Plasma proteomics identifies proteins and pathways associated with incident depression in 46,165 adults.

Proteomic alterations preceding the onset of depression offer valuable insights into its development and potential interventions. Leveraging data from 46,165 UK Biobank participants and 2920 plasma proteins profiled at baseline, we conducted a longitudinal analysis with a median follow-up of 14.5 years to explore the relationship between plasma proteins and incident depression. Linear regression was then used to assess associations between depression-related proteins and brain structures, genetic factors, and stress-related events. Our analysis identified 157 proteins associated with incident depression (P <1.71 × 10-5), including novel associations with proteins such as GAST, PLAUR, LRRN1, BCAN, and ITGA11. Notably, higher expression levels of GDF15 (P = 6.18 × 10-26) and PLAUR (P = 2.88 × 10-14) were linked to an increased risk of depression, whereas higher levels of LRRN1 (P = 4.28 × 10-11) and ITGA11 (P = 3.68 × 10-9) were associated with a decreased risk. Dysregulation of the 157 proteins is correlated with brain regions implicated in depression, including the hippocampus and middle temporal gyrus. Additionally, these protein alterations were strongly correlated with stress-related events, including self-harm events, adult, and childhood trauma. Biological pathway enrichment analysis highlighted the critical roles of the immune response. EGFR and TNF emerged as key proteins in the protein-protein interaction network. BTN3A2, newly linked to incident depression (P = 4.35 × 10-10), was confirmed as a causal factor through Mendelian randomization analysis. In summary, our research identified the proteomic signatures associated with the onset of depression, highlighting its potential for early intervention and tailored therapeutic avenues.

Left ventricular structure and function in relation to sodium dietary intake and renal handling in untreated Chinese patients.

Whether left ventricular structure and function is associated with sodium dietary intake and renal handling while considering blood pressure (BP) remains unclear. Consecutive untreated patients referred for ambulatory BP monitoring were recruited. Standard echocardiography was performed to measure left ventricular structure and function. Fractional excretion of lithium (FELi) and fractional distal reabsorption rate of sodium (FDRNa) were calculated as markers of proximal and distal tubular sodium handling, respectively. The 952 participants (51.0% women; mean age, 50.8 years) included 614 (64.5%) ambulatory hypertension and 103 (10.8%) left ventricular hypertrophy. There were significant interactions of urinary sodium excretion with FELi (P ≤ 0.045), but not FDRNa (P ≥ 0.36), in relation to left ventricular posterior wall thickness (LVPW), mass (LVM) and mass index (LVMI), but not functional measurements. Only in tertile 1 of FELi, the multivariate-adjusted regression coefficients for urinary sodium excretion reached statistical significance (P ≤ 0.049), being 0.16 ± 0.05 mm, 4.32 ± 1.48 g, and 1.64 ± 0.83 g/m2 for LVPW, LVM and LVMI, respectively. In mutually adjusted analyses, the regression coefficient for LVMI was statistically significant for FELi, FDRNa and 24-h systolic BP, being -2.17 ± 0.49, -1.95 ± 0.54, and 2.99 ± 0.51 g/m2, respectively (P < 0.001). Multivariable analysis of variance showed that sodium renal handling indexes (P ≥ 0.14), but not sodium urinary excretion (P = 0.007), were similarly as 24-h BP associated with LVMI. Heat maps on left ventricular hypertrophy provided a graphical confirmation of the findings. Sodium dietary intake and renal handling interact to be associated with left ventricular structure. Renal handling indexes were similarly in size as, jointly in action with and independently of 24-h BP.

A pilot study on the detection of microsatellite instability using long mononucleotide repeats in solid tumors.

Microsatellite instability (MSI) status is a prognostic biomarker for immunotherapy in certain types of cancers, such as colorectal cancers (CRCs) and endometrial cancers (ECs). Tumors that are categorized as having high MSI (MSI-H) express high levels of neoantigens for immune recognition. The typical MSI test measures the length of short mononucleotide repeats (SMR) poly(A) 21-27; however, a limitation of this test is the difficulty in determining the shift size, particularly in endometrial cancer. To investigate an MSI detection assay with improved performance, the present study analyzed the use of poly(A) 40-44 mononucleotide repeats to detect the MSI status of 100 patients with either CRC (n=50) or EC (n=50). Capillary electrophoresis was used to evaluate five long mononucleotide repeat (LMR) markers, including poly(A) 40-A, 40-B, 40-C, 40-D and 44. The concordance rate of the LMR-MSI assay compared with an immunohistochemistry MSI detection assay was 96.0 and 95.1% for CRCs and ECs respectively, with the detection limit of the LMR-MSI assay demonstrated to be 2.5% MSI-H in HCT116 colorectal carcinoma cell lines. The LMR-MSI assay yielded a 95.1% concordance rate in ECs compared with that in the SMR-MSI test (87.8%). The LMR-MSI test identified a significantly higher mean shift size (13 bp) in MSI-H tumors compared with the SMR-MSI test (10 bp), in both EC and CRC tissue samples. Together, the present study suggested that the LMR-MSI test could potentially be a sensitive and practical technology for molecular laboratory testing, particularly in the use of immunotherapy for patients with CRCs and ECs.

Genomic instabilities in hepatocellular carcinoma: biomarkers and application in immunotherapies.

Hepatocellular carcinoma (HCC) is one of the deadliest cancers. For patients with advanced HCC, liver function decompensation often occurs, which leads to poor tolerance to chemotherapies and other aggressive treatments. Therefore, it remains critical to develop effective therapeutic strategies for HCC. Etiological factors for HCC are complex and multifaceted, including hepatitis virus infection, alcohol, drug abuse, chronic metabolic abnormalities, and others. Thus, HCC has been categorized as a "genomically unstable" cancer due to the typical manifestation of chromosome breakage and aneuploidy, and oxidative DNA damage. In recent years, immunotherapy has provided a new option for cancer treatments, and the degree of genomic instability positively correlates with immunotherapy efficacies. This article reviews the endogenous and exogenous causes that affect the genomic stability of liver cells; it also updates the current biomarkers and their detection methods for genomic instabilities and relevant applications in cancer immunotherapies. Including genomic instability biomarkers in consideration of cancer treatment options shall increase the patients' well-being.

Genome-wide meta-analysis identifies ancestry-specific loci for Alzheimer's disease.

INTRODUCTION: Alzheimer's disease (AD) is a devastating neurological disease with complex genetic etiology. Yet most known loci have only identified from the late-onset type AD in populations of European ancestry. METHODS: We performed a two-stage genome-wide association study (GWAS) of AD totaling 6878 Chinese and 63,926 European individuals. RESULTS: In addition to the apolipoprotein E (APOE) locus, our GWAS of two independent Chinese samples uncovered three novel AD susceptibility loci (KIAA2013, SLC52A3, and TCN2) and a novel ancestry-specific variant within EGFR (rs1815157). More replicated variants were observed in the Chinese (31%) than in the European samples (15%). In combining genome-wide associations and functional annotations, EGFR and TCN2 were prioritized as two of the most biologically significant genes. Phenome-wide Mendelian randomization suggests that high mean corpuscular hemoglobin concentration might protect against AD. DISCUSSION: The current study reveals novel AD susceptibility loci, emphasizes the importance of diverse populations in AD genetic research, and advances our understanding of disease etiology. HIGHLIGHTS: Loci KIAA2013, SLC52A3, and TCN2 were associated with Alzheimer's disease (AD) in Chinese populations. rs1815157 within the EGFR locus was associated with AD in Chinese populations. The genetic architecture of AD varied between Chinese and European populations. EGFR and TCN2 were prioritized as two of the most biologically significant genes. High mean corpuscular hemoglobin concentrations might have protective effects against AD.

A trivalent protein-based pan-Betacoronavirus vaccine elicits cross-neutralizing antibodies against a panel of coronavirus pseudoviruses.

The development of broad-spectrum coronavirus vaccines is essential to prepare for future respiratory virus pandemics. We demonstrated broad neutralization by a trivalent subunit vaccine, formulating the receptor-binding domains of SARS-CoV, MERS-CoV, and SARS-CoV-2 XBB.1.5 with Alum and CpG55.2. Vaccinated mice produced cross-neutralizing antibodies against all three human Betacoronaviruses and others currently exclusive to bats, indicating the epitope preservation of the individual antigens during co-formulation and the potential for epitope broadening.

Large-scale whole-exome sequencing analyses identified protein-coding variants associated with immune-mediated diseases in 350,770 adults.

The genetic contribution of protein-coding variants to immune-mediated diseases (IMDs) remains underexplored. Through whole exome sequencing of 40 IMDs in 350,770 UK Biobank participants, we identified 162 unique genes in 35 IMDs, among which 124 were novel genes. Several genes, including FLG which is associated with atopic dermatitis and asthma, showed converging evidence from both rare and common variants. 91 genes exerted significant effects on longitudinal outcomes (interquartile range of Hazard Ratio: 1.12-5.89). Mendelian randomization identified five causal genes, of which four were approved drug targets (CDSN, DDR1, LTA, and IL18BP). Proteomic analysis indicated that mutations associated with specific IMDs might also affect protein expression in other IMDs. For example, DXO (celiac disease-related gene) and PSMB9 (alopecia areata-related gene) could modulate CDSN (autoimmune hypothyroidism-, psoriasis-, asthma-, and Graves' disease-related gene) expression. Identified genes predominantly impact immune and biochemical processes, and can be clustered into pathways of immune-related, urate metabolism, and antigen processing. Our findings identified protein-coding variants which are the key to IMDs pathogenesis and provided new insights into tailored innovative therapies.

Multiplex cerebrospinal fluid proteomics identifies biomarkers for diagnosis and prediction of Alzheimer's disease.

Recent expansion of proteomic coverage opens unparalleled avenues to unveil new biomarkers of Alzheimer's disease (AD). Among 6,361 cerebrospinal fluid (CSF) proteins analysed from the ADNI database, YWHAG performed best in diagnosing both biologically (AUC = 0.969) and clinically (AUC = 0.857) defined AD. Four- (YWHAG, SMOC1, PIGR and TMOD2) and five- (ACHE, YWHAG, PCSK1, MMP10 and IRF1) protein panels greatly improved the accuracy to 0.987 and 0.975, respectively. Their superior performance was validated in an independent external cohort and in discriminating autopsy-confirmed AD versus non-AD, rivalling even canonical CSF ATN biomarkers. Moreover, they effectively predicted the clinical progression to AD dementia and were strongly associated with AD core biomarkers and cognitive decline. Synaptic, neurogenic and infectious pathways were enriched in distinct AD stages. Mendelian randomization did not support the significant genetic link between CSF proteins and AD. Our findings revealed promising high-performance biomarkers for AD diagnosis and prediction, with implications for clinical trials targeting different pathomechanisms.

Generation and Characterization of In Vitro Transcribed mRNA.

Here we describe the in vitro preparation of mRNA from DNA templates, including setting up the transcription reaction, mRNA capping, and mRNA labeling. We then describe methods used for mRNA characterization, including UV and fluorescence spectrophotometry, as well as gel electrophoresis. Moreover, characterization of the in vitro transcribed RNA using the Bioanalyzer instrument is described, allowing a higher resolution analysis of the target molecules. For the in vitro testing of the mRNA molecules, we include protocols for the transfection of various primary cell cultures and the confirmation of translation by intracellular staining and western blotting.

Cellular mechanism underlying leptin-induced anion secretion of rat epididymal epithelial cells.

BACKGROUND: A large number of studies have shown that leptin plays an important role in the regulation of fertility via the hypothalamus-pituitary-gonad axis. However, its peripheral function in epididymis was still elusive. OBJECTIVE: The purpose of this study was to determine the pro-secretion effect of leptin on the rat epididymal epithelium. MATERIALS AND METHODS: In the present study, real-time quantitative polymerase chain reaction, western blot, and immunohistochemical analysis were employed to detect the expression pattern of leptin receptors in rat epididymis. The pro-secretion effect of leptin on epididymal epithelial cells was measured by short-circuit current, and the prostaglandin E2 and cyclic adenosine monophosphate level was evaluated by enzyme-linked immunosorbent assay. RESULTS: We verified that the leptin receptor was located on the epididymal epithelium, with a relatively high expression level in corpus and cauda epididymis. Ussing chamber experiments showed that leptin stimulated a significant rise of the short-circuit current in rat epididymal epithelial cells, which could be abolished by the specific leptin receptor antagonist peptide Allo-aca, or by removing the ambient Cl- and HCO3 -. Furthermore, the leptin-stimulated short-circuit current response could be abrogated by blocking the apical cystic fibrosis transmembrane regulator or the basolateral Na+-K+-2Cl- cotransporter. Our pharmacological experiments manifested that interfering with the prostaglandin H synthase-2-prostaglandin E2-EP2/EP4-adenylate cyclase pathways could significantly blunt the cystic fibrosis transmembrane regulator-mediated anion secretion induced by leptin. The enzyme-linked immunosorbent assay demonstrated that leptin could induce a substantial increase in prostaglandin E2 release and cyclic adenosine monophosphate synthesis of primary cultured rat cauda epididymal epithelial cells. Our data also suggested that JAK2, ERK, and PI3K-dependent phosphorylation may be involved in the activation of prostaglandin H synthase-2 and the subsequent prostaglandin E2 production. CONCLUSIONS: The present study demonstrated the pro-secretion function of leptin in rat epididymal epithelium via the activation of cystic fibrosis transmembrane regulator and Na+-K+-2Cl- cotransporter, which was dependent on the paracrine/autocrine prostaglandin E2 stimulated EP2/EP4-adenylate cyclase pathways, and thus contributed to the formation of an appropriate microenvironment essential for sperm maturation.

Single Extracellular Vesicle Imaging and Computational Analysis Identifies Inherent Architectural Heterogeneity.

Evaluating the heterogeneity of extracellular vesicles (EVs) is crucial for unraveling their complex actions and biodistribution. Here, we identify consistent architectural heterogeneity of EVs using cryogenic transmission electron microscopy (cryo-TEM), which has an inherent ability to image biological samples without harsh labeling methods while preserving their native conformation. Imaging EVs isolated using different methodologies from distinct sources, such as cancer cells, normal cells, immortalized cells, and body fluids, we identify a structural atlas of their dominantly consistent shapes. We identify EV architectural attributes by utilizing a segmentation neural network model. In total, 7,576 individual EVs were imaged and quantified by our computational pipeline. Across all 7,576 independent EVs, the average eccentricity was 0.5366 ± 0.2, and the average equivalent diameter was 132.43 ± 67 nm. The architectural heterogeneity was consistent across all sources of EVs, independent of purification techniques, and compromised of single spherical, rod-like or tubular, and double shapes. This study will serve as a reference foundation for high-resolution images of EVs and offer insights into their potential biological impact.

High Prevalence of Cardiometabolic Risks and Health Needs Among Patients With Hepatocellular Carcinoma After Treatment: A Cross-sectional Study.

BACKGROUND: Many studies have indicated that inadequate health-related behavior is associated with the progression of cancer and cardiometabolic disorders. Because patients with hepatocellular carcinoma may adopt inadequate health behaviors, they are at risk for cancer recurrence, mortality, cardiometabolic disease progression, and worse quality of life. OBJECTIVE: To explore the prevalence of cardiometabolic risks and health-promoting behaviors associated with quality of life among patients with hepatocellular carcinoma after treatment. METHODS: A cross-sectional study was conducted from October 2021 to August 2022. Data were collected through face-to-face interviews using a structured questionnaire, and cardiometabolic information was recorded from medical charts. RESULTS: In total, 115 patients with liver cancer after treatment were enrolled; 73% were male. The mean age was 67.7 years, and high prevalence rates of central obesity (72.2%) and metabolic syndrome (47%) were noted. Inadequate exercise, oral hygiene, and cigarette smoking were common. The health-promoting score was significantly associated with exercise, the number of remaining teeth, and metabolic syndrome, which correlated with quality of life, including positive functional and negative symptoms dimensions. CONCLUSIONS: The findings demonstrated a high prevalence of cardiometabolic risks and inadequate health-related behaviors among patients with liver cancer after treatment. This study highlights the need for healthcare providers to help patients increase health literacy for preventing cardiometabolic risks at outpatient clinics. IMPLICATIONS FOR PRACTICE: Findings from this study can be used to advise healthcare providers to educate patients with liver cancer during and after treatment on improving their health-promoting behaviors.

Aberrant trophoblastic differentiation in human cancer: An emerging novel therapeutic target (Review).

Various types of human cancer may develop aberrant trophoblastic differentiation, including histological changes and altered expression of ß­human chorionic gonadotropin (ß­hCG). Aberrant trophoblastic differentiation in epithelial cancer is usually associated with poor differentiation, tumor metastasis, unfavorable prognosis and treatment resistance. Since ß­hCG­targeting vaccines have failed in an early phase II trial, it is crucial to obtain a better understanding of the molecular pathogenesis of trophoblastic differentiation in human cancer. The present review summarizes the clinical and translational research on this topic with the aim of accelerating the development of an effective targeted therapy. Ectopic expression of ß­hCG promotes proliferation, migration, invasion, vasculogenesis and epithelial­mesenchymal transition (EMT) in vitro, and enhances metastatic and tumorigenic capabilities in vivo. Signaling cascades modulated by ß­hCG include the TGF­ß receptor pathway, EMT­related pathways, the c­MET receptor tyrosine kinase and mitogen­activated protein kinase/ERK pathways, and the SMAD2/4 pathway. Taken together, these findings indicated that TGF­ß receptors, c­MET and ERK1/2 are potential therapeutic targets. Nevertheless, further investigation on the molecular basis of aberrant trophoblastic differentiation is mandatory to improve the design of precision therapy for this aggressive type of human cancer.

Biophysical and biochemical characterization of a recombinant Lyme disease vaccine antigen, CspZ-YA.

Lyme disease, caused by Lyme Borrelia spirochetes, is the most common vector-borne illness in the United States. Despite its global significance, with an estimated 14.5 % seroprevalence, there is currently no licensed vaccine. Previously, we demonstrated that CspZ-YA protein conferred protection against Lyme Borrelia infection, making it a promising vaccine candidate. However, such a protein was tagged with hexahistidine, and thus not preferred for vaccine development; furthermore, the formulation to stabilize the protein was understudied. In this work, we developed a two-step purification process for tag-free E. coli-expressed recombinant CspZ-YA. We further utilized various bioassays to analyze the protein and determine the suitable buffer system for long-term storage and formulation as a vaccine immunogen. The results indicated that a buffer with a pH between 6.5 and 8.5 stabilized CspZ-YA by reducing its surface hydrophobicity and colloidal interactions. Additionally, low pH values induced a change in local spatial conformation and resulted in a decrease in α-helix content. Lastly, an optimal salinity of 22-400 mM at pH 7.5 was found to be important for its stability. Collectively, this study provides a fundamental biochemical and biophysical understanding and insights into the ideal stabilizing conditions to produce CspZ-YA recombinant protein for use in vaccine formulation and development.

Relationship Between Rectal Swab and Tissue Samples in Mucosa-associated Microbiota in Patients With Inflammatory Bowel Disease.

BACKGROUND: Gut mucosa-associated microbiota is more closely correlated with disease phenotypes than fecal microbiota; however sampling via tissue biopsy is more invasive and uncomfortable. Rectal swab may be a suitable substitute for tissue biopsy, but its effectiveness is controversial. This study aimed to evaluate differences in the microbiota at these sites in patients with inflammatory bowel disease (IBD). METHODS: Inflammatory bowel disease patients and a control group were enrolled when surveillance colonoscopy was scheduled. Samples of colon biopsy tissues, rectal swabs during colonoscopy, and feces before bowel preparation were collected to analyze microbial composition. To explore the short-term effects of bowel preparation on swab microbiota, prepreparation swab samples were also collected from 27 IBD patients. RESULTS: A total of 33 Crohn's disease, 54 ulcerative colitis, and 21 non-IBD patients were enrolled. In beta diversity analysis, fecal microbiota clearly differed from swab and tissue microbiota in the 3 disease groups. The swab microbiota was closer to, but still different from, the tissue microbiota. Consistently, we identified that swab samples differed more in abundant genera from feces than from tissue. Beta diversity analysis did not reveal a difference in swab microbiota before and after bowel preparation, but the genus composition of most individuals varied markedly. CONCLUSIONS: Swab microbiota more closely resembled tissue microbiota relative to fecal microbiota, but there were still differences. Bowel preparation did not alter the overall swab microbiota in the short term but markedly changed the microbial composition in most patients.

Non-invasive left ventricular pressure-strain loop study on cardiac fibrosis in primary aldosteronism: a comparative study with cardiac magnetic resonance imaging.

We investigated the potential diagnostic value of the myocardial work indices based on speckle tracking echocardiography for cardiac fibrosis in patients with primary aldosteronism. Our observational study included 48 patients with primary aldosteronism. We performed conventional echocardiography and the left ventricular pressure-strain loop analysis. We also performed cardiac magnetic resonance imaging to evaluate cardiac replacement fibrosis defined as late gadolinium enhancement (LGE). Patients with LGE (n = 30, 62.5%) had longer duration of hypertension and higher plasma NT-proBNP than those without LGE. Besides, they had a significantly (P ≤ 0.04) higher left ventricular mass index (121.3 ± 19.5 vs. 103.3 ± 20.0 g/m2) and global wasted work (205 ± 78 vs. 141 ± 36 mmHg%) and lower global longitudinal strain (-17.7 ± 1.8 vs. -19.0 ± 2.4%) and work efficiency (GWE, 90.9 ± 2.4 vs. 93.8 ± 1.5%). Receiver Operating Characteristics analysis showed that GWE ≤ 92% had a sensitivity and specificity of 76.7% and 83.3%, respectively, for LGE with the area under curve 0.85 (P < 0.001). In conclusion, both cardiac structure and function were impaired in patients with primary aldosteronism and cardiac fibrosis. The myocardial work index GWE showed significant value for the indication of cardiac fibrosis. Characterization of cardiac fibrosis in primary aldosteronism and the detective value of clinical and echocardiographic indices. Cardiac fibrosis was presented in 30 of the 48 analyzed primary aldosteronism patients with focal high signal intensity in mid-layer myocardium in limited segments as its characterization. The global work efficiency (GWE) had a significantly higher detective value for myocardial replacement fibrosis than other measurements such as left ventricular mass index (LVMI) and NT-proBNP.

Clinical implications of PNA­sequencing as a complementary test for EGFR mutation analysis in human lung cancer.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the first-line regimen for the treatment of non-small cell lung cancer (NSCLC) patients with EGFR mutations. However, false-negative results are occasionally observed, even with FDA-approved molecular tests. Such examples in have been reported in our pilot study showing a slightly upward-shifted amplification curve using commercial reverse transcription-quantitative (RT-q)PCR. Verification using peptide nucleic acid (PNA) clamping-sequencing, which has a sensitivity of ~0.1%, may allow better prediction of which patients will benefit from EGFR-TKI therapy. To confirm this hypothesis, samples were prospectively collected from 1,783 lung cancer cases diagnosed in National Cheng Kung University Hospital between 2012-2018. An independent lung cancer cohort of 1,944 cases was also recruited from other hospitals. The clinical significance of mutant-enriched PCR with PNA-sequencing was analyzed and patient outcomes were followed. A total of 17 of 34 cases (50%) were found to harbor EGFR mutations by PNA-sequencing. A total of 22 cases were discovered in the independent lung cancer cohort, and 14 of these (63.6%) cases had EGFR mutations. TKIs were administered to 14 of the 17 mutation-positive patients, and a partial response was observed in 4 cases and stable disease in 10 cases. Patients with EGFR mutations receiving a TKI regimen had a longer overall survival (OS) (median: 40.0 vs. 10.0 months) compared with those without treatment. The difference in OS was not significant. Based on the results of the present study, combining RT-qPCR with PNA-sequencing may be a practical supplementary technology in a clinical molecular laboratory for a subset of lung cancer patients in selection of EGFR TKI therapy.

A Recombinant Protein XBB.1.5 RBD/Alum/CpG Vaccine Elicits High Neutralizing Antibody Titers against Omicron Subvariants of SARS-CoV-2.

(1) Background: We previously reported the development of a recombinant protein SARS-CoV-2 vaccine, consisting of the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, adjuvanted with aluminum hydroxide (alum) and CpG oligonucleotides. In mice and non-human primates, our wild-type (WT) RBD vaccine induced high neutralizing antibody titers against the WT isolate of the virus, and, with partners in India and Indonesia, it was later developed into two closely resembling human vaccines, Corbevax and Indovac. Here, we describe the development and characterization of a next-generation vaccine adapted to the recently emerging XBB variants of SARS-CoV-2. (2) Methods: We conducted preclinical studies in mice using a novel yeast-produced SARS-CoV-2 XBB.1.5 RBD subunit vaccine candidate formulated with alum and CpG. We examined the neutralization profile of sera obtained from mice vaccinated twice intramuscularly at a 21-day interval with the XBB.1.5-based RBD vaccine, against WT, Beta, Delta, BA.4, BQ.1.1, BA.2.75.2, XBB.1.16, XBB.1.5, and EG.5.1 SARS-CoV-2 pseudoviruses. (3) Results: The XBB.1.5 RBD/CpG/alum vaccine elicited a robust antibody response in mice. Furthermore, the serum from vaccinated mice demonstrated potent neutralization against the XBB.1.5 pseudovirus as well as several other Omicron pseudoviruses. However, regardless of the high antibody cross-reactivity with ELISA, the anti-XBB.1.5 RBD antigen serum showed low neutralizing titers against the WT and Delta virus variants. (4) Conclusions: Whereas we observed modest cross-neutralization against Omicron subvariants with the sera from mice vaccinated with the WT RBD/CpG/Alum vaccine or with the BA.4/5-based vaccine, the sera raised against the XBB.1.5 RBD showed robust cross-neutralization. These findings underscore the imminent opportunity for an updated vaccine formulation utilizing the XBB.1.5 RBD antigen.