The type VI secretion system (T6SS) is a major virulence factor in , but its pathogenic mechanisms are poorly understood or still not fully understood. This study investigates how two critical T6SS1 structural components, VipA1 and Hcp1, contribute to bacterial virulence and host inflammatory responses. Comparative proteomics revealed 149 secreted proteins dependent on T6SS1, including 28 core proteins requiring both VipA1 and Hcp1 for secretion. These proteins were functionally linked to metabolic pathways such as folate-mediated one-carbon metabolism and lysine degradation, as well as structural processes like flagellar assembly. Phenotypic analysis revealed that the Δ double mutant showed markedly attenuated virulence: 52.7% reduction in antibacterial activity compared to the wild-type strain. Biofilm formation increased 2.1-fold at 30°C and 2.8-fold at 37°C in Δ, while swimming and swarming motility decreased by 30.9% and 35.5%. , Δ caused only 50% mortality in mice, compared to 91.7% for the wild-type strain, and exhibited 3- to 15-fold lower bacterial loads in the blood, liver, and spleen. Histopathological analysis confirmed that the Δ failed to induce tissue damage, unlike the wild-type strain. At the host interface, deletion of and led to significantly elevated inflammatory cytokine (IL-1β, IL-8, and IL-6) mRNA levels. Mechanistically, T6SS1 inhibited NF-κB activation by stabilizing IκBα and reducing p65 nuclear translocation (40.0% in wild-type-infected cells vs 85.8% in double mutant-infected cells). These findings establish VipA1 and Hcp1 as critical regulators of T6SS1-mediated coordinating effector secretion, virulence, immune evasion, and lethality, providing novel mechanistic insights into pathogenesis.

Current vaccine development efforts encompass diverse and innovative approaches; however, studies with basic vaccines (e.g., whole cell inactivated) continue to inform these efforts. Perhaps the world's most effective and durable human vaccine, the query (Q) fever vaccine known as Q-VAX, can trigger a severe post-vaccination hypersensitivity reaction, precluding its widespread deployment. The history of Q fever vaccine development serves as a rich example of the power of scientific collaboration, elegant experimentation, and the study of adverse post-vaccination events. Here, we review the history of Q fever vaccine development, profiling seminal studies while also relating this information to modern vaccine development efforts.

There are no licensed vaccines against enterotoxigenic (ETEC), a group of strains that produce a heat-labile toxin and/or a heat-stable toxin (STa). ETEC is one of the top four leading causes of diarrhea in children in developing countries (children's diarrhea) and is the most common cause of diarrhea among international travelers (travelers' diarrhea). Remarkable progress has been achieved in understanding disease mechanisms and developing vaccines against ETEC-associated diarrhea. With an understanding of the disease mechanism and identification of virulence determinants, efforts have focused on developing vaccines that target these virulence determinants using either a cellular (whole-cell) vaccine expressing these antigens or an acellular (subunit) approach that primarily targets ETEC adhesins and/or enterotoxins. However, it remains challenging to develop either a cellular or an acellular ETEC vaccine that effectively protects against ETEC strains and associated diarrheal disease, as ETEC strains produce approximately 30 immunologically heterogeneous adhesins and two distinctive enterotoxins, including the potent and poorly immunogenic STa toxin. Additionally, the prevalence of these virulence factors, particularly adhesins, varies over time and across different geographical regions. In this review article, we summarize the ETEC vaccine candidates that have progressed in the last decade and further discuss the potential challenges associated with the leading candidates. We also highlight the novel epitope- and structure-based multiepitope fusion antigen platform and its application in developing cross-protective multivalent precision vaccines.

Lysin motif (LysM) domain-containing receptors are evolutionarily conserved pattern recognition receptors (PRRs) that serve as key mediators of glycan sensing and innate immune activation in plants and mammals. In invertebrates, however, their role in activating innate immunity remains poorly understood, although some evidence for immunosuppressive functions exists. In this study, we performed structural analyses and identified a putative LYSMD3 homolog (XP_004933441.1). This protein exhibits high structural similarity in the LysM domain to human LYSMD3, with a root-mean-square deviation (RMSD) of 0.559 Å, indicating close structural alignment. RNA-seq analysis of hemocytes isolated from silkworm larvae injected with -acetylchitohexaose (GN6), a chitin-derived oligosaccharide and known ligand of human LYSMD3, revealed transcriptional activation of innate immune effectors, including antimicrobial peptide (AMP) genes such as . GN6 also induced transcription in isolated hemocytes , and Western blotting of hemolymph confirmed elevated cecropin B protein levels. Furthermore, GN6 and chitin significantly improved survival outcomes against infection, with median effective doses (ED₅₀) values of 0.62 and 0.48  µg/larva, respectively. In contrast, -acetylglucosamine (GlcNAc) and shorter oligosaccharides (GN2-GN5) were ineffective. These findings provide the first molecular-level evidence of a putative glycan receptor in silkworms based on the structural similarity to known LysM domains. Moreover, GN6-induced antimicrobial peptide expression and enhanced infection resistance demonstrate immune activation in this model, supporting an evolutionarily conserved glycan-sensing pathway in invertebrates.

Leptospirosis is a neglected disease caused by pathogenic spp., affecting an estimated 1 million people annually and resulting in approximately 60,000 deaths. The disease can lead to hepatic, renal, and pulmonary dysfunctions and may contribute to the development of chronic kidney disease. The Complement System plays an important role in eliminating bacteria by lysis, generating opsonins and anaphylatoxins, which degranulate mastocytes and basophils, and attracting immune cells to the site of infection, among other important functions. We aimed to investigate the role of C3 during chronic infection by strain FIOCRUZ L1-130 (LIC) in C57BL/6 wild-type (WT) and C3 knockout (C3KO) mice, monitored for 15, 30, 60, 90, or 180 days post-infection (d.p.i.). LIC-infected C3KO mice exhibited significantly higher leptospiral loads in the kidneys compared to WT counterparts. While both groups showed local inflammation at 15 and 30 d.p.i., LIC-infected C3KO showed a higher number of DNA copies at 30 d.p.i. At this same time point, C3KO LIC-infected mice developed a larger fibrotic area than WT mice. Additionally, levels of specific IgG2b and IgG3 antibodies were significantly higher in LIC-infected C3KO mice compared to WT mice. The number of naïve T lymphocytes (both CD4 and CD8) was also increased in LIC-infected C3KO mice. This study demonstrates that during LIC infection, the absence of C3 does not impact mouse survival but results in increased renal leptospiral load and fibrosis. It also highlights the role of C3 in promoting the maturation and differentiation of T lymphocytes into pre-effector cells.

Avian Pathogenic (APEC) is a major cause of economic loss in poultry, exacerbated by the rising prevalence of antibiotic resistance. While sulfur metabolism is essential for bacterial growth, its specific role and regulation in APEC virulence remain poorly understood. This study identifies the LsrR-cysN axis as a novel regulatory pathway that critically governs APEC virulence. We demonstrate that the quorum-sensing regulator LsrR directly binds to the promoter, activating its transcription. Functional analysis revealed that deletion drastically attenuated virulence, significantly reducing biofilm formation, serum resistance, adhesion, invasion, and motility. The APEC94∆cysN also exhibited altered antibiotic resistance profiles, which were linked to the upregulation of efflux pumps and . Crucially, in a murine model, the APEC94∆cysN showed a 75% reduction in mortality and severe impairment in colonization of blood, lungs, liver, spleen, and kidneys. This attenuation was associated with a skewed host immune response, characterized by reduced levels of IL-2 and IL-6 and elevated levels of IL-4 and TNF-α. Our findings establish the LsrR-cysN axis as a central regulator connecting quorum sensing to virulence in APEC, revealing a promising target for novel anti-virulence strategies.

is the leading cause of bacterial sexually transmitted infection in the United States. The high rate of asymptomatic cases and absence of a vaccine often leave infections untreated, increasing the risk of serious complications in women, like pelvic inflammatory disease, ectopic pregnancy, and infertility. The generation of mutants is crucial for studying gene function, identifying potential vaccine candidates, and understanding host-pathogen interactions. However, the obligate intracellular nature of the bacteria hinders the development of genetic tools for mutagenesis. Counterselectable markers are effective systems for selecting bacterial mutants; however, such systems have yet to be optimized for use in . In this study, we created a toxin-antitoxin (TA) system-based counterselection marker. Two TA systems were tested, toxin CcdB and its antitoxin CcdA (CcdAB), and toxin MvpT and its antitoxin MvpA (MvpAT). For each system, the antitoxin was expressed from a constitutive promoter, while the toxin was controlled by an inducible promoter. We first showed that, in , toxin induction in both TA systems overcame the protective effect of the antitoxin, resulting in growth inhibition. The two systems were subsequently tested in . While the CcdAB system did not significantly inhibit the growth of , the MvpAT system did. Altogether, we have developed an MvpAT-based counterselection system for use in . Implementation of this system will enable more efficient genetic manipulation, facilitating the identification of bacterial virulence factors and advancing translational research toward improved treatment and prevention.

Infection induces unfavorable environments in the host that can be detrimental to the survival of commensal and pathogenic bacteria. Although the adaptive strategies employed by pathogenic bacteria to overcome harsh environments are characterized, similar capabilities of the commensal bacteria to survive in hostile host niches during infection remain understudied. The human oral pathogen group A streptococcus (GAS) encounters host-induced zinc (Zn) limitation at infection sites that limits bacterial proliferation. However, GAS employs the Zn-sensing transcription regulator AdcR to monitor Zn levels and evades host-imposed Zn scarcity by upregulating the AdcR regulon. To elucidate the adaptive responses of oropharyngeal commensal streptococci to Zn scarcity, we analyzed the oropharyngeal pathogenic and commensal streptococcal genomes for the presence of the AdcR regulon. GAS has the full repertoire of the AdcR regulon that includes , Zn importer , extracellular Zn binding proteins and , and Zn-free alternative ribosomal S14 subunit, . Contrarily, except for the conserved presence of and , the oropharyngeal commensal streptococci varied in the composition of the AdcR regulon. Specifically, the gene encoding was absent in the screened commensal streptococcal genomes. We further demonstrated that is critical for the survival of GAS in Zn-limiting environments including human saliva, whereas the commensal that lacks several components of the AdcR regulon, including , is defective in survival in Zn-deficient conditions. Together, we identified a pathogen-specific adaptive strategy that aids evasion of host-imposed Zn limitation and confers survival advantage over oropharyngeal commensal streptococci during Zn scarcity.

is an important member of the human gut microbiota, where it contributes to immune modulation, intestinal barrier integrity, and colonization resistance. Despite its beneficial roles as a symbiont in the gut, is also the most commonly isolated anaerobe in clinical infections, implicated in intra-abdominal abscesses, bloodstream infections, and soft tissue infections. Antimicrobial resistance (AMR) is increasingly recognized as a major factor in its transition from symbiont to opportunist; however, the relationship between resistance and anatomical site of isolation remains poorly defined. Here, we compared AMR phenotypes and genotypes between intestinal and extra-intestinal isolates to assess whether clinical strains are enriched for resistance determinants. Surprisingly, we found comparable susceptibility profiles and AMR gene content between the two groups. Minimal inhibitory concentrations (MICs) were broadly similar, and β-lactamase activity was detected in ~70% of the isolates regardless of the isolation site. We found that resistance genes were similarly distributed across both intestinal and clinical strains. A microbial genome-wide association study (mGWAS) confirmed the known resistance markers, such as , , and and identified novel associations with conjugative transposons, efflux transporters, regulatory genes, and previously uncharacterized loci. These findings suggest that intestinal strains serve as a reservoir of clinically relevant resistance determinants that may be mobilized under selective pressure. Although prior work has largely focused on clinical isolates, our findings highlight the need to surveil AMR within the gut microbiota, where widespread resistance in commensal bacteria has the potential to complicate treatment of extra-intestinal infections.

Adverse pregnancy outcomes represent a global health burden. Bacterial infection and subsequent inflammation in gestational membranes lead to immunological and physiological changes that contribute to adverse pregnancy outcomes. Although animal models of infection during pregnancy are useful to interrogate tissue and cellular level changes in host responses, these models also have numerous drawbacks, including cost, complexity, and ethical considerations. The advent of organ-on-a-chip models provides cutting-edge new approaches to model host-pathogen interactions in multicellular organ and tissue environments. In this work, we employ an organ-on-a-chip model of the maternal-fetal interface as a tool to study immunological responses to infection with the perinatal pathogen, Group B (GBS). Furthermore, we validate the organ-on-a-chip assays using an culture model of primary human gestational membranes. GBS infection leads to enhanced production of EGF, FGF-2, G-CSF, GRO-α, IL-6, IL-8, MCP-1, MIP-1α, TNF-β, IL-10, IL-17F in gestational membranes and both the maternal and fetal chambers of the organ-on-a-chip model. Additionally, GBS infection is associated with enhanced TNF-α, RANTES, IL-12p70, IP-10, MIG, FLT3L, GM-CSF, IL-1β, IL-2, PDGF-AB/BB, and IL-17E/IL-25 cytokine production in gestational membranes and the maternal compartment of the organ-on-a-chip model. Gestational membranes challenged with GBS produce IL-15, IL-27, M-CSF, MCP-3, MDC, and MIP-1β, a result that was not seen in the organ-on-a-chip model. GBS infection leads to enhanced production of eotaxin, IFN-γ, IL-1α, IL-4, IL-12p40, IL-13, and SCD40L in the maternal and fetal chambers of the organ-on-a-chip model, but not the gestational membranes . Together, these results indicate that GBS infection induces comparable production of a repertoire of cytokines and chemokines in both models, with some salient differences, underscoring the utility of these complementary approaches to study immunological responses to infection at the maternal-fetal interface.

infections are sharply on the rise among at-risk populations. has nine serogroups of O-antigens. Recently, additional O-antigen subtypes within these serogroups have been identified; the contributions of these subtypes to pathogenic fitness and their immunogenicity, functional antibody responses, and cross-reactivity are unknown. We investigated how the addition of the single-branched galactose in O-antigen subtype O2b compared to O2a alters its virulence and host immune responses. We deleted the region of an O2b strain of , converting it to an otherwise isogenic O2a strain. Complementation of this mutant allowed us to identify the specific genes responsible for the addition of the single branched galactose of O2b. Experiments using the O2a mutant and its parent O2b strain confirmed similar phenotypic expression of virulence factors beyond the O-antigen. Well-established murine models of pneumonia were used to determine the pulmonary fitness of the strains and assess the host innate immune responses. Complement-mediated killing assays suggested differences in susceptibility to innate immune defenses, with the O2a mutant being more susceptible to serum killing. Lastly, using polysaccharide-protein bioconjugate vaccines against these specific O-antigen subtypes, we determined that only partial cross-reactivity and protection are elicited. These studies advance our understanding of the immune response to O-antigens by defining a fitness advantage of O2b compared to O2a and informing vaccine design to combat this drug-resistant pathogen.

Mucosal DNA vaccination using a non-invasive (LL) vector has been investigated. However, its immunogenicity and plasmid transfer mechanisms remain largely unknown. In this study, we investigated the intranasal delivery of LL carrying a mammalian enhanced green fluorescent protein (EGFP)-expressing plasmid and the cellular pathways underlying DNA transfer. Intranasally administered LL was primarily localized on the nasal epithelial surfaces, and a smaller fraction penetrated the subepithelial tissues. Intranasal administration of LL-carrying pLEC-EGFP plasmid induces antigen-specific serum IgG and mucosal IgA responses. co-culture analyses demonstrated that plasmid delivery and expression occurred in phagocytic cell lines but not in epithelial cell lines. This transfer was inhibited by compounds specific for phagocytosis, consistent with the observed time course of DNA transfer and localization of LL within Lamp-1 phagolysosomes. In contrast, compounds for bactericidal mechanisms, including lysosomal acidification, reactive oxygen species, and reactive nitrogen species, did not affect DNA transfer. As our findings suggest that phagocytosis is the primary pathway for plasmid delivery by non-invasive LL vectors in cell culture assays, further studies to confirm these findings in animal models are warranted to develop new strategies for improved LL-based mucosal DNA vaccines.

Antibiotic-induced microbiome injury, defined as a reduction of ecological diversity and obligate anaerobe taxa, is associated with negative health outcomes in hospitalized patients, and healthy individuals who received antibiotics in the past are at higher risk for autoimmune diseases. Postbiotics contain mixtures of bacterial fermentation metabolites and bacterial cell wall components that have the potential to modulate microbial communities. Yet, it is unknown if a fermentation-derived postbiotic can reduce antibiotic-induced microbiome injury. Here, we present the results from a single-center, randomized placebo-controlled trial involving 32 patients who received an oral, fermentation-derived postbiotic alongside oral antibiotic and probiotic therapy for non-gastrointestinal (GI) infections. At the end of the antibiotic course, patients receiving the postbiotic ( = 16) had significantly higher fecal bacterial alpha diversity (+40%, inverse Simpson index) compared to the placebo group ( = 16), and the treatment was well-tolerated. Analysis of 157 longitudinal fecal samples revealed that this increased diversity was driven by enrichment of health-associated taxa, notably obligate anaerobic Firmicutes, particularly Lachnospiraceae. In contrast, species, often linked to pathogenicity and antibiotic resistance, were reduced in postbiotic-treated patients at the end of antibiotic treatment and remained lower up to 10 days later. Our findings suggest that postbiotic co-administration during antibiotic therapy may augment health-associated gut microbiome composition and mitigate antibiotic-induced microbiome injury.Trial registration ISRCTN30327931 retrospectively registered.

Currently, no fungal vaccine exists for clinical use, while fungal infections are responsible for over 1.5 million deaths every year. Our previous studies identified a mutant strain Δ as a potential vaccine candidate. This strain contains deletion of the F-box protein Fbp1, a key subunit of the SCF E3 ligase complex necessary for ubiquitin-mediated proteolysis. Vaccination with heat-killed Δ (HK-) can elicit an interferon gamma (IFN-γ)-dependent Type 1 immune response and provide protection against and its sibling species . However, we have yet to decipher the immunogenic factor(s) expressed by the ∆ mutant that are responsible for the induction of the protective immune response. In this study, we have identified that the capsule plays an important role in HK- vaccine-mediated protection as acapsular HK- cells showed diminished protection against wild-type challenge. Additionally, our studies have shown that Cytokine Inducing Glycoprotein 1 (Cig1), a GPI-anchored mannoprotein, is regulated by Fbp1 and contributes to the immunogenicity of HK-. Deletion of Cig1 in the Δ background resulted in decreased recruitment of antifungal effector T cells and diminished production of protective inflammatory cytokines by the host. Furthermore, loss of Cig1 in the Δ mutant resulted in reduced protection in vaccination survival studies at lower vaccine inoculum doses compared to HK-. In aggregate, these findings demonstrate Cig1 is an antigen contributing to the immunogenicity of HK- that may be utilized to further optimize the HK- fungal vaccine as a tool in the arsenal against invasive fungal infections.

A key challenge in immunology is understanding how the innate immune system achieves specificity against diverse pathogens. Our previous work in identified NMUR-1, a neuronal G protein-coupled receptor homologous to mammalian neuromedin U receptors, as a regulator of pathogen-specific innate immune responses. Here, we used quantitative proteomics and functional analyses to show that NMUR-1 modulates the expression of mitochondrial FF ATP synthase subunits and regulates ATP levels during infection, linking neuronal signaling to host energy metabolism. Loss of NMUR-1 leads to reduced ATP and reactive oxygen species (ROS) concentrations in infected animals, altering survival outcomes in a pathogen-specific manner. We further demonstrate that ATP availability and its contribution to host defense are neurally controlled by the NMUR-1 ligand CAPA-1 and its source neurons, ASG. These findings uncover a neuroimmune mechanism whereby NMUR-1 regulates energy homeostasis as a determinant of innate immune specificity. Our study also provides mechanistic insights into the emerging roles of conserved NMU signaling in neuroimmune regulation across animal phyla.

The intracellular survival and replication of rely on the precise manipulation of host signaling pathways. Host kinases are instrumental in the modulation of host signaling during infection. However, the potential contribution of host phosphatases to chlamydial pathogenesis remains poorly understood. Here, we identified the host tyrosine phosphatase PTP1B as a positive regulator of intracellular development. Gain-of-function approaches revealed that PTP1B promotes inclusion development and increases the production of infectious elementary bodies, whereas loss-of-function by chemical inhibition or silencing leads to a reduction in both inclusion size and bacterial infectivity. Interestingly, PTP1B inhibition did not affect invasion efficiency, suggesting a specific role during the developmental phase of the chlamydial life cycle. To explore the functional relevance of PTP1B and its potential interaction with chlamydial effectors, we focused on the early-secreted effector Tarp, which undergoes tyrosine phosphorylation upon host cell entry. biochemical assays demonstrated that recombinant PTP1B can dephosphorylate both native and recombinant forms of Tarp. However, PTP1B inhibition during infection did not significantly alter Tarp phosphorylation levels, possibly owing to the overpowering influence of host tyrosine kinases. These findings suggest that while Tarp may not be a major physiological substrate, PTP1B is capable of interacting with phosphorylated chlamydial effectors. Together, these results establish PTP1B as a host factor that supports chlamydial development and underscore the underappreciated role of host phosphatases in bacterial pathogenesis. This study provides a foundation for future work exploring phosphatase-mediated regulation of infection and potential host-directed therapeutic strategies.

(.), the leading bacterial cause of sexually transmitted infections, replicates within a unique intracellular compartment called the inclusion, which is modified by secreted proteins known as inclusion membrane (Inc) proteins. Here, we further characterize CpoS, an Inc protein previously shown to be critical for bacterial replication and inclusion development. We demonstrate that CpoS directly binds multiple coiled-coil region-containing Incs and engages Rab GTPases at a separate site. Notably, CpoS-InaC interactions facilitate the recruitment of select Arf GTPases to the inclusion membrane, while Rab recruitment occurs independently of these interactions. Biochemical and biophysical analyses revealed that Incs self-oligomerize to form higher-ordered structures, with CpoS adopting a tetrameric conformation resembling that of eukaryotic SNARE proteins. We propose that these assemblies serve as scaffolds to orchestrate vesicle docking, tethering, and fusion. Our findings highlight the intricate interplay between bacterial and host factors, revealing how . leverages both Inc-Inc interactions and host protein engagement to manipulate vesicular trafficking and sustain infection.

is an emerging fungal pathogen recognized among the Centers for Disease Control and Prevention's urgent threats and designated a critical priority by the World Health Organization due to its global spread, high mortality rates, potential for pan-drug resistance, and its persistent transmission within healthcare settings. The clinical management of infections is further hindered by the lack of both rapid/specific diagnosis and effective antifungals. These challenges emphasize the urgent need for alternative therapeutic strategies. In this study, we investigated the antifungal, immunomodulatory, and protective effects of engineered Lectin-Fc(IgG) fusion proteins against a fluconazole-resistant strain. Specifically, Dectin-1-Fc(IgG2a), Dectin-1-Fc(IgG2b), and wheat germ agglutinin (WGA)-Fc(IgG2a) demonstrated dose-dependent binding to key fungal cell wall components, β-1,3-glucan and chitin, with Dectin-1-Fc(IgG2b) exhibiting the highest reactivity, followed by Dectin-1-Fc(IgG2a) and WGA-Fc(IgG2a). , all constructs exhibited fungistatic activity and reduced the biofilm biomass and metabolism, with the Dectin-1-Fc(IgG) variants displaying the most potent effects. As opsonins, Lectin-Fc(IgG)s significantly enhanced the macrophage-yeast association and macrophage-mediated killing of . In a systemic murine infection model, a single therapeutic administration of Dectin-1-Fc(IgG2b) or WGA-Fc(IgG2a) conferred 100% protection, while Dectin-1-Fc(IgG2a) achieved >80% protection, with all treated mice manifesting clinical improvement. Quantification of fungal burden at day 7 post-infection revealed at least a ~1 log reduction in colony-forming units in the spleen, kidney, and liver of Lectin-Fc(IgG)-treated animals. Cytokine profiling indicated a Th1-type-skewed immune response in Lectin-Fc(IgG)-treated mice. Collectively, these findings support the antifungal and immunotherapeutic potential of Lectin-Fc(IgG)s against , offering a novel broad-spectrum strategy to overcome current therapeutic limitations.

Placental malaria (PM) causes mortality and severe morbidity in areas with stable transmission. The selective placental accumulation of -infected erythrocytes (IEs) is mediated by VAR2CSA, a PfEMP1-type parasite ligand that binds exclusively to placenta-restricted CSA. VAR2CSA-specific IgG is therefore generally restricted to women exposed to infection during pregnancy. However, widespread acquisition of VAR2CSA-reactive IgG outside pregnancy among Colombian and Brazilian individuals has been reported, supposedly due to cross-reactivity between VAR2CSA and the -specific antigen PvDBP. Here, we measured levels and Fc-afucosylation of VAR2CSA-reactive IgG in plasma from pregnant Brazilian women at delivery, using full-length VAR2CSA (FV2) expressed in baculovirus-transfected insect cells (FV2) or Chinese hamster ovary cells (FV2) as well as the corresponding native antigen (IT4VAR04) on the IE surface. We also measured levels of IgG specific for GLURP (specific) and PvDBP (-specific). FV2-specific IgG levels were lower than FV2-reactive IgG levels. Furthermore, only FV2-specific IgG was restricted to women exposed to during pregnancy. Levels of PvDBP-specific IgG were significantly higher among -exposed pregnant women but did not correlate with FV2-specific IgG levels. Finally, FV2-specific IgG was markedly Fc-afucosylated in contrast to FV2-reactive IgG. Our findings caution against using levels of IgG reacting with recombinant proteins expressed in insect cells as a measure of exposure to VAR2CSA during pregnancy, at least in South America. Furthermore, our data do not support the hypothesis that exposure to PvDBP induces IgG that cross-reacts with VAR2CSA and contributes to protection against PM.

Rocky Mountain spotted fever (RMSF) caused by is the most fatal tick-borne disease in people and dogs in the Americas. This pathogen is transmitted by several hard ticks: species, , and . RMSF can quickly progress to a life-threatening illness with fatalities ranging from 30% to 80%. Doxycycline is the only treatment option, and currently, no methods are available to prevent RMSF. We previously reported that vaccination with whole cell antigen vaccine (WCAV) with Montanide gel adjuvant offers protection against virulent infection in dogs. Here, we compared three adjuvants to optimize the safety and immunogenicity of WCAV: Alhydrogel, Montanide, and Quil A. Independent of adjuvants, all vaccinees were protected, whereas unvaccinated dogs developed the clinical disease. Vaccination reduced the pathogen to undetectable levels in blood and various tissues. An specific IgG response was observed following primary vaccination in all vaccinated groups, which augmented after booster. The vaccine with Quil A had the highest IgG response with a significant rise in CD4 and CD8 T cell numbers, while Montanide and Alhydrogel resulted in a balanced IgG response. IgG2 was the primary antibody detected in unvaccinated infection controls. Several systemic proinflammatory cytokines varied after infection in both vaccinees and controls. Plasma concentration of intercellular adhesion molecule 1 was higher in unvaccinated compared to vaccinees in the first 9 days after infection. This study demonstrates that the WCAV efficacy is independent of the adjuvant, although Quil A induced a higher IgG response and expansion of CD4 and CD8 T cells.

(), a common nosocomial pathogen causing severe pulmonary infections, is often complicated by coinfections. Bacterial ghosts, which are empty bacterial cell envelopes, hold significant promise as vaccine adjuvants. This study aims to develop and evaluate a novel combination vaccine platform utilizing ghosts (KP ghosts) to explore their intrinsic immunogenic properties as both vaccine and natural adjuvants. In this study, we showed that KP ghosts enhanced maturation and activation of bone marrow-derived dendritic cells, increasing surface markers (CD40, CD80, CD86, and MHC II) and cytokine secretion (IL-1β, TNF-α, and IL-12p70). The KP ghost-based vaccine provided strong immune protection in mice, significantly improving survival rates and reducing bacterial loads in organs after bacterial challenge. Additionally, to assess the adjuvant potential of KP ghosts, C57BL/6 mice were co-immunized with KP ghosts and a model antigen, ovalbumin (OVA). In comparison to OVA alone, the combination of OVA and KP ghosts elicited higher levels of specific IgG antibodies. Furthermore, OVA combined with KP ghosts increased the expression of the early activation marker CD69 on T cells after antigen stimulation and raised the frequencies of central memory T cells (Tcm) and CD4 IFN-γ T cells. In conclusion, KP ghosts are effective as both vaccine and adjuvant components, enhancing the innate immune response of dendritic cells and the antigen-specific response of T cells. These findings highlight KP ghosts as a dual-purpose vaccine/adjuvant platform for broader antibacterial vaccine development.