Vaccines

Background: Leptospirosis is a potentially fatal infectious disease. Therefore, annual revaccination of dogs is recommended, but this can lead to diagnostic interference due to vaccine-induced antibodies. This study determined the prevalence of Leptospira spp.-specific antibodies in 97 healthy adult dogs revaccinated with a 4-serovar vaccine (Nobivac^® L4). Methods: Antibodies were measured with a microscopic agglutination test against 12 serovars before (week 0) and 2, 4, 12, 26, and 52 weeks after revaccination. Logistic regression analysis was performed to determine the presence of pre-revaccination antibodies. Mixed-effect logistic regression analyses and chi-squared tests were used to compare differences between antibodies against vaccine serovars and between vaccine and non-vaccine serovars at different time points. Results: Overall, 63/97 dogs (64.9%) had antibodies against vaccine serovars before revaccination. During the study period, antibodies against $\ge$1 vaccine serovars were detected in all 97 dogs (100.0%). The highest likelihood of detectable antibodies was present in weeks 2 and 4, but 71/97 dogs (73.2%) had antibodies persisting 52 weeks after revaccination. Of 97 dogs, 75 dogs (78.4%) even had antibodies against $\ge$1 non-vaccine serovars. Among those, 19/75 (25.0%) had a fourfold titre increase. Conclusions: These findings suggest that high levels of antibody titres against Leptospira spp. occur frequently and cross-reactivity against non-vaccine serovars is likely. The detection of vaccine-induced antibodies can therefore complicate the diagnosis of leptospirosis. Full article

African swine fever virus (ASFV) has inflicted severe devastation on the global pig industry, yet a globally approved vaccine remains unavailable. Given that cellular immunity is critical for ASFV prevention, the development of vaccines based on T-cell epitopes emerges as a promising strategy to control this virus. This review synthesizes the recent advancements and challenges in the research on ASFV T-cell epitopes, while offering insights into the potential impact of novel T-cell epitope-based vaccines. Notably, only a limited number of ASFV T-cell epitopes have been experimentally identified to date, covering fewer than 20 ASFV proteins. This bottleneck is attributed to challenges such as high swine leukocyte antigen (SLA) polymorphism, suboptimal accuracy of predicting tools, and complex experimental validation procedures. Although current studies on ASFV-specific T-cell immune responses and epitope identification are insufficient to meet vaccine development needs, continuous progress in T-cell immunology research in recent years has brought this goal closer to reality. Full article

Background: Influenza-related absenteeism causes significant economic implications. Vaccination is the most effective intervention for preventing influenza infection and its complications. This study aimed to assess the prevalence of seasonal influenza vaccination as well as to identify factors associated with seasonal influenza vaccination among working-age adults in Poland. Methods: This study is a secondary analysis of a dataset generated during the representative cross-sectional survey among adults aged 18–64 years in Poland (December 2024). In the study group (n = 5006), 49.9% were women. Results: Among all respondents, 16.9% declared getting vaccinated against influenza in the last 3 years: 8.2% were vaccinated several times during this period, and 8.8% were vaccinated once. There were several socio-demographic differences (p < 0.05) in the influenza vaccination uptake. Among working-age adults, male gender (OR: 1.83, 95% CI: 1.55–2.15, p < 0.001), age 18–24 years (OR: 2.63, 95% CI: 2.05–3.39; p < 0.001), living in cities over 100,000 residents (p < 0.05), having a part-time job (OR: 1.37; 95% CI: 1.08–1.73; p < 0.01), very good household financial situation (OR: 1.64; 95% CI: 1.19–2.24; p < 0.01), frequent infections throughout the year (p < 0.05), having chronic diseases (p < 0.05), taking dietary supplements regularly (OR: 1.66; 95% CI: 1.36–2.03; p < 0.001) and personal beliefs on doctors’ competencies (p < 0.05) were significantly associated with getting vaccinated against influenza in the last 3 years. Conclusions: This study revealed very low influenza vaccination coverage rates in working-age adults in Poland. Public health interventions are needed to address gaps in influenza vaccination uptake among working-age adults. Full article

Background: Peptide-loaded antigen-presenting cell (APC)-based vaccines have been under investigation as a therapeutic approach for treating cancer. However, in general they have demonstrated limited efficacy in clinical trials. Dendritic cells (DCs) have been the primary choice for APC-based vaccines given their ability to cross-present antigens. B cells have been less studied as APCs for vaccines. Here we compare the phenotype and anti-tumor activity of activated T cells that result from peptide-specific priming using either B cells or DCs. Methods: B cells and DCs were isolated from C57Bl/6 mice, and either treated or not treated with lipopolysaccharide (LPS) for maturation, and then either loaded or not loaded with SIINFEKL peptide to prime CD8+ T cells from OT-1 mice. Activated T cells were then analyzed for their phenotype and anti-tumor efficacy. Results: We report that both immature B cells and immature DCs were similarly capable of activating antigen-specific CD8+ T cells. However, LPS-matured DCs generated a stronger CD8+ T cell activation profile in vitro compared to LPS-matured B cells. Immature B cells, mature DCs and immature DCs all generated a similar anti-tumor response upon adoptive transfer of primed CD8+ T cells to tumor-bearing mice. Conclusions: Collectively, our data suggests that B cells and DCs are each capable of priming CD8+ T cells and generating anti-tumor responses. Given that B cells are relatively easier to culture and expand compared to DCs, our study suggests that, following further validation, B cells could be further investigated as APCs for peptide-based human cancer vaccines. Full article

Background/Objectives: Group B Streptococcus (GBS) is a significant cause of perinatal infection in neonates and infants. Complications could include neonatal sepsis and meningitis, preterm birth, stillbirth, or death. Though no GBS vaccine is currently licensed, maternal immunization is expected to be a highly effective strategy to address invasive GBS disease—particularly in low- and middle-income countries (LMICs), where the disease burden is the greatest and access to existing interventions is limited. In this study, we present a novel hexavalent GBS vaccine candidate with a unique combination of serotypes (ST)—Ia, Ib, II, III, V, and VII—that could be an efficacious and cost-effective intervention, with the broadest coverage of 99% against circulating serotypes globally. Methods: The 6-valent conjugate vaccine candidate, GBS-06, is developed using a novel approach by linking the six polysaccharides (PS) to recombinant cross-reactive material 197 (rCRM197) carrier protein derivatized with a hydrazide-polyethylene glycol-hydrazide (HZ-PEG-HZ) linker. A repeat-dose GLP toxicology study with GBS-06 was conducted at the highest clinical dose of 20 µg in rabbits with saline as the placebo control. Results: The results reveal induction of robust anti-capsular polysaccharide-specific IgG responses against each of the six serotypes after each dose with the highest antibody GMCs at Day 49 following the third dose. Conclusions: Hence, this work is the first demonstration of strong immunogenicity achieved using a linker (HZ-PEG-HZ) for GBS glycoconjugate vaccine development. The positive data from the study have strong implications in the advancement of the candidate for evaluation in clinical trials and provide a licensure pathway for maternal immunization. Full article

Background: The efficacy of a novel combined vaccine targeting porcine circovirus types 2a/d (PCV2a/d), Mycoplasma hyopneumoniae, and M. hyorhinis was evaluated in a controlled challenge study. Methods: A total of 45 pigs were randomly allocated into nine groups (five pigs per group). Vaccinated groups received a single 2 mL intramuscular dose of the combined vaccine and were subsequently challenged with PCV2a, PCV2d, M. hyopneumoniae, and M. hyorhinis. Unvaccinated groups received a single 2 mL intramuscular dose of phosphate-buffered saline (0.01 M, pH 7.4). Growth performance, systemic adaptive immune (humoral and cellular) responses, viremia, laryngeal and nasal mycoplasma loads, and histopathological lesions were assessed. Results: Vaccinated pigs exhibited enhanced growth performance and elicited systemic immune responses, including both humoral and cellular immunity, against all four pathogens. Vaccination also significantly reduced viremia, mycoplasmal loads in laryngeal and nasal swabs, and the severity of associated lesions compared with unvaccinated controls. Conclusions: These results indicated that the combined vaccine was efficacious and conferred protection against PCV2a, PCV2d, M. hyopneumoniae, and M. hyorhinis challenge under experimental conditions. This combined vaccine represented an effective strategy to enhance growth performance and control complex co-infection in swine populations. Full article

This comprehensive review examines the multifaceted interactions between influenza viruses and the ocular system, integrating viral pathogenesis, clinical manifestations, and vaccine-related considerations. Influenza A subtypes (H7, H1N1, H5N1) and influenza B viruses induce a spectrum of ocular complications, from mild conjunctivitis—predominantly associated with H7 avian strains—to sight-threatening disorders like uveal effusion syndrome, acute macular neuroretinopathy, and optic neuritis. Experimental evidence confirms viral replication in human corneal and retinal cells, with H7N7 demonstrating unique tropism for ocular tissues via NF-κB-mediated inflammatory pathways. Clinical cases highlight direct viral invasion and immune-mediated mechanisms, such as Vogt–Koyanagi–Harada disease exacerbation and retinal vasculitis. Rarely, influenza vaccination has been linked to oculorespiratory syndrome, uveitis, and demyelinating events, though large-scale epidemiological studies (e.g., WHO safety reports) confirm vaccines’ favorable risk–benefit profile, distinguishing true adverse events from temporal associations. This synthesis emphasizes the need for ophthalmologists to prioritize surveillance during influenza seasons, integrating diagnostic tools like conjunctival RT-PCR and optical coherence tomography. Future research should focus on defining viral receptor-binding mechanisms in ocular tissues and developing targeted therapies for severe retinopathies, while reinforcing vaccination as a cornerstone of public health despite rare ocular risks. Full article

Background/Objectives: Despite the lifting of the COVID-19 public health emergency, SARS-CoV-2 infections continue to be recorded worldwide. The continued prevalence of infection has been attributed to the ability of the virus to evade host immune responses, including neutralizing antibody-derived immunity. The vast majority of antibody escape mutations has been associated with the S1 subunit of the spike protein. The other region of the spike, the S2 subunit, is the most conserved region amongst coronaviruses. We hypothesized that S2-specific antibody levels are modest in vaccinated and SARS-CoV-2-infected patients, resulting in suboptimal neutralization of distant coronaviruses. Methods: Here, we analyzed S1- and S2-specific antibody levels in SARS-CoV-2-infected individuals, including a mixed cohort of those with and without immunosuppression and prior vaccination. Results: We found that S2-specific antibody responses were generally lower than S1-specific antibody responses. Intriguingly, Omicron-S1-specific antibody levels were higher than Wuhan-S1-specific antibody levels despite all vaccinated participants having received Wuhan-spike-based immunogens. This emphasizes the importance of the infecting variant and vaccine immunogen in the production of spike-targeting antibodies and associated hybrid immunity. Although S1-specific antibody levels were generally higher than their S2-specific counterparts, the correlation between neutralization and binding antibody levels was mostly higher in S2- compared with S1-specific responses. Conclusions: We conclude that S2-based immunogens are suitable for the induction of antibody-based immunity against novel SARS-CoV-2 variants but also against more distant coronaviruses, which would support a better protection for the immunocompromised as well as other vulnerable populations. Full article

Background: Indonesia launched a nationwide school-based HPV immunization program in August 2023. Despite this, regional disparities in vaccine uptake persist. Therefore, we undertook a study in North Sumatra Province to assess HPV vaccination coverage and analyze the main factors affecting the uptake of HPV vaccination. Methods: This study employed a mixed-methods approach and was carried out in Medan and Deli Serdang of North Sumatra Province. Quantitative data were used to examine HPV coverage rates among school-aged girls in 2024, while qualitative interviews with parents, teachers, and health officers explored administrative, social, and behavioral barriers and facilitators. Results: In 2024, HPV vaccine coverage in Deli Serdang reached 62.09%, while Kota Medan lagged behind at just 27.20%. High-coverage schools in the Galang subdistrict benefited from proactive engagement between Puskesmas (community health clinics) and parents. In contrast, lower-coverage areas experienced logistical and communication challenges. Parents expressed a preference for face-to-face communication over written consent forms and emphasized the importance of clear, empathetic messaging. Conclusions: The stark contrast in coverage—particularly the low uptake in urban Kota Medan—highlights the need for more responsive and localized implementation strategies. Strengthening direct communication, addressing administrative inefficiencies, and fostering trust through tailored community engagement are critical. These findings suggest a need for targeted improvements in urban settings and further research across diverse regions to inform policy development and strategies for improved coverage of HPV vaccinations. Full article

Background: Trust in information sources is essential to enhance an individual’s understanding of the message and boost their willingness to change or act on specific health behavior, including vaccine uptake. This study explores the association between trust in information sources and parents’ knowledge, attitudes, and practices regarding their children’s 13-valent pneumococcal conjugate vaccine (PCV13) uptake across seven cities in the Yangtze River Delta (YRD) region in China. Methods: A cross-sectional web-based survey was conducted from May to June 2023. Adult parents (N = 1304) who had at least one child aged 24 months or less and lived in the YRD region were recruited. The Adjusted Ordinary Least Squares (OLSs) regression model was applied to estimate the association between participants’ level of trust in different information sources and their knowledge, attitudes, and practices of children’s PCV13 vaccination. Results: Information from the Disease Control and Prevention Center (CDC) source received the highest trust score. Age, gender, education, and annual household income were related to varied trust levels in specific sources. Trust in the health service provider source was significantly associated with a better command of PCV13 knowledge, acceptance of PCV13, and a higher likelihood of vaccination. Trust in online community sources was positively associated with vaccine uptake. Conclusions: The study participants highly trusted information from health service provider sources. These sources may be effective channels with potential to enhance parents’ vaccine knowledge and acceptance of PCV13. Public health workers could utilize trusted sources to disseminate the benefits of the PCV13 and encourage the uptake of the vaccine. Full article

Background: Bacterial Chondronecrosis with Osteomyelitis (BCO) is a significant issue affecting the welfare and economy of the broiler industry, causing substantial revenue losses annually. This disease is frequently associated with Staphylococcus spp. and Enterococcus spp. infections and necrosis of leg and vertebral bones. The typical annual lameness incidence of approximately 3–5% may increase to 30% during outbreaks. Neither the etiology or pathogenesis of the disease has been comprehended, nor have effective preventative measures been identified. Electron beam (eBeam) technology is renowned for producing efficient whole-cell vaccines by preventing bacterial multiplication through irreversible DNA shredding while preserving the integrity of membrane proteins (immunogenic epitopes). This study aims to reduce BCO-induced lameness in broiler chickens via in ovo immunization using eBeam-inactivated multi-strain Staphylococcus. Methods: A total 1080 birds were assigned to four vaccination groups: eBeam-inactivated, formalin-inactivated, combination of eBeam- and formalin-inactivated, and sham (vehicle). The birds were directly exposed to aerosolized, natural BCO challenge until 56 days of age. Results: Birds vaccinated with the eBeam-inactivated Staphylococcus vaccine showed a significant reduction (>50%) in daily cumulative lameness compared to other groups and a decrease in Staphylococcus colonization was observed in the leg joints of treated birds. Conclusions: the eBeam-inactivated Staphylococcus vaccine successfully prevented BCO lameness in broiler chickens. Full article

Background/Objectives: Meningococcal disease (MD) remains a significant public health concern worldwide. In Serbia, mandatory immunization against MD with the meningococcal polysaccharide vaccine (MenAC) for high-risk groups and international travelers was introduced in 2006. Since 2017, the polysaccharide vaccine has been replaced with the quadrivalent meningococcal conjugate vaccine (MenACWY). The aim of this study was to analyze long-term trends in incidence, age-specific patterns, seasonality, and lethality of invasive meningococcal disease (IMD) in the Autonomous Province of Vojvodina (AP Vojvodina), Serbia, over a 28-year period. Methods: A descriptive study analyzed all reported cases of IMD in AP Vojvodina, from 1997 to 2024. Data were obtained from the regional communicable disease surveillance system, based on mandatory hospital reporting and case classification according to national and WHO guidelines. Temporal, demographic, and clinical characteristics, along with disease outcomes, were analyzed. Results: From 1997 to 2024, 175 IMD cases were reported in AP Vojvodina. The annual incidence peaked in 1997 (1.24/100,000), with smaller surges in 2003 and 2005. Since 2006, coinciding with the introduction of immunization against MD, a sustained decline has been observed, with incidence rarely exceeding 0.30/100,000. A slight resurgence occurred in 2023–2024, with 13 cases reported. From 1997 to 2024, IMD in AP Vojvodina exhibited a clear seasonal pattern, with most cases occurring in winter and early spring, peaking in January (17%), March (12%), and February (11%), and the fewest cases occuring in the summer months. Throughout the study period, the highest IMD incidence rates were consistently observed among infants <1 year of age and children aged 1–4 years, with peaks of up to 22.9/100,000 and 16.0/100,000, respectively. Incidence was much lower in older age groups, especially adults. After a 2006 peak, rates declined across all ages, with a slight resurgence in 2023–2024 among children and adolescents. Children aged 1–4 years made up the largest share of IMD cases, peaking in January–March (45.1%). Half of the infant cases were recorded in October–November, while cases in older children, adolescents, and adults were fewer and showed varied monthly patterns, with small peaks in winter and early spring. During the 28-year study period, the highest IMD mortality rate was observed among infants <1 year of age (0.59 per 100,000 population), followed by children aged 1–4 years (0.32 per 100,000). Mortality rates declined progressively with increasing age, with the lowest rate recorded among individuals aged ≥40 years (0.01 per 100,000). Of the 175 IMD cases reported in AP Vojvodina (1997–2024), 21 were fatal (case fatality rate [CFR] = 12.0%). The CFR of IMD varied across age groups. The highest CFR was observed among individuals aged ≥40 years (21.4%), followed by the 5–9 years (17.4%) and <1 year (16.7%) age groups. None of the patients had been vaccinated against MD. Fatal outcomes were more common in children aged 1–4 years and among rural residents, though differences were not statistically significant (p > 0.05). Most deaths (57.1%) occurred in the first quarter of the year. A strong association was found between clinical form and outcome, with meningococcal sepsis being significantly more frequently associated with fatality than meningitis (p = 0.0002). Deaths were sporadic over time, with most occurring within 1–2 days of notification. All confirmed fatal cases were due to serogroup B. Conclusions: MD remains a rare yet serious public health threat in AP Vojvodina. Mortality rates indicate that the public health impact of this disease is greatest among the youngest age groups; however, the risk of death, i.e., disease severity, does not appear to be age dependent. The recent rise in cases, high fatality among sepsis patients, and absence of prior vaccination among all IMD cases highlight the need for enhanced surveillance, physician education, and consideration of introducing both MenACWY and MenB vaccines for high-risk groups. Full article

Background: The COVID-19 pandemic provided a unique opportunity to evaluate how the human immune system responded to a novel pathogen and to determine whether immune responses initiated through natural infection differ from those elicited by vaccination against the same antigen. Here, we provide a comprehensive analysis of SARS-CoV-2 Spike (S-antigen)-reactive memory B cells (B_mem) elicited in previously immunologically naïve subjects following their first infection with the original Wuhan-Hu-1 (WH1)-like strain or their initial COVID-19 mRNA prime-boost regimen encoding the same WH1-S-antigen. In particular, we tested the hypothesis that the primary encounter of SARS-CoV-2 S-antigen in lung mucosal tissues during infection vs. intramuscular COVID-19 mRNA injection would elicit different B_mem responses. Methods: Cryopreserved peripheral blood mononuclear cell (PBMC) samples collected following primary infection with the WH1 strain or completion of the initial prime-boost vaccination regimen were tested in ImmunoSpot^® assays to assess the frequency, Ig class/subclass usage, and cross-reactivity of the S-antigen-reactive B_mem compartment; pre-pandemic blood draws served as naïve controls. Results: The B_mem repertoires generated post-infection vs. post-vaccination were found to be quite similar but with some subtle differences. In both cases, the prevalent induction of IgG1-expressing B_mem in similar frequencies was seen, ~30% of which targeted the receptor binding domain (RBD) of the WH1-S-antigen. Also, the extent of cross-reactivity with the future Omicron (BA.1) RBD was found to be similar for both cohorts. However, IgA⁺ B_mem were preferentially induced after infection, while IgG4⁺ B_mem were detected only after vaccination. Conclusions: B_mem elicited in naïve human subjects following SARS-CoV-2 infection or after WH1-S encoding mRNA vaccination were only subtly different, although the relevance of these differences as it relates to immune protection warrants further investigation. Our findings serve to illustrate the usefulness and feasibility of performing comprehensive monitoring of antigen-specific B cell memory in larger cohorts using the ImmunoSpot^® technique. Full article

Background/Objectives: We previously demonstrated that dendritic cell (DC) expression of CXCR5 is required for T_H2 priming in mice infected with the helminth Heligmosomoides polygyrus (Hp). In this manuscript we examined how CXCR5 controls DC mediated CD4 T helper 2 cell (T_H2) development. Methods: We used in vitro T_H2 priming assays, RNA-seq analyses and in vivo Hp infection mouse models to identify roles for the CXCR5-expressing DCs in T_H2 development. Results: We showed that migratory conventional type 2 dendritic cells (cDC2) express CXCR5 and that deletion of Cxcr5 prevents migratory DC priming of T_H2 cells in vitro while overexpression of CXCR5 enhances migratory DC priming of T_H2 cells in vitro. To understand how CXCR5 facilitates the T_H2 priming capabilities of migratory cDC2 cells, we performed RNAseq analysis on wildtype and Cxcr5^−/− DC subsets isolated from msLN of Hp-infected mice. We observed that CXCR5 expression specifically by the migratory cDC2 subset promoted a pro-proliferative transcriptional program in cDC2 cells and was required for cDC2 cell accumulation in the msLN following Hp infection. We demonstrated that CXCR5 expression specifically by cDC2 cells was necessary for upregulation of Chitinase 3-like-1 (Chi3l1), which encodes a secreted protein (Chi3l1) that regulates allergic T_H2 responses. We showed that addition of recombinant Chi3l1 protein to in vitro T_H2 priming cultures enhanced T_H2 development and that deletion of Chi3l1 specifically in DCs resulted in fewer cDC2 cells and decreased T_H2 development in vivo following Hp infection. Conclusions: CXCR5 expressed by cDC2 cells is required for induction of Chi3l1, which in turn promotes the T_H2 priming capacity of these DCs. These findings provide insight into the actions of CXCR5 and Chi3l1 in helminth infection. Full article

Background/Objectives: Nocardia seriolae and Aeromonas veronii are two important pathogens that can affect a wide range of fish species and cause substantial economic losses. However, a vaccine that simultaneously protects fish from these two bacterial infections is not yet available. Methods: Three formalin-inactivated whole-cell vaccines prepared from N. seriolae and A. veronii (Monovalent Av, Monovalent Ns and Bivalent Av-Ns) were generated, and their efficacy was evaluated through a range of tests. The immune-related gene expression in the spleen and head kidney, enzyme activity, and specific antibody levels in serum were also detected. Results: All groups of vaccinated fish exhibited increased serum enzymatic activity compared with control fish, which peaked at week 3 after vaccination; in particular, that of the Bivalent Av-Ns group increased remarkably. The expression of immune-related genes in the spleen, head, and kidneys increased after immunization and were significantly enhanced (p < 0.05) in the bivalent vaccine group. Specific antibodies were produced at the 1st wpv, peaked at the 4th to the 5th wpv, and then decreased at the 6th wpv in all vaccinated groups. The Monovalent Av and Monovalent Ns against A. veronii and N. seriolae showed 56.67% and 22.22% RPS, respectively. Moreover, Bivalent Av-Ns offered 33.33% and 76.67% RPS for single infection with N. seriolae or A. veronii, as well as providing 44.44% RPS for dual infection with combined N. seriolae and A. veronii. Conclusions: Our findings indicate that the administration of the A. veronii and N. seriolae bivalent vaccine can protect largemouth bass from both bacterial infections. Full article

Introduction: Dengue virus (DENV) remains a global health threat, with four distinct serotypes (DENV1-4) that complicate vaccine development due to low-affinity, cross-reactive antibodies that increase the risk of antibody-dependent enhancement (ADE). Objective: To address the challenge of inducing strictly serotype-specific immune responses, this study explored the use of targeting individual lymph nodes (LNs) for the creation of simultaneous but independent immune responses as a targeted approach to reduce cross-reactivity and improve vaccine specificity. Methods: In the initial experiments, targeting individual LN successfully induced specific germinal centers (GCs) for different antigens in distinct LNs, highlighting its potential to enhance immune specificity. This approach was further tested using two virus-like particle (VLP)-based vaccines based on AP205 for DENV1 and DENV4, selected due to their genetic divergence and to probe the potential to minimize cross-reactive immune responses. In this setup, AP205-DV1 and AP205-DV4 were administered in targeted separate LNs, and the specificity of the immune response was compared to subcutaneous administration of a mixture of both vaccines. Results: Our data show that targeting distinct LNs elicited antibodies with significantly higher avidity, which is a critical factor in determining the neutralizing capacity of the immune response. Avidity measurements confirmed that this segregation approach results in a more refined selection of high-affinity B cells. Neutralization experiments demonstrated that targeting distinct LNs with individual vaccines induced a more potent and serotype-specific neutralizing response, compared to the injection of a vaccine mixture. Conclusions: These findings suggest that targeting individual LNs could be a promising method for enhancing both the specificity and potency of immune responses, particularly for flaviviruses. Targeting distinct LNs by direct administration of individual vaccines into distinct watersheds rather than individual lymph nodes will offer the opportunity to facilitate the approach in humans. Full article

Chronic viral infections and virus-induced cancers have been actively studied for decades, with many significant advancements in basic science, disease cure, treatment, and prevention. Yet, today, these infections and pathologies remain major contributors to morbidity and mortality worldwide. The international online conference “VIRCAN2024: Chronic viral infections and cancer, openings for Vaccines and Cure” aimed to address the remaining issues, present the research carried out in this broad field, and prognose directions for its development. The conference covered oncogenicity mechanisms and new approaches in the development of treatments and vaccines. VIRCAN2024 was held on the platform of Riga Stradins University, Riga, Latvia. The conference was supported by the Latvian Science Council grant “Human papillomavirus genome associated correlates of disease progression and treatment response for cervical neoplasms and cancer”, and the scientific journal Vaccines (MDPI). This report summarizes the lectures and presentations given at the conference. Full article

Background/Objectives: This study investigated susceptibility factors that may contribute to Post-Polio Syndrome (PPS) in elderly polio survivors. Methods: Serum immunoglobulin (Ig) levels, poliovirus neutralizing antibodies (PV NAb), and vitamin D status were evaluated in 80 PPS patients, 40 family members, and 89 healthy controls. Results: A significant number of PPS patients and their family members showed reduced levels of total IgG and/or IgA, and specific IgG subclasses, indicating a high prevalence of primary humoral immunodeficiencies within these groups. Despite these Ig deficits, PV NAb titers were similar across all groups, indicating high protection against poliovirus, likely due to vaccination campaigns with live virus in Italy and intense exposure to poliovirus, especially in long-term rehabilitation institutions. However, a small group of PPS subjects lacked neutralizing antibodies for specific poliovirus serotypes, suggesting more severe antibody deficiencies. Additionally, PPS subjects had a high prevalence of vitamin D deficiency, which likely increases their risk for osteoporosis/osteopenia and fractures. It is unclear if this deficiency was also present in their infancy, potentially enhancing their susceptibility to poliovirus. Conclusions: Overall, the findings indicate that genetic, immunological, or nutritional factors may increase individual susceptibility to the pathogenic effects of poliovirus. This study—limited to serum antibodies—highlights the complex relationship between immune status and long-term health in aging polio survivors. The results emphasize the need for potent poliovirus drugs and vaccines to help contain possible outbreaks but also—for poliomyelitis survivors—to avoid or mitigate the progression to PPS, the latest phase of this devastating disease. Full article

Background: Racial and ethnic differences in vaccine responses, particularly within Hispanic populations, remain underexplored. Disparities in immune function may be influenced by metabolic and inflammatory mechanisms. Methods: The current study investigated humoral immune responses to influenza vaccination in a diverse cohort of Hispanic individuals from South Florida, encompassing both White and Black Hispanics. Antibody responses were assessed post-vaccination, and B cell phenotypes were analyzed to evaluate inflammatory and metabolic characteristics. In vitro experiments were conducted to determine whether blocking metabolic pathways could alter the inflammatory phenotype of B cells. Data were analyzed using an unpaired Student’s t-test (two-tailed), and correlation analysis was conducted with Pearson correlation. Results: Our findings indicated that Black Hispanic individuals exhibited significantly reduced antibody responses compared to White Hispanics (p < 0.01) following influenza vaccination. This diminished humoral response correlated with inversely with serum LDH (r = −0.58; p = 0.0005) and other intrinsic inflammatory phenotypes in blood-derived B cells and was supported by changes in metabolic activity. In vitro blockade of metabolic pathways effectively reduced the inflammatory phenotype of B cells from Black Hispanic individuals, suggesting a mechanistic link between metabolic dysfunction and impaired vaccine-induced immunity. Conclusion: This study is the first to reveal racial disparities in influenza vaccine responses within a Hispanic population, highlighting reduced antibody production in Black Hispanics. These findings suggest that metabolically driven B cell inflammation may play a critical role and point to potential therapeutic strategies to address disparities in vaccine-induced immunity. Full article