Evaluation of Swine Protection with Three Commercial Foot-and-Mouth Disease Vaccines against Heterologous Challenge with Type A ASIA/G-VII Lineage Viruses.

Outbreaks caused by foot-and-mouth disease (FMD) A/ASIA/G-VII lineage viruses have often occurred in Middle Eastern and Southeast Asian countries since 2015. Because A/ASIA/G-VII lineage viruses are reported to have distinct antigenic relatedness with available commercial FMD vaccine strains, it is necessary to investigate whether inoculation with vaccines used in Korea could confer cross-protection against A/ASIA/G-VII lineage viruses. In the present study, we conducted two vaccination challenge trials to evaluate the efficacy of three commercial FMD vaccines (O/Manisa + O/3039 + A/Iraq, O/Campos + A/Cruzeiro + A/2001, and O/Primorsky + A/Zabaikalsky) against heterologous challenge with ASIA/G-VII lineage viruses (A/TUR/13/2017 or A/BHU/3/2017 strains) in pigs. In each trial, clinical signs, viremia, and salivary shedding of virus were measured for 7 days after challenge. In summary, the O/Campos + A/Cruzeiro + A/2001 vaccine provided full protection against two A/ASIA/G-VII lineage viruses in vaccinated pigs, where significant protection was observed. Although unprotected animals were observed in groups vaccinated with O/Manisa + O/3039 + A/Iraq or O/Primorsky + A/Zabaikalsky vaccines, the clinical scores and viral RNA levels in the sera and oral swabs of vaccinated animals were significantly lower than those of unvaccinated controls.

Evaluation of Binding and Neutralizing Antibodies for Inactivated SARS-CoV-2 Vaccine Immunization.

The circulating severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variant presents an ongoing challenge for surveillance and detection. It is important to establish an assay for SARS-CoV-2 antibodies in vaccinated individuals. Numerous studies have demonstrated that binding antibodies (such as S-IgG and N-IgG) and neutralizing antibodies (Nabs) can be detected in vaccinated individuals. However, it is still unclear how to evaluate the consistency and correlation between binding antibodies and Nabs induced by inactivated SARS-CoV-2 vaccines. In this study, serum samples from humans, rhesus macaques, and hamsters immunized with inactivated SARS-CoV-2 vaccines were analyzed for S-IgG, N-IgG, and Nabs. The results showed that the titer and seroconversion rate of S-IgG were significantly higher than those of N-IgG. The correlation between S-IgG and Nabs was higher compared to that of N-IgG. Based on this analysis, we further investigated the titer thresholds of S-IgG and N-IgG in predicting the seroconversion of Nabs. According to the threshold, we can quickly determine the positive and negative effects of the SARS-CoV-2 variant neutralizing antibody in individuals. These findings suggest that the S-IgG antibody is a better supplement to and confirmation of SARS-CoV-2 vaccine immunization.

Rational design of a cross-type HPV vaccine through immunodominance shift guided by a cross-neutralizing antibody.

In vaccine development, broadly or cross-type neutralizing antibodies (bnAbs or cnAbs) are frequently targeted to enhance protection. Utilizing immunodominant antibodies could help fine-tune vaccine immunogenicity and augment the precision of immunization strategies. However, the methodologies to capitalize on the attributes of bnAbs in vaccine design have not been clearly elucidated. In this study, we discovered a cross-type neutralizing monoclonal antibody, 13H5, against human papillomavirus 6 (HPV6) and HPV11. This nAb exhibited a marked preference for HPV6, demonstrating superior binding activity to virus-like particles (VLPs) and significantly higher prevalence in anti-HPV6 human serum as compared to HPV11 antiserum (90% vs. 31%). Through co-crystal structural analysis of the HPV6 L1 pentamer:13H5 complex, we delineated the epitope as spanning four segments of amino acids (Phe42-Ala47, Gly172-Asp173, Glu255-Val275, and Val337-Tyr351) on the L1 surface loops. Further interaction analysis and site-directed mutagenesis revealed that the Ser341 residue in the HPV6 HI loop plays a critical role in the interaction between 13H5 and L1. Substituting Ser341 with alanine, which is the residue type present in HPV11 L1, almost completely abolished binding activity to 13H5. By swapping amino acids in the HPV11 HI loop with corresponding residues in HPV6 L1 (Ser341, Thr338, and Thr339), we engineered chimeric HPV11-6HI VLPs. Remarkably, the chimeric HPV11-6HI VLPs shifted the high immunodominance of 13H5 from HPV6 to the engineered VLPs and yielded comparable neutralization titers for both HPV6 and HPV11 in mice and non-human primates. This approach paves the way for the design of broadly protective vaccines from antibodies within the main immunization reservoir.

A Novel, Comprehensive A129 Mouse Model for Investigating Dengue Vaccines and Evaluating Pathogenesis.

In search of a mouse model for use in evaluating dengue vaccines, we assessed A129 mice that lacked IFN-α/ß receptors, rendering them susceptible to dengue virus (DENV) infection. To our knowledge, no reports have evaluated dengue vaccine efficiency using A129 mice. A129 mice were given a single intraperitoneal (IP) or subcutaneous (SC) injection of the vaccine, Dengvaxia. After 14 days of immunization via the IP or SC injection of Dengvaxia, the A129 mice exhibited notably elevated levels of anti-DENV immunoglobulin G and neutralizing antibodies (NAb) targeting all four DENV serotypes, with DENV-4 displaying the highest NAb levels. After challenge with DENV-2, Dengvaxia and mock-immunized mice survived, while only the mock group exhibited signs of morbidity. Viral genome levels in the serum and tissues (excluding the brain) were considerably lower in the immunized mice compared to those in the mock group. The SC administration of Dengvaxia resulted in lower viremia levels than IP administration did. Therefore, given that A129 mice manifest dengue-related morbidity, including viremia in the serum and other tissues, these mice represent a valuable model for investigating novel dengue vaccines and antiviral drugs and for exploring dengue pathogenesis.

Allergic Reactions to E. coli Asparaginase are Associated with Decreased Asparaginase Activity in an Indonesian Pediatric Population with ALL.

PURPOSE: The asparaginase's (ASP) utility for ALL treatment is limited by neutralizing antibodies, which is problematic in countries whose access limited to alternative preparations. ASP antibody levels and activity was measured during remission induction and associated with allergy manifestations. METHODS: E. coli ASP was dosed at 7500 IU/m2. ASP IgG antibody levels were quantified at the beginning and end of induction. ASP activity was measured 24 hours after 1st and 5th dose (standard-risk) or 7th dose (high-risk patients) administration, and within 24 hours in case of allergic reactions. Allergy was monitored by CTCAE version 3. Parametric and non-parametric was performed for data analysis. RESULTS: ASP antibody and activity levels were available in 41/63 consecutive patients. Allergic manifestations occurred in 13/41, with urticaria being the most frequent. There were no significant differences in subject characteristics based on allergic reactions. The 5th dose was the most frequent time of onset. Antibody levels in allergy group at the end of induction did not differ from those at baseline (p<0.05). Using a 24-hour level of 100 mU/mL as a threshold for adequate ASP activity, 6/13 patients with allergy had adequate levels compared to 26/28 patients without (p<0.05). The ASP activity level at the end of induction phase in both groups did not show a significant decrement. CONCLUSION: The E. coli ASP activity with adequate levels were significantly higher in non-allergy group. Its activity level was not accompanied by increment of IgG in allergic group indicates other factors might affect activity levels in allergy group.

A Pseudovirus-Based Entry Assay to Evaluate Neutralizing Activity against Respiratory Syncytial Virus.

Respiratory syncytial virus (RSV) infection can cause life-threatening pneumonia and bronchiolitis, posing a significant threat to human health worldwide, especially to children and the elderly. Currently, there is no specific treatment for RSV infection. The most effective measures for preventing RSV infection are vaccines and prophylactic medications. However, not all population groups are eligible for the approved vaccines or antibody-based preventive medications. Therefore, there is an urgent need to develop novel vaccines and prophylactic drugs available for people of all ages. High-throughput assays that evaluate the efficacy of viral entry inhibitors or vaccine-induced neutralizing antibodies in blocking RSV entry are crucial for evaluating vaccine and prophylactic drug candidates. We developed an efficient entry assay using a lentiviral pseudovirus carrying the fusion (F) protein of type A or B RSV. In addition, the essential parameters were systematically optimized, including the number of transfected plasmids, storage conditions of the pseudovirus, cell types, cell numbers, virus inoculum, and time point of detection. Furthermore, the convalescent sera exhibited comparable inhibitory activity in this assay as in the authentic RSV virus neutralization assay. We established a robust pseudovirus-based entry assay for RSV, which holds excellent promise for studying entry mechanisms, evaluating viral entry inhibitors, and assessing vaccine-elicited neutralizing antibodies against RSV.

Analysing transcriptomic signatures and identifying potential genes for the protective effect of inactivated COVID-19 vaccines.

Inactivated vaccines are one of the most effective strategies for controlling the coronavirus disease 2019 (COVID-19) pandemic. However, the response genes for the protective effect of inactivated vaccines are still unclear. Herein, we analysed the neutralization antibody responses elicited by vaccine serum and carried out transcriptome sequencing of RNAs isolated from the PBMCs of 29 medical staff receiving two doses of the CoronaVac vaccine. The results showed that SARS-CoV-2 neutralization antibody titers varied considerably among individuals, and revealed that many innate immune pathways were activated after vaccination. Furthermore, the blue module revealed that NRAS, YWHAB, SMARCA5, PPP1CC and CDC5L may be correlated with the protective effect of the inactivated vaccine. Additionally, MAPK1, CDC42, PPP2CA, EP300, YWHAZ and NRAS were demonstrated as the hub genes having a significant association with vaccines. These findings provide a basis for understanding the molecular mechanism of the host immune response induced by inactivated vaccines.

Pre-existing immunity to SARS-CoV-2 associates with strong T cell responses induced by inactivated COVID-19 vaccines.

Individuals with a recent common cold coronavirus infection, which leads to pre-existing immunity against SARS-CoV-2, displayed a less severe course of COVID-19. However, the relationship between pre-existing immunity against SARS-CoV-2 and the inactivated-vaccine-induced immune response is still unknown. Here, 31 healthcare workers who received standard two doses of inactivated COVID-19 vaccines (Weeks 0 and 4, respectively) were enrolled, vaccine-induced neutralization and T cell responses were detected, and the correlation between the pre-existing SARS-CoV-2-specific immunity was analyzed. We found the SARS-CoV-2-specific antibodies, pseudovirus neutralization test (pVNT) titers, and spike-specific interferon gamma (IFN-γ) production in CD4+ and CD8+ T cells were significantly elevated after two doses of inactivated vaccines. Interestingly, the pVNT titers after the second dose of vaccination displayed no significant correlation with the pre-existing SARS-CoV-2-specific antibodies or B cells, nor the pre-existing spike-specific CD4+ T cells. Notably, the spike-specific T cell response after the second dose of vaccination was positively correlated with the pre-existing receptor binding domain (RBD)-specific B cells and CD4+ T cells, which were documented by the frequencies of RBD-binding B cells, the breadth of RBD-specific B cell epitopes, and the frequency of IFN-γ-expressing RBD-specific CD4+ T cells. Overall, the inactivated-vaccine-induced T cell responses, not the inactivated-vaccine-induced neutralization, closely correlated with pre-existing immunity to SARS-CoV-2. Our results provide a better understanding of inactivated-vaccine-induced immunity and help predict the immunogenicity induced by inactivated vaccines in individuals.

Enhancement of Humoral and Cellular Immunity Against Severe Acute Respiratory Syndrome Coronavirus 2 by a Third Dose of BNT162b2 Vaccine in Japanese Healthcare Workers.

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has raised concerns regarding vaccine effectiveness. We investigated humoral and cellular immune responses against SARS-CoV-2 in healthcare workers before and after a third (booster) dose of the BNT162b2 messenger RNA vaccine. It significantly enhanced both humoral and cellular immunity in previously uninfected individuals. However, cellular immunity was not enhanced in previously infected persons, suggesting that 3 antigenic stimuli by vaccination or natural infection reached a plateau of cellular immunity. Even with reinforced immunity to SARS-CoV-2, we confirmed several postbooster breakthrough cases caused by the Omicron variant.

An Alternative Serological Measure for Assessing Foot-and-Mouth Disease Vaccine Efficacy against Homologous and Heterologous Viral Challenges in Pigs.

To analyze the relationship between homologous and heterologous serological titers of immunized pigs and their protection statuses against FMD virus challenges, in the present study, the correlation between the virus neutralization titers at 21 and 28 dpv and the protection statuses at 28 dpv against challenge with FMD virus was analyzed using data sets comprising five different combinations of homologous or heterologous challenge experiments in pigs vaccinated with type O (n = 96), A (n = 69), and Asia 1 (n = 74). As a result, the experiments were divided into three groups (21D-1, 21D-2, and 21D-3) in the 21-dpv model and two groups (28D-1 and 28D-2) in the 28-dpv model. Each response curve of groups 21D-1 and 21D-2 in the 21-dpv model was very similar to each curve of groups 28D-1 and 28D-2 in the 28-dpv model, respectively, even though there was an exceptional extra group (21D-3) in the 21-dpv model. The average titers estimating 0.75 probability of protection ranged from 1.06 to 1.62 log10 in the 21-dpv model and from 1.26 to 1.64 log10 in the 28-dpv model. In summary, we demonstrated that the serological method is useful for predicting the homologous and heterologous protection statuses of vaccinated pigs.

SARS-CoV-2 intra-host single-nucleotide variants associated with disease severity.

Variants of severe acute respiratory syndrome coronavirus 2 frequently arise within infected individuals. Here, we explored the level and pattern of intra-host viral diversity in association with disease severity. Then, we analyzed information underlying these nucleotide changes to infer the impetus including mutational signatures and immune selection from neutralizing antibody or T-cell recognition. From 23 January to 31 March 2020, a set of cross-sectional samples were collected from individuals with homogeneous founder virus regardless of disease severity. Intra-host single-nucleotide variants (iSNVs) were enumerated using deep sequencing. Human leukocyte antigen (HLA) alleles were genotyped by Sanger sequencing. Medical records were collected and reviewed by attending physicians. A total of 836 iSNVs (3-106 per sample) were identified and distributed in a highly individualized pattern. The number of iSNVs paced with infection duration peaked within days and declined thereafter. These iSNVs did not stochastically arise due to a strong bias toward C > U/G > A and U > C/A > G substitutions in reciprocal proportion with escalating disease severity. Eight nonsynonymous iSNVs in the receptor-binding domain could escape from neutralization, and eighteen iSNVs were significantly associated with specific HLA alleles. The level and pattern of iSNVs reflect the in vivo viral-host interaction and the disease pathogenesis.

Epidural intracranial abscesses and multiple bone metastases caused by disseminated Mycobacterium avium complex infection: illustrative case.

BACKGROUND: Mycobacterium avium complex (MAC) generally causes localized pulmonary infections in immunocompromised hosts, but rarely in other organs and tissues, which is called disseminated MAC infection. OBSERVATIONS: The authors herein present a 48-year-old male patient with disseminated MAC infectious lesions in the lungs and on the cranial, vertebral, femoral, and pelvic bones, a normal CD4 count, and immunopositivity for the interferon-ɤ (IFN-ɤ) neutralization antibody. Cranial lesions were multiple osteolytic lesions associated with abscesses in the cranial bones. The patient initially received conservative treatment with multiple antibiotics; however, cranial lesions worsened. Therefore, multiple cranial lesions were removed via osteoplastic craniectomy and the postoperative course was uneventful. Pathological findings revealed MAC infection. The patient was discharged without recurrence or complications. LESSONS: Multiple cranial MAC dissemination with immunopositivity for the IFN-ɤ antibody is rare. The authors herein present the clinical course of a rare surgical case of MAC dissemination with a literature review.

Assessment of antibody responses against SARS-CoV-2 in unvaccinated individuals and vaccinees from Omicron-BA.2 infection in Zhaoqing, Guangdong Province, China.

Currently, the majority of the global population has been vaccinated with the COVID-19 vaccine, and characterization studies of antibodies in vivo from Omicron breakthrough infection and naive infection populations are urgently needed to provide pivotal clues about accurate diagnosis, treatment, and next-generation vaccine design against SARS-CoV-2 infection. We showed that after infection with Omicron-BA.2, the antibody levels of specific IgM against the Wuhan strain and specific IgG against Omicron were not significantly elevated within 27 days of onset. Interestingly, in this study, the levels of humoral immunity against Omicron-specific IgM were significantly increased after breakthrough infection, suggesting that the detection of Omicron-specific IgM antibodies can be used as a test criterion of Omicron breakthrough infection. In addition, we observed that serums from unvaccinated individuals and the majority of vaccinated infections possessed only low or no neutralizing activity against Omicron at the onset of Omicron breakthrough infections, and at the later stage of Omicron-BA.2 breakthrough infection, levels of neutralization antibody against the Wuhan and Omicron strains were elevated in infected individuals. The findings of this study provide important clues for the diagnosis of Omicron breakthrough infections, antibody characterization studies and vaccine design against COVID-19.

Recombinant COVID-19 vaccine based on recombinant RBD/Nucleoprotein and saponin adjuvant induces long-lasting neutralizing antibodies and cellular immunity.

SARS-CoV-2 has caused a global pandemic, infecting millions of people. An effective preventive vaccine against this virus is urgently needed. Here, we designed and developed a novel formulated recombinant receptor-binding domain (RBD) nucleocapsid (N) recombinant vaccine candidates. The RBD and N were separately expressed in E. coli and purified using column chromatography. The female Balb/c mice were immunized subcutaneously with the combination of purified RBD and N alone or formulated with saponin adjuvant in a two-week interval in three doses. Neutralization antibody (Nabs) titers against the SARS-CoV-2 were detected by a Surrogate Virus Neutralization (sVNT) Test. Also, total IgG and IgG1, and IgG2a isotypes and the balance of cytokines in the spleen (IFN-γ, Granzyme B, IL-4, and IL-12) were measured by ELISA. The percentages of CD4+ and CD8+ T cells were quantified by flow cytometry. The lymphoproliferative activity of restimulated spleen cells was also determined. The findings showed that the combination of RBD and N proteins formulated with saponin significantly promoted specific total IgG and neutralization antibodies, elicited robust specific lymphoproliferative and T cell response responses. Moreover, marked increase in CD4+ and CD8+ T cells were observed in the adjuvanted RBD and N vaccine group compared with other groups. The results suggest that the formulations are able to elicit a specific long-lasting mixed Th1/Th2 balanced immune response. Our data indicate the significance of the saponin-adjuvanted RBD/N vaccine in the design of SARS-CoV-2 vaccines and provide a rationale for the development of a protective long-lasting and strong vaccine.

First-in-Human Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of a Rapidly Developed SARS-CoV-2 Therapeutic Antibody, AOD01, in Healthy Adults.

INTRODUCTION: AOD01 is a novel, fully human immunoglobulin (Ig) G1 neutralizing monoclonal antibody that was developed as a therapeutic against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). This first-in-human study assessed safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of AOD01 in healthy volunteers. METHODS: Intravenous doses of AOD01 were evaluated in escalating cohorts [four single-dose cohorts (2, 5, 10, and 20 mg/kg) and one two-dose cohort (two doses of 20 mg/kg, 24 h apart)]. RESULTS: Twenty-three subjects were randomized to receive AOD01 or a placebo in blinded fashion. A total of 34 treatment-emergent adverse events (TEAEs) were reported; all were mild in severity. Related events (headache and diarrhea) were reported in one subject each. No event of infusion reactions, serious adverse event (SAE), or discontinuation due to AE were reported. The changes in laboratory parameters, vital signs, and electrocardiograms were minimal. Dose-related exposure was seen from doses 2 to 20 mg/kg as confirmed by Cmax and AUC0-tlast. The median Tmax was 1.5-3 h. Clearance was dose independent. Study results revealed long half-lives (163-465 h). Antidrug antibodies (ADA) to AOD01 were not detected among subjects, except in one subject of the two-dose cohort on day 92. Sustained ex vivo neutralization of SARS-CoV-2 was recorded until day 29 with single doses from 2 to 20 mg/kg and until day 43 with two doses of 20 mg/kg. CONCLUSIONS: AOD01 was safe and well tolerated, demonstrated dose-related PK, non-immunogenic status, and sustained ex vivo neutralization of SARS-CoV-2 after single intravenous dose ranging from 2 to 20 mg/kg and two doses of 20 mg/kg and show good potential for treatment of SARS-CoV-2 infection. (Health Sciences Authority identifier number CTA2000119).

Neutralization Activity of Anti-drug Antibodies Against a Biotherapeutic Can Be Predicted from a Comprehensive Pharmacokinetics, Pharmacodynamics, and Anti-drug Antibody Data Analysis.

Historically, a neutralization antibody (NAb) assay is considered critical in immunogenicity assessment of biologic therapeutics, even with low anti-drug antibody (ADA) positive rates. In 2019, FDA new guidelines issued on immunogenicity testing acknowledged the possibility of using "a highly sensitive PD marker or an appropriately designed PK assay or both that generate data that inform clinical activity" to replace a NAb assay. In the current manuscript, we present data for PK, PD, and ADA assays which collectively succeed to replace the standalone NAb assay. The data include a total LC/MS-based PK assay, a serum neutralization antibody (SNA) assay that essentially measures pharmacodynamically functional PK and can detect NAb activity in the presence of 1:1 ratio of drug, and a highly drug-tolerant ADA assay. In addition, a model-based meta-analysis (MBMA) demonstrated that the ability of SNA assay to detect NAb at 1:1 ratio of drug is sensitive enough to monitor clinically meaningful efficacy change, which is 50% reduction of SNA titer. Our strategy of preparing a holistic data package discussed here may provide a roadmap to the community for alternatives in assaying neutralizing activity of ADA.

Efficient Gene Transfer to Kidney Using a Lentiviral Vector Pseudotyped with Zika Virus Envelope Glycoprotein.

Gene therapy's entrance into clinical settings has made it an ever more attractive field of study for various diseases. However, relatively little progress has been made in targeting kidney diseases due to poor gene delivery efficiency in renal cells. The development of novel gene therapy vectors for medical intervention to treat kidney diseases is needed. In this study, we designed and produced a pseudotyped lentiviral vector with envelope glycoproteins of Zika virus (ZIKV), and evaluated its potential use in viral vector entry, neutralization assay, and gene delivery especially in the renal context. The lentiviral vector, simplified as ZIKV-E, is pseudotyped with Env/G-TC representing the transmembrane (TM) and cytoplasmic (CY) domains of Env replaced with the TM and CY domains of the glycoprotein (G) of the vesicular stomatitis virus. In vivo results show that ZIKV-E induced efficient transduction in tubular epithelial cells in mouse kidneys, demonstrating >100-fold higher expression of exogenous green fluorescent protein gene compared with that achieved by vesicular stomatitis virus G (VSV-G) protein pseudotyped lentiviral vector. The results also showed that the vector ZIKV-E transduced cells in a pH-independent manner and the transduction was inhibited by anti-ZIKV Env domain III antibodies. Results also show that ZIKV-E can be used as a surrogate for studies of ZIKV entry mechanisms and neutralization antibody assay. In all, this study successfully demonstrated a novel pseudotyped lentiviral vector ZIKV-E for inducing high transduction efficiency in renal tubular epithelial cells that could serve as a foundation for gene therapy for the treatment of inherited renal diseases in humans.

Anti-Spike Antibody Response to Natural Infection with SARS-CoV-2 and Its Activity against Emerging Variants.

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has substantially affected human health globally. Spike-specific antibody response plays a major role in protection against SARS-CoV-2 infection. Here, we examined serological anti-spike antibody and memory B cell responses in adults with acute SARS-CoV-2 infection. Twenty-five adult patients were enrolled between January and September 2020, and 21 (84%) had a detectable spike-binding antibody response in serum on day 21 ± 8 (6 to 33) after the onset of illness. Among those with positive spike-binding antibody response, 19 (90%) had a positive hemagglutination titer and 15 (71%) had angiotensin-converting enzyme 2 (ACE2)-blocking serological activities. Follow-up serum samples collected 11 ± 1 (7 to 15) months after infection exhibited an average of 2.6 ± 1.0 (1.0 to 3.5)-fold reduction in the spike-binding antibody response. Moreover, convalescent and follow-up serum samples showed 83 ± 82 (15 to 306)- and 165 ± 167 (12 to 456)-fold reductions in the neutralization activity against the Omicron variant, respectively. Upon acute infection, spike-specific memory B cell responses were elicited, with an average frequency of 1.3% ± 1.2% of peripheral B cells on day 19 ± 7 (6 to 33) after the onset of illness. IgM memory B cells were predominantly induced. Patients with fever and pneumonia showed significantly stronger spike-binding, ACE2-blocking antibody, and memory B cell responses. In conclusion, spike-specific antibody response elicited upon acute SARS-CoV-2 infection may wane over time and be compromised by the emergence of viral variants. IMPORTANCE As spike protein-specific antibody responses play a major role in protection against SARS-CoV-2, we examined spike-binding and ACE2-blocking antibody responses in SARS-CoV-2 infection at different time points. We found robust responses following acute infection, which waned approximately 11 months after infection. Patients with fever and pneumonia showed significantly stronger spike-binding, ACE2-blocking antibody, and memory B cell responses. In particular, spike-specific antibody response in the convalescent and follow-up serum samples was substantially affected by emerging variants, especially Beta and Omicron variants. These results warrant continued surveillance of spike-specific antibody responses to natural infections and highlight the importance of maintaining functional anti-spike antibodies through immunization.

Association of neutralizing breadth against SARS-CoV-2 with inoculation orders of heterologous prime-boost vaccines.

BACKGROUND: Emerging evidence suggests heterologous prime-boost COVID-19 vaccination as a superior strategy than homologous schedules. Animal experiments and clinical observations have shown enhanced antibody response against influenza variants after heterologous vaccination; however, whether the inoculation order of COVID-19 vaccines in a prime-boost schedule affects antibody response against SARS-CoV-2 variants is not clear. METHODS: We conducted immunological analyses in a cohort of health care workers (n = 486) recently vaccinated by three types of inactivated COVID-19 vaccines under homologous or heterologous prime-boost schedules. Antibody response against ancestral SARS-CoV-2 (Wuhan-Hu-1) was assessed by total antibody measurements, surrogate virus neutralization tests, and pseudovirus neutralization assays (PNA). Furthermore, serum neutralization activity against SARS-CoV-2 variants of concern was also measured by PNA. FINDINGS: We observed strongest serum neutralization activity against the widely circulating SARS-CoV-2 variant B.1.617.2 among recipients of heterologous BBIBP-CorV/CoronaVac and WIBP-CorV/CoronaVac. In contrast, recipients of CoronaVac/BBIBP-CorV and CoronaVac/WIBP-CorV showed significantly lower B.1.617.2 neutralization titers than recipients of reverse schedules. Laboratory tests revealed that neutralizing activity against common variants but not the ancestral SARS-CoV-2 was associated with the inoculation order of heterologous prime-boost vaccines. Multivariable regression analyses confirmed this association after adjusting for known confounders. CONCLUSIONS: Our data provide clinical evidence of inoculation order-dependent expansion of neutralizing breadth against SARS-CoV-2 in recipients of heterologous prime-boost vaccination and call for further studies into its underlying mechanism. FUNDING: National Key R&D Program of China, National Development and Re-form Commission of China, National Natural Science Foundation of China, Shenzhen Science and Technology Innovation Commission, and US Department of Veterans Affairs.