in long covid care and reduce unwarranted variation in services-evolved to focus on examining the reasons why standardizing care was so challenging in this condition. METHODS: In 2021-2023, we ran a quality improvement collaborative across 10 UK sites. The dataset reported here was mostly but not entirely qualitative. It included data on the origins and current context of each clinic, interviews with staff and patients, and ethnographic observations at 13 clinics (50 consultations) and 45 multidisciplinary team (MDT) meetings (244 patient cases). Data collection and analysis were informed by relevant lenses from clinical care (e.g. evidence-based guidelines), improvement science (e.g. quality improvement cycles) and philosophy of knowledge. RESULTS: Participating clinics made progress towards standardizing assessment and management in some topics; some variation remained but this could usually be explained. Clinics had different histories and path dependencies, occupied a different place in their healthcare ecosystem and served a varied caseload including a high proportion of patients with comorbidities. A key mechanism for achieving high-quality long covid care was when local MDTs deliberated on unusual, complex or challenging cases for which evidence-based guidelines provided no easy answers. In such cases, collective learning occurred through idiographic (case-based) reasoning, in which practitioners build lessons from the particular to the general. This contrasts with the nomothetic reasoning implicit in evidence-based guidelines, in which reasoning is assumed to go from the general (e.g. findings of clinical trials) to the particular (management of individual patients). CONCLUSION: Not all variation in long covid services is unwarranted. Largely because long covid's manifestations are so varied and comorbidities common, generic "evidence-based" standards require much individual adaptation. In this complex condition, quality improvement resources may be productively spent supporting MDTs to optimise their case-based learning through interdisciplinary discussion. Quality assessment of a long covid service should include review of a sample of individual cases to assess how guidelines have been interpreted and personalized to meet patients' unique needs. STUDY REGISTRATION: NCT05057260, ISRCTN15022307.

The spike-specific TCRß repertoire shows distinct features in unvaccinated or vaccinated patients with SARS-CoV-2 infection.

BACKGROUND: The evolving variants of SARS-CoV-2 may escape immunity from prior infections or vaccinations. It's vital to understand how immunity adapts to these changes. Both infection and mRNA vaccination induce T cells that target the Spike protein. These T cells can recognize multiple variants, such as Delta and Omicron, even if neutralizing antibodies are weakened. However, the degree of recognition can vary among people, affecting vaccine efficacy. Previous studies demonstrated the capability of T-cell receptor (TCR) repertoire analysis to identify conserved and immunodominant peptides with cross-reactive potential among variant of concerns. However, there is a need to extend the analysis of the TCR repertoire to different clinical scenarios. The aim of this study was to examine the Spike-specific TCR repertoire profiles in natural infections and those with combined natural and vaccine immunity. METHODS: A T-cell enrichment approach and bioinformatic tools were used to investigate the Spike-specific TCRß repertoire in peripheral blood mononuclear cells of previously vaccinated (n = 8) or unvaccinated (n = 6) COVID-19 patients. RESULTS: Diversity and clonality of the TCRß repertoire showed no significant differences between vaccinated and unvaccinated groups. When comparing the TCRß data to public databases, 692 unique TCRß sequences linked to S epitopes were found in the vaccinated group and 670 in the unvaccinated group. TCRß clonotypes related to spike regions S135-177, S264-276, S319-350, and S448-472 appear notably more prevalent in the vaccinated group. In contrast, the S673-699 epitope, believed to have super antigenic properties, is observed more frequently in the unvaccinated group. In-silico analyses suggest that mutations in epitopes, relative to the main SARS-CoV-2 variants of concern, don't hinder their cross-reactive recognition by associated TCRß clonotypes. CONCLUSIONS: Our findings reveal distinct TCRß signatures in vaccinated and unvaccinated individuals with COVID-19. These differences might be associated with disease severity and could influence clinical outcomes. TRIAL REGISTRATION: FESR/FSE 2014-2020 DDRC n. 585, Action 10.5.12, noCOVID19@UMG.

Epidemiological characteristics and antibody kinetics of elderly population with booster vaccination following both Omicron BA.5 and XBB waves in China.

After the termination of zero-COVID-19 policy, the populace in China has experienced both Omicron BA.5 and XBB waves. Considering the poor antibody responses and severe outcomes observed among the elderly following infection, we conducted a longitudinal investigation to examine the epidemiological characteristics and antibody kinetics among 107 boosted elderly participants following the Omicron BA.5 and XBB waves. We observed that 96 participants (89.7%) were infected with Omicron BA.5, while 59 (55.1%) participants were infected with Omicron XBB. Notably, 52 participants (48.6%) experienced dual infections of both Omicron BA.5 and XBB. The proportion of symptomatic cases appeared to decrease following the XBB wave (18.6%) compared to that after the BA.5 wave (59.3%). Omicron BA.5 breakthrough infection induced lower neutralizing antibody titers against XBB.1.5, BA.2.86, and JN.1, while reinfection with Omicron XBB broadened the antibody responses against all measured Omicron subvariants and may alleviate the wild type-vaccination induced immune imprinting. Boosted vaccination type and comorbidities were the significant factors associated with antibody responses. Updated vaccines based on emerging severe acute respiratory syndrome coronavirus 2 variants are needed to control the Coronavirus Disease 2019 pandemic in the elderly.

Clinical characteristics and immunogenicity after Omicron breakthrough infection in patients with chronic hepatitis B infection: A longitudinal observational study.

The clinical and immunological features after breakthrough infection (BTI) during Omicron wave in patients with chronic hepatitis B virus infection (CHB) are still unclear. A total of 101 patients with CHB from our previous coronavirus disease 2019 (COVID-19) vaccination cohort (NCT05007665), were continued to be followed up at the Second Affiliated Hospital of Chongqing Medical University after BTI, while an additional 39 healthcare workers after BTI were recruited as healthy controls (HCs). Clinical data were collected using questionnaire survey and electronic medical record. Blood samples were used to determine the antibody responses, as well as B and T cell responses. After BTI, the clinical symptoms of COVID-19 were mild to moderate in patients with CHB, with a median duration of 5 days. Compared with HCs, patients with CHB were more susceptible to develop moderate COVID-19. The liver function was not significantly damaged, and HBV-DNA was not activated in patients with CHB after BTI. Patients with CHB could elicit robust antibody responses after BTI (NAbs 13.0-fold, BA.5 IgG: 24.2-fold, respectively), which was also significantly higher than that in every period after vaccination (all p < 0.001), and compared to that in HCs after BTI. The CD4+, cTfh, and CD8+ T cell responses were also augmented in patients with CHB after BTI, while exhibiting comparability to those observed in HCs. In patients with CHB after BTI, the immune imprint was observed in B cell responses, rather than in T cell responses. In conclusion, Omicron breakthrough infection induced mild to moderate COVID-19 symptoms in patients with CHB, without exacerbating the progress of liver diseases. Meanwhile, BTI demonstrated the ability to induce robust antibody and T cell responses in patients with CHB, which was comparable to those observed in HCs.

Th2 and Th17-associated immunopathology following SARS-CoV-2 breakthrough infection in Spike-vaccinated ACE2-humanized mice.

Vaccines have demonstrated remarkable effectiveness in protecting against COVID-19; however, concerns regarding vaccine-associated enhanced respiratory diseases (VAERD) following breakthrough infections have emerged. Spike protein subunit vaccines for SARS-CoV-2 induce VAERD in hamsters, where aluminum adjuvants promote a Th2-biased immune response, leading to increased type 2 pulmonary inflammation in animals with breakthrough infections. To gain a deeper understanding of the potential risks and the underlying mechanisms of VAERD, we immunized ACE2-humanized mice with SARS-CoV-2 Spike protein adjuvanted with aluminum and CpG-ODN. Subsequently, we exposed them to increasing doses of SARS-CoV-2 to establish a breakthrough infection. The vaccine elicited robust neutralizing antibody responses, reduced viral titers, and enhanced host survival. However, following a breakthrough infection, vaccinated animals exhibited severe pulmonary immunopathology, characterized by a significant perivascular infiltration of eosinophils and CD4+ T cells, along with increased expression of Th2/Th17 cytokines. Intracellular flow cytometric analysis revealed a systemic Th17 inflammatory response, particularly pronounced in the lungs. Our data demonstrate that aluminum/CpG adjuvants induce strong antibody and Th1-associated immunity against COVID-19 but also prime a robust Th2/Th17 inflammatory response, which may contribute to the rapid onset of T cell-mediated pulmonary immunopathology following a breakthrough infection. These findings underscore the necessity for further research to unravel the complexities of VAERD in COVID-19 and to enhance vaccine formulations for broad protection and maximum safety.