Bivalent COVID-19 vaccines that contain BA.1 or BA.4/BA.5 have been introduced worldwide in response to pandemic waves of Omicron subvariants. This prospective cohort study was aimed to compare neutralizing antibodies (Nabs) against Omicron subvariants (BA.1, BA.5, BQ.1.1, BN.1, and XBB.1) before and 3–4 weeks after bivalent booster by the types of SARS-CoV-2 variants in prior infections and bivalent vaccine formulations. A total of 21 participants were included. Prior BA.1/BA.2-infected, and BA.5-infected participants showed significantly higher geometric mean titers of Nab compared to SARS-CoV-2-non-infected participants after bivalent booster (BA.1, 8156 vs. 4861 vs. 1636; BA.5, 6515 vs. 4861 vs. 915; BQ.1.1, 697 vs. 628 vs. 115; BN.1, 1402 vs. 1289 vs. 490; XBB.1, 434 vs. 355 vs. 144). When compared by bivalent vaccine formulations, Nab titers against studied subvariants after bivalent booster did not differ between BA.1 and BA.4/BA.5 bivalent vaccine (BA.1, 4886 vs. 5285; BA.5, 3320 vs. 4118; BQ.1.1, 311 vs. 572; BN.1, 1028 vs. 1095; XBB.1, 262 vs. 362). Both BA.1 and BA.4/BA.5 bivalent vaccines are immunogenic and provide enhanced neutralizing activities against Omicron subvariants. However, even after the bivalent booster, neutralizing activities against the later Omicron strains (BQ.1.1, BN.1, and XBB.1) would be insufficient to provide protection.

During the emergence of infectious diseases, evaluating the efficacy of newly developed vaccines requires antigen proteins. Available methods enhance antigen protein productivity; however, structural modifications may occur. Therefore, we aimed to construct a novel transient overexpression vector capable of rapidly producing large quantities of antigenic proteins in mammalian cell lines. This involved expanding beyond the exclusive use of the human cytomegalovirus (CMV) promoter, and was achieved by incorporating a transcriptional enhancer (CMV enhancer), a translational enhancer (woodchuck hepatitis virus post-transcriptional regulatory element), and a promoter based on the CMV promoter. Twenty novel transient expression vectors were constructed, with the vector containing the human elongation factor 1-alpha (EF-1a) promoter showing the highest efficiency in expressing foreign proteins. This vector exhibited an approximately 27-fold higher expression of enhanced green fluorescent protein than the control vector containing only the CMV promoter. It also expressed the highest level of severe acute respiratory syndrome coronavirus 2 receptor-binding domain protein. These observations possibly result from the simultaneous enhancement of the transcriptional activity of the CMV promoter and the human EF-1a promoter by the CMV enhancer. Additionally, the synergistic effect between the CMV and human EF-1a promoters likely contributed to the further enhancement of protein expression.

Nosema ceranae is an obligate intracellular fungal parasite that causes mortality in honey bees and enhances the susceptibility of honey bees to other pathogens. Efficient purification of Nosema spores from the midgut of infected honey bees is very important because Nosema is non-culturable and only seasonably available. To achieve a higher yield of spores from honey bees, in this study, we considered that the initial release of spores from the midgut tissues was the most critical step. The use of 2 mm beads along with enzymatic treatment with collagenase and trypsin enhanced the homogenization of tissues and the yield of released spores by approximately 2.95 times compared with the use of common 3 mm beads alone. The optimal time for the enzyme treatment was determined to be 1 hr as measured by the yield and viability of the spores. A one-step filtration using a filter paper with an 8–11 μm pore size was sufficient for removing cell debris. This method may be useful to purify not only N. ceranae spores but also other Nosema spp. spores.

Background/Objectives: Messenger RNA (mRNA) vaccines have enabled rapid vaccine development and have become an important platform for pandemic preparedness; however, clinical evaluation of alternative co-transcriptional 5′ cap technologies remains limited. Here, we report the first-in-human safety, tolerability, and immunogenicity of STP2104, a SARS-CoV-2 mRNA vaccine incorporating the novel co-transcriptional 5′ cap analogue SmartCap^® SC101. Methods: In this Phase I, multicenter, open-label, dose-escalation study, 30 healthy adults with no known history of SARS-CoV-2 infection received two intramuscular doses of STP2104 at either 25 μg or 50 μg on Days 0 and 28. Safety and tolerability were evaluated, along with humoral and cellular immune responses, including neutralizing antibodies, binding antibodies, and antigen-specific IFN-γ ELISpot responses. All participants completed the planned two-dose vaccination schedule before early study termination. Results: STP2104 demonstrated an acceptable short-term safety and tolerability profile across both dose cohorts, with no treatment-emergent serious adverse events, Grade ≥ 3 treatment-emergent adverse events under the protocol-defined clinical severity criteria, or events leading to study discontinuation. However, one participant experienced a transient Grade 3 platelet-count laboratory abnormality, which was recorded in the Clinical Study Report (CSR) as a Grade 1 thrombocytopenia treatment-emergent adverse event. Neutralizing antibody titers increased following vaccination in both dose cohorts, reaching their post-boost maximum at Day 35 and remaining above baseline at Day 56. Binding-antibody concentrations also increased following vaccination, and antigen-specific IFN-γ ELISpot responses were detected in both dose cohorts. Conclusions: This first-in-human Phase I study shows that SmartCap^® SC101 can be incorporated into an mRNA–LNP vaccine construct for clinical evaluation. STP2104 had an acceptable short-term safety and tolerability profile and induced measurable humoral and cellular immune responses. These results support further clinical evaluation of SmartCap^® SC101-containing mRNA constructs with updated or alternative antigens.

Background/Objectives: Cervical cancer, predominantly driven by persistent infection with high-risk human papillomaviruses (HPVs), is one of the most common malignancies and an important cause of cancer-related mortality among women worldwide. Although existing licensed prophylactic HPV vaccines confer excellent protection, their global use remains suboptimal due to concentrated manufacturing capacity and high production costs. This study aimed to establish a cost-effective multivalent HPV virus-like particle (VLP) vaccine platform. Specifically, we used an enhanced baculovirus expression vector system to produce a 12-valent HPV VLP vaccine to improve antigen yield, thereby reducing manufacturing costs and ultimately improving affordability and availability in low- and middle-income countries. Methods: Optimized expression cassettes and an insect cell culture process were designed to enhance productivity across 12 HPV L1 genotypes. A scalable purification scheme integrating ion-exchange and adsorption chromatography was developed to produce high-purity VLPs with consistent structural integrity. Immunogenicity was assessed in a murine model. Elicited HPV type-specific IgG antibody responses were compared with those induced by the licensed 9-valent HPV vaccine. Results: The assembled 12-valent VLPs were comprehensively characterized using biophysical and immunochemical analyses, confirming structural stability and correct antigenicity. In vivo immunogenicity studies in mice showed strong and serotype-specific IgG responses, comparable or superior to those induced by the licensed 9-valent commercial vaccine. Conclusions: The enhanced baculovirus expression vector system is a versatile and economically sustainable platform for next-generation HPV vaccine production. This technology offers a promising approach to lowering vaccine manufacturing costs and improving global access, particularly in low- and middle-income regions heavily burdened by HPV-associated diseases.