NAb Titers Research Articles

SARS-CoV-2 reinfection broadens the antibody responses and promotes the phenotypic differentiation of virus-specific memory T cells in adolescents.

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariants raises concerns regarding the effectiveness of immunity acquired from previous Omicron subvariants breakthrough infections (BTIs) or reinfections (RIs) against the current circulating Omicron subvariants. In this study, we prospectively investigate the dynamic changes of virus-specific antibody and T cell responses among 77 adolescents following Omicron BA.2.3 BTI with or without subsequent Omicron BA.5 RI. Notably, the neutralizing antibodies (NAbs) titers against various detected SARS-CoV-2 variants, especially the emerging Omicron CH.1.1, XBB.1.5, XBB.1.16, EG.5.1, and JN.1 subvariants, exhibited a significant decrease along the time. A lower level of IgG and NAbs titers post-BTI was found to be closely associated with subsequent RI. Elevated NAbs levels and shortened antigenic distances were observed following Omicron BA.5 RI. Robust T cell responses against both Omicron BA.2- and CH.1.1-spike peptides were observed at each point visited. The exposure to Omicron BA.5 promoted phenotypic differentiation of virus-specific memory T cells, even among the non-seroconversion adolescents. Therefore, updated vaccines are needed to provide effective protection against newly emerging SARS-CoV-2 variants among adolescents.

Anti-SARS-CoV-2 antibody dynamics after primary vaccination with two-dose inactivated whole-virus vaccine, heterologous mRNA-1273 vaccine booster, and Omicron breakthrough infection in Indonesian health care workers

BackgroundData on the dynamics and persistence of humoral immunity against SARS-CoV-2 after primary vaccination with two-dose inactivated vaccine (CoronaVac) are limited. This study evaluated the sequential effects of prior infection, heterologous boosting with mRNA-1273 (Moderna), and the occurrence of Omicron vaccine-breakthrough infection (VBI) thereafter.MethodsWe evaluated anti-spike IgG (Abbott) and neutralising (cPASS/GenScript) antibody (nAb) titers up to one year after mRNA-1273 boost in two-dose-CoronaVac-primed Indonesian healthcare workers (August 2021-August 2022). We used linear mixed modeling to estimate the rate of change in antibody levels, and logistic regression to examine associations between antibody levels and VBI.ResultsOf 138 participants, 52 (37.7%) had a prior infection and 78 (56.5%) received an mRNA-1273 booster. After two-dose CoronaVac, antibody titers had significantly declined within 180 days, irrespective of prior infection. After mRNA-1273 booster, anti-spike IgG (1.47% decline/day) and Omicron B.1.1.529/BA.2 nAbs declined between day 28–90, and IgG titers plateaued between day 90–360. During the BA.1/BA.2 wave (February–March 2022), 34.6% (27/78) of individuals experienced a VBI (median 181 days after mRNA-1273), although none developed severe illness. VBI was associated with low pre-VBI anti-spike IgG and B.1.1.529/BA.2 nAbs, which were restored post-VBI.ConclusionsmRNA-1273 booster after two-dose CoronaVac did not prevent BA.1/BA.2 VBI. Periodic vaccine boosters may be warranted against emerging SARS-CoV-2 variants.

Overcoming the age-dependent SARS-CoV-2 vaccine response through hybrid immunity: analysis of humoral and cellular immunity with mass cytometry profiling

BackgroundAge-dependent immune responses to coronavirus disease 2019 (COVID-19) vaccinations and breakthrough infections (BIs) in young and middle-aged individuals are unclear.MethodsThis nationwide multicenter prospective cohort study analyzed immune responses in participants of the ChAdOx1 (ChAd)-ChAd-mRNA vaccine group using cytometry by time-of-flight, anti-spike protein antibody (Sab) and anti-nucleocapsid antibody (Nab) titers, plaque reduction neutralization tests (PRNTs), and interferon-gamma (IFN-γ) release assays at various time points.ResultsWe evaluated 347 participants with an average age of 38.9 ± 9.4 years (range: 21–63). There was a significant inverse correlation between age and Sab levels after the second dose (slope − 14.96, P = 0.032), and this was more pronounced after the third dose (slope − 208.9, P < 0.001). After BIs, older participants showed significantly higher Sab titers (slope 398.8, P = 0.001), reversing the age-related decline observed post-vaccination. This reversal was also observed in PRNTs against wild-type SARS-CoV-2 and the BA.1 and BA.5 variants. IFN-γ responses increased markedly after the third dose and Bis, but showed a weak positive correlation with age, without statistical significance. Immune cell profiling revealed an age-dependent decrease in the proportions of B-cell lineage cells. The proportions of naive CD4+ and CD8+ T cells were inversely correlated with age, whereas the proportions of mature T cell subsets with memory function, including memory CD4+ T, CD8+ TEM, CD8+ TEMRA, and TFH cells, increased with age.ConclusionsAge-dependent waning of the serologic response to COVID-19 vaccines occurred even in middle-aged individuals, but was reversed after BIs. IFN-γ responses were preserved, compensating for the decrease in naive T cell populations, with an increase in memory T cell populations.

Profiling of viral load, antibody and inflammatory response of people with monkeypox during hospitalization: a prospective longitudinal cohort study in China

The dynamics of viral shedding and the specific humoral response against monkeypox virus (MPXV) have not been well characterized in patients across their disease course during hospitalisation. The aim of this study was to determine the viral load and the levels of antibodies against MPXV using longitudinal paired-collected samples from hospitalized patients. Patients who were hospitalised with mpox were recruited at Beijing Ditan Hospital Capital Medical University in China between June 2 and September 23, 2023. Paired samples, including samples from skin lesions, the oropharynx, saliva, faeces, urine, plasma, and serum, were serially collected at days 1, 3, 7, and 14 after admission until discharge. Not all of the patients had samples obtained at all of the timepoints. All the samples were analysed via quantitative PCR. Virus isolation was performed by using clinical samples and Vero cells. The presence of IgM, IgA, IgG, and neutralising antibodies (NAbs) against MPXV was evaluated. The first collected plasma sample was taken when the patient was hospitalised, and the levels of cytokines and chemokines were measured in the sample. The demographic data, smallpox vaccination status, history of known exposure to MPVX, HIV status and other clinical data were collected using a standard case report form. A total of 510 specimens were serially collected from 39 recruited people with mpox. Among all the samples, the skin lesions had the highest viral DNA detection rates and viral loads, and the saliva samples had the second highest rates and viral loads. One day before discharge, 85% of the dry scrabs (median Ct 28.2, range 19.0-38.3) and 70% of the saliva samples (median Ct 32.4, range 24.5-38.1) were positive for viral DNA, Of which, 23.1% of dry scrabs were positive in viral culture. The rate of viral DNA detection in the oropharyngeal, saliva, and faecal samples decreased with time, while the rates in the plasma, serum, and urine samples increased quickly before 10 days post symptom onset (PSO). The median days of appearance of MPXV-IgM, MPXV-IgA, MPXV-IgG, and NAb were at 8(interquartile range [IQR] 7-9), 9 (7-10), 12 (9-15), and 12 (9-15) PSO, respectively. The IgM, IgA, IgG, and NAb titres increased with time. Between days 11 and 21 PSO, the NAb titres were lower in people living with HIV (PWH) than in people living without HIV (PWOH). Increased NAb titres were associated with decreased viral loads in the saliva (r=0.28, p=0.025), faeces (r=0.35, p=0.021), plasma (r=0.30, p=0.0044), and serum samples (r=0.37, p=0.001). Compared with PWOH, PWH had higher plasma levels of MIP-1α, MIP-1β, G-CSF, IL-4, and FGF-basic. The high positive viral culture rate of clinical samples of patients when they are discharged from the hospital indicates that effective public health management strategies are needed for people with mpox. The low NAb titres and high levels of cytokines in PWH shows that earlier treatment is needed to control inflammation in high-risk populations. National Natural Science Foundation of China, Chinese Academy of Medical Sciences, Fundamental Research Funds for the Central Universities for Peking Union Medical College, National Key R&D Program of China.

Semiquantitative Paper-Based Microfluidic Surrogate Virus Neutralization Test for SARS-CoV-2 Neutralizing Antibodies.

Neutralizing antibodies (nAbs) produced from infection or vaccination play an important role in acquired immunity. Determining virus-specific nAb titers is a useful tool for measuring aquired immunity in an individual. The standard methods to do so rely on titrating serum samples against live virus and monitoring viral infection in cultured cells which requires high biosafety level containment. The surrogate virus neutralization test (sVNT) reduces the biohazards and it is suitable for designing rapid test device in a lateral flow assay (LFA) format. Here, we introduce the fabrication and development of a unique paper-based LFA device for determining the level of SARS-CoV-2 nAb in a sample with a semiquantitative direct colorimetric readout. A LFA-based gradient assay design was used to facilitate the sVNT, where the spike glycoprotein receptor binding domain (RBD) and angiotensin-converting enzyme 2 (ACE2) stand in as proxies for viruses and cells, respectively. The gradient assay employed multiple test dots of ACE2 spotted in increasing concentration along the sample flow path and gold nanoparticle-conjugated RBD for readout. In this way, the number of developed spots is inversely proportional to the concentration of nAbs present in the sample. The assay was tested with both standard solutions of nAb as well as human serum samples. We have demonstrated that the device can effectively provide semiquantitative test results of nAbs by direct instrument-free colorimetric detection.

A novel virus-like particles vaccine induces broad immune protective against deltacoronavirus in piglets

Coronaviruses (CoVs) comprise a group of important human and animal pathogens that threaten public health because of their interspecies transmission potential to humans. However, virus-like particles (VLPs) constitute versatile tools in CoVs vaccine development due to their favorable immunological characteristics. Here, we engineered the VLPs composed of the spike (S), membrane (M), and envelope (E) structural proteins of the Porcine deltacoronavirus (PDCoV) and examined their immune responses in mice. Neutralization assays and flow Cytometry demonstrated that PDCoV VLPs induced highly robust neutralizing antibodies (NAbs) and elicited cellular immunity. To assess the protective efficacy of VLPs in newborn piglets, pregnant sows received vaccinations with either a PDCoV-inactivated vaccine or VLPs at 40 and 20 days before delivery. Five days post-farrowing, piglets were orally challenged with the PDCoV strain. Severe diarrhea, high viral RNA copies, and substantial intestinal villus atrophy were detected in piglets born to unimmunized sows. However, piglets from sows immunized with VLPs exhibited high NAbs titers and markedly reduced microscopic damage to the intestinal tissues, with no piglet showing diarrhea. Hence, the results indicate that the VLPs are a potential clinical candidate for PDCoV vaccination, while the strategy may serve as a platform for developing other coronavirus vaccines.

COVID-19 Vaccine Side Effects and Long-Term Neutralizing Antibody Response : A Prospective Cohort Study.

Concern about side effects is a common reason for SARS-CoV-2 vaccine hesitancy. To determine whether short-term side effects of SARS-CoV-2 messenger RNA (mRNA) vaccination are associated with subsequent neutralizing antibody (nAB) response. Prospective cohort study. San Francisco Bay Area. Adults who had not been vaccinated against or exposed to SARS-CoV-2, who then received 2 doses of either BNT162b2 or mRNA-1273. Serum nAB titer at 1 month and 6 months after the second vaccine dose. Daily symptom surveys and objective biometric measurements at each dose. 363 participants were included in symptom-related analyses (65.6% female; mean age, 52.4 years [SD, 11.9]), and 147 were included in biometric-related analyses (66.0% female; mean age, 58.8 years [SD, 5.3]). Chills, tiredness, feeling unwell, and headache after the second dose were each associated with 1.4 to 1.6 fold higher nAB at 1 and 6 months after vaccination. Symptom count and vaccination-induced change in skin temperature and heart rate were all positively associated with nAB across both follow-up time points. Each 1 °C increase in skin temperature after dose 2 was associated with 1.8 fold higher nAB 1 month later and 3.1 fold higher nAB 6 months later. The study was conducted in 2021 in people receiving the primary vaccine series, making generalizability to people with prior SARS-CoV-2 vaccination or exposure unclear. Whether the observed associations would also apply for neutralizing activity against non-ancestral SARS-CoV-2 strains is also unknown. Convergent self-report and objective biometric findings indicate that short-term systemic side effects of SARS-CoV-2 mRNA vaccination are associated with greater long-lasting nAB responses. This may be relevant in addressing negative attitudes toward vaccine side effects, which are a barrier to vaccine uptake. National Institute on Aging.

Effectiveness after immunization with BNT162b2 and Gam-COVID-Vac for SARS-CoV-2 and neutralizing antibody titers in health care workers

Abstract Objectives The aim of this study was to describe the effectiveness of the vaccines (Tozinameran and Sputnik V), administered on a convenience sample of healthcare workers, and also to describe the relationship between the levels of neutralizing antibodies (NAbs) and the type of vaccine used, as well as their association with incident cases during follow-up. Methods The study included 262 participants, who underwent vaccination during the period from September 2021 until August 2022. For determining the levels of NAbs we used the CLIA based method, and all the samples were processed with the SNIBE Maglumi 800 analyzer. The patients were observed for one year for occurrence of incident infection. Results The participants with prior SARS-CoV-2 positivity showed substantially higher titer of NAbs (8.86 vs. 0.94, p&lt;0.001). The participants in the Gam-COVID-Vac group had median levels of NAbs of 1.57 (IQR 0.42–5.73), while they in the Tozinameran group showed substantially higher levels of 2.37 (IQR 0.9–6.27). The incident cases after immunization had substantially lower median values of NAbs when compared to the rest (0.48 vs. 3.97, p&lt;0.001), and the interval between the second dose and the serological measurements were similar. Conclusions The current study showed that the tested vaccines demonstrated vaccine effectiveness of over 50 % during the first year after the vaccination in a sample of health care workers. Although health care workers remain separate population group, when compared to the rest, the results could be extrapolated to populations with similar age and immune experience.

Clinical presentation, viral shedding, and neutralizing antibody responses of mpox cases in South Korea: Single center experience

BackgroundA global mpox outbreak occurred in 2022, and a domestic outbreak started in South Korea in April 2023. This study aimed to evaluate the clinical characteristics, viral shedding, and immune response of mpox in South Korea. MethodsPatients hospitalized with mpox in the National Medical Center between September 2022 and June 2023 were included in this study. Oropharyngeal (OP), anogenital lesion (AL), and skin lesion (SL) swabs and blood samples were collected, and monkeypox virus (MPXV) DNA using real-time polymerase chain reaction (RT-PCR) and culture assays were performed. Neutralizing antibodies (NAbs) against MPXV A.2.1, B.1.1, and B.1.3 were detected using plaque reduction neutralization tests. ResultsEighteen patients were enrolled, of whom 17 (94.4 %) were male, with a median (IQR) age of 32.5 (24–51) years. While nine (50 %) were HIV-infected individuals, none of them revealed CD4+ counts less than 200 cells/μL. MPXV DNA was detected in 87.3 % and 82.7 % of patient's ALs and SLs, respectively, until 2 weeks after symptom onset. While MPXV was isolated for up to 15 days in all three sample types, the culture positivity decreased to 53.8 % and 42.9 % in ALs and SLs after 10 days, respectively, and 28.6 % and 22.2 %, respectively, after 2 weeks from symptom onset. The NAb titers against MPXV A.2.1 were significantly lower than those against B.1.1 and B.1.3. ConclusionsInfectious MPXV was isolated from various anatomical sites up to 15 days after symptom onset. The MPXV NAb response was varied among different lineages, and this implies limited cross-lineage protection.

Poor immune response to inactivated COVID-19 vaccine in patients with hypertension.

The safety and efficacy of vaccination in people with hypertension (HTN) is important. There are currently a few data on the immunogenicity and safety of inactivated SARS-CoV-2 vaccinations in hypertension patients. After receiving a two-dose immunization, 94 hypertension adult patients and 74 healthy controls (HCs) in this study, the evaluation included looking at antibodies (Abs) against receptor binding domain (RBD) IgG, SARS-CoV-2 neutralizing antibodies (NAbs), RBD-specific B cells, and memory B cells (MBCs). There was no discernible difference in the overall adverse events (AEs) over the course of 7 or 30 days between HTN patients and HCs. HTN patients had lower frequencies of RBD-specific memory B cells and the seropositivity rates and titers of Abs compared with HCs (all, p < 0.05). HTN patients with cardiovascular and cerebrovascular conditions (CCVD) have lower titers of CoV-2 NAb than in HCs. The titers of both Abs in HTN declined gradually over time. Inactivated COVID-19 vaccinations were safe in hypertension patients; however humoral immune was limited, especially merged CCVD and declined gradually over time.

Wa-VP4* as a candidate rotavirus vaccine induced homologous and heterologous virus neutralizing antibody responses in mice, pigs, and cynomolgus monkeys

Group A rotavirus (RVA) is the primary etiological agent of acute gastroenteritis (AGE) in children under 5 years of age. Despite the global implementation of vaccines, rotavirus infections continue to cause over 120,000 deaths annually, with a majority occurring in developing nations. Among infants, the P[8] rotavirus strain is the most prevalent and can be categorized into four distinct lineages. In this investigation, we expressed five VP4(aa26-476) proteins from different P[8] lineages of human rotavirus in E. coli and assessed their immunogenicity in rabbits. Among the different P[8] strains, the Wa-VP4 protein, derived from the MT025868.1 strain of the P[8]-1 lineage, exhibited successful purification in a highly homogeneous form and significantly elicited higher levels of neutralizing antibodies (nAbs) against both homologous and heterologous rotaviruses compared to other VP4 proteins derived from different P[8] lineages in rabbits. Furthermore, we assessed the immunogenicity of the Wa-VP4 protein in mice, pigs, and cynomolgus monkeys, observing that it induced robust production of nAbs in all animals. Interestingly, there was no significant difference between in nAb titers against homologous and heterologous rotaviruses in pigs and mankeys. Collectively, these findings suggest that the Wa-VP4* protein may serve as a potential candidate for a rotavirus vaccine.

An investigation of the immune epitopes of adeno-associated virus capsid-derived peptides among hemophilia patients

Adeno associated virus (AAV) is an optimal gene vector for monogenic disorders. However, neutralizing antibodies (Nab) against AAV hinder its widespread application in gene therapy. In this study, we biosynthesized peptides recognized by the Binding Antibodies (Bab) from the sera containing high Nab titer against AAV2. We established four immunological methods to detect immune epitopes of the AAV2-derived peptides, including Bab assay, Nab assay, B-cell receptors (BCR) detecting assay and immunoglobin-producing B cells enzyme-linked immunosorbent spot (B-cell ELISpot) assay. Correlations among the epitopes determined by these four methods were analyzed using the serum samples and peripheral blood mononuclear cells (PBMC) from 89 hemophilia A/B patients. As decoys, the peptides' ability to block the Nab of AAV2 particles was assessed using AAV transduction models both in vitro and in vivo. Overall, we provide insights into AAV2 capsid-derived peptides immune epitopes, involving the Nab, Bab, BCR, and B-cell ELISpot, offering alternative immunological evaluation approaches and strategy to overcome Nab barriers in AAV-mediated gene therapy.

The Biodistribution of Replication-Defective Simian Adenovirus 1 Vector in a Mouse Model.

The administration route affects the biodistribution of a gene transfer vector and the expression of a transgene. A simian adenovirus 1 vector carrying firefly luciferase and GFP reporter genes (SAdV1-GFluc) were constructed, and its biodistribution was investigated in a mouse model by bioluminescence imaging and virus DNA tracking with real-time PCR. Luciferase activity and virus DNA were mainly found in the liver and spleen after the intravenous administration of SAdV1-GFluc. The results of flow cytometry illustrated that macrophages in the liver and spleen as well as hepatocytes were the target cells. Repeated inoculation was noneffective because of the stimulated serum neutralizing antibodies (NAbs) against SAdV-1. A transient, local expression of low-level luciferase was detected after intragastric administration, and the administration could be repeated without compromising the expression of the reporter gene. Intranasal administration led to a moderate, constant expression of a transgene in the whole respiratory tract and could be repeated one more time without a significant increase in the NAb titer. An immunohistochemistry assay showed that respiratory epithelial cells and macrophages in the lungs were transduced. High luciferase activity was restricted at the injection site and sustained for a week after intramuscular administration. A compromised transgene expression was observed after a repeated injection. When these mice were intramuscularly injected for a third time with the human adenovirus 5 (HAdV-5) vector carrying a luciferase gene, the luciferase activity recovered and reached the initial level, suggesting that the sequential use of SAdV-1 and HAdV-5 vectors was practicable. In short, the intranasal inoculation or intramuscular injection may be the preferred administration routes for the novel SAdV-1 vector in vaccine development.

SARS-CoV-2 Neutralizing Antibodies in Three African Countries Following Multiple Distinct Immune Challenges.

The COVID-19 pandemic has affected Madagascar, Cameroon, and the Central African Republic (CAR), with each experiencing multiple waves by mid-2022. This study aimed to evaluate immunity against SARS-CoV-2 strains Wuhan (W) and BA.2 (BA.2) among healthcare workers (HCWs) in these countries, focusing on vaccination and natural infection effects. HCWs' serum samples were analyzed for neutralizing antibodies (nAbs) against W and BA.2 variants, with statistical analyses comparing responses between countries and vaccination statuses. Madagascar showed significantly higher nAb titers against both strains compared to CAR and Cameroon. Vaccination notably increased nAb levels against W by 2.6-fold in CAR and 1.8-fold in Madagascar, and against BA.2 by 1.6-fold in Madagascar and 1.5-fold in CAR. However, in Cameroon, there was no significant difference in nAb levels between vaccinated and unvaccinated groups. This study highlights the complex relationship between natural and vaccine-induced immunity, emphasizing the importance of assessing immunity in regions with varied epidemic experiences and low vaccination rates.

Abstract 3249: Simple, rapid, and robust bioluminescent cell-based assay for detecting neutralizing antibodies against AAV in serum

Abstract Adeno-associated viruses (AAV) are prevalent gene therapy vectors, delivering therapeutic transgenes to treat various diseases including cancer and rare monogenic diseases. Individuals with pre-existing immunity to AAVs are less likely to benefit from AAV-based therapies due to both, a reduction in cellular AAV uptake and activation of a cytotoxic T-cell response to transduced cells, decreasing efficacy or changing the safety profile. Measurement of serum neutralizing antibodies (NAbs) against AAV is essential to determine treatment eligibility and to identify clinical trial candidates. Here we introduce a cell-based assay using NanoLuc® luciferase to detect NAbs in serum samples. The superior brightness of NanoLuc® luciferase in our AAV reporter system results in the need of low concentrations of AAV and a short 24h assay time. The minimal AAV concentration in our assay aids in detecting low NAb titers in serum samples, reducing false negatives and enhancing decision-making accuracy. Testing 60 human serum samples against a range of AAV serotypes, we found that a large fraction of the population had pre-existing NAbs to at least one serotype, and of the pre-exposed individuals a majority displayed NAbs against multiple AAV serotypes. Interestingly, fewer samples were seropositive for AAV-DJ than for either parental serotype (AAV2, AAV8 or AAV9), highlighting the assays utility in the development of engineered capsids. Furthermore, the broad dynamic range of our assay facilitates serum sample categorization into four NAb tiers: negative, low, medium, and high using a single serum dilution. Neutralizing titers (ND50) which was determined by serial dilution of the serum samples strongly agreed with the assigned NAb tiers. Our study with 40 naïve mice further validated the assay's robustness, showing a clear correlation between NAb levels and injected AAV viral loads. Taken together, this rapid, highly sensitive, and reliable assay enabled by NanoLuc® AAV reporter technology precisely measures NAbs against AAVs in both human and animal serum. Further validation of the assay is required for future use in a clinical setting. Citation Format: Morten Seirup, Kirsten Wingate, Jeff Nelson, Kara Machleidt, Vanessa Ott, Trish Hoang, Marjeta Urh. Simple, rapid, and robust bioluminescent cell-based assay for detecting neutralizing antibodies against AAV in serum [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3249.

A phase 3 randomized, open-label study evaluating the immunogenicity and safety of concomitant and staggered administration of a live, pentavalent rotavirus vaccine and an inactivated poliomyelitis vaccine in healthy infants in China

ABSTRACT This open-label, randomized, phase 3 study in China (V260-074; NCT04481191) evaluated the immunogenicity and safety of concomitant and staggered administration of three doses of an oral, live, pentavalent rotavirus vaccine (RV5) and three doses of an intramuscular, inactivated poliomyelitis vaccine (IPV) in 400 healthy infants. The primary objective was the non-inferiority of neutralizing antibody (nAb) responses in the concomitant- versus the staggered-use groups. Antibody responses were measured at baseline and 1-month post-dose 3 (PD3). Parents/legal guardians recorded adverse events for 30 or 15 d after study vaccinations in the concomitant-use or staggered-use groups, respectively. At PD3, >98% of participants seroconverted to all three poliovirus types, and the primary objective was met as lower bounds of the two-sided 95% CI for between-group difference in nAb seroconversion percentages ranged from − 4.3% to − 1.6%, for all poliovirus types, p < .001. At PD3, geometric mean titers (GMTs) of nAb responses to poliovirus types 1, 2, and 3 in the concomitant-use group and the staggered-use group were comparable; 100% of participants had nAb titers ≥1:8 and ≥1:64 for all poliovirus types. Anti-rotavirus serotype-specific IgA GMTs and participants with ≥3-fold rise in postvaccination titers from baseline were comparable between groups. Administration of RV5 and IPV was well tolerated with comparable safety profiles in both groups. The immunogenicity of IPV in the concomitant-use group was non-inferior to the staggered-use group and RV5 was immunogenic in both groups. No safety concerns were identified. These data support the concomitant use of RV5 and IPV in healthy Chinese infants.

Natural and hybrid immunity after SARS-CoV-2 infection in children and adolescents.

In contrast to adults, immune protection against SARS-CoV-2 in children and adolescents with natural or hybrid immunity is still poorly understood. The aim of this study was to analyze different immune compartments in different age groups and whether humoral immune reactions correlate with a cellular immune response. 72 children and adolescents with a preceding SARS-CoV-2 infection were recruited. 37 were vaccinated with an RNA vaccine (BNT162b2). Humoral immunity was analyzed 3-26 months (median 10 months) after infection by measuring Spike protein (S), nucleocapsid (NCP), and neutralizing antibodies (nAB). Cellular immunity was analyzed using a SARS-CoV-2-specific interferon-γ release assay (IGRA). All children and adolescents had S antibodies; titers were higher in those with hybrid immunity (14,900 BAU/ml vs. 2118 BAU/ml). NCP antibodies were detectable in > 90%. Neutralizing antibodies (nAB) were more frequently detected (90%) with higher titers (1914 RLU) in adolescents with hybrid immunity than in children with natural immunity (62.5%, 476 RLU). Children with natural immunity were less likely to have reactive IGRAs (43.8%) than adolescents with hybrid immunity (85%). The amount of interferon-γ released by T cells was comparable in natural and hybrid immunity. Spike antibodies are the most reliable markers to monitor an immune reaction against SARS-CoV-2. High antibody titers of spike antibodies and nAB correlated with cellular immunity, a phenomenon found only in adolescents with hybrid immunity. Hybrid immunity is associated with markedly higher antibody titers and a higher probability of a cellular immune response than a natural immunity.

Incidence of COVID-19 mRNA vaccine symptomatic breakthrough infections during Omicron circulation in adults with or without infection prior to vaccination

ObjectivesCOVID-19 vaccine breakthrough infections were frequently reported during circulation of the Omicron variant. The ANRS|MIE CoviCompareP study investigated these infections in adults vaccinated and boosted with BNT162b2 [Pfizer-BioNTech] and with/without SARS-CoV-2 infection before vaccination. MethodsIn the first half of 2021, healthy adults (aged 18–45, 65–74 and 75 or older) received either one dose of BNT162b2 (n = 120) if they had a documented history of SARS-CoV-2 infection at least five months previously, or two doses (n = 147) if they had no history confirmed by negative serological tests. A first booster dose was administered at least 6 months after the primary vaccination, and a second booster dose, if any, was reported in the database. Neutralizing antibodies (NAbs) against the European (D614G) strain and the Omicron BA.1 variant were assessed up to 28 days after the first booster dose. A case-control analysis was performed for the 252 participants who were followed up in 2022, during the Omicron waves. ResultsFrom January to October 2022, 78/252 (31%) had a documented symptomatic breakthrough infection after full vaccination: 21/117 (18%) in those who had been infected before vaccination vs. 57/135 (42%) in those who had not. In a multivariate logistic regression model, factors associated with a lower risk of breakthrough infection were older age, a higher number of booster doses, and higher levels of Omicron BA.1 NAb titers in adults with infection before vaccination, but not in those without prior infection. ConclusionOur results highlight the need to consider immune markers of protection in association with infection and vaccination history.

The investigation of the dynamics of changes in neutralizing antibody titers against type 5 adenovirus in the context of vaccination against a new coronavirus infection

This research focuses on analyzing the dynamics of neutralizing antibody (nAbs) titers against type 5 adenovirus (Ad5) in the adult population of Russia following vaccination against the novel coronavirus infection with recombinant adenovirus type-5 COVID-19 vaccine (CanSino Biologics, China). The impact of the Ad5 vector on nAb titers was investigated using 302 blood serum samples from individuals who received a single dose of the Ad5-nCoV vector vaccine. The research revealed that 33.8% of adults in Russia had pre-existing anti-Ad5 nAbs before the pandemic. Notably, 40% of vaccinated individuals did not exhibit an increase in nAbs titers upon receiving the Ad5-based vaccine. However, in the group with no or low titers of anti-Ad5 nAbs (1:10–1:40), a significant 8-16-fold increase in nAb titers to Ad5 was observed.

Single MVA-SARS-2-ST/N Vaccination Rapidly Protects K18-hACE2 Mice against a Lethal SARS-CoV-2 Challenge Infection.

The sudden emergence of SARS-CoV-2 demonstrates the need for new vaccines that rapidly protect in the case of an emergency. In this study, we developed a recombinant MVA vaccine co-expressing SARS-CoV-2 prefusion-stabilized spike protein (ST) and SARS-CoV-2 nucleoprotein (N, MVA-SARS-2-ST/N) as an approach to further improve vaccine-induced immunogenicity and efficacy. Single MVA-SARS-2-ST/N vaccination in K18-hACE2 mice induced robust protection against lethal respiratory SARS-CoV-2 challenge infection 28 days later. The protective outcome of MVA-SARS-2-ST/N vaccination correlated with the activation of SARS-CoV-2-neutralizing antibodies (nABs) and substantial amounts of SARS-CoV-2-specific T cells especially in the lung of MVA-SARS-2-ST/N-vaccinated mice. Emergency vaccination with MVA-SARS-2-ST/N just 2 days before lethal SARS-CoV-2 challenge infection resulted in a delayed onset of clinical disease outcome in these mice and increased titers of nAB or SARS-CoV-2-specific T cells in the spleen and lung. These data highlight the potential of a multivalent COVID-19 vaccine co-expressing S- and N-protein, which further contributes to the development of rapidly protective vaccination strategies against emerging pathogens.