Establishment of the First National Standard for Neutralizing Antibodies against SARS-CoV-2 XBB Variants.

Neutralizing antibodies (NtAbs) against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are indicators of vaccine efficacy that enable immunity surveillance. However, the rapid mutation of SARS-CoV-2 variants prevents the timely establishment of standards required for effective XBB vaccine evaluation. Therefore, we prepared four candidate standards (No. 11, No. 44, No. 22, and No. 33) using plasma, purified immunoglobulin, and a broad-spectrum neutralizing monoclonal antibody. Collaborative calibration was conducted across nine Chinese laboratories using neutralization methods against 11 strains containing the XBB and BA.2.86 sublineages. This study demonstrated the reduced neutralization potency of the first International Standard antibodies to SARS-CoV-2 variants of concern against XBB variants. No. 44 displayed broad-spectrum neutralizing activity against XBB sublineages, effectively reduced interlaboratory variability for nearly all XBB variants, and effectively minimized the geometric mean titer (GMT) difference between the live and pseudotyped virus. No. 22 showed a broader spectrum and higher neutralizing activity against all strains but failed to reduce interlaboratory variability. Thus, No. 44 was approved as a National Standard for NtAbs against XBB variants, providing a unified NtAb measurement standard for XBB variants for the first time. Moreover, No. 22 was approved as a national reference reagent for NtAbs against SARS-CoV-2, offering a broad-spectrum activity reference for current and potentially emerging variants.

A superior heterologous prime-boost vaccination strategy against COVID-19: A bivalent vaccine based on yeast-derived RBD proteins followed by a heterologous vaccine.

Various vaccines have been challenged by SARS-CoV-2 variants. Here, we reported a yeast-derived recombinant bivalent vaccine (Bivalent wild-type [Wt]+De) based on the wt and Delta receptor-binding domain (RBD). Yeast derived RBD proteins based on the wt and Delta mutant were used as the prime vaccine. It was found that, in the presence of aluminium hydroxide (Alum) and unmethylated CpG-oligodeoxynucleotides (CpG) adjuvants, more cross-protective immunity against SARS-CoV-2 prototype and variants were elicited by bivalent vaccine than monovalent wtRBD or Delta RBD. Furthermore, a heterologous boosting strategy consisting of two doses of bivalent vaccines followed by one dose adenovirus vectored vaccine exhibited cross-neutralization capacity and specific T cell responses against Delta and Omicron (BA.1 and BA.4/5) variants in mice, superior to a homologous vaccination strategy. This study suggested that heterologous prime-boost vaccination with yeast-derived bivalent protein vaccine could be a potential approach to address the challenge of emerging variants.

Blended BA.5 infection within 8 days after a boosted bivalent mRNA vaccination strengthens and lengthens the host immunity.

The impact of SARS-CoV-2 infection shortly after vaccination on vaccine-induced immunity is unknown, which is also one of the concerns for some vaccinees during the pandemic. Here, based on a cohort of individuals who encountered BA.5 infection within 8 days after receiving the fourth dose of a bivalent mRNA vaccine, preceded by three doses of inactivated vaccines, we show that booster mRNA vaccination provided 48% protection efficacy against symptomatic infections. At Day 7 postvaccination, the level of neutralizing antibodies (Nabs) against WT and BA.5 strains in the uninfected group trended higher than those in the symptomatic infection group. Moreover, there were greater variations in Nabs levels and a significant decrease in virus-specific CD4+ T cell response observed in the symptomatic infection group. However, symptomatic BA.5 infection significantly increased Nab levels against XBB.1.9.1 and BA.5 (symptomatic > asymptomatic > uninfected group) at Day 10 and resulted in a more gradual decrease in Nabs against BA.5 compared to the uninfected group at Day 90. Our data suggest that BA.5 infection might hinder the early generation of Nabs and the recall of the CD4+ T cell response but strengthens the Nab and virus-specific T cell response in the later phase. Our data confirmed that infection can enhance host immunity regardless of the short interval between vaccination and infection and alleviate concerns about infections shortly after vaccination, which provides valuable guidance for developing future vaccine administration strategies.

Progress and challenges in the clinical evaluation of immune responses to respiratory mucosal vaccines.

INTRODUCTION: Following the coronavirus disease pandemic, respiratory mucosal vaccines that elicit both mucosal and systemic immune responses have garnered increasing attention. However, human physiological characteristics pose significant challenges in the evaluation of mucosal immunity, which directly impedes the development and application of respiratory mucosal vaccines. AREAS COVERED: This study summarizes the characteristics of immune responses in the respiratory mucosa and reviews the current status and challenges in evaluating immune response to respiratory mucosal vaccines. EXPERT OPINION: Secretory Immunoglobulin A (S-IgA) is a major effector molecule at mucosal sites and a commonly used indicator for evaluating respiratory mucosal vaccines. However, the unique physiological structure of the respiratory tract pose significant challenges for the clinical collection and detection of S-IgA. Therefore, it is imperative to develop a sampling method with high collection efficiency and acceptance, a sensitive detection method, reference materials for mucosal antibodies, and to establish a threshold for S-IgA that correlates with clinical protection. Sample collection is even more challenging when evaluating mucosal cell immunity. Therefore, a mucosal cell sampling method with high operability and high tolerance should be established. Targets of the circulatory system capable of reflecting mucosal cellular immunity should also be explored.

Immune escape of BA.2.86 is comparable to XBB subvariants from the plasma of BA.5- and BA.5-XBB-convalescent subpopulations.

The EG.5.1 variant of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been prevalent since mid-July 2023 in the United States and China. The variant BA.2.86 has become a major concern because it is 34 mutations away from the parental variant BA.2 and >30 mutations from XBB.1.5. There is an urgent need to evaluate whether the immunity of the population and current vaccines are protective against EG.5.1 and BA.2.86. Based on a cohort of two breakthrough-infected groups, the levels of neutralizing antibodies (NAbs) against different subvariants were measured using pseudovirus-based neutralization assays. XBB.1.5, EG.5.1, and BA.2.86 are comparably immune-evasive from neutralization by the plasma of individuals recovered from BA.5 infection (BA.5-convalescent) or XBB.1.9.2/XBB.1.5 infection following BA.5 infection (BA.5-XBB-convalescent). NAb levels against EG.5.1 and BA.2.86 subvariants remained >120 geometric mean titers (GMTs) in BA.5-XBB-convalescent individuals 2 months postinfection but were <40 GMTs in BA.5-convalescent individuals. Furthermore, the XBB-targeting messenger RNA (mRNA) vaccine RQ3033 induced higher levels of NAbs against XBB.1.5, EG.5.1, and BA.2.86 than against BA.5-XBB infection. The results suggest that BA.2.86 and EG.5.1 are unlikely to cause more severe concerns than the currently circulating XBB subvariants and that the XBB.1.5-targeting mRNA vaccine tested has promising protection against EG.5.1 and BA.2.86.

Dynamic immune landscape in vaccinated-BA.5-XBB.1.9.1 reinfections revealed a 5-month protection-duration against XBB infection and a shift in immune imprinting.

BACKGROUND: The impact of previous vaccination on protective immunity, duration, and immune imprinting in the context of BA.5-XBB.1.9.1 reinfection remains unknown. METHODS: Based on a 2-year longitudinal cohort from vaccination, BA.5 infection and XBB reinfection, several immune effectors, including neutralizing antibodies (Nabs), antibody-dependent cellular cytotoxicity (ADCC), virus-specific T cell immunity were measured to investigate the impact of previous vaccination on host immunity induced by BA.5 breakthrough infection and BA.5-XBB.1.9.1 reinfection. FINDINGS: In absence of BA.5 Nabs, plasma collected 3 months after receiving three doses of inactivated vaccine (I-I-I) showed high ADCC that protected hACE2-K18 mice from fatality and significantly reduced viral load in the lungs and brain upon BA.5 challenge, compared to plasma collected 12 months after I-I-I. Nabs against XBB.1.9.1 induced by BA.5 breakthrough infection were low at day 14 and decreased to a GMT of 10 at 4 months and 28% (9/32) had GMT ≤4, among whom 67% (6/9) were reinfected with XBB.1.9.1 within 1 month. However, 63% (20/32) were not reinfected with XBB.1.9.1 at 5 months post BA.5 infection. Interestingly, XBB.1.9.1 reinfection increased Nabs against XBB.1.9.1 by 24.5-fold at 14 days post-reinfection, which was much higher than that against BA.5 (7.3-fold) and WT (4.5-fold), indicating an immune imprinting shifting from WT to XBB antigenic side. INTERPRETATION: Overall, I-I-I can provide protection against BA.5 infection and elicit rapid immune response upon BA.5 infection. Furthermore, BA.5 breakthrough infection effectively protects against XBB.1.9.1 lasting more than 5 months, and XBB.1.9.1 reinfection results in immune imprinting shifting from WT antigen induced by previous vaccination to the new XBB.1.9.1 antigen. These findings strongly suggest that future vaccines should target variant strain antigens, replacing prototype strain antigens. FUNDING: This study was supported by R&D Program of Guangzhou National Laboratory (SRPG23-005), National Key Research and Development Program of China (2022YFC2604104, 2019YFC0810900), S&T Program of Guangzhou Laboratory (SRPG22-006), and National Natural Science Foundation of China (81971485, 82271801, 81970038), Emergency Key Program of Guangzhou Laboratory (EKPG21-30-3), Zhongnanshan Medical Foundation of Guangdong Province (ZNSA-2020013), and State Key Laboratory of Respiratory Disease (J19112006202304).

Safety, tolerability, and immunogenicity of a CpG/Alum adjuvanted SARS-CoV-2 recombinant protein vaccine (ZR202-CoV) in healthy adults: Preliminary report of a phase 1, randomized, double-blind, placebo-controlled, dose-escalation trial.

This was a phase 1 dose-escalation study of ZR202-CoV, a recombinant protein vaccine candidate containing a pre-fusion format of the spike (S)-protein (S-trimer) combined with the dual-adjuvant system of Alum/CpG. A total of 230 participants were screened and 72 healthy adults aged 18-59 years were enrolled and randomized to receive two doses at a 28-day interval of three different ZR202-CoV formulations or normal saline. We assessed the safety for 28 days after each vaccination and collected blood samples for immunogenicity evaluation. All formulations of ZR202-CoV were well-tolerated, with no observed solicited adverse events ≥ Grade 3 within 7 days after vaccination. No unsolicited adverse events ≥ Grade 3, or serious adverse events related to vaccination occurred as determined by the investigator. After the first dose, detectable immune responses were observed in all subjects. All subjects that received ZR202-CoV seroconverted at 14 days after the second dose by S-binding IgG antibody, pseudovirus and live-virus based neutralizing antibody assays. S-binding response (GMCs: 2708.7 ~ 4050.0 BAU/mL) and neutralizing activity by pseudovirus (GMCs: 363.1 ~ 627.0 IU/mL) and live virus SARS-CoV-2 (GMT: 101.7 ~ 175.0) peaked at 14 days after the second dose of ZR202-CoV. The magnitudes of immune responses compared favorably with COVID-19 vaccines with reported protective efficacy.

Safety, immunogenicity, and efficacy of an mRNA COVID-19 vaccine (RQ3013) given as the fourth booster following three doses of inactivated vaccines: a double-blinded, randomised, controlled, phase 3b trial.

Background: Heterologous vaccine schedules have been recommended to provide superior immunity and protection against emergent SARS-CoV-2 variants of concern. We aimed to evaluate the safety, immunogenicity, and efficacy of an mRNA COVID-19 vaccine RQ3013 compared with adenoviral vectored vaccine Ad5-nCoV and protein subunit vaccine ZF2001 as the fourth dose in adults primed with three doses of inactivated vaccines in China. Methods: We conducted a double-blinded, randomised, controlled, phase 3b trial among healthy Chinese adults at Lancang County, Yunnan, China. Adults who had received three doses of inactivated COVID-19 vaccines at least 6 months prior were randomly allocated (3:1:1) to receive heterologous boosters with RQ3013, Ad5-nCoV, or ZF2001. We assessed safety within 28 days post boost and the serum geometric mean titres (GMTs) of neutralising antibodies (NAbs) against the live SARS-CoV-2 omicron variant BA.5 on day 14 post-boost. We used Poisson regression to assess the vaccine efficacy against the first episode of virologically confirmed symptomatic COVID-19 occurring at least 7 days post boost. Subgroup analyses categorized by age and sex were also performed for safety and immunogenicity outcomes. This trial has been registered with the Chinese Clinical Trial Registry (ChiCTR2200065281) and is now complete. Findings: Between December 12 and December 18, 2022, a total of 1382 adults were screened, and 1250 were enrolled and randomly assigned to receive one dose of RQ3013 (n = 750), Ad5-nCoV (n = 250), or ZF2001 (n = 250). Although solicited adverse reactions within 28 days post boost were more frequent in the RQ3013 group (175 [23.3%]) compared to the control groups (24 [9.6%] in both the Ad5-nCOV and ZF2001 groups, P < 0.05), incidences of Grade 3 events were low (9 [0.7%]) and comparable across three groups (P > 0.05). On day 14 post-boost, RQ3013 (GMT 69.14, 95% CI 47.90-99.81) elicited 4.8-fold and 5.6-fold higher concentrations of NAbs against BA.5 than did Ad5-nCoV (14.37, 7.78-26.56) and ZF2001 (12.21, 5.13-29.06), respectively. On day 28 post-boost, RQ3013 demonstrated a relative efficacy of 62.2% (95% CI 13.7-83.1, P = 0.02) compared to Ad5-nCoV, and of 69.0% (33.5-85.7, P = 0.002) compared to ZF2001. Interpretation: The administrations of all the three heterologous boosters were well tolerated. The heterologous prime-boost regimen with RQ3013 elicited superior immune responses and demonstrated better protection against symptomatic SARS-CoV-2 infections compared with Ad5-nCoV or ZF2001, supporting the use of RQ3013 as a booster vaccination in adults. Funding: Yunnan Province Science and Technology Department (grant no.202302AA310047).

Safety, immunogenicity, and efficacy of the mRNA vaccine CS-2034 as a heterologous booster versus homologous booster with BBIBP-CorV in adults aged ≥18 years: a randomised, double-blind, phase 2b trial.

BACKGROUND: Heterologous boosting is suggested to be of use in populations who have received inactivated COVID-19 vaccines. We aimed to assess the safety and immunogenicity of a heterologous vaccination with the mRNA vaccine CS-2034 versus the inactivated BBIBP-CorV as a fourth dose, as well as the efficacy against the SARS-CoV-2 omicron (BA.5) variant. METHODS: This trial contains a randomised, double-blind, parallel-controlled study in healthy participants aged 18 years or older (group A) and an open-label cohort in participants 60 years and older (group B), who had received three doses of inactivated whole-virion vaccines at least 6 months before enrolment. Pregnant women and people with major chronic illnesses or a history of allergies were excluded. Eligible participants in group A were stratified by age (18-59 years and ≥60 years) and then randomised by SAS 9.4 in a ratio of 3:1 to receive a dose of the mRNA vaccine (CS-2034, CanSino, Shanghai, China) or inactivated vaccine (BBIBP-CorV, Sinopharm, Beijing, China). Safety and immunogenicity against omicron variants of the fourth dose were evaluated in group A. Participants 60 years and older were involved in group B for safety observations. The primary outcome was geometric mean titres (GMTs) of the neutralising antibodies against omicron and seroconversion rates against BA.5 variant 28 days after the boosting, and incidence of adverse reactions within 28 days. The intention-to-treat group was involved in the safety analysis, while all patients in group A who had blood samples taken before and after the booster were involved in the immunogenicity analysis. This trial was registered at the Chinese Clinical Trial Registry Centre (ChiCTR2200064575). FINDINGS: Between Oct 13, and Nov 22, 2022, 320 participants were enrolled in group A (240 in the CS-2034 group and 80 in the BBIBP-CorV group) and 113 in group B. Adverse reactions after vaccination were more frequent in CS-2034 recipients (158 [44·8%]) than BBIBP-CorV recipients (17 [21·3%], p<0·0001). However, most adverse reactions were mild or moderate, with grade 3 adverse reactions only reported by eight (2%) of 353 participants receiving CS-2034. Heterologous boosting with CS-2034 elicited 14·4-fold (GMT 229·3, 95% CI 202·7-259·4 vs 15·9, 13·1-19·4) higher concentration of neutralising antibodies to SARS-CoV-2 omicron variant BA.5 than did homologous boosting with BBIBP-CorV. The seroconversion rates of SARS-CoV-2-specific neutralising antibody responses were much higher in the mRNA heterologous booster regimen compared with BBIBP-CorV homologous booster regimen (original strain 47 [100%] of 47 vs three [18·8%] of 16; BA.1 45 [95·8%] of 48 vs two [12·5%] 16; and BA.5 233 [98·3%] of 240 vs 15 [18·8%] of 80 by day 28). INTERPRETATION: Both the administration of mRNA vaccine CS-2034 and inactivated vaccine BBIBP-CorV as a fourth dose were well tolerated. Heterologous boosting with mRNA vaccine CS-2034 induced higher immune responses and protection against symptomatic SARS-CoV-2 omicron infections compared with homologous boosting, which could support the emergency use authorisation of CS-2034 in adults. FUNDING: Science and Technology Commission of Shanghai, National Natural Science Foundation of China, Jiangsu Provincial Science Fund for Distinguished Young Scholars, and Jiangsu Provincial Key Project of Science and Technology Plan. TRANSLATION: For the Chinese translation of the abstract see Supplementary Materials section.

Safety and immunogenicity of heterologous boosting with orally aerosolised or intramuscular Ad5-nCoV vaccine and homologous boosting with inactivated vaccines (BBIBP-CorV or CoronaVac) in children and adolescents: a randomised, open-label, parallel-controlled, non-inferiority, single-centre study.

BACKGROUND: Heterologous booster immunisation with orally administered aerosolised Ad5-nCoV vaccine (AAd5) has been shown to be safe and highly immunogenic in adults. Here, we aimed to assess the safety and immunogenicity of heterologous booster immunisation with orally administered AAd5 in children and adolescents aged 6-17 years who had received two doses of inactivated vaccine (BBIBP-CorV or CoronaVac). METHODS: We did a randomised, open-label, parallel-controlled, non-inferiority study to assess the safety and immunogenicity of heterologous booster immunisation with AAd5 (0·1 mL) or intramuscular Ad5-nCoV vaccine (IMAd5; 0·3 mL) and homologous booster immunisation with inactivated vaccine (BBIBP-CorV or CoronaVac; 0·5 mL) in children (aged 6-12 years) and adolescents (aged 13-17 years) who had received two doses of inactivated vaccine at least 3 months earlier in Hunan, China. Children and adolescents who were previously immunised with two-dose BBIBP-CorV or CoronaVac were recruited for eligibility screening at least 3 months after the second dose. A stratified block method was used for randomisation, and participants were stratified by age and randomly assigned (3:1:1) to receive AAd5, IMAd5, or inactivated vaccine. The study staff and participants were not masked to treatment allocation. Laboratory and statistical staff were masked during the study. In this interim analysis, adverse events within 14 days and geometric mean titre (GMT) of serum neutralising antibodies on day 28 after the booster vaccination, based on the per-protocol population, were used as the primary outcomes. The analysis of non-inferiority was based on comparison using a one-sided 97·5% CI with a non-inferiority margin of 0·67. This study was registered at ClinicalTrials.gov, NCT05330871, and is ongoing. FINDINGS: Between April 17 and May 28, 2022, 436 participants were screened and 360 were enrolled: 220 received AAd5, 70 received IMAd5, and 70 received inactivated vaccine. Within 14 days after booster vaccination, vaccine-related adverse reactions were reported: 35 adverse events (in 13 [12%] of 110 children and 22 [20%] of 110 adolescents) in 220 individuals in the AAd5 group, 35 (in 18 [51%] of 35 children and 17 [49%] of 35 adolescents) in 70 individuals in the IMAd5 group, and 13 (in five [14%] of 35 children and eight [23%] of 35 adolescents) in 70 individuals in the inactivated vaccine group. Solicited adverse reactions were also reported: 34 (13 [12%] of 110 children and 21 [10%] of 110 adolescents) in 220 individuals in the AAd5 group, 34 (17 [49%] of 35 children and 17 [49%] of 35 adolescents) in 70 individuals in the IMAd5 group, and 12 (five [14%] of 35 children and seven [20%] of 35 adolescents) in 70 individuals in the inactivated vaccine group. The GMTs of neutralising antibodies against ancestral SARS-CoV-2 Wuhan-Hu-1 (Pango lineage B) in the AAd5 group were significantly higher than the GMTs in the inactivated vaccine group (adjusted GMT ratio 10·2 [95% CI 8·0-13·1]; p<0·0001). INTERPRETATION: Our study shows that a heterologous booster with AAd5 is safe and highly immunogenic against ancestral SARS-CoV-2 Wuhan-Hu-1 in children and adolescents. FUNDING: National Key R&D Program of China.

Establishment of national standard for anti-SARS-Cov-2 neutralizing antibody in China: The first National Standard calibration traceability to the WHO International Standard.

Neutralizing antibody (NtAb) levels are key indicators in the development and evaluation of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines. Establishing a unified and reliable WHO International Standard (IS) for NtAb is crucial for the calibration and harmonization of NtAb detection assays. National and other WHO secondary standards are key links in the transfer of IS to working standards but are often overlooked. The Chinese National Standard (NS) and WHO IS were developed by China and WHO in September and December 2020, respectively, the application of which prompted and coordinated sero-detection of vaccine and therapy globally. Currently, a second-generation Chinese NS is urgently required owing to the depletion of stocks and need for calibration to the WHO IS. The Chinese National Institutes for Food and Drug Control (NIFDC) developed two candidate NSs (samples 33 and 66-99) traced to the IS according to the WHO manual for the establishment of national secondary standards through a collaborative study of nine experienced labs. Either NS candidate can reduce the systematic error among different laboratories and the difference between the live virus neutralization (Neut) and pseudovirus neutralization (PsN) methods, ensuring the accuracy and comparability of NtAb test results among multiple labs and methods, especially for samples 66-99. At present, samples 66-99 have been approved as the second-generation NS, which is the first NS calibrated tracing to the IS with 580 (460-740) International Units (IU)/mL and 580 (520-640) IU/mL by Neut and PsN, respectively. The use of standards improves the reliability and comparability of NtAb detection, ensuring the continuity of the use of the IS unitage, which effectively promotes the development and application of SARS-CoV-2 vaccines in China.

SARS-CoV-2 epitope-specific T cells: Immunity response feature, TCR repertoire characteristics and cross-reactivity.

The devastating COVID-19 pandemic caused by SARS-CoV-2 and multiple variants or subvariants remains an ongoing global challenge. SARS-CoV-2-specific T cell responses play a critical role in early virus clearance, disease severity control, limiting the viral transmission and underpinning COVID-19 vaccine efficacy. Studies estimated broad and robust T cell responses in each individual recognized at least 30 to 40 SARS-CoV-2 antigen epitopes and associated with COVID-19 clinical outcome. Several key immunodominant viral proteome epitopes, including S protein- and non-S protein-derived epitopes, may primarily induce potent and long-lasting antiviral protective effects. In this review, we summarized the immune response features of immunodominant epitope-specific T cells targeting different SRAS-CoV-2 proteome structures after infection and vaccination, including abundance, magnitude, frequency, phenotypic features and response kinetics. Further, we analyzed the epitopes immunodominance hierarchy in combination with multiple epitope-specific T cell attributes and TCR repertoires characteristics, and discussed the significant implications of cross-reactive T cells toward HCoVs, SRAS-CoV-2 and variants of concern, especially Omicron. This review may be essential for mapping the landscape of T cell responses toward SARS-CoV-2 and optimizing the current vaccine strategy.

Development of SARS-CoV-2 animal vaccines using a stable and efficient NDV expression system.

With the continuation of the coronavirus disease 2019 pandemic and the emergence of new severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants, the control of the spread of the virus remains urgent. Various animals, including cats, ferrets, hamsters, nonhuman primates, minks, tree shrews, fruit bats, and rabbits, are susceptible to SARS-CoV-2 infection naturally or experimentally. Therefore, to avoid animals from becoming mixing vessels of the virus, vaccination of animals should be considered. In the present study, we report the establishment of an efficient and stable system using Newcastle disease virus (NDV) as a vector to express SARS-CoV-2 spike protein/subunit for the rapid generation of vaccines against SARS-CoV-2 in animals. Our data showed that the S and S1 protein was sufficiently expressed in rNDV-S and rNDV-S1-infected cells, respectively. The S protein was incorporated into and displayed on the surface of rNDV-S viral particles. Intramuscular immunization with rNDV-S was found to induce the highest level of binding and neutralizing antibodies, as well as strong S-specific T-cell response in mice. Intranasal immunization with rNDV-S1 provoked a robust T-cell response but barely any detectable antibodies. Overall, the NDV-vectored vaccine candidates were able to induce profound humoral and cellular immunity, which will provide a good system for developing vaccines targeting both T-cell and antibody responses.

Heterologous Omicron-adapted vaccine as a secondary booster promotes neutralizing antibodies against Omicron and its sub-lineages in mice.

Over one billion people have received 2-3 dosages of an inactivated COVID-19 vaccine for basic immunization. Whether a booster dose should be delivered to protect against the Omicron variant and its sub-lineages, remains controversial. Here, we tested different vaccine platforms targeting the ancestral or Omicron strain as a secondary booster of the ancestral inactivated vaccine in mice. We found that the Omicron-adapted inactivated viral vaccine promoted a neutralizing antibody response against Omicron in mice. Furthermore, heterologous immunization with COVID-19 vaccines based on different platforms remarkably elevated the levels of cross- neutralizing antibody against Omicron and its sub-lineages. Omicron-adapted vaccines based on heterologous platforms should be prioritized in future vaccination strategies to control COVID-19.

Xanthones from securidaca inappendiculata antagonizes the anti-rheumatic effect of methotrexate by inhibiting reduced folate carrier 1.

BACKGROUND: The first-line anti-rheumatic drug methotrexate (MTX) is used in the combination. Because of the unpredictable adverse reactions, optimization of relevant regimens is necessary and meaningful. This study aimed to study the possible interaction between Securidaca inappendiculate Hassk. Derived xanthones and MTX. METHODS: We established adjuvant-induced arthritis (AIA) model, which was treated with MTX and MTX + xanthone-rich fraction (XRF). The clinical efficacy was evaluated by histopathological examination, and LC-MS was used to monitor the blood concentration of MTX. Western blotting and immunohistochemistry were used to detect protein expression. In vitro, we assessed the activity of related transporters by cellular uptake assay based on HEK-293T cells. RESULTS: Compared with MTX-treated rats, inflammation in the immunized rats in the MTX + XRF group was obvious, indicating that XRF antagonized the anti-rheumatic effect of MTX. Meanwhile, XRF reduced liver and kidney injuries caused by MTX in addition to MTX. Results from immunohistochemical and nappendiculat assays suggested that XRF may reduce uptake of MTX by down-regulating reduced folate carrier 1 (RFC1). CONCLUSION: This study indicated that XRF could reduce the plasma concentration of MTX by inhibiting the expression of RFC1, antagonize the therapeutic effect of MTX on AIA rats, and reduce its oral bioavailability. The combination of S. inappendiculate and MTX should be further optimized to achieve the goal of increasing efficiency and reducing toxicity.

Virus infection pattern imprinted and diversified the differentiation of T-cell memory in transcription and function.

Introduction: Memory T (Tm) cells are a subpopulation of immune cells with great heterogeneity. Part of this diversity came from T cells that were primed with different viruses. Understanding the differences among different viral-specific Tms will help develop new therapeutic strategies for viral infections. Methods: In this study, we compared the transcriptome of Tm cells that primed with CMV, EBV and SARS-CoV-2 with single-cell sequencing and studied the similarities and differences in terms of subpopulation composition, activation, metabolism and transcriptional regulation. Results: We found that CMV is marked by plentiful cytotoxic Temra cells, while EBV is more abundant in functional Tem cells. More importantly, we found that CD28 and CTLA4 can be used as continuous indicators to interrogate the antiviral ability of T cells. Furthermore, we proposed that REL is a main regulatory factor for CMV-specific T cells producing cytokines and plays an antiviral role. Discussion: Our data gives deep insight into molecular characteristics of Tm subsets from different viral infection, which is important to understand T cell immunization. Furthermore, our results provide basic background knowledges for T cell based vaccine development in future.

SARS-CoV-2 vaccination-infection pattern imprints and diversifies T cell differentiation and neutralizing response against Omicron subvariants.

The effects of different SARS-CoV-2 vaccinations and variant infection histories on imprinting population immunity and their influence on emerging escape mutants remain unclear. We found that Omicron (BA.1) breakthrough infection, regardless of vaccination with two-dose mRNA vaccines (M-M-o) or two-dose inactivated vaccines (I-I-o), led to higher neutralizing antibody levels against different variants and stronger T-cell responses than Delta breakthrough infection after two-dose inactivated vaccine vaccination (I-I-δ). Furthermore, different vaccination-infection patterns imprinted virus-specific T-cell differentiation; M-M-ο showed higher S/M/N/E-specific CD4+ T cells and less portion of virus-specific CD45RA+CD27-CD8+ T cells by ex vivo assay. Breakthrough infection groups showed higher proliferation and multi-function capacity by in vitro assay than three-dose inactivated vaccine inoculated group (I-I-I). Thus, under wide vaccination coverage, the higher immunogenicity with the Omicron variant may have helped to eliminate the population of Delta variant. Overall, our data contribute to our understanding of immune imprinting in different sub-populations and may guide future vaccination programs.

Cutting Edge: High-Dose Live Attenuated Influenza Vaccines Elicit Pulmonary Tissue-Resident Memory CD8+ T Cells in the Face of Pre-Existing Humoral Immunity.

In this study, we investigated how pre-existing Ab immunity to influenza virus established from prior immunizations affects the development of CD8+ T cell responses evoked after vaccination with a live attenuated vaccine. Using a mouse model and a panel of live attenuated influenza virus vaccine candidates (cold adapted and single cycle), we show that pre-existing influenza-specific Abs directed against the vaccine backbone attenuate the size and quality of the vaccine-induced CD8+ T cell response. Importantly, we show that increasing the vaccine dose can overcome this impediment, resulting in improved vaccine-induced circulating and tissue-resident memory CD8+ T cell responses, which were protective against heterologous influenza challenge. Thus, the reduced size and quality of the T cell response elicited by a live attenuated influenza virus vaccine imparted by the influenza-specific Ab landscape of the vaccinee can be overcome by increasing vaccine dose.