Long-Term Course of Humoral and Cellular Immune Responses in Outpatients After SARS-CoV-2 Infection

Interferon-γ Release Assay in the Assessment of Cellular Immunity-A Single-Centre Experience with mRNA SARS-CoV-2 Vaccine in Patients with Juvenile Idiopathic Arthritis

Background: As the SARS-CoV-2 virus remains one of the main causes of severe respiratory system infections, the Food and Drug Administration strongly advises the continuation of current vaccination programs, including the distribution of updated boosters, especially in high-risk groups of patients. Therefore, there is an unceasing need for further research on the safety and, no less importantly, the clinical effectivity of the vaccines, with an extra focus on cohorts of patients with underlying health problems. This study aimed to assess the efficacy of the SARS-CoV-2 vaccine in possibly immunocompromised children with rheumatic disease while utilizing the interferon-gamma release assay (IGRA) as a marker for COVID-19 immunity in the study follow-up. Methods: This prospective study was performed in a group of 55 pediatric patients diagnosed with juvenile idiopathic arthritis. Eight participants were immunized with the Comirnaty mRNA vaccine before the research commenced, while the rest of the group (n = 47) had not been vaccinated against SARS-CoV-2. At the study baseline, the cellular response to the virus antigen was measured using a specific quantitative IGRA in whole blood; subsequently, the anti-SARS-CoV-2 test was performed, marking the antibodies' levels in serum. Around four months after the enrollment of the last patient in the study, a follow-up survey regarding the events of COVID-19 infection within the cohort was conducted. Results: The study confirmed that all the vaccinated children developed specific T-cell (p = 0.0016) and humoral (p = 0.001 for IgA antibodies, p = 0.008 for IgG antibodies) responses to the inoculation, including those receiving biological treatment and those on conventional disease-modifying anti-rheumatic drugs. The study also showed the different patterns of immunity elicited both after infection and post-vaccination, with higher levels of antibodies and T-cell response after inoculation than after natural exposure to the pathogen. According to the follow-up survey, six children developed PCR-confirmed SARS-CoV-2 infection, whereas the additional 10 patients admitted to having COVID-like symptoms with no laboratory verification. Conclusions: SARS-CoV-2 vaccinations elicit valid immune responses in pediatric rheumatic patients. Including the assessment of T-cell immunity in the evaluation of inoculation-induced immunization can enhance the accuracy of sole humoral response assays.

SARS-CoV-2 infection and long COVID among California farmworkers

PURPOSE

The purpose of this cross-sectional study was to determine the prevalence of long COVID and identify its clinical manifestations among farmworkers in California.

METHODS

We collected data on sociodemographic characteristics, anthropometrics, clinical chemistries and anti-SARS-CoV-2 immunoglobulin G antibodies, self-reported SARS-CoV-2 infection history, and standardized health tests and scales from 297 farmworkers in California between February and July 2022.

RESULTS

Most participants were born in Mexico or Central America, had less than a high school diploma, and were overweight or obese. The prevalence of long COVID (defined as self-reported SARS-CoV-2 infection with symptoms >28 days) among farmworkers with a suspected or test-confirmed infection was 61.8%. Participants with long COVID had higher mean [95% CI] body mass index (32.9 [31.6-34.1]) and high-sensitivity C-reactive protein levels (4.8 [3.7, 6.0]) than those with no COVID-19 history (30.5 [29.3-31.7], and 3.3 [2.2, 4.3], respectively). Farmworkers with long COVID also reported greater fatigue, dyspnea, taste and smell problems, and overall poorer mental and physical health, than those with no COVID-19 history. Farmworkers with long COVID had increased odds of functional limitations compared to those with a self-reported SARS-CoV-2 infection with symptoms ≤28 days (OR [95% CI]: 7.46 [3.26, 17.09]).

CONCLUSIONS

A significant proportion of farmworkers experience long COVID with persistent symptoms that limit their ability to perform their work. A comprehensive approach that addresses the unique needs and challenges of farmworkers is warranted given this population's high prevalence of long COVID and the essential nature of their work.

Dynamics of immunity over time: decline of anti-SARS-CoV-2 IgG antibodies and T-cell responses after mRNA vaccination in residents and health care workers in nursing homes and homes with assisted living support

Background

In the present study, we investigated the dynamics of immunity over time by measuring anti SARS-CoV-2 IgG antibodies and SARS-CoV-2 specific T-cell responses (interferon-gamma release assay) after two doses of vaccines in residents and health care workers (HCW). Mostly, 224 (98%) residents and 244 (89%) HCW received two doses of mRNA vaccine (BNT162b2, Pfizer-BioNTech); the rest of the participants received heterologous vaccinations with mRNA and vector vaccines. The study was conducted at the time when the Delta variant of SARS-CoV-2 prevailed.

Methods

We analyzed blood samples of 228 residents (median age 83.8 years) and of 273 HCW (median age 49.7 years) from five nursing homes and one home for the elderly with assisted living support at one specific time point. Participants received two vaccinations. The blood samples were analyzed for SARS-CoV-2 specific IgG antibody and T-cell responses.

Results

The initial immune responses in the younger participants were about 30% higher than in the older age group. Over time the estimated mean of the parameters (estimated from the study sample for the total population) decreased in all groups within the maximum observation period of 232 days. Comorbidities such as coronary heart disease or diabetes mellitus reduced the initial immune responses regardless of age. With regard to measured IgG antibody levels, absolute values decreased over time, whereas the interferon-gamma response remained at a constant level between day 120 and 180 and seemed to be less dependent on the time elapsed after vaccination.

Conclusions

Based on our data, it does not seem possible to determine a reliable threshold of robust immunity, but we suggest that high titres of neutralizing capacity and interferon-gamma response might be an indicator of protection against severe COVID-19 courses.

Long-term evaluation of the seroprevalence of SARS-CoV-2 IgG and IgM antibodies in recovered patients: a meta-analysis

Estimating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) -specific immunoglobulin G (IgG) immunoglobulin M (IgM) antibodies are increasingly important for tracking the spread of infection and defining herd immunity barrier and individual immunization levels in the ongoing coronavirus disease 2019 (COVID-19) pandemic. Therefore, we conducted the present systematic review and meta-analysis to evaluate the seroprevalence of SARS-CoV-2 IgM and IgG antibodies of recovered COVID-19 patients in long-term follow-up studies. A systematic search of the MEDLINE, Embase, COVID-19 Primer, PubMed, CNKI, and the Public Health England library databases was conducted. Twenty-fourth eligible studies were included. Meta-analysis showed that 27% (95%CI: 0.04-0.49) and 66% (95%CI:0.47-0.85) were seropositive for SARS-CoV-2 IgM and IgG, respectively, while in long-term 12 months following up studies, the seroprevalences of IgM antibody (17%) decreased and IgG antibody (75%) was higher than 6 months follow-up patients. However, due to the limited number of relevant studies, the high level of heterogeneity, and the large gap in studies conducted, the findings of our study may not accurately reflect the true seroprevalence status of SARS-CoV-2 infection. Nevertheless, sequential vaccination or booster immunization is considered to be a necessary long-term strategy to sustain the fight against the pandemic.

Correlation between Clinical Characteristics and Antibody Levels in COVID-19 Convalescent Plasma Donor Candidates

COVID-19 convalescent plasma (CCP) with high neutralizing antibodies has been suggested in preventing disease progression in COVID-19. In this study, we investigated the relationship between clinical donor characteristics and neutralizing anti-SARS-CoV-2 antibodies in CCP donors. COVID-19 convalescent plasma donors were included into the study. Clinical parameters were recorded and anti-SARS-CoV-2 antibody levels (Spike Trimer, Receptor Binding Domain (RBD), S1, S2 and nucleocapsid protein) as well as ACE2 binding inhibition were measured. An ACE2 binding inhibition < 20% was defined as an inadequate neutralization capacity. Univariate and multivariable logistic regression analysis was used to detect the predictors of inadequate neutralization capacity. Ninety-one CCP donors (56 female; 61%) were analyzed. A robust correlation between all SARS-CoV-2 IgG antibodies and ACE2 binding inhibition, as well as a positive correlation between donor age, body mass index, and a negative correlation between time since symptom onset and antibody levels were found. We identified time since symptom onset, normal body mass index (BMI), and the absence of high fever as independent predictors of inadequate neutralization capacity. Gender, duration of symptoms, and number of symptoms were not associated with SARS-CoV-2 IgG antibody levels or neutralization. Neutralizing capacity was correlated with SARS-CoV-2 IgG antibodies and associated with time since symptom onset, BMI, and fever. These clinical parameters can be easily incorporated into the preselection of CCP donors.

Long term SARS-CoV-2-specific cellular immunity after COVID-19 in liver transplant recipients

PURPOSE

Long-term immunity after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in immunosuppressed patients is not well characterized. We aimed to explore the long-term natural immunity against SARS-CoV-2 in liver transplant (LT) recipients compared to the non-transplanted population (control group).

METHODS

Fifteen LT recipients and 15 controls matched according to variables associated with disease severity were included at 12 months following the coronavirus disease 2019 (COVID-19) onset. Peripheral blood mononuclear cells were stimulated with peptide pools covering spike (S), nucleocapside (N), and membrane (M) proteins. Reactive CD4+ and CD8+ T cells were identified using flow cytometry, and cytokine production was evaluated in the culture supernatants using cytometric bead array. Serum anti-N and anti-S IgG antibodies were detected with chemiluminescence.

RESULTS

The percentage of patients with a positive response in both CD4+ and CD8+ T cells against each viral protein and IL2, IL10, TNF-α, and IFN-γ levels was similar between LT recipients and controls. IFN-γ levels were positively correlated with the percentage of reactive CD4+ (p = 0.022) and CD8+ (p = 0.043) T cells to a mixture of M + N + S peptide pools. The prevalence and levels of anti-N and anti-S IgG antibodies were slightly lower in the LT recipients, but the difference was not statistically significant.

CONCLUSION

LT recipients exhibited a similar T cell response compared to non-transplanted individuals one year after COVID-19 diagnosis.

COVID-19 therapy and vaccination: a clinical narrative review

The SARS-CoV-2 pandemic is the most globally impacting health issue our world has faced over the last century. As of January 7, 2022, around 300 million cases have been reported worldwide, with over 5 million deaths. The SARS-CoV-2 infection causes a hyperactive host immune response leading to an excessive inflammatory reaction with the release of many cytokines - cytokine storm - commonly noticed in acute respiratory distress syndrome, sepsis and fulminant multiorgan failure. Since the beginning of the pandemic, the scientific medical community has worked on therapeutic procedures that interfere with the exaggerated immune response. Thromboembolic complications are widespread in patients who are critically ill with COVID-19. Anticoagulant therapy was initially considered a cornerstone in hospitalized patients and even in the early post-discharge period; however, later trials have aborted the clinical benefits except for suspicion of or confirmed thrombosis. Immunomodulatory therapies are still crucial in moderate to severe COVID-19. Immunomodulator therapies include various medications from steroids to hydroxychloroquine, tocilizumab and Anakinra. Anti-inflammatory agents, vitamin supplements and antimicrobial therapy had initial encouraging evidence, but there are limited data to review. Convalescent plasma, immunoglobulins, eculizumab, neutralizing IgG1 monoclonal antibodies and remdesivir have positively impacted inpatient mortality and hospital length of stay. Eventually, wide population vaccination was proven to be the best tool to overcome the SARS-CoV-2 pandemic and help humanity return to regular life. Many vaccines and various strategies have been used since December 2020. This review discusses how the SARS-CoV-2 pandemic has progressed and surged, and summarizes the safety and efficacy of the most used therapies and vaccines in the light of recent evidence.

Persistent humoral and CD4+ TH cell immunity after mild SARS-COV-2 infection-The CoNAN long-term study

Understanding persistent cellular and humoral immune responses to SARS-CoV-2 will be of major importance to terminate the ongoing pandemic. Here, we assessed long-term immunity in individuals with mild COVID-19 up to 1 year after a localized SARS-CoV-2 outbreak. CoNAN was a longitudinal population-based cohort study performed 1.5 months, 6 months, and 12 months after a SARS-CoV-2 outbreak in a rural German community. We performed a time series of five different IgG immunoassays assessing SARS-CoV-2 antibody responses on serum samples from individuals that had been tested positive after a SARS-CoV-2 outbreak and in control individuals who had a negative PCR result. These analyses were complemented with the determination of spike-antigen specific TH cell responses in the same individuals. All infected participants were presented as asymptomatic or mild cases. Participants initially tested positive for SARS-CoV-2 infection either with PCR, antibody testing, or both had a rapid initial decline in the serum antibody levels in all serological tests but showed a persisting T_H cell immunity as assessed by the detection of SARS-CoV-2 specificity of T_H cells for up to 1 year after infection. Our data support the notion of a persistent T-cell immunity in mild and asymptomatic cases of SARS-CoV-2 up to 1 year after infection. We show that antibody titers decline over 1 year, but considering several test results, complete seroreversion is rare.

Trial registration

German Clinical Trials Register DRKS00022416.

From immune equilibrium to immunodynamics

Objective

The immunology field has long been short of a universally applicable theoretical model that can quantitatively describe the immune response, and the theory of immune equilibrium (balance) is usually limited to the interpretation of the philosophical significance of immune phenomena. Therefore, it is necessary to establish a new immunological theory, namely, immunodynamic theory, to reanalyze the immune response.

Methods

By quantifying the immune dynamic equilibrium as the ratio of positive and negative immune power, the immune dynamic equilibrium equation was established. Then, the area under the curve of the positive and negative immune power was assumed to be equal in the whole process of immune response (regardless of correct or not), and through thought experiments based on this key hypothesis, a series of new concepts and expressions were derived, to establish a series of immunodynamic equations.

Results

New concepts of immune force and immune braking force and their expression equations, namely, the theoretical equations of immunodynamics, were derived through thought experiments, and the theoretical curves of immunodynamics were obtained according to these equations. Via the equivalent transformation of the theoretical equations and practical calculation of functional data, and by the methods of curve comparison and fitting, some practical equations of immunodynamics were established, and these practical equations were used to solve theoretical and practical problems that are related to the immunotherapy of infectious diseases and cancers.

Conclusion

The traditional theory of immune equilibrium has been mathematized and transformed from a philosophical category into a new concrete scientific theory, namely the theory of immunodynamics, which solves the dilemma that the traditional theory cannot guide individualized medical practice for a long time. This new theory may develop into one of the core theories of immunology in the future.

Seroprevalence of SARS-CoV-2 antibodies in vaccinated healthcare workers in Marrakech (Morocco)

INTRODUCTION

The SARS-CoV-2 pandemic has had a considerable impact, causing millions of deaths worldwide, including many healthcare workers (HCWs). The pharmaceutical industry has been working diligently since the start of the pandemic to develop various vaccines to fight the spread of the virus and protect the population.

OBJECTIVE

To study the seroprevalence of neutralizing anti-SARS-CoV-2 antibodies in vaccinated HCWs at the Mohamed VI University Hospital in Marrakech and to determine the parameters that can influence immune response.

METHODS

A cross-sectional study of 138 HCWs was performed between October and December 2021 by measuring IgG antibodies directed against the spike antigen of SARS-CoV-2 using an Abbott Architect^® SARS-CoV-2 IgG II assay.

RESULTS

The mean age was 31.42 years, the sex ratio was 2.94 women to each man, and the overall prevalence was 97%. We found 39.5% of the participants had experienced COVID-19 infections pre-vaccination, which decreased to 26.8% after vaccination. Neutralizing antibody titers were dependent on the type of vaccine: they were higher with the Pfizer-BioNTech vaccine, the number of doses (p < .001), and post-vaccine COVID-19 form. The post-vaccine COVID-19 infection rates were lower with the Sinopharm vaccine.

CONCLUSION

Heterologous vaccination with non-mRNA and mRNA vaccines and the consideration of post-vaccination COVID-19 infection as a booster could help optimize vaccine results while reducing potential side effects.

An Immune Response to Heterologous ChAdOx1/BNT162b2 Vaccination against COVID-19: Evaluation of the anti-RBD Specific IgG Antibodies Titers and Interferon Gamma Release Assay (IGRA) Test Results

This study aimed to assess the magnitude of anti-SARS-CoV-2 immunoglobulin G (IgG) titers and Interferon-Gamma Release Assay (IGRA) test results following administration of booster BNT162b2 in 48 ChAd-primed participants (vaccination schedule: ChAd/ChAd/BNT). Whole blood samples were collected: first, before and second, 21 days after the booster dose. The IgG level was measured using chemiluminescent immunoassay; the intensity of the T-cell response—IFNγ concentration—was assessed using IGRA test. At 21 days after the booster, all subjects achieved reactive/positive anti-SARS-CoV-2 IgG, and IGRA test results showed a significant increase compared to the results before booster administration. We compared the results before and after the booster between participants with and without prior history of COVID-19. The IFNγ concentrations in both cohorts were higher in convalescents (both before booster and 21 days after). The IgG titers were subtly lower in COVID-19 convalescents than in naïve but without statistical significance. Data on cell-mediated immunity are scarce, especially with regard to the general population. A better understanding of the complexity of the immune response to SARS-CoV-2 could contribute to developing more effective vaccination strategies.

Plasma biomarkers for systemic inflammation in COVID-19 survivors

BACKGROUND

While the majority of COVID-19 patients fully recover from the infection and become asymptomatic, a significant proportion of COVID-19 survivors experience a broad spectrum of symptoms lasting weeks to months post-infection, a phenomenon termed "post-acute sequelae of COVID-19 (PASC)." The aim of this study is to determine whether inflammatory proteins are dysregulated and can serve as potential biomarkers for systemic inflammation in COVID-19 survivors.

METHODS

We determined the levels of inflammatory proteins in plasma from 22 coronavirus disease 2019 (COVID-19) long haulers (COV-LH), 22 COVID-19 asymptomatic survivors (COV-AS), and 22 healthy subjects (HS) using an Olink proteomics assay and assessed the results by a beads-based multiplex immunoassay.

RESULTS

Compared to HS, we found that COVID-19 survivors still exhibited systemic inflammation, as evidenced by significant changes in the levels of multiple inflammatory proteins in plasma from both COV-LH and COV-AS. CXCL10 was the only protein that significantly upregulated in COV-LH compared with COV-AS and HS.

CONCLUSIONS

Our results indicate that several inflammatory proteins remain aberrantly dysregulated in COVID-19 survivors and CXCL10 might serve as a potential biomarker to typify COV-LH. Further characterization of these signature inflammatory molecules might improve the understanding of the long-term impacts of COVID-19 and provide new targets for the diagnosis and treatment of COVID-19 survivors with PASC.

Humoral and Cellular Immune Responses to Vector, Mix-and-Match, or mRNA Vaccines against SARS-CoV-2 and the Relationship between the Two Immune Responses

We investigated how differences in age, sex, or vaccine type can affect humoral and cellular immune responses after vaccination with vector (ChAdOx1 nCoV-19), mix-and-match (first, ChAdOx1 nCoV-19, and second, BNT162b2), or mRNA (BNT162b2 or mRNA-1273) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Venous blood was collected from 573 subjects (vector, 396; mix-and-match, 96; and mRNA, 81) before the first vaccination (T0), 7 to 8 weeks (vector) or 3 to 4 weeks (mRNA) after the first vaccination (T1), and 3 to 4 weeks after the second vaccination (T2). The humoral and cellular immune responses were evaluated using Elecsys anti-SARS-CoV-2 (Roche), Alinity SARS-CoV-2 IgG II Quant (Abbott), cPass SARS-CoV-2 neutralization antibody detection (GenScript), and QuantiFERON SARS-CoV-2 (Qiagen) kits. At T1, the levels of the receptor-binding domain antibodies (RBD Ab) and neutralizing antibodies (NAb) decreased with aging, but interferon gamma release (IGR) levels increased. The RBD Ab, NAb, and IGR levels were higher in females than in males at T1 and T2. The NAb levels were higher in the mix-and-match and mRNA vaccine groups than in the vector vaccine group at T2. The RBD Ab and IGR levels were higher in the mRNA vaccine group than in the vector or mix-and-match vaccine groups at T2. The optimal cutoffs for RBD Ab and NAb, which were used to determine the presence of T cell responses, were 5.7 binding antibody units per milliliter (BAU mL-1) and 12.0 IU mL-1, respectively. Age, sex, and vaccine type affected the humoral and cellular immune responses, and T cell responses could be estimated from RBD Ab and NAb levels. IMPORTANCE There have been few studies that comprehensively evaluated factors affecting immune responses and the correlation between humoral and cellular immune responses after vector, mix-and-match, and mRNA vaccines against SARS-CoV-2. Therefore, we analyzed the effects of age, sex, and the different vaccine regimens on the immune responses to vaccination against SARS-CoV-2. The correlation between humoral and cellular immune responses and the cutoffs were derived for RBD antibodies and neutralizing antibodies to predict the presence of the cellular immune responses. In this comprehensive study, we demonstrated that there were differences in the immune responses induced after vaccination depending on the age and sex of an individual. Among the three vaccine regimens, the mix-and-match and mRNA vaccines induced the most robust immune responses. Finally, the proposed optimal cutoffs for RBD and neutralizing antibodies may be useful for predicting cellular immune responses when assays for cellular immune responses are not available.

Assessment of humoral immune response to two mRNA SARS-CoV-2 VACCINES (Moderna and Pfizer) in healthcare workers fully vaccinated with and without a history of previous infection

Aims

Presence of anti‐S1 region of SARS‐CoV‐2 spike protein was analysed, at two and eight months, in 477 immunocompetent healthcare workers in Zaragoza, Spain, vaccinated with mRNA‐1273 (Moderna) or BNT162b2 (Pfizer).

Methods and results

Antibody analysis was performed with Alinity i System (Abbott). At 2 months, 100% of vaccinated had anti‐S1 IgG (mean = 13,285 AU ml⁻¹). This value was significantly higher with Moderna (18,192 AU ml⁻¹) than with Pfizer (10,441 AU ml⁻¹). The mean value of anti‐S1 IgG after vaccination was significantly higher in patients with than without previous infection (18,539 vs. 7919 AU ml⁻¹); in both groups was significantly higher with Moderna than with Pfizer (21,881 vs. 15,733 AU ml⁻¹ and 11,949 vs. 6387 AU ml⁻¹), respectively. At 8 months, 100% of patients were IgG positive, with higher levels with Moderna than with Pfizer. Nevertheless, in ensemble of cases, a mean decrease of antibody levels of 11,025 AU ml⁻¹ was observed.

Conclusion

At 2 and 8 months after vaccination, IgG response persists with both vaccines but with important decrease which suggests the need for revaccination.

Significance and impact of study

The study contributes to know the immune status after vaccination with two of more used anti‐SARS‐CoV‐2 vaccines. This knowledge is important for establishing the best vaccination strategy

Complete (Humoral and Cellular) Response to Vaccination against COVID-19 in a Group of Healthcare Workers-Assessment of Factors Affecting Immunogenicity

Vaccination is the best way to limit the extent of the COVID pandemic. Knowledge of the duration of the immune response will allow the planning of a vaccination protocol. This study aims to validate the complete (humoral and cellular) immune responses over time in large population groups following the full vaccination of healthcare professionals in real-life conditions and to assess the relationship between antibody levels and T-cell activity in relation to the characteristics of the study group. The samples for the study were obtained from volunteers (staff of two hospitals) on three occasions: before vaccination, T0, then 4–9 weeks after full vaccination (two doses BNT162b2), T1, and 7–9 months after vaccination, T2. The humoral response was investigated by the titre of anti-SARS-CoV-2 IgG antibodies to S1 protein. Assays were performed three times at intervals. The cellular response was assessed in a subgroup of 189 subjects by QuanT-Cell SARS-CoV-2 (IGRA). The assay was performed once. A group of 344 subjects fully vaccinated with the BNT162b2 vaccine were included in the study. The humoral response was observed in 100% of subjects at both 4–7 weeks and 7–9 months, but antibody titres fell by almost 90% in this interval. The cellular response was observed in 94% (177/189) of subjects 7–9 months after the second dose of vaccine. In subjects with a negative cellular response, eight out of 12 smoked. A factor associated with greater immunogenicity of vaccination was past SARS-CoV-2 infection. The administration of full BNT162b2 vaccination (two doses) induces humoral and cellular responses detectable even more than six months after vaccination. Smoking may be a factor associated with impaired cellular response to vaccination.

Cellular Immune Response in Patients Immunized with Three Vaccine Doses of Different Vaccination Schemes Authorized by the Chilean Ministry of Health in January 2022

In December 2019, a case of atypical pneumonia was reported in Wuhan, China. It was named COVID-19 and caused by SARS-CoV-2. In a few months, scientific groups around the world developed vaccines to reduce the disease’s severity. The objective was to evaluate the humoral and cellular immune response post immunization with three different vaccination schedules administered in Chile until January 2022. Sixty volunteers were recruited with a three-dose schedule, who had no history of infection nor close contact with a positive patient. IgG against the spike antigenic domain was detected, and the neutralization capacity against two groups of variants, Original/Alpha and Beta/Gamma, was also measured. Finally, the cellular response with interferon release was measured through IGRA. Results showed that there were significant differences in the neutralizing antibodies for the original and alpha variant when comparing three Comirnaty doses with Coronavac and Vaxzevria. A high number of reactive subjects against the different SARS-CoV-2 variants, alpha, gamma, and delta, were observed, with no significant differences between any of the three schemes, confirming the existence of a cellular immune response against SARS-CoV-2. In conclusion, the three vaccine schemes generated a cellular immune response in these volunteers.

Cellular and Humoral Immune Responses and Breakthrough Infections After Two Doses of BNT162b Vaccine in Healthcare Workers (HW) 180 Days After the Second Vaccine Dose

Background

Immunity and clinical protection induced by mRNA vaccines against SARS-CoV-2 have been shown to decline overtime. To gather information on the immunity profile deemed sufficient in protecting against hospitalization, we tested IgG levels, interferon-gamma (IFN-γ) secretion, and neutralizing antibodies 180 days (d180) after the second shot of BNT162b vaccine, in HW.

Methods

A total of 392 subjects were enrolled. All received BioNTech/Pfizer from February 2020 to April 2021. The vaccine-specific humoral response was quantitatively determined by testing for IgG anti-S1 domain of SARS-CoV-spike protein. Live virus microneutralization (MN) was evaluated by an assay performing incubation of serial 2-fold dilution of human serum samples, starting from 1:10 to 1:5120, with an equal volume of Wuhan strain and Delta VOC viral solution and assessing the presence/absence of a cytopathic effect. SARS-CoV-2-spike protein-specific T-cell response was determined by a commercial IFN-γ release assay.

Results

In 352 individuals, at d180, IgG levels decreased substantially but no results below the assay's positivity threshold were observed. Overall, 22 naive (8.1%) had values above the highest threshold. Among COVID-naive, the impact of age, which was observed at earlier stages, disappeared at d180, while it remained significant for 81 who had experienced a previous infection. Following the predictive model of protection by Khoury, we transformed the neutralizing titers in IU/ml and used a 54 IU/ml threshold to identify subjects with 50% protective immunity. Overall, live virus MN showed almost all subjects with previous exposure to SARS-CoV-2 neutralized the virus as compared to 33% of naive double-dosed subjects (p < 0.0001). All previously exposed subjects had strong IFN-γ secretion (>200 mIU/ml); among 271 naive, 7 (2.58%) and 17 (6.27%) subjects did not show borderline or strong secretion, respectively.

Conclusions

In naive subjects, low IgG titers are relatively long-lasting. Only a third of naive subjects maintain neutralizing responses. After specific stimulation, a very limited number of naive were unable to produce IFN-γ. The results attained in the small group of subjects with breakthrough infection suggest that simultaneous neutralizing antibody titers <20, binding antibody levels/ml <200, and IFN-γ <1,000 mIU/ml in subjects older than 58 may identify at-risk groups.

Long Lasting Cellular Immune Response Induced by mRNA Vaccination: Implication for Prevention Strategies

As the COVID19 pandemic continues to spread and vaccinations are administered throughout the world at different rates and with different strategies, understanding the multiple aspects of the immune response to vaccinations is required to define more efficient vaccination strategies. To date, the duration of protection induced by COVID19 vaccines is still matter of debate. To assess whether 2-doses vaccination with BNT162b2 mRNA COVID-19 vaccine was sufficient to induce a persistent specific cellular immune response, we evaluated the presence of SARS-COV2 Spike-specific B and T lymphocytes in 28 healthcare workers 1 and 7 months after completing the vaccination cycle. The results showed that at 7 months after second dose a population of Spike-specific B lymphocytes was still present in 86% of the immunized subjects, with a higher frequency when compared to not-immunized controls (0.38% ± 0.07 vs 0.13% ± 0.03, p<0.001). Similarly, specific CD4+ and CD8+ T lymphocytes, able to respond in vitro to stimulation with Spike derived peptides, were found at 7 months. These results confirm that vaccination with BNT162b2 is able to induce a specific immune response, potentially long lasting, and could be helpful in defining future vaccination strategies.

Persistence of Immune Response in Health Care Workers After Two Doses BNT162b2 in a Longitudinal Observational Study

Background

The mRNA-based vaccine BNT162b2 of BioNTech/Pfizer has shown high efficacy against SARS-CoV-2 infection and a severe course of the COVID-19 disease. However, little is known about the long-term durability of the induced immune response resulting from the vaccination.

Methods

In a longitudinal observational study in employees at a German hospital we compared the humoral and cellular immune response in 184 participants after two doses of the BioNTech/Pfizer vaccine (BNT162b2) with a mid-term follow-up after 9 months. Anti-SARS-CoV-2 binding antibodies were determined using both a quantitative and a semi-quantitative assay. For a qualitative assessment of the humoral immune response, we additionally measured neutralizing antibodies. Cellular immune response was evaluated by measuring Interferon-gamma release after stimulating blood-cells with SARS-CoV-2 specific peptides using a commercial assay.

Results

In the first analysis, a 100% humoral response rate was described after two doses of BNT162b2 vaccine with a mean antibody ratio of 8.01 ± 1.00. 9 months after the second dose of BNT162b2, serological testing showed a significant decreased mean antibody ratio of 3.84 ± 1.69 (p < 0.001). Neutralizing antibodies were still detectable in 96% of all participants, showing an average binding inhibition value of 68.20% ± 18.87%. Older age (p < 0.001) and obesity (p = 0.01) had a negative effect on the antibody persistence. SARS-CoV-2 specific cellular immune response was proven in 75% of individuals (mean Interferon-gamma release: 579.68 mlU/ml ± 705.56 mlU/ml).

Conclusion

Our data shows a declining immune response 9 months after the second dose of BNT162b2, supporting the potentially beneficial effect of booster vaccinations, the negative effect of obesity and age stresses the need of booster doses especially in these groups.

Humoral and cellular responses after a third dose of SARS-CoV-2 BNT162b2 vaccine in patients with lymphoid malignancies

Patients with hematological malignancies have impaired immune response after two doses of BNT162b2 (Pfizer/BioNTech) vaccine against SARS-CoV-2. Here, in this observational study (registration number HDH F20210324145532), we measure SARS-CoV-2 anti-Spike antibodies, neutralizing antibodies and T-cell responses after immune stimulation with a third dose (D3) of the same vaccine in patients with chronic lymphocytic leukemia (n = 13), B cell non-Hodgkin lymphoma (n = 14), and multiple myeloma (n = 16)). No unexpected novel side effects are reported. Among 25 patients with positive anti-S titers before D3, 23 (92%) patients increase their anti-S and neutralizing antibody titer after D3. All 18 (42%) initially seronegative patients remain negative. D3 increases the median IFN-γ secretion in the whole cohort and induces IFN-γ secretion in a fraction of seronegative patients. Our data thus support the use of a third vaccine dose amongst patients with lymphoid malignancies, even though some of them will still have vaccine failure.

Long-Lasting Immunity Against SARS-CoV-2: Dream or Reality?

Since its declaration as a pandemic in March 2020, SARS-CoV-2 has infected more than 217 million people worldwide and despite mild disease in the majority of the cases, more than 4.5 million cases of COVID-19-associated death have been reported as of September 2021. The question whether recovery from COVID-19 results in prevention of reinfection can be answered with a "no" since cases of reinfections have been reported. The more important question is whether during SARS-CoV-2 infection, a protective immunity is built and maintained afterwards in a way which protects from possibly severe courses of disease in case of a reinfection. A similar question arises with respect to vaccination: as of September 2021, globally, more than 5.2 billion doses of vaccines have been administered. Therefore, it is of utmost importance to study the cellular and humoral immunity toward SARS-CoV-2 in a longitudinal manner. In this study, reconvalescent COVID-19 patients have been followed up for more than 1 year after SARS-CoV-2 infection to characterize in detail the long-term humoral as well as cellular immunity. Both SARS-CoV-2-specific T cells and antibodies could be detected for a period of more than 1 year after infection, indicating that the immune protection established during initial infection is maintained and might possibly protect from severe disease in case of reinfection or infection with novel emerging variants. Moreover, these data demonstrate the opportunity for immunotherapy of hospitalized COVID-19 patients via adoptive transfer of functional antiviral T cells isolated from reconvalescent individuals.