Intracellular Cytokine Staining Assay Research Articles

Characteristics of Norovirus capsid protein-specific CD8+ T-Cell responses in previously infected individuals

ABSTRACT Norovirus (NV) infection causes acute gastroenteritis in children and adults. Upon infection with NV, specific CD8+ T cells, which play an important role in anti-infective immunity, are activated in the host. Owing to the NV’s wide genotypic variability, it is challenging to develop vaccines with cross-protective abilities against infection. To aid effective vaccine development, we examined specific CD8+ T-cell responses towards viral-structural protein (VP) epitopes, which enable binding to host susceptibility receptors. We isolated peripheral blood mononuclear cells from 196 participants to screen and identify predominant core peptides towards NV main and small envelope proteins using ex vivo and in vitro intracellular cytokine staining assays. Human leukocyte antigen (HLA) restriction characteristics were detected using next-generation sequencing. Three conservative immunodominant VP-derived CD8+ T-cell epitopes, VP294–102 (TDAARGAIN), VP2153–161 (RGPSNKSSN), and VP1141–148 (FPHIIVDV), were identified and restrictively presented by HLA-Cw * 0102, HLA-Cw * 0702, and HLA-A *1101 alleles, separately. Our findings provide useful insights into the development of future vaccines and treatments for NV infection.

High Frequency of Prior SARS-CoV-2 Infection by Sensitive Nucleocapsid Assays.

Prior infection with SARS-CoV-2 is typically measured by nucleocapsid serology assays. In this study, we show that the Simoa serology assays and T cell intracellular cytokine staining assays are more sensitive than the clinical Elecsys assay for detection of nucleocapsid-specific immune responses. These data suggest that the prevalence of prior SARS-CoV-2 infection in the population may be higher than currently appreciated.

Proficiency tests to evaluate the impact on assay outcomes of harmonized influenza-specific Intracellular Cytokine Staining (ICS) and IFN-ɣ Enzyme-Linked ImmunoSpot (ELISpot) protocols

The magnitude and quality of cell-mediated immune responses elicited by natural infection or vaccination are commonly measured by Interferon-ɣ (IFN-ɣ) Enzyme-Linked ImmunoSpot (ELISpot) and Intracellular Cytokine Staining (ICS). To date, laboratories apply a variety of in-house procedures which leads to diverging results, complicates interlaboratory comparisons and hampers vaccine evaluations. During the FLUCOP project, efforts have been made to develop harmonized Standard Operating Procedures (SOPs) for influenza-specific IFN-ɣ ELISpot and ICS assays. Exploratory pilot studies provided information about the interlaboratory variation before harmonization efforts were initiated. Here we report the results of two proficiency tests organized to evaluate the impact of the harmonization effort on assay results and the performance of participating FLUCOP partners.The introduction of the IFN-ɣ ELISpot SOP reduced variation of both background and stimulated responses. Post-harmonization background responses were all lower than an arbitrary threshold of 50 SFU/million cells. When stimulated with A/California and B/Phuket, a statistically significant reduction in variation (p < 0.0001) was observed and CV values were strongly reduced, from 148% to 77% for A/California and from 126% to 73% for B/Phuket. The harmonizing effect of applying an ICS SOP was also confirmed by an increased homogeneity of data obtained by the individual labs. The application of acceptance criteria on cell viability and background responses further enhanced the data homogeneity. Finally, as the same set of samples was analyzed by both the IFN-ɣ ELISpot and the ICS assays, a method comparison was performed. A clear correlation between the two methods was observed, but they cannot be considered interchangeable.In conclusion, proficiency tests show that a limited harmonization effort consisting of the introduction of SOPs and the use of the same in vitro stimulating antigens leads to a reduction of the interlaboratory variation of IFN-ɣ ELISpot data and demonstrate that substantial improvements for the ICS assay are achieved as comparable laboratory datasets could be generated. Additional steps to further reduce the interlaboratory variation of ICS data can consist of standardized gating templates and detailed data reporting instructions as well as further efforts to harmonize reagent and instrument use.

HIV-1 protective epitope-specific CD8+ T cells in HIV-1-exposed seronegative individuals

Although previous studies have reported HIV-1-specific Tcell responses in HIV-1-exposed seronegative (HESN) individuals, there has been no detailed analysis of these Tcells against HIV-1 infection. We investigated HIV-1-specific CD8+ Tcell responses in 200 Japanese HESN men who have sex with men (MSM). Tcell responses to 143 well-characterized HIV-1 epitope peptides were analyzed by intracellular cytokine staining assay consisting of 3-week cultures of PBMCs stimulated with peptides. HLA-B∗51:01-restricted Pol TI8-specific and HLA-A∗02:06-restricted Pol SV9-specific CD8+ Tcells were identified in two and one individuals, respectively, whereas CD8+ Tcells specific for other HLA-A∗02:06-restricted or HLA-B∗51:01 epitopes were not present in these individuals. These epitope-specific Tcells recognized HIV-1-infected cells. Because these two epitopes were previously reported to be protective in HIV-1-infected individuals, these protective epitope-specific Tcells might suppress HIV-1 replication in HESN-MSM individuals. The present study suggests the contribution of protective epitope-specific Tcells to protection against HIV-1 infection.

An attenuated herpesvirus vectored vaccine candidate induces T-cell responses against highly conserved porcine reproductive and respiratory syndrome virus M and NSP5 proteins that are unable to control infection.

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a leading cause of economic loss in pig farming worldwide. Existing commercial vaccines, all based on modified live or inactivated PRRSV, fail to provide effective immunity against the highly diverse circulating strains of both PRRSV-1 and PRRSV-2. Therefore, there is an urgent need to develop more effective and broadly active PRRSV vaccines. In the absence of neutralizing antibodies, T cells are thought to play a central role in controlling PRRSV infection. Herpesvirus-based vectors are novel vaccine platforms capable of inducing high levels of T cells against encoded heterologous antigens. Therefore, the aim of this study was to assess the immunogenicity and efficacy of an attenuated herpesvirus-based vector (bovine herpesvirus-4; BoHV-4) expressing a fusion protein comprising two well-characterized PRRSV-1 T-cell antigens (M and NSP5). Prime-boost immunization of pigs with BoHV-4 expressing the M and NSP5 fusion protein (vector designated BoHV-4-M-NSP5) induced strong IFN-γ responses, as assessed by ELISpot assays of peripheral blood mononuclear cells (PBMC) stimulated with a pool of peptides representing PRRSV-1 M and NSP5. The responses were closely mirrored by spontaneous IFN-γ release from unstimulated cells, albeit at lower levels. A lower frequency of M and NSP5 specific IFN-γ responding cells was induced following a single dose of BoHV-4-M-NSP5 vector. Restimulation using M and NSP5 peptides from PRRSV-2 demonstrated a high level of cross-reactivity. Vaccination with BoHV-4-M-NSP5 did not affect viral loads in either the blood or lungs following challenge with the two heterologous PRRSV-1 strains. However, the BoHV-4-M-NSP5 prime-boost vaccination showed a marked trend toward reduced lung pathology following PRRSV-1 challenge. The limited effect of T cells on PRRSV-1 viral load was further examined by analyzing local and circulating T-cell responses using intracellular cytokine staining and proliferation assays. The results from this study suggest that vaccine-primed T-cell responses may have helped in the control of PRRSV-1 associated tissue damage, but had a minimal, if any, effect on controlling PRRSV-1 viral loads. Together, these results indicate that future efforts to develop effective PRRSV vaccines should focus on achieving a balanced T-cell and antibody response.

Mpox vaccine and infection-driven human immune signatures: an immunological analysis of an observational study

Monkeypox virus has recently infected more than 88 000 people, raising concerns about our preparedness against this emerging viral pathogen. Licensed and approved for mpox, the JYNNEOS vaccine has fewer side-effects than previous smallpox vaccines and has shown immunogenicity against monkeypox in animal models. This study aims to elucidate human immune responses to JYNNEOS vaccination compared with mpox-induced immunity. Peripheral blood mononuclear cells and sera were obtained from ten individuals vaccinated with one or two doses of JYNNEOS and six individuals diagnosed with monkeypox virus infection. Samples were obtained from seven individuals before vaccination to serve as a baseline. We examined the polyclonal serum (ELISA) and single B-cell (heavy chain gene and transcriptome data) antibody repertoires and T-cell responses (activation-induced marker and intracellular cytokine staining assays) induced by the JYNNEOS vaccine versus monkeypox virus infection. All participants were men between the ages of 21 and 60 years, except for one woman in the group of mpox-convalescent individuals, and none had previous orthopoxvirus exposure. All mpox cases were mild. Vaccinee samples were collected 6-33 days after the first dose and 5-40 days after the second dose. Mpox-convalescent samples were collected 20-102 days after infection. In vaccine recipients, gene-level plasmablast and antibody responses were negligible and sera displayed moderate binding to recombinant orthopoxviral proteins (A29L, A35R, E8L, A30L, A27L, A33R, B18R, and L1R) and native proteins from the 2022 monkeypox outbreak strain. By contrast, recent monkeypox virus infection (within 20-102 days) induced robust serum antibody responses to monkeypox virus proteins and to native monkeypox virus proteins from a viral isolate obtained during the 2022 outbreak. JYNNEOS vaccine recipients presented robust orthopoxviral CD4+ and CD8+ T-cell responses. Infection with monkeypox virus resulted in robust B-cell and T-cell responses, whereas immunisation with JYNNEOS elicited more robust T-cell responses. These data can help to inform vaccine design and policies for preventing mpox in humans. National Cancer Institute (National Institutes of Health), National Institute of Allergy and Infectious Diseases (National Institutes of Health), and Icahn School of Medicine.

The recombinant truncated envelope protein of West Nile virus adjuvanted with Alum/CpG induces potent humoral and T cell immunity in mice

West Nile virus (WNV) is a mosquito-transmitted flavivirus distributed globally for decades and can cause disease in humans and animals. So far, no WNV vaccine has been licensed for human use. Therefore, the development of novel candidate vaccines and the improvement of vaccination strategies is imperative. As the WNV envelope (E) glycoprotein plays an important role in mediating viral binding to cellular receptors and virus-cell membrane fusion, it is a critical target for the host humoral response. Here, we prepared a recombinant truncated envelope protein of WNV (rWNV-80E) and developed a WNV subunit vaccine formulation with a combination of aluminum hydroxide (alum) and a synthetic oligonucleotide CpG as adjuvants. C57BL/6 mice were immunized twice intramuscularly at 28-day intervals with 5 µg purified rWNV-80E adjuvanted with Alum/CpG. WNV E-specific IgG was detected by enzyme-linked immunosorbent assay and neutralizing antibodies (nAbs) was detected using single-round infectious particles of WNV. Furthermore, T cell immunity was detected by enzyme-linked immunospot assay and intracellular cytokine staining assay. Notably, rWNV-80E was highly immunogenic and elicited potent humoral and cell immunity, as evidenced by significant levels of IFN-γ and TNF-α secretion in the T cells of mice. In summary, the Alum/CpG-adjuvanted rWNV-80E subunit vaccine elicited potent and balanced B- and T-cell immunity in mice, and therefore it is a promising candidate vaccine that warrants further investigation for use in human or veterinary applications.

Abstract 913: Engineering allogeneic off-the-shelf CD19-directed CAR-iNKT cells without additional genetic manipulations for the treatment of hematological malignancies

Abstract Despite the approval of three autologous CAR-T cell products, B-cell malignancies still represent an unmet need as several of the relapsed/refractory patients are ineligible for autologous CART cell therapies. Invariant natural killer T (iNKT) cells are a unique subset of immune cells that display properties of both T cells and natural killer cells and bridge the innate and adaptive immune responses upon antigen recognition. Unlike conventional β T cells, iNKT cells express an invariant T cell receptor (TCR) that recognize glycolipids presented in the context of the monomorphic, MHC-class I related molecule, CD1d. iNKT cells are ideal cell types for allogeneic, off the shelf approach as they can target cancers without the risk of graft-versus-host disease (GvHD), circumventing the need to delete or knock out the endogenous TCR. Here, we report the engineering of ‘off-the-shelf’ iNKT cells directed against CD19 and their robust in vitro and in vivo functional profile. Briefly, peripheral blood derived iNKT cells were isolated from healthy donors and were engineered to express a CD19 CAR using a 3rd generation lentiviral vector. To demonstrate the CAR-dependent and independent anti-tumor activity, CAR19-iNKT cells were compared in vitro against non-transduced (NT) iNKT cells in cytotoxicity assays and intracellular cytokine staining assays. Allogeneic CAR19-iNKT cells upregulated activation markers, secreted cytokines, and lysed cancer cell lines and primary tumor cells from chronic lymphocytic leukemia and marginal zone lymphoma patients in an antigen-specific manner. Excellent post thaw recovery and viability was noted in cryopreserved CAR19-iNKT cells. Finally, the anti-tumor activity of cryopreserved CAR19-iNKT cells were evaluated in an established aggressive NSG mice model of SEM-luc, a B cell lymphoblastic leukemia cell line expressing luciferase. Robust antitumor activity by CAR19-iNKT cells was observed without any obvious adverse effects compared to controls (untreated and NT iNKT cells). The persistence of CAR19-iNKT cells in this model is currently being evaluated. These data demonstrate a unique, off the shelf CAR19-iNKT cell platform for targeting hematological malignancies that combines the specificity of CD19 targeting CAR with the innate features of iNKT cells. The data indicates that iNKT cells are a potent cell type for generating allogeneic off the shelf products for treating a broad spectrum of hematological malignancies and solid tumors by targeting different receptors on the respective tumors. Citation Format: Kanagaraju Ponnusamy, Janani Kanagaraju, Yingxin Wang, Bryan Lye, Hongwei Ren, Sandhya Buchanan, Michael J. Baker, Mini Bharathan, Anastasios Karadimitris. Engineering allogeneic off-the-shelf CD19-directed CAR-iNKT cells without additional genetic manipulations for the treatment of hematological malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 913.

HBV Core-specific CD4+ T cells correlate with sustained viral control upon off-treatment in HBeAg-positive chronic hepatitis B patients

Background & aimsTreatment with nucleos(t)ide analogue (NA) efficiently suppresses viral replication in patients with chronic HBV infection, yet HBV relapses frequently upon NA withdrawal; the detailed immunomodulatory compounds for sustained viral control of HBV upon NA interruption have yet to be fully clarified. This study aimed to elucidate the role of T cells specific for distinct HBV peptides in sustained response upon discontinuation of antiviral treatment. MethodsA total of 48 patients with HBeAg-positive chronic hepatitis B receiving NA treatment and withdrawal were included longitudinally in a retrospective and prospective cohort. Enzyme-linked immunosorbent spot (ELISpot) and intracellular cytokine staining (ICS) assays were performed to detect IFN-γ producing HBV-specific T cells following stimulation with overlapping peptides covering the whole HBV genome after 10 days of in vitro expansion. ResultsICS assays revealed that T cells specific for HBV Core and Polymerase induced more robust IFN-γ responses compared to Envelope and HBx. Notably, at the time of NA discontinuation, the intensity and breadth of HBV Core peptides-induced responses, predominately targeted by CD4+ T cells but not CD8+ T cells, were associated with sustained viral control upon off-treatment. Further exploration of longitudinal features in patients with sustained viral control revealed that the breadth of HBV-specific T cell responses does not increase following treatment cessation. ConclusionThis report emphasizes the essential role of HBV Core-specific CD4+ T cells in sustained response after therapy withdrawal, indicating it is a potential candidate for immunotherapeutic approaches in chronic HBV patients.

Effects of SARS-CoV-2 Omicron BA.1 Spike Mutations on T-Cell Epitopes in Mice.

T-cell immunity plays an important role in the control of SARS-CoV-2 and has a great cross-protective effect on the variants. The Omicron BA.1 variant contains more than 30 mutations in the spike and severely evades humoral immunity. To understand how Omicron BA.1 spike mutations affect cellular immunity, the T-cell epitopes of SARS-CoV-2 wild-type and Omicron BA.1 spike in BALB/c (H-2d) and C57BL/6 mice (H-2b) were mapped through IFNγ ELISpot and intracellular cytokine staining assays. The epitopes were identified and verified in splenocytes from mice vaccinated with the adenovirus type 5 vector encoding the homologous spike, and the positive peptides involved in spike mutations were tested against wide-type and Omicron BA.1 vaccines. A total of eleven T-cell epitopes of wild-type and Omicron BA.1 spike were identified in BALB/c mice, and nine were identified in C57BL/6 mice, only two of which were CD4+ T-cell epitopes and most of which were CD8+ T-cell epitopes. The A67V and Del 69-70 mutations in Omicron BA.1 spike abolished one epitope in wild-type spike, and the T478K, E484A, Q493R, G496S and H655Y mutations resulted in three new epitopes in Omicron BA.1 spike, while the Y505H mutation did not affect the epitope. These data describe the difference of T-cell epitopes in SARS-CoV-2 wild-type and Omicron BA.1 spike in H-2b and H-2d mice, providing a better understanding of the effects of Omicron BA.1 spike mutations on cellular immunity.

Delivery of spike-RBD by bacterial type three secretion system for SARS-CoV-2 vaccine development.

COVID-19 pandemic continues to spread throughout the world with an urgent demand for a safe and protective vaccine to effectuate herd protection and control the spread of SARS-CoV-2. Here, we report the development of a bacterial vector COVID-19 vaccine (aPA-RBD) that carries the gene for the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. Live-attenuated strains of Pseudomonas aeruginosa (aPA) were constructed which express the recombinant RBD and effectively deliver RBD protein into various antigen presenting cells through bacterial type 3 secretion system (T3SS) in vitro. In mice, two-dose of intranasal aPA-RBD vaccinations elicited the development of RBD-specific serum IgG and IgM. Importantly, the sera from the immunized mice were able to neutralize host cell infections by SARS-CoV-2 pseudovirus as well as the authentic virus variants potently. T-cell responses of immunized mice were assessed by enzyme-linked immunospot (ELISPOT) and intracellular cytokine staining (ICS) assays. aPA-RBD vaccinations can elicit RBD-specific CD4+and CD8+T cell responses. T3SS-based RBD intracellular delivery heightens the efficiency of antigen presentation and enables the aPA-RBD vaccine to elicit CD8+T cell response. Thus, aPA vector has the potential as an inexpensive, readily manufactured, and respiratory tract vaccination route vaccine platform for other pathogens.

AW-NI-1: ANGIOTENSIN II EXAGGERATES SARS-COV-2 SPECIFIC T-CELL RESPONSE IN CONVALESCENT INDIVIDUALS FOLLOWING COVID-19

Background: Coronavirus disease 2019 (COVID-19) is an emerging respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Recent studies have suggested numerous hypotheses that may explain multi-organ dysfunction during a COVID-19 infection. One possible hypothesis posits that the renin-angiotensin system dysregulation before SARS-CoV-2 infection could exacerbate disease symptoms and severity, especially in COVID-19 patients with underlying comorbidities. Objective: This study sought to investigate the effect of exogenous angiotensin II (Ang II) on peripheral blood mononuclear cells (PBMCs) stimulated with SARS-CoV-2 peptide pool. Methods: PBMCs from recovered COVID-19 patients (n = 18) were used in this study. SARS-CoV-2 specific t-cell responses were measured using activation induced cell marker assay and intracellular cytokine staining (ICS) assay, while enzyme-linked immunosorbent assay (ELISA) and ICS assays determined functional capability and polarization. Additionally, the relative level of protein phosphorylation in PBMCs was measured using a phosphokinase array. Results: Our results showed that in vitro Ang II treatment significantly increased the magnitude of SARS-CoV-2 specific t-cell response in stimulated PBMCs with SARS-CoV-2 peptide pool. Moreover, the phosphorylation level of numerous proteins implicated in cardiovascular diseases, inflammation, and viral infection showed significant increase in the presence of Ang II. Mitogenic stimulation of PBMCs after Ang II and SARS-CoV-2 peptide pool stimulation showed functional polarization of CD4+ and CD8+ t-cells toward Th1/Th17 and Th17 phenotypes, respectively. Meanwhile, ELISA showed an increased production of IL-1b and IL-6 in Ang II-stimulated PBMCs without affecting the reduction of IL-10 level resulting from SARS-CoV-2 peptide pool stimulation. Conclusion: To our knowledge, the present study is the first to demonstrate that Ang II exaggerates SARS-CoV-2 specific t-cells response. Therefore, during COVID-19 infection Ang II may aggravate the inflammatory response and change the immune response toward a more inflammatory profile against SARS-CoV-2 infection, leading to serious complications and worse outcomes during COVID-19 infection.

Effect of Immunomodulation in Turkeys Infected with Haemorrhagic Enteritis Virus on the Percentage of CD4+ and CD8α+ T Lymphocyte Subpopulations Synthesising IFN-γ.

Haemorrhagic enteritis virus (HEV) is a common turkey pathogen which suppresses the immune function. The immunosuppressive potential of both field and vaccine strains of HEV makes it necessary to seek substances which can limit or prevent this phenomenon. The aim of the presented work was to investigate the effect of two immunomodulators in the immune response of HEV-infected turkeys. The immunomodulators were synthetic methisoprinol and a natural preparation containing 34.2% β-glucans (β-1,3/1,6) and 12% mannan oligosaccharides (MOS). The synthetic immunomodulator was administered to female Big 6 turkey chicks at a dose of 200 mg/kg b.w. in drinking water i) for 3 days before, ii) for 5 days after, or iii) for 3 days before, on the day of infection, and for 5 days after experimental HEV infection in turkeys. The natural counterpart was also given to female Big 6 turkey chicks at a dose of 500 g/tonne of feed i) for 14 days before, ii) for 5 days after, or iii) for 14 days before, on the day of infection, and for 5 days after infection. Their effect was evaluated on the synthesis of interferon gamma (IFN-γ) by splenic CD4+ and CD8α+ T cells in response to mitogen stimulation in vitro. Samples were taken 3, 5 and 7 days after infection and analysed by intracellular cytokine staining assay. Methisoprinol was shown to increase the CD4+IFN-γ+ and CD8α+IFN-γ+ T cell count in these birds over the same cell count in control turkeys. A similar effect was obtained in turkeys that received the natural immunomodulator. The evaluated immunomodulators may be used to attenuate the effects of immunosuppression in HEV-infected turkeys.

Harmonization and qualification of intracellular cytokine staining to measure influenza-specific CD4+ T cell immunity within the FLUCOP consortium.

Despite the knowledge that cell-mediated immunity (CMI) contributes to the reduction of severe influenza infection, transmission, and disease outcome, the correlates of protection for cell-mediated immunity remain still unclear. Therefore, measuring the magnitude and quality of influenza-specific T cell responses in a harmonized way is of utmost importance to improve characterisation of vaccine-induced immunity across different clinical trials. The present study, conducted as part of the FLUCOP project, describes the development of a consensus protocol for the intracellular cytokine staining (ICS) assay, in order to reduce inter-laboratory variability, and its qualification. In order to develop a consensus protocol, the study was divided into different stages. Firstly, two pilot studies evaluated critical parameters in the analytical (read-outs) and post-analytical (gating strategies and data analysis) methods applied by eight different laboratories within the FLUCOP consortium. The methods were then harmonized by fixing the critical parameters and the subsequent consensus protocol was then qualified by one FLUCOP member. The antigen-specific cell population was defined as polypositive CD4+ T cells (i.e. positive for at least two markers among CD40L/IFNγ/IL2/TNFα), which was shown to be the most sensitive and specific read-out. The qualification of this consensus protocol showed that the quantification of polypositive CD4+ T cells was precise, linear and accurate, and sensitive with a lower limit of quantification of 0.0335% antigen-specific polypositive CD4+ T cells. In conclusion, we provide the description of a harmonized ICS assay, which permits quantitative and qualitative evaluation of influenza vaccine-induced T cell responses. Application of this harmonized assay may allow for future comparisons of T cell responses to different influenza vaccines. It may facilitate future assessments of potential correlates of protection with the promise of application across other pathogens.

Comparison between enzyme-linked immunospot assay and intracellular cytokine flow cytometry assays for the evaluation of T cell response to SARS-CoV-2 after symptomatic COVID-19.

IntroductionEvaluation of different cell‐based assays for the study of adaptive immune responses against SARS‐CoV‐2 is crucial for studying long‐term and vaccine‐induced immunity.MethodsEnzyme‐linked immunospot assay (ELISpot) and intracellular cytokine staining (ICS) using peptide pools spanning the spike protein and nucleoprotein of SARS‐CoV‐2 were performed in 25 patients who recovered from paucisymptomatic (n = 19) or severe COVID‐19 (n = 6).ResultsThe proportion of paucisymptomatic patients with detectable SARS‐CoV‐2 T cells was low, as only 44% exhibit a positive T cell response with the ICS and 67% with the ELISpot. The magnitude of SARS‐CoV‐2 T cell responses was low, both with ICS (median at 0.12% among total T cells) and ELISpot (median at 61 SFCs/million peripheral blood mononuclear cells [PBMC]) assays. Moreover, T cell responses in paucisymptomatic patients seemed lower than among patients with severe disease. In the paucisymptomatic patients, the two assays were well correlated with 76% of concordant responses and a Cohen's kappa of 55. Furthermore, in four patients SARS‐CoV‐2 T cells were detected by ELISpot but not with ICS. Short‐term culture could improve the detection of specific T cells.ConclusionsIn patients who recovered from paucisymptomatic COVID‐19, the proportion of detectable anti‐SARS‐CoV‐2 responses and their magnitude seemed lower than in patients with more severe symptoms. The ELISpot appeared to be more sensitive than the ICS assay. Short‐term culture revealed that paucisymptomatic patients had nonetheless few SARS‐CoV‐2 T cells at a very low rate in peripheral blood. These data indicate that various ex‐vivo assays may lead to different conclusions about the presence or absence of SARS‐CoV‐2 T cell immunity.

Durability of Heterologous and Homologous COVID-19 Vaccine Boosts

Antibody responses elicited by current messenger RNA (mRNA) COVID-19 vaccines decline rapidly and require repeated boosting. To evaluate the immunogenicity and durability of heterologous and homologous prime-boost regimens involving the adenovirus vector vaccine Ad26.COV2.S and the mRNA vaccine BNT162b2. In this cohort study at a single clinical site in Boston, Massachusetts, 68 individuals who were vaccinated at least 6 months previously with 2 immunizations of BNT162b2 were boosted with either Ad26.COV2.S or BNT162b2. Enrollment of participants occurred from August 12, 2021, to October 25, 2021, and this study involved 4 months of follow-up. Data analysis was performed from November 2021 to February 2022. Participants who were previously vaccinated with BNT162b2 received a boost with either Ad26.COV2.S or BNT162b2. Humoral immune responses were assessed by neutralizing, binding, and functional antibody responses for 16 weeks following the boost. CD8+ and CD4+ T-cell responses were evaluated by intracellular cytokine staining assays. Among 68 participants who were originally vaccinated with BNT162b2 and boosted with Ad26.COV2.S (41 participants; median [range] age, 36 [23-84] years) or BNT162b2 (27 participants; median [range] age, 35 [23-76] years), 56 participants (82%) were female, 7 (10%) were Asian, 4 (6%) were Black, 4 (6%) were Hispanic or Latino, 3 (4%) were more than 1 race, and 53 (78%) were White. Both vaccines were found to be associated with increased humoral and cellular immune responses, including against SARS-CoV-2 variants of concern. BNT162b2 boosting was associated with a rapid increase of Omicron neutralizing antibodies that peaked at a median (IQR) titer of 1018 (699-1646) at week 2 and declined by 6.9-fold to a median (IQR) titer of 148 (95-266) by week 16. Ad26.COV2.S boosting was associated with increased Omicron neutralizing antibodies titers that peaked at a median (IQR) of 859 (467-1838) week 4 and declined by 2.1-fold to a median (IQR) of 403 (208-1130) by week 16. Heterologous Ad26.COV2.S boosting was associated with durable humoral and cellular immune responses in individuals who originally received the BNT162b2 vaccine. These data suggest potential benefits of heterologous prime-boost vaccine regimens for SARS-CoV-2.

Angiotensin II Exaggerates SARS-CoV-2 Specific T-Cell Response in Convalescent Individuals following COVID-19.

Dysregulation of renin−angiotensin systems during coronavirus disease 2019 (COVID-19) infection worsens the symptoms and contributes to COVID-19 severity and mortality. This study sought to investigate the effect of exogenous angiotensin II (Ang-II) on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T-cells response in recovered COVID-19 patients. Human peripheral blood mononuclear cells (PBMCs) were treated with Ang II and then stimulated with a SARS-CoV-2 peptide pool. T-cell responses were measured using flow cytometry, while enzyme-linked immunosorbent assay (ELISA) and intracellular cytokine staining (ICS) assays determined functional capability and polarization. Additionally, the relative level of protein phosphorylation was measured using a phosphokinase array. Our results showed that Ang II treatment significantly increased the magnitude of SARS-CoV-2-specific T-cell response in stimulated PBMCs with a SARS-CoV-2 peptide pool. Moreover, the phosphorylation levels of numerous proteins implicated in cardiovascular diseases, inflammation, and viral infection showed significant increases in the presence of Ang II. The mitogenic stimulation of PBMCs after Ang II and SARS-CoV-2 peptide pool stimulation showed functional polarization of T-cells toward Th1/Th17 and Th17 phenotypes, respectively. Meanwhile, ELISA showed increased productions of IL-1β and IL-6 in Ang II-stimulated PBMCs without affecting the IL-10 level. To our knowledge, this study is the first to demonstrate that Ang II exaggerates SARS-CoV-2-specific T-cells response. Therefore, during COVID-19 infection, Ang II may aggravate the inflammatory response and change the immune response toward a more inflammatory profile against SARS-CoV-2 infection.

Combining intramuscular and intranasal homologous prime-boost with a chimpanzee adenovirus-based COVID-19 vaccine elicits potent humoral and cellular immune responses in mice

ABSTRACT The efficacy of many coronavirus disease 2019 (COVID-19) vaccines has been shown to decrease to varying extents against new severe acute respiratory syndrome coronavirus 2 variants, which are responsible for the continuing COVID-19 pandemic. Combining intramuscular and intranasal vaccination routes is a promising approach for achieving more potent immune responses. We evaluated the immunogenicity of prime-boost protocols with a chimpanzee adenovirus serotype 68 vector-based vaccine, ChAdTS-S, administered via both intranasal and intramuscular routes in BALB/c mice. Intramuscular priming followed by an intranasal booster elicited the highest levels of IgG, IgA, and pseudovirus neutralizing antibody titres among all the protocols tested at day 42 after prime immunization compared with the intranasal priming/intramuscular booster and prime-boost protocols using only one route. In addition, intramuscular priming followed by an intranasal booster induced high T-cell responses, measured using the IFN-γ ELISpot assay, that were similar to those observed upon intramuscular vaccination. All ChAdTS-S vaccination groups induced Th1-skewing of the T-cell response according to intracellular cytokine staining and Meso Scale Discovery cytokine profiling assays on day 56 after priming. This study provides reference data for assessing vaccination schemes of adenovirus-based COVID-19 vaccines with high immune efficacy.

Achieving intracellular cytokine staining assay concordance on two continents to assess HIV vaccine-induced T-cell responses.

The HIV Vaccine Trials Network (HVTN) conducts clinical trials on 4 continents in pursuit of a safe and effective HIV vaccine. Cellular immune responses to vaccination that define vaccine immunogenicity and/or immune correlates of protection can be measured using multiparameter intracellular cytokine staining (ICS) assays. The HVTN cellular immunology laboratory, located in Seattle, WA, conducts ICS assays for vaccine trials according to Good Clinical Laboratory Practices (GCLP). In 2013, the HVTN established a second GCLP compliant cellular immunology laboratory in Cape Town, South Africa to assess vaccine immunogenicity for HVTN trials conducted on the African continent. To ensure ICS readouts in the 2 laboratories were directly comparable, we conducted concordance testing using PBMC from healthy controls and vaccine trial participants. Despite standardized procedures and instrumentation, shared quality control measures and quality assurance oversight, several factors impacted our ability to obtain close agreement in T-cell responses measured in the 2 laboratories. One of these was the type of fetal bovine serum (FBS) used in the assay, which impacted lymphocyte cell viability and background responses. In addition, the differences in supernatant removal technique also significantly affected our ability to detect positive responses to vaccine antigens. Standardization of these factors allowed us to achieve and maintain ICS assay concordance across the 2 laboratories over multiple years, accelerating our efforts to evaluate HIV vaccines. The insights gained in this process are valuable for assay transfer efforts by groups of investigators that need to directly compare data generated in different laboratories around the globe.

Early and Polyantigenic CD4 T Cell Responses Correlate with Mild Disease in Acute COVID-19 Donors.

We assessed SARS-CoV-2-specific CD4+ and CD8+ T cell responses in samples from 89 acute COVID-19 patients, utilizing blood samples collected during the first wave of COVID-19 in Italy. The goal of the study was to examine correlations between SARS-CoV-2-specific T cell responses in the early phase comparing mild, moderate, or severe COVID-19 disease outcomes. T cell responses to the spike (S) and non-S proteins were measured in a combined activation-induced marker (AIM) and intracellular cytokine staining (ICS) assay. Early CD4+ T cell responses to SARS-CoV-2 S correlated with milder disease by both AIM and IFNγ ICS readouts. The correlation of S-specific CD4+ T cell responses with milder disease severity was most striking within the first two weeks of symptom onset compared to later time points. Furthermore, donors with milder disease were associated with polyantigenic CD4+ T cell responses that recognized more prominently non-S proteins in addition to S, while severe acute COVID-19 was characterized by lower magnitudes of CD4+ T cell responses and a narrower repertoire. In conclusion, this study highlights that both the magnitude and breadth of early SARS-CoV-2-specific CD4+ T cell responses correlated with milder disease outcomes in acute COVID-19 patients.