With the development of novel vaccine strategies, T-cell epitope-based vaccines have become promising prophylactic and therapeutic tools against infectious diseases that cannot be controlled via traditional vaccines. T-cell epitope-based vaccines leverage specific immunogenic peptides to elicit protective T-cell responses against infectious pathogens. Compared to traditional vaccines, they provide superior efficacy and safety, minimizing the risk of adverse side effects. In this review, we summarized and compared the prediction and identification methods of T-cell epitopes. By integrating bioinformatic prediction and experimental validation, efficient and precise screening of T-cell epitopes can be achieved. Importantly, we delved into the development approaches to diverse T-cell epitope-based vaccines, comparing their merits and demerits, as well as discussing the prevalent challenges and perspectives in their applications. This review offers fresh perspectives for the formulation of safe and efficacious epitope-based vaccines for the devastating diseases against which no vaccines are currently available.

Background/Objectives: African swine fever (ASF), caused by African swine fever virus (ASFV), poses a significant threat to the global swine industry. This underscores the urgent need for safe and effective ASF vaccines. Methods: Here, we constructed five bacterium-like particles (BLPs) that each display one of the five ASFV antigens (F317L, H171R, D117L, B602L, and p54) based on the Gram-positive enhancer matrix-protein anchor (GEM-PA) system. GEM is a bacterial particle that contains only peptidoglycan, while PA is composed of three lysin motifs (Lysm) derived from the C-terminus of the AcmA protein, capable of non-covalently binding to GEM. By fusing the ASFV antigens with PA, the ASFV antigens can be firmly attached to the surface of GEM. Subsequently, the piglets were immunized via intramuscular injection with a mixture of BLPs-F317L, BLPs-H171R, BLPs-D117L, BLPs-B602L, and BLPs-p54. Results: The results showed that the piglets developed detectable serum IgG antibodies 2 weeks after the first immunization, and these high antibody levels were maintained 4 weeks after the booster immunization. Moreover, these piglets produced more IFN-γ-producing lymphocytes than the control piglets. Conclusions: The data indicate that the generated BLPs mixture can stimulate both humoral and cellular immune responses in piglets, these five ASFV proteins are promising antigens, and the BLPs generated represent candidate ASF vaccines.

Background/Objectives: Inadequate characterization of protective antigens poses a significant challenge to the development of vaccines for African swine fever (ASF), particularly for antigen-dependent formulations such as subunit, mRNA, and recombinant viral vector vaccines. To address this, we aimed to screen African swine fever virus (ASFV) antigens and enhance their immunogenicity using a nanoparticle delivery platform. Methods: Here, six ASFV antigens (p30, p54, pE120R, pH124R, pE184L, and CD2v) were purified and used to immunize pigs individually. The effects of antibodies induced by these six antigens on ASFV replication or hemadsorption was evaluated in primary porcine alveolar macrophages (PAMs). These six antigens were, respectively, conjugated to ferritin via SpyTag/SpyCatcher to prepare six ferritin nanoparticles. A cocktail of the six mixed antigens or a cocktail of the six mixed nanoparticles was used to immunize pigs separately, and the differences in induced humoral and cellular immune responses were compared. Results: Antibodies generated against p30, p54, pE120R, pH124R, and pE184L in immunized pigs significantly inhibited ASFV replication in PAMs, while anti-CD2v antibodies specifically obstructed the hemadsorption of ASFV. Notably, immunization with a cocktail of these antigen-conjugated nanoparticles elicited a stronger virus-inhibitory antibody response compared to immunization with a cocktail of antigen monomers. Furthermore, nanoparticle immunization induced robust cellular immunity, evidenced by elevated serum IFN-γ, increased numbers of ASFV-specific IFN-γ-secreting cells, and an expanded CD8⁺ T cell population. Conclusions: Our study identifies a set of promising ASFV antigen candidates and demonstrates that ferritin nanoparticle delivery synergistically enhances both humoral and cellular immune responses against ASFV, providing a rational strategy for multi-antigen ASF vaccine design.

Background/Objectives: Pseudorabies virus (PRV) variant strains have caused widespread outbreaks in China since 2011, and currently available vaccines provide suboptimal protection. Glycoprotein D (gD), the principal target of virus-neutralizing antibodies, represents a promising antigen for subunit vaccine development. However, CHO cell-based production systems suitable for large-scale manufacturing remain insufficiently explored. This study aimed to develop a potentially scalable CHO cell-derived PRV gD subunit vaccine and evaluate its immunogenicity and protective efficacy in mice. Methods: A stable Chinese hamster ovary (CHO) suspension cell line secreting the extracellular domain of PRV gD was established through signal peptide optimization and stepwise serum-free adaptation. The recombinant gD protein was purified using Ni²⁺- Sepharose High-Performance affinity chromatography and subsequently formulated with MONTANIDE ISA 206 adjuvant. Immunogenicity and protective efficacy were assessed in BALB/c mice through serological analysis, neutralization assays, lethal challenge experiments, and quantitative PCR. Results: The gD subunit vaccine induced rapid seroconversion of gD-specific IgG antibodies as early as 7 days post immunization and exhibited a strong booster effect, maintaining high antibody levels. Neutralizing antibodies were first detected at 14 days and increased significantly after booster immunization, with titers markedly exceeding those induced by a commercial inactivated PRV vaccine at 42 days (p = 0.001). Following lethal challenge with 10⁴ TCID₅₀ of the highly virulent PRV-TJ variant strain, vaccinated mice achieved 100% survival without clinical signs. Viral genome copy numbers in the brain and spinal cord were reduced by approximately 3.3 to 4.4 log₁₀ relative to the PBS control group. Conclusions: The CHO cell-derived PRV gD subunit vaccine elicits robust humoral immune responses and provides complete protection against lethal PRV variant challenge in mice. These findings support its further evaluation in the natural swine host toward the development of a safe and scalable subunit vaccine for pseudorabies control.