Analysis of the Probiotic Potential of Lactiplantibacillus plantarum LB1_P46 Isolated from the Mexican Fermented Pulque Beverage: A Functional and Genomic Analysis.

The traditional Mexican fermented beverage pulque has been considered a healthy product for treating gastrointestinal disorders. Lactic acid bacteria (LAB) have been identified as one of the most abundant microbial groups during pulque fermentation. As traditional pulque is consumed directly from the fermentation vessel, the naturally associated LABs are ingested, reaching the consumer's small intestine alive, suggesting their potential probiotic capability. In this contribution, we assayed the probiotic potential of the strain of Lactiplantibacillus plantarum LB1_P46 isolated from pulque produced in Huitzilac, Morelos State, Mexico. The characterization included resistance to acid pH (3.5) and exposure to bile salts at 37 °C; the assay of the hemolytic activity and antibiotic resistance profiling; the functional traits of cholesterol reduction and ß-galactosidase activity; and several cell surface properties, indicating that this LAB possesses probiotic properties comparable to other LAB. Additionally, this L. plantarum showed significance in in vitro antimicrobial activity against several Gram-negative and Gram-positive bacteria and in vivo preventive anti-infective capability against Salmonella in a BALB/c mouse model. Several functional traits and probiotic activities assayed were correlated with the corresponding enzymes encoded in the complete genome of the strain. The genome mining for bacteriocins led to the identification of several bacteriocins and a ribosomally synthesized and post-translationally modified peptide encoding for the plantaricin EF. Results indicated that L. plantarum LB1_P46 is a promising probiotic LAB for preparing functional non-dairy and dairy beverages.

Splenocytes and thymocytes migration patterns between lymphoid organs in pregnancy.

Background: Cell migration is essential for the immune system and is frequently analyzed in adult non-pregnant animals but poorly explored in pregnant animals. However, a physiologic increased size in the spleen and periaortic lymph nodes had been reported in pregnant mice. Methods: Using a mouse model, we transferred PKH26-stained thymocytes and splenocytes from pregnant or non-pregnant animals to receptor mice in the presence or absence of pregnancy. Percentage of PKH-26 cells and Mean Fluorescence Intensity were calculated. Non-parametric ANOVA analysis was performed. Results: We detected that the percentage of PKH26+ thymocytes in the spleen, lymph nodes, and peripheral blood is higher in females than in males (p = 0.039). Our results showed a similar frequency of thymocytes and splenocytes from pregnant and non-pregnant mice located in receptor lymphoid organs (p > 0.05). Also, the location of marked cells was similar during the perinatal period (p > 0.05). Conclusions: The mobility of thymocytes and splenocytes in pregnant and non-pregnant mice is similar. Therefore, we suggest that the larger size of the spleen and periaortic lymph nodes noted previously in pregnant mice could result from the retention of leukocytes in the secondary lymphoid organs.

Neuroprotection mediated by prolactin against streptozotocin injury in brain rat areas.

Prolactin has been recognized as neuroprotective hormone against various types of neuronal damage. This study was aimed to determine if prolactin protects against streptozotocin injury. A series of experiments were performed to determine neuronal survival by counting total neurons in medial hippocampus cortex and cerebellum. Astrogliosis was determined by immunofluorescence assays using GFAP, and behavioral improvement by prolactin after neuronal damage was determined by open-field and light-dark box tests. Results demonstrated that prolactin induced significant neuronal survival in both the hippocampus and cortex, but not in the cerebellum. No increase in astrogliosis was identified, but a significant reduction in anxiety levels was observed. Overall data indicate that prolactin may protect against a complex form of cell damage including oxidant stress and metabolic disruption by streptozotocin. Prolactin may be helpful strategy in the treatment of neuronal damage in neurological diseases.

Molecular Characterization of Bacterial Agents Causing External Ocular Infections Isolates of Patients in a Third Level Hospital.

Empirical use of antibiotics in the treatment of eye infections leads to bacterial pathogens becoming resistant to antibiotics; consequently, treatment failure and eye health complications occur. The aim of this study was to describe the phenotype and genotype of the resistance and adherence of bacterial agents causing eye infections in patients at Hospital Juárez de México. An observational, prospective, cross-sectional, and descriptive study was carried out in patients with signs and symptoms of ocular infection. Bacterial agents were isolated and identified by classical microbiology and mass spectrometry. Antibiotic resistance and adherence profiles were determined. Finally, resistance (mecA/SCCmec) and virulence (icaA and icaD) genes were detected in the Gram-positive population. The results showed that blepharitis was the most prevalent condition in the study population. A MALDI-TOF analysis revealed that Staphylococcus and Pseudomonas genus were the most prevalent as causal agents of infection. Resistances to ß-lactams were detected of 44 to 100%, followed by clindamycins, aminoglycosides, folate inhibitors, and nitrofurans. A multiple correspondence analysis showed a relationship between mecA genotype and ß-lactams resistance. The identification of SCCmecIII and SCCmecIV elements suggested community and hospital sources of infection. Finally, the coexistence of icaA+/icaD+/mecA(SCCmecIII) and icaA+/icaD+/mecA(SCCmecIV) genotypes was detected in S. aureus. The identification of resistant and virulent isolates highlights the importance of developing protocols that address the timely diagnosis of ocular infections. Herein, implications for the failure of antimicrobial therapy in the treatment of ocular infections in susceptible patients are analysed and discussed.

Typing of Candida spp. from Colonized COVID-19 Patients Reveal Virulent Genetic Backgrounds and Clonal Dispersion.

Advances in the knowledge of the pathogenesis of SARS-CoV-2 allowed the survival of COVID-19 patients in intensive care units. However, due to the clinical characteristics of severe patients, they resulted in the appearance of colonization events. Therefore, we speculate that strains of Candida spp. isolated from COVID-19 patients have virulent genetic and phenotypic backgrounds involved in clinical worsening of patients. The aim of this work was to virutype Candida spp. strains isolated from colonized COVID-19 patients, analyze their genomic diversity, and establish clonal dispersion in care areas. The virulent potential of Candida spp. strains isolated from colonized COVID-19 patients was determined through adhesion tests and the search for genes involved with adherence and invasion. Clonal association was done by analysis of intergenic spacer regions. Six species of Candida were involved as colonizing pathogens in COVID-19 patients. The genotype analysis revealed the presence of adherent and invasive backgrounds. The distribution of clones was identified in the COVID-19 care areas, where C. albicans was the predominant species. Evidence shows that Candida spp. have the necessary genetic tools to be able colonize the lungs, and could be a possible causal agent of coinfections in COVID-19 patients. The detection of dispersion of opportunistic pathogens can be unnoticed by classical epidemiology. Epidemiological surveillance against opportunistic fungal pathogens in COVID-19 patients is an immediate need, since the findings presented demonstrate the potential virulence of Candida spp.

Serum thymic stromal lymphopoietin (TSLP) levels in atopic dermatitis patients: a systematic review and meta-analysis.

Thymic stromal lymphopoietin (TSLP) is critical in developing allergic responses, including atopic dermatitis (AD). We systematically reviewed the literature to complete a meta-analysis to quantitatively summarize the levels of serum TSLP in AD. The study was prospectively registered in the PROSPERO database (ID = CRD42021242628). The PUBMED, SCOPUS, and Cochrane Library databases were reviewed, and original articles investigating serum TSLP in AD patients were included. Differences in TSLP levels of AD patients and controls were summarized by standardized mean differences (SMD) using a random effects model. Study quality was assessed by applying the Newcastle‒Ottawa Scale. Fourteen studies, which included 1,032 AD patients and 416 controls, were included. Meta-analysis showed that TSLP levels were significantly higher in the AD group than in the control group (SMD = 2.21, 95% CI 1.37-3.06, p < 0.001). Stratification by geographical region, age, disease severity, TSLP determination method, sample size, and study quality revealed significantly elevated TSLP levels in European AD patients (SMD = 3.48, 95% CI 1.75-5.21, p < 0.0001), adult AD patients (SMD = 4.10, 95% CI 2.00-6.21, p < 0.0001), child AD patients (SMD = 0.83, 95% CI 0.08-1.59, p = 0.031), and all severity groups with AD compared with the control group (mild: SMD = 1.15, 95% CI 0.14-2.16, p = 0.025; moderate: SMD = 2.48, 95% CI 0.33-4.62, p = 0.024; and severe: SMD = 8.28, 95% CI 4.82-11.74, p = 2.72e-6). Noticeably, adults showed higher serum TSLP levels than children with AD, and serum TSL levels increased according to AD severity. In conclusion, our meta-analysis demonstrates that circulating TSLP levels are elevated in patients with AD. Future studies are warranted to further elucidate the sources of heterogeneity.

Characterization of immunoglobulin loci in the gigantic genome of Ambystoma mexicanum.

Background: The axolotl, Ambystoma mexicanum is a unique biological model for complete tissue regeneration. Is a neotenic endangered species and is highly susceptible to environmental stress, including infectious disease. In contrast to other amphibians, the axolotl is particularly vulnerable to certain viral infections. Like other salamanders, the axolotl genome is one of the largest (32 Gb) and the impact of genome size on Ig loci architecture is unknown. To better understand the immune response in axolotl, we aimed to characterize the immunoglobulin loci of A. mexicanum and compare it with other model vertebrates. Methods: The most recently published genome sequence of A. mexicanum (V6) was used for alignment-based annotation and manual curation using previously described axolotl Ig sequences or reference sequences from other vertebrates. Gene models were further curated using A. mexicanum spleen RNA-seq data. Human, Xenopus tropicalis, Danio rerio (zebrafish), and eight tetrapod reference genomes were used for comparison. Results: Canonical A. mexicanum heavy chain (IGH), lambda (IGL), sigma (IGS), and the putative surrogate light chain (SLC) loci were identified. No kappa locus was found. More than half of the IGHV genes and the IGHF gene are pseudogenes and there is no clan I IGHV genes. Although the IGH locus size is proportional to genome size, we found local size restriction in the IGHM gene and the V gene intergenic distances. In addition, there were V genes with abnormally large V-intron sizes, which correlated with loss of gene functionality. Conclusion: The A. mexicanum immunoglobulin loci share the same general genome architecture as most studied tetrapods. Consistent with its large genome, Ig loci are larger; however, local size restrictions indicate evolutionary constraints likely to be imposed by high transcriptional demand of certain Ig genes, as well as the V(D)J recombination over very long genomic distance ranges. The A. mexicanum has undergone an extensive process of Ig gene loss which partially explains a reduced potential repertoire diversity that may contribute to its impaired antibody response.

CD4+ and CD8+ Circulating Memory T Cells Are Crucial in the Protection Induced by Vaccination with Salmonella Typhi Porins.

Salmonella enterica serovar Typhi (S. Typhi) porins, OmpC and OmpF, are potent inducers of the immune response against S. Typhi in mice and humans. Vaccination with porins induces the protection against 500 LD50 of S. Typhi, life-lasting bactericidal antibodies and effector T cell responses in mice; however, the nature of the memory T cell compartment and its contribution to protection remains unknown. In this work, we firstly observed that vaccination with porins induces in situ (skin) CD4+ and CD8+ T cell responses. Analysis of the porin-specific functional responses of skin CD4+ and CD8+ T cells showed IFN-gamma- and IL-17-producing cells in both T cell populations. The memory phenotype of porin-specific T cells indicated the presence of resident and effector memory phenotypes in the skin, and a central memory phenotype in the skin-draining lymph node. In addition, we demonstrated that vaccination with porins via skin reduces the bacterial burden following challenge. Finally, evaluating the role of the circulating T cell memory population in protection, we showed that circulating memory CD4+ and CD8+ T cells are crucial in porin-mediated protection against S. Typhi. Overall, this study highlights the importance of inducing circulating memory T cell responses in order to achieve the optimal protection provided by porins, showing a mechanism that could be sought in the rational development of vaccines.

Cryotherapy as a coadjuvant in crotaline snakebite management with F(ab')2 antivenom: A randomized pilot study.

INTRODUCTION: Local cryotherapy induces vasoconstriction, which leads to a reduction in the inflammatory process. However, the effectiveness of local cryotherapy as a coadjuvant in the treatment of snakebite with F(ab')2 antivenom is unknown. OBJECTIVE: To describe the clinical effectiveness of local cryotherapy as a coadjuvant in patients with snakebite treated with F(ab')2 antivenom therapy at the Hospital Juárez de Mexico. MATERIAL AND METHODS: Patients with grade II snakebite envenomation according to the Christopher-Rodning classification system were enrolled from the Clinical Toxicology Service of the Hospital Juárez de México. One group of patients received F(ab')2 antivenom therapy (Antivipmyn®) plus local cryotherapy, and the other group received only F(ab')2 antivenom therapy. RESULTS: Thirty-eight patients were included, of whom 86.8 % were male (n = 33). Approximately 81.5 % of the subjects were injured in an upper extremity, while 18.5 % were injured in a lower extremities; 47.3 % of the subjects reported treatment of the snakebite prior to hospitalization (suction, the application of a tourniquet, incision of the bite site, or the application of traditional medicine). No differences were found concerning edema, swelling, and pain between the groups. The group that received local cryotherapy as a coadjuvant to F(ab')2 antivenom therapy had a shorter hospital stay (Cohen's d = 1.33; 95 % confidence interval [95 % CI] = 0.74-1.62; p < 0.01) and received fewer doses of F(ab')2 antivenom therapy (Cohen's d = 0.69; 95 % CI = 0.19-3.80; p = 0.03). CONCLUSIONS: The use of adequate local cryotherapy as a coadjuvant to F(ab')2 antivenom therapy reduces the length of hospital stay and the number of doses of F(ab')2 antivenom therapy used.

Medical Outcomes in Women Who Became Pregnant after Vaccination with a Virus-Like Particle Experimental Vaccine against Influenza A (H1N1) 2009 Virus Tested during 2009 Pandemic Outbreak.

The clinical effects and immunological response to the influenza vaccine in women who later become pregnant remain to be thoroughly studied. Here, we report the medical outcomes of 40 women volunteers who became pregnant after vaccination with an experimental virus-like particle (VLP) vaccine against pandemic influenza A(H1N1)2009 (influenza A(H1N1)pdm09) and their infants. When included in the VLP vaccine trial, none of the women were pregnant and were randomly assigned to one of the following groups: (1) placebo, (2) 15 µg dose of VLP vaccine, or (3) 45 µg dose of VLP vaccine. These 40 women reported becoming pregnant during the follow-up phase after receiving the placebo or VLP vaccine. Women were monitored throughout pregnancy and their infants were monitored until one year after birth. Antibody titers against VLP were measured in the mothers and infants at delivery and at six months and one year after birth. The incidence of preeclampsia, fetal death, preterm delivery, and premature rupture of membranes was similar among groups. All vaccinated women and their infants elicited antibody titers (≥1:40). Women vaccinated prior to pregnancy had no adverse events that were different from the nonvaccinated population. Even though this study is limited by the sample size, the results suggest that the anti-influenza A(H1N1)pdm09 VLP experimental vaccine applied before pregnancy is safe for both mothers and their infants.

Conservation of the OmpC Porin Among Typhoidal and Non-Typhoidal Salmonella Serovars.

Salmonella enterica infections remain a challenging health issue, causing significant morbidity and mortality worldwide. Current vaccines against typhoid fever display moderate efficacy whilst no licensed vaccines are available for paratyphoid fever or invasive non-typhoidal salmonellosis. Therefore, there is an urgent need to develop high efficacy broad-spectrum vaccines that can protect against typhoidal and non-typhoidal Salmonella. The Salmonella outer membrane porins OmpC and OmpF, have been shown to be highly immunogenic antigens, efficiently eliciting protective antibody, and cellular immunity. Furthermore, enterobacterial porins, particularly the OmpC, have a high degree of homology in terms of sequence and structure, thus making them a suitable vaccine candidate. However, the degree of the amino acid conservation of OmpC among typhoidal and non-typhoidal Salmonella serovars is currently unknown. Here we used a bioinformatical analysis to classify the typhoidal and non-typhoidal Salmonella OmpC amino acid sequences into different clades independently of their serological classification. Further, our analysis determined that the porin OmpC contains various amino acid sequences that are highly conserved among both typhoidal and non-typhoidal Salmonella serovars. Critically, some of these highly conserved sequences were located in the transmembrane ß-sheet within the porin ß-barrel and have immunogenic potential for binding to MHC-II molecules, making them suitable candidates for a broad-spectrum Salmonella vaccine. Collectively, these findings suggest that these highly conserved sequences may be used for the rational design of an effective broad-spectrum vaccine against Salmonella.

Salmonella Typhi Porins OmpC and OmpF Are Potent Adjuvants for T-Dependent and T-Independent Antigens.

Several microbial components, such as bacterial DNA and flagellin, have been used as experimental vaccine adjuvants because of their inherent capacity to efficiently activate innate immune responses. Likewise, our previous work has shown that the major Salmonella Typhi (S. Typhi) outer membrane proteins OmpC and OmpF (porins) are highly immunogenic protective antigens that efficiently stimulate innate and adaptive immune responses in the absence of exogenous adjuvants. Moreover, S. Typhi porins induce the expression of costimulatory molecules on antigen-presenting cells through toll-like receptor canonical signaling pathways. However, the potential of major S. Typhi porins to be used as vaccine adjuvants remains unknown. Here, we evaluated the adjuvant properties of S. Typhi porins against a range of experimental and clinically relevant antigens. Co-immunization of S. Typhi porins with ovalbumin (OVA), an otherwise poorly immunogenic antigen, enhanced anti-OVA IgG titers, antibody class switching, and affinity maturation. This adjuvant effect was dependent on CD4+ T-cell cooperation and was associated with an increase in IFN-γ, IL-17A, and IL-2 production by OVA-specific CD4+ T cells. Furthermore, co-immunization of S. Typhi porins with an inactivated H1N1 2009 pandemic influenza virus experimental vaccine elicited higher hemagglutinating anti-influenza IgG titers, antibody class switching, and affinity maturation. Unexpectedly, co-administration of S. Typhi porins with purified, unconjugated Vi capsular polysaccharide vaccine (Vi CPS)-a T-independent antigen-induced higher IgG antibody titers and class switching. Together, our results suggest that S. Typhi porins OmpC and OmpF are versatile vaccine adjuvants, which could be used to enhance T-cell immune responses toward a Th1/Th17 profile, while improving antibody responses to otherwise poorly immunogenic T-dependent and T-independent antigens.

[Purification of Salmonella Typhimurium OmpD porin induces long-term high levels of antibodies: implications on the development of vaccines against non-typhoid salmonella]. / La porina OmpD de Salmonella Typhimurium induce altos títulos de anticuerpos de larga duración: implicaciones en el desarrollo de vacunas contra la salmonelosis no tifoídica.

In the present work, we report, for the first time, on the purification of the Salmonella Typhimurium OmpD porin. We assessed the integrity and purity of the protein and evaluated the immunogenicity of the protein and its ability to induce antibody without exogenous adjuvant. We observed that 10 µg OmpD induced high antibody levels of IgM and IgG, which were maintained for more than 260 days after immunization. Immunization with OmpD induced multiple IgG antibody isotypes including IgG1, IgG2a, IgG2b, and IgG3 subclasses. Furthermore, these antibodies were able to recognize and bind to the bacterial surface. Our results demonstrate the high immunogenicity of S. Typhimurium OmpD porin, which induces long-lasting antibodies which may be and important target of the immune response against Salmonella infection. In conclusion, we propose the OmpD porin could be used within novel subunit vaccine formulations that do not need additional adjuvant and that confer long lasting humoral immunity against Salmonella infections.

[Modulation of immune response by bacterial lipopolysaccharides]. / Modulación de la respuesta inmune por los lipopolisacáridos bacterianos.

Lipopolysaccharide (LPS) is a molecule that is profusely found on the outer membrane of Gram-negative bacteria and is also a potent stimulator of the immune response. As the main molecule on the bacterial surface, is also the most biologically active. The immune response of the host is activated by the recognition of LPS through Toll-like receptor 4 (TLR4) and this receptor-ligand interaction is closely linked to LPS structure. Microorganisms have evolved systems to control the expression and structure of LPS, producing structural variants that are used for modulating the host immune responses during infection. Examples of this include Helicobacter pylori, Francisella tularensis, Chlamydia trachomatis and Salmonella spp. High concentrations of LPS can cause fever, increased heart rate and lead to septic shock and death. However, at relatively low concentrations some LPS are highly active immunomodulators, which can induce non-specific resistance to invading microorganisms. The elucidation of the molecular and cellular mechanisms involved in the recognition of LPS and its structural variants has been fundamental to understand inflammation and is currently a pivotal field of research to understand the innate immune response, inflammation, the complex host-pathogen relationship and has important implications for the rational development of new immunomodulators and adjuvants.

El lipopolisacárido (LPS) se encuentra abundantemente en la membrana externa de las bacterias gramnegativas y es un potente estimulador de la respuesta inmunitaria. Al ser la molécula predominante en la superficie bacteriana también es la de mayor actividad biológica. La respuesta del sistema inmunitario del hospedero es activada por el reconocimiento molecular del LPS mediante el receptor tipo Toll 4 (TLR4), por lo que está íntimamente ligada a su estructura. Los microorganismos cuentan con sistemas que les permiten controlar la expresión y estructura del LPS, lo cual les es útil para modular la respuesta inmunitaria del hospedero y lograr la infección. Algunos ejemplos incluyen a Helicobacter pylori, Francisella tularensis, Chlamydia trachomatis y varias especies de Salmonella. Altas concentraciones de LPS pueden inducir fiebre, aumento del ritmo cardíaco y dar lugar a choque séptico y la muerte. En concentraciones relativamente bajas, algunos LPS son inmunomoduladores muy activos que pueden inducir la resistencia no específica a los microorganismos invasores. El esclarecimiento de los mecanismos moleculares y celulares involucrados en el reconocimiento del LPS y de sus variantes estructurales permite entender la respuesta inmune innata, la inflamación y la compleja relación hospedero-patógeno, para el desarrollo de nuevos inmunomoduladores y adyuvantes.

Antibody Persistence in Adults Two Years after Vaccination with an H1N1 2009 Pandemic Influenza Virus-Like Particle Vaccine.

The influenza virus is a human pathogen that causes epidemics every year, as well as potential pandemic outbreaks, as occurred in 2009. Vaccination has proven to be sufficient in the prevention and containment of viral spreading. In addition to the current egg-based vaccines, new and promising vaccine platforms, such as cell culture-derived vaccines that include virus-like particles (VLPs), have been developed. VLPs have been shown to be both safe and immunogenic against influenza infections. Although antibody persistence has been studied in traditional egg-based influenza vaccines, studies on antibody response durations induced by VLP influenza vaccines in humans are scarce. Here, we show that subjects vaccinated with an insect cell-derived VLP vaccine, in the midst of the 2009 H1N1 influenza pandemic outbreak in Mexico City, showed antibody persistence up to 24 months post-vaccination. Additionally, we found that subjects that reported being revaccinated with a subsequent inactivated influenza virus vaccine showed higher antibody titres to the pandemic influenza virus than those who were not revaccinated. These findings provide insights into the duration of the antibody responses elicited by an insect cell-derived pandemic influenza VLP vaccine and the possible effects of subsequent influenza vaccination on antibody persistence induced by this VLP vaccine in humans.

Differential Immune Profiles in Two Pandemic Influenza A(H1N1)pdm09 Virus Waves at Pandemic Epicenter.

BACKGROUND AND AIMS: Severe influenza A(H1N1)pdm2009 virus infection cases are characterized by sustained immune activation during influenza pandemics. Seasonal flu data suggest that immune mediators could be modified by wave-related changes. Our aim was to determine the behavior of soluble and cell-related mediators in two waves at the epicenter of the 2009 influenza pandemic. METHODS: Leukocyte surface activation markers were studied in serum from peripheral blood samples, collected from the 1(st) (April-May, 2009) and 2(nd) (October 2009-February 2010) pandemic waves. Patients with confirmed influenza A(H1N1)pdm2009 virus infection (H1N1), influenza-like illness (ILI) or healthy donors (H) were analyzed. RESULTS: Serum IL-6, IL-4 and IL-10 levels were elevated in H1N1 patients from the 2(nd) pandemic wave. Additionally, the frequency of helper and cytotoxic T cells was reduced during the 1(st) wave, whereas CD69 expression in helper T cells was increased in the 2(nd) wave for both H1N1 and ILI patients. In contrast, CD62L expression in granulocytes from the ILI group was increased in both waves but in monocytes only in the 2(nd) wave. Triggering Receptor Expressed on Myeloid cells (TREM)-1 expression was elevated only in H1N1 patients at the 1(st) wave. CONCLUSIONS: Our results show that during the 2009 influenza pandemic a T cell activation phenotype is observed in a wave-dependent fashion, with an expanded activation in the 2(nd) wave, compared to the 1(st) wave. Conversely, granulocyte and monocyte activation is infection-dependent. This evidence collected at the pandemic epicenter in 2009 could help us understand the differences in the underlying cellular mechanisms that drive the wave-related immune profile behaviors that occur against influenza viruses during pandemics.

Antibody responses to influenza viruses in paediatric patients and their contacts at the onset of the 2009 pandemic in Mexico.

INTRODUCTION: On April 2009, the Mexican Ministry of Health received notification of cases of severe pneumonia mostly affecting young healthy people; this was the beginning of the first influenza pandemic of the 21st century. The nature of the immune response to the influenza A(H1N1)2009 pandemic strain in Mexico at the beginning of the pandemic outbreak has not been completely defined. We describe the serological response to the 2009 pandemic influenza virus in paediatric patients with influenza-like illness, their household contacts (HHCs), and exposed health-care workers (HCWs) at the beginning of the pandemic outbreak in Mexico City. METHODOLOGY: thirty pre-epidemic and 129 epidemic samples were collected and serum antibodies were measured against A(H1N1)2009 pandemic virus and two non-pandemic swine influenza viruses by an haemagglutination inhibition assay . RESULTS: 91% (29/32) of the convalescence samples from confirmed patients had an antibody titre ≥ 10 (GMT 25), 63% (41/65) of the HHCs (GMT 12), 41% of HCWs (GMT 6) and 13% (4/30) of pre-epidemic samples (GMT 6) for the pandemic influenza virus. Of the 32 confirmed cases, 60% had an antibody titre ≥ 40 for the pandemic strain, 53% for the A/swine/Iowa(H1N1) virus (GMT 62) and 43% for the A/swine/Texas(H3N2) virus (GMT 66). CONCLUSION: The antibody response to 2009 pandemic influenza virus was widespread in convalescence samples from patients with confirmed pandemic influenza infection but the GMT was below the protective titre. There was no evidence that antibodies to the swine influenza viruses had cross-protective effect against the 2009 pandemic influenza virus.

PD-L1 expression induced by the 2009 pandemic influenza A(H1N1) virus impairs the human T cell response.

PD-L1 expression plays a critical role in the impairment of T cell responses during chronic infections; however, the expression of PD-L1 on T cells during acute viral infections, particularly during the pandemic influenza virus (A(H1N1)pdm09), and its effects on the T cell response have not been widely explored. We found that A(H1N1)pdm09 virus induced PD-L1 expression on human dendritic cells (DCs) and T cells, as well as PD-1 expression on T cells. PD-L1 expression impaired the T cell response against A(H1N1)pdm09 by promoting CD8⁺ T cell death and reducing cytokine production. Furthermore, we found increased PD-L1 expression on DCs and T cells from influenza-infected patients from the first and second 2009 pandemic waves in Mexico City. PD-L1 expression on CD8⁺ T cells correlated inversely with T cell proportions in patients infected with A(H1N1)pdm09. Therefore, PD-L1 expression on DCs and T cells could be associated with an impaired T cell response during acute infection with A(H1N1)pdm09 virus.

Salmonella Typhi OmpS1 and OmpS2 porins are potent protective immunogens with adjuvant properties.

Salmonella enterica serovar Typhi (S. Typhi) is the causal agent of typhoid fever, a disease that primarily affects developing countries. Various antigens from this bacterium have been reported to be targets of the immune response. Recently, the S. Typhi genome has been shown to encode two porins--OmpS1 and OmpS2--which are expressed at low levels under in vitro culture conditions. In this study, we demonstrate that immunizing mice with either OmpS1 or OmpS2 induced production of specific, long-term antibody titres and conferred protection against S. Typhi challenge; in particular, OmpS1 was more immunogenic and conferred greater protective effects than OmpS2. We also found that OmpS1 is a Toll-like receptor 4 (TLR4) agonist, whereas OmpS2 is a TLR2 and TLR4 agonist. Both porins induced the production of tumour necrosis factor and interleukin-6, and OmpS2 was also able to induce interleukin-10 production. Furthermore, OmpS1 induced the over-expression of MHC II molecules in dendritic cells and OmpS2 induced the over-expression of CD40 molecules in macrophages and dendritic cells. Co-immunization of OmpS1 or OmpS2 with ovalbumin (OVA) increased anti-OVA antibody titres, the duration and isotype diversity of the OVA-specific antibody response, and the proliferation of T lymphocytes. These porins also had adjuvant effects on the antibody response when co-immunized with either the Vi capsular antigen from S. Typhi or inactivated 2009 pandemic influenza A(H1N1) virus [A(H1N1)pdm09]. Taken together, the data indicate that OmpS1 and OmpS2, despite being expressed at low levels under in vitro culture conditions, are potent protective immunogens with intrinsic adjuvant properties.

TLR2 and TLR4 signaling shapes specific antibody responses to Salmonella typhi antigens.

TLR directly induce innate immune responses by sensing a variety of microbial components and are critical for the fine-tuning of subsequent adaptive immune responses. However, their impact and mechanism of action on antibody responses against bacterial antigens are not yet fully understood. Salmonella enterica serovar Typhi (S. typhi) porins have been characterized as inducers of long-lasting specific antibody responses in mice. In this report, we show that immunization of TLR4-deficient (TLR4(-/-)), myeloid differentiating gene 88-deficient and Toll/IL-R domain-containing adaptor-inducing IFN-beta-deficient mice with S. typhi porins led to significantly reduced B-cell responses. TLR2(-/-) mice, as well, showed reduced IgG titers with a more pronounced impairment in the production of IgG3 anti-porins antibodies. Adoptive transfer of TLR2(-/-)- or TLR4(-/-)-B cells into B-cell-deficient mice revealed a direct effect of TLR4 on B cells for the primary IgM response, whereas stimulation of B cells via TLR2 was important for IgG production. Furthermore, S. typhi porins were found to efficiently elicit maturation of CD11c(+) conventional DC. Taken together, S. typhi porins represent not only a suitable B-cell antigen for vaccination, but exhibit potent TLR-dependent stimulatory functions on B cells and DC, which help to further enhance and shape the antibody response.