The Influence of Cross-Reactive T Cells in COVID-19

Immunological Disorders: Gradations and the Current Approach in Laboratory Diagnostics

Currently, understanding the immune response, its abnormalities, and its diagnostic possibilities is a key point in the management of patients with various diseases, from infectious to oncological ones. The aim of this review was to analyze the data presented in the current literature on immune disorders and the possibility of their laboratory diagnostics in combination with clinical manifestations. We have performed a systematic analysis of the literature presented in international databases over the last ten years. We have presented data on the possibility of diagnosing immunopathological processes due to changes in immune cells and soluble molecules involved in the pathogenesis of a wide range of diseases, as well as the determination of antibodies to detect autoimmune processes. By applying laboratory techniques such as hematology, flow cytometry, ELISA, etc., available to most clinical laboratories worldwide, clinical data on immune system dysfunction in a wide range of diseases are being collected. This process is unfortunately still very far from being completed. However, with all the diversity of accumulated knowledge, we can currently state that the pathogenesis of the vast majority of immune-mediated diseases is not yet known. At the same time, the current success in dividing immune-mediated diseases into distinct clusters based on different types of inflammatory responses that are based on the involvement of different populations of T helper cells and cytokine molecules represents significant progress. Further research in this direction seems very promising, as it allows the identification of new target cells and target molecules for both improved diagnostics and targeted therapies.

The Role of Memory T-Cell Mediated Immunity in Long-term COVID-19: Effects of Vaccination Status

T-cell-mediated immunity is essential for controlling severe acute respiratory syndrome coronavirus 2 (SARSCoV2) infection, preventing severe disease, and potentially reducing the risk of long-term coronavirus disease (COVID). This study investigated the impact of natural infection, vaccination, and hybrid immunity on T-cell responses, with a particular emphasis on the role of memory T-cells in long-term COVID-19. The present study reviewed current literature on T-cell responses, including memory T-cell development, in individuals with natural SARS-CoV-2 infection, those vaccinated with messenger RNA (mRNA) vaccines, and those with hybrid immunity. It examined studies that compared T-cell activity, immune regulation, and the prevalence of long-term COVID-19 across these groups. Natural infection induces variable T-cell responses, with severe cases showing stronger but sometimes dysregulated immunological activity, which may contribute to prolonged COVID-19. Vaccination, particularly with mRNA vaccines, elicits targeted and consistent T-cell responses, including memory T-cells, reducing disease severity, and the incidence of long-term COVID-19. Hybrid immunity combines natural infection and vaccination, provides the most robust protection, enhanceds memory T-cell responses, and reduces the risk of long-term COVID-19 through balanced immune regulation. Memory T-cells play a critical role in mitigating long-term COVID-19. Vaccination significantly enhances T-cell-mediated immunity, minimizing the risk of chronic symptoms compared to natural infection alone. Hybrid immunity provides the most effective defense, emphasizing the importance of vaccination, even after natural infection, to prevent long-term COVID-19.

QuantiFERON SARS-CoV-2 assay for the evaluation of cellular immunity after immunization with mRNA SARS-CoV-2 vaccines: a systematic review and meta-analysis

A systematic review and meta-analysis were performed to evaluate the virus-specific T-cell response after COVID-19 mRNA vaccination, using the QuantiFERON SARS-CoV-2 interferon-γ release assay. A search was conducted (June 8, 2023) in the PUBMED, SCOPUS, and medRxiv databases, to identify studies reporting the QuantiFERON SARS-CoV-2 (Starter (two antigen tubes) or Starter + Extended Pack (three antigen tubes), cut-off ≥ 0.15 IU/mL) positivity rate (PR) in immunocompetent adults, following the administration of two or three COVID-19 mRNA vaccine doses. Study quality was evaluated with the Critical Appraisal Skills Programme Tool. A meta-analysis was conducted using a random-effects model. Heterogeneity and publication bias were assessed. Eleven eligible studies (with 5-73 vaccinated immunocompetent participants) were identified. For COVID-19-naïve participants, ≤ 3 months after the second dose, the pooled PR (random-effects model) was 86 (95% confidence interval (95% CI) 78-95%). Comparing the Starter vs. the Starter + Extended Pack, a significant difference in PRs was detected (80.6% vs. 100% p-value < 0.001). At 3-6 and >6 months after the second dose and ≥ 3 months after the third dose, the pooled PRs were 59% (95% CI 45-72%), 79% (95% CI 66-92%), and 66% (95% CI 50-82%), respectively. For convalescent participants, ≥ 6 months after the third dose, the pooled PR was 81% (95% CI 67-95%). Limitations include heterogeneity and a small number of studies, at some timepoints. In conclusion, following the second or third COVID-19 mRNA vaccine dose, QuantiFERON SARS-CoV-2 detected positive responses in a certain percentage of the vaccinees, possibly because of waning immunity, reduced assay sensitivity, or lack of T-cell response induction in some vaccinees. The detection of positive responses was higher when the Starter + Extended Pack was used. PROSPERO Registration Number: CRD42023431315.

Bioinformatic Tools for Studying the Cellular Immune Response to SARS-CoV-2, Vaccine Efficacy, and Future Pandemics at the Global Population Level

Antigen recognition by human leukocyte antigen (HLA) restriction is critical for an adequate antiviral response in both natural infection and vaccination. However, the overwhelming polymorphism of HLA, with nearly 40,000 alleles identified, is an important limitation for the global analysis of cellular immune responses and vaccine efficacy. In this narrative review, we included several immunoinformatics studies performed in our laboratory to circumvent this limitation. These analyses focused on studying the cellular immune responses restricted by the most common HLA alleles, and their role in vaccine efficacy. Computational studies validated experimentally, such as our laboratory has carried out, represent a useful, rapid, and cost-effective strategy to combat future pandemics.

Mucosal immunization with dual influenza/COVID-19 single-replication virus vector protects hamsters from SARS-CoV-2 challenge

The COVID-19 pandemic has highlighted the need for mucosal vaccines as breakthrough infections, short-lived immune responses and emergence of new variants have challenged the efficacy provided by the first generation of vaccines against SARS-CoV-2 viruses. M2SR SARS-CoV-2, an M2-deleted single-replication influenza virus vector modified to encode the SARS-CoV-2 receptor binding domain, was evaluated following intranasal delivery in a hamster challenge model for protection against Wuhan SARS-CoV-2. An adjuvanted inactivated SARS-CoV-2 whole virus vaccine administered intramuscularly was also evaluated. The intranasal M2SR SARS-CoV-2 was more effective than the intramuscular adjuvanted inactivated whole virus vaccine in providing protection against SARS-CoV-2 challenge. M2SR SARS-CoV-2 elicited neutralizing serum antibodies against Wuhan and Omicron SARS-CoV-2 viruses in addition to cross-reactive mucosal antibodies. Furthermore, M2SR SARS-CoV-2 generated serum HAI and mucosal antibody responses against influenza similar to an H3N2 M2SR influenza vaccine. The intranasal dual influenza/COVID M2SR SARS-CoV-2 vaccine has the potential to provide protection against both influenza and COVID.