Influenza Virus-Derived CD8 T Cell Epitopes: Implications for the Development of Universal Influenza Vaccines

CD8+ T cell-based immunotherapy: Promising frontier in human diseases

The abundant cell components of the adaptive immune system called T lymphocytes (T cells) play important roles in mediating immune responses to eliminate the invaders and create the memory of the germs to form a new immunity for the next encounter. Among them, cytotoxic T cells expressing cell-surface CD8 are the most critical effector cells that directly eradicate the target infected cells by recognizing antigens presented by major histocompatibility complex class I molecules to protect our body from pathological threats. In the continuous evolution of immunotherapy, various CD8+ T cell-based therapeutic strategies have been developed based on the role and molecular concept of CD8+ T cells. The emergence of such remarkable therapies provides promising hope for multiple human disease treatments such as autoimmunity, infectious disease, cancer, and other non-infectious diseases. In this review, we aim to discuss the current knowledge on the utilization of CD8+ T cell-based immunotherapy for the treatment of various diseases, the molecular basis involved, and its limitations. Additionally, we summarize the recent advances in the use of CD8+ T cell-based immunotherapy and provide a comprehensive overview of CD8+ T cells, including their structure, underlying mechanism of function, and markers associated with CD8+ T cell exhaustion. Building upon these foundations, we delineate the advancement of CD8+ T cell-based immunotherapies with fundamental operating principles followed by research studies, and challenges, as well as illustrate human diseases involved in this development.

Application of Humanized MHC Transgenic Mice in the Screening of HLA-Restricted T Cell Epitopes for Influenza Vaccines

BACKGROUND

Annual influenza epidemics pose a significant burden on the global healthcare system. The currently available vaccines mainly induce the production of neutralizing antibodies against hemagglutinin and neuraminidase, which are prone to antigenic variation, and this can reduce vaccine efficacy. Vaccines designed to target T cell epitopes can be potentially valuable. Considering the difficulties in obtaining clinical samples and the unique advantages of mice in disease-related research, a mouse model that can simulate human immune responses can be a superior alternative to peripheral blood mononuclear cells for epitope screening.

METHODS

The T cell epitopes of the A/California/07/2009 (H1N1) virus were predicted and utilized to evaluate the cellular immune responses of HLA-A2/DR1 and HLA-A11/DR1 transgenic mice during epitope screening. The selected peptides were used to immunize these two groups of transgenic mice, followed by a viral challenge to assess their protective efficacy.

RESULTS

The epitopes that were predicted and screened could stimulate cellular immune responses in HLA-A2/DR1 transgenic mice, HLA-A11/DR1 transgenic mice, and C57BL/6 mice. Moreover, the transgenic mice exhibited stronger ability to produce IFN-γ than that of the wild-type mice. Upon immunization and subjecting to viral challenge, the selected peptides exhibited protective effects against the influenza virus.

CONCLUSIONS

The HLA-A2/DR1 and HLA-A11/DR1 transgenic mouse models can be used for the direct screening and validation of influenza virus T cell epitopes, which is crucial for designing T cell epitope vaccines against influenza viruses. Further, this method can be applied in epitope screening and vaccine designing before the spread of other emerging and sudden infectious diseases, thereby supporting epidemic control.

Immune History Modifies Disease Severity to HPAI H5N1 Clade 2.3.4.4b Viral Challenge

The most recent outbreak of highly pathogenic avian H5 influenza (HPAI) virus in cattle is now widespread across the U.S. with spillover events happening to other mammals, including humans. Several human cases have been reported with clinical signs ranging from conjunctivitis to respiratory illness. However, most of those infected report mild to moderate symptoms, while previously reported HPAI H5Nx infections in humans have had mortality rates upwards of 50%. We recently reported that mice with pre-existing immunity to A/Puerto Rico/08/1934 H1N1 virus were protected from lethal challenge from highly pathogenic clade 2.3.4.4b H5N1 influenza virus. Here, we demonstrate that mice infected with the 2009 pandemic H1N1 virus strain A/California/04/2009 (Cal09) or vaccinated with a live-attenuated influenza vaccine (LAIV) were moderately-to-highly protected against a lethal A/bovine/Ohio/B24OSU-439/2024 H5N1 virus challenge. We also observed that ferrets with mixed pre-existing immunity-either from LAIV vaccination and/or from Cal09 infection-showed protection against a HPAI H5N1 clade 2.3.4.4b virus isolated from a cat. Notably, this protection occurred independently of any detectable hemagglutination inhibition titers (HAIs) against the H5N1 virus. To explore factors that may contribute to protection, we conducted detailed T cell epitope mapping using previously published sequences from H1N1 strains. This analysis revealed a high conservation of amino acid sequences within the internal proteins of our bovine HPAI H5N1 virus strain. These data highlight the necessity to explore additional factors that contribute to protection against HPAI H5N1 viruses, such as memory T cell responses, in addition to HA-inhibition or neutralizing antibodies.