Longitudinal investigation of pathogenic bacterial colonization in early childhood: Emphasis on the determinants of Moraxella catarrhalis colonization.

BACKGROUND: Moraxella catarrhalis is a common, potential pathogen colonizing the respiratory tract in children. However, there is little information regarding the determinants of M. catarrhalis colonization and disease development. METHODS: A population-based cohort study was conducted to collect nasopharyngeal swabs from children aged 1, 2, 4, 6, 12, 18, 24, 36, and 60 months for the detection of four common respiratory tract pathogens, including Staphylococcus aureus, M. catarrhalis, Streptococcus pneumoniae, and Haemophilus influenzae. Questionnaires on breastfeeding status were administered during each visit. RESULTS: A total of 921 children were enrolled between 2012 and 2018. S.aureus was the most common pathogen, although the rates declined during the initial 18 months of life; in contrast, the other three pathogens increased during the first 5 years of life. M. catarrhalis was the second most common colonizing pathogen in all age groups, with prevalence ranging from 0.8% (7/842) at one month to 20.4% (33/162) at 60 months of age. Breastfed children (odds ratio [OR]: 0.56; 95% confidence interval [CI]: 0.35-0.92; P = 0.02) had a lower potential for M. catarrhalis carriage; however, infants with a longer duration of exclusive breastfeeding (OR: 1.12; 95% CI: 1.01-1.25; P = 0.04), especially >12 months of age, had a higher rate of M. catarrhalis carriage. CONCLUSION: Breastfeeding should be promoted because it may be correlated with a lower risk of M. catarrhalis carriage. However, an extended period of exclusive breastfeeding may be positively associated with M. catarrhalis colonization.

A Retrospective Study of the Safety and Immunogenicity of MVC-COV1901 Vaccine for People Living with HIV.

BACKGROUND: This study aimed to assess the safety and immunogenicity of MVC-COV1901, a recombinant COVID-19 protein vaccine, containing S-2P protein adjuvanted with CpG 1018 and aluminum hydroxide, for people living with HIV (PWH). METHODS: A total of 57 PWH of ≥20 years of age who are on stable antiretroviral therapy were compared with 882 HIV-negative participants. Participants received two doses of MVC-COV1901 28 days apart. RESULTS: No vaccine-related serious adverse events (SAEs) were recorded. Seroconversion rates (SCRs) of 100% and 99.8% were achieved in PWH and comparators, respectively, 28 days after the second dose. After adjusting for sex, age, BMI category, and comorbidity, the adjusted GMT ratio of comparator/PWH was 3.2 (95% CI 2.5-4). A higher CD4/CD8 ratio was associated with a higher GMT (R = 0.27, p = 0.039). MVC-COV1901 has shown robust safety but elicited weaker immune responses in PWH. CONCLUSIONS: Further investigations may be needed to determine whether PWH require distinct immunization strategies with improved immunogenicity. The main study is registered at ClinicalTrials.gov (NCT04695652).

Safety and immunogenicity of MVC-COV1901 vaccine in older adults: Phase 2 randomized dose-comparison trial.

INTRODUCTION: Older adults are subject to higher COVID-19 infection and mortality rates. Safety and immunogenicity of MVC-COV1901, a protein subunit vaccine have been demonstrated in phase 2 clinical trial for the general population, and negative correlations have been observed between immune responses and age, however, older adults were under-represented. METHODS: A double-blind, randomized, multi-center study compared safety and immunogenicity of high-dose (25 mcg) to mid-dose (15 mcg) of MVC-COV1901 administered 2 times 28 days apart in 420 participants of 65 years and older. The results have been stratified by the comorbidity status. RESULTS: Both high and mid-dose regimens elicited mostly mild adverse events and robust immune responses when measured as neutralizing and binding antibodies titers. High doses elicited better immune responses in the group without comorbidities. CONCLUSION: Given the general population-associated safety and immunogenicity of MVC-COV1901, we recommend high dose for immunization of elder adults with MVC-COV1901. The clinical trial was registered at https://clinicaltrials.gov/ (NCT04822025).

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.

Effectiveness of case isolation and class suspension in mitigation of enterovirus transmission in children.

BACKGROUND: Appropriate mitigation strategy to minimize enterovirus (EV) transmission among children is essential to control severe EV epidemics. Scientific evidence for the effectiveness of case isolation and class suspension is lacking. METHODS: EV-infected children ≤ eight years are asked to stay at home for seven days. Classes were suspended for seven days if there are more than two classmates having an onset of herpangina or hand, foot, and mouth disease in one classroom within one week. Study subjects are divided into two groups, group A with class suspension for one week and group B without class suspension. RESULTS: Among 4153 reported EV-infected children from 1085 classes in May and June, 2015 were enrolled. Median incidence of EV infection in a class was 7% (range 3% -60%). The incidence was higher in group A (median 14%, range 3-60%) than that in group B (median 6%, range 3-80%) (P < 0.01). The median incidence is highest in day care center (20%), followed by kindergarten (8%), and primary school (4%) (P < 0.01). Most secondary cases in group A appeared within seven days after the disease onset of index case in the same class. The incidence of EV infection remained low and was similar between the two groups eight days and beyond after the disease onset of index cases. CONCLUSIONS: Targeted class suspension for seven days with case isolation for seven days is an effective measure to mitigate transmission of EV infection in children.

Correction: Breadth and function of antibody response to acute SARS-CoV-2 infection in humans.

[This corrects the article DOI: 10.1371/journal.ppat.1009352.].

Safety and immunogenicity of CpG 1018 and aluminium hydroxide-adjuvanted SARS-CoV-2 S-2P protein vaccine MVC-COV1901: interim results of a large-scale, double-blind, randomised, placebo-controlled phase 2 trial in Taiwan.

BACKGROUND: MVC-COV1901, a recombinant protein vaccine containing pre-fusion-stabilised spike protein S-2P adjuvanted with CpG 1018 and aluminium hydroxide, has been shown to be well tolerated with a good safety profile in healthy adults aged 20-49 years in a phase 1 trial, and provided a good cellular and humoral immune responses. We present the interim safety, tolerability, and immunogenicity results of a phase 2 clinical trial of the MVC-COV1901 vaccine in Taiwan. METHODS: This is a large-scale, double-blind, randomised, placebo-controlled phase 2 trial done at ten medical centres and one regional hospital in Taiwan. Individuals aged 20 years or older who were generally healthy or had stable pre-existing medical conditions were eligible for enrolment. Exclusion criteria included (but were not limited to) travel overseas within 14 days of screening, intention to travel overseas within 6 months of the screening visit, and the absence of prespecified medical conditions, including immunosuppressive illness, a history of autoimmune disease, malignancy with risk to recur, a bleeding disorder, uncontrolled HIV infection, uncontrolled hepatitis B and C virus infections, SARS-CoV-1 or SARS-CoV-2 infections, an allergy to any vaccine, or a serious medical condition that could interfere with the study. Study participants were randomly assigned (6:1) to receive two doses of either MVC-COV1901 or placebo, administered via intramuscular injection on day 1 and day 29. MVC-COV1901 contained 15 µg of S-2P protein adjuvanted with 750 µg CpG 1018 and 375 µg aluminium hydroxide in a 0·5 mL aqueous solution, and the placebo contained the same volume of saline. Randomisation was done centrally by use of an interactive web response system, stratified by age (≥20 to <65 years and ≥65 years). Participants and investigators were masked to group assignment. The primary outcomes were to evaluate the safety, tolerability, and immunogenicity of MVC-COV1901 from day 1 (the day of the first dose) to day 57 (28 days after the second dose). Safety was assessed in all participants who received at least one dose. Immunogenicity was assessed by measuring geometric mean titres (GMTs) and seroconversion rates of neutralising antibody and antigen-specific IgG in the per-protocol population. This study is registered with ClinicalTrials.gov, NCT04695652. FINDINGS: Of 4173 individuals screened between Dec 30, 2020, and April 2, 2021, 3854 were enrolled and randomly assigned: 3304 to the MVC-COV1901 group and 550 to the placebo group. A total of 3844 participants (3295 in the MVC-COV1901 group and 549 in the placebo group) were included in the safety analysis set, and 1053 participants (903 and 150) had received both doses and were included in the per-protocol immunogenicity analysis set. From the start of this phase 2 trial to the time of interim analysis, no vaccine-related serious adverse events were recorded. The most common solicited adverse events in all study participants were pain at the injection site (2346 [71·2%] of 3295 in the MVC-COV1901 group and 128 [23·3%] of 549 in the placebo group), and malaise or fatigue (1186 [36·0%] and 163 [29·7%]). Fever was rarely reported (23 [0·7%] and two [0·4%]). At 28 days after the second dose of MVC-COV1901, the wild-type SARS-CoV-2 neutralising antibody GMT was 662·3 (95% CI 628·7-697·8; 408·5 IU/mL), the GMT ratio (geometric mean fold increase in titres at day 57 vs baseline) was 163·2 (155·0-171·9), and the seroconversion rate was 99·8% (95% CI 99·2-100·0). INTERPRETATION: MVC-COV1901 has a good safety profile and elicits promising immunogenicity responses. These data support MVC-COV1901 to enter phase 3 efficacy trials. FUNDING: Medigen Vaccine Biologics and Taiwan Centres for Disease Control, Ministry of Health and Welfare.

Structures and therapeutic potential of anti-RBD human monoclonal antibodies against SARS-CoV-2.

Background: Administration of potent anti-receptor-binding domain (RBD) monoclonal antibodies has been shown to curtail viral shedding and reduce hospitalization in patients with SARS-CoV-2 infection. However, the structure-function analysis of potent human anti-RBD monoclonal antibodies and its links to the formulation of antibody cocktails remains largely elusive. Methods: Previously, we isolated a panel of neutralizing anti-RBD monoclonal antibodies from convalescent patients and showed their neutralization efficacy in vitro. Here, we elucidate the mechanism of action of antibodies and dissect antibodies at the epitope level, which leads to a formation of a potent antibody cocktail. Results: We found that representative antibodies which target non-overlapping epitopes are effective against wild type virus and recently emerging variants of concern, whilst being encoded by antibody genes with few somatic mutations. Neutralization is associated with the inhibition of binding of viral RBD to ACE2 and possibly of the subsequent fusion process. Structural analysis of representative antibodies, by cryo-electron microscopy and crystallography, reveals that they have some unique aspects that are of potential value while sharing some features in common with previously reported neutralizing monoclonal antibodies. For instance, one has a common VH 3-53 public variable region yet is unusually resilient to mutation at residue 501 of the RBD. We evaluate the in vivo efficacy of an antibody cocktail consisting of two potent non-competing anti-RBD antibodies in a Syrian hamster model. We demonstrate that the cocktail prevents weight loss, reduces lung viral load and attenuates pulmonary inflammation in hamsters in both prophylactic and therapeutic settings. Although neutralization of one of these antibodies is abrogated by the mutations of variant B.1.351, it is also possible to produce a bi-valent cocktail of antibodies both of which are resilient to variants B.1.1.7, B.1.351 and B.1.617.2. Conclusions: These findings support the up-to-date and rational design of an anti-RBD antibody cocktail as a therapeutic candidate against COVID-19.

Breadth and function of antibody response to acute SARS-CoV-2 infection in humans.

Serological and plasmablast responses and plasmablast-derived IgG monoclonal antibodies (MAbs) have been analysed in three COVID-19 patients with different clinical severities. Potent humoral responses were detected within 3 weeks of onset of illness in all patients and the serological titre was elicited soon after or concomitantly with peripheral plasmablast response. An average of 13.7% and 3.5% of plasmablast-derived MAbs were reactive with virus spike glycoprotein or nucleocapsid, respectively. A subset of anti-spike (10 of 32) antibodies cross-reacted with other betacoronaviruses tested and harboured extensive somatic mutations, indicative of an expansion of memory B cells upon SARS-CoV-2 infection. Fourteen of 32 anti-spike MAbs, including five anti-receptor-binding domain (RBD), three anti-non-RBD S1 and six anti-S2, neutralised wild-type SARS-CoV-2 in independent assays. Anti-RBD MAbs were further grouped into four cross-inhibiting clusters, of which six antibodies from three separate clusters blocked the binding of RBD to ACE2 and five were neutralising. All ACE2-blocking anti-RBD antibodies were isolated from two recovered patients with prolonged fever, which is compatible with substantial ACE2-blocking response in their sera. Finally, the identification of non-competing pairs of neutralising antibodies would offer potential templates for the development of prophylactic and therapeutic agents against SARS-CoV-2.

Structural basis for the neutralization of SARS-CoV-2 by an antibody from a convalescent patient.

The COVID-19 pandemic has had an unprecedented health and economic impact and there are currently no approved therapies. We have isolated an antibody, EY6A, from an individual convalescing from COVID-19 and have shown that it neutralizes SARS-CoV-2 and cross-reacts with SARS-CoV-1. EY6A Fab binds the receptor binding domain (RBD) of the viral spike glycoprotein tightly (KD of 2 nM), and a 2.6-Å-resolution crystal structure of an RBD-EY6A Fab complex identifies the highly conserved epitope, away from the ACE2 receptor binding site. Residues within this footprint are key to stabilizing the pre-fusion spike. Cryo-EM analyses of the pre-fusion spike incubated with EY6A Fab reveal a complex of the intact spike trimer with three Fabs bound and two further multimeric forms comprising the destabilized spike attached to Fab. EY6A binds what is probably a major neutralizing epitope, making it a candidate therapeutic for COVID-19.