Gabriela Perdigón

The advent of omic platforms revealed the significant benefits of probiotics in the prevention of many infectious diseases. This led to a growing interest in novel strains of probiotics endowed with health characteristics related to microbiome and immune modulation. Therefore, autochthonous bacteria in plant ecosystems might offer a good source for novel next-generation probiotics. The main objective of this study was to analyze the effect of Rouxiella badensis acadiensis Canan (R. acadiensis) a bacterium isolated from the blueberry biota, on the mammalian intestinal ecosystem and its potential as a probiotic microorganism. R. acadiensis, reinforced the intestinal epithelial barrier avoiding bacterial translocation from the gut to deep tissues, even after feeding BALB/c mice for a prolonged period of time. Moreover, diet supplementation with R. acadiensis led to increases in the number of Paneth cells, well as an increase in the antimicrobial peptide α defensin. The anti-bacterial effect of R. acadiensis against Staphylococcus aureus and Salmonella enterica serovar Typhimurium was also reported. Importantly, R. acadiensis-fed animals showed better survival in an in vivo Salmonella enterica serovar Typhimurium challenge compared with those that received a conventional diet. These results demonstrated that R. acadiensis possesses characteristics of a probiotic strain by contributing to the reinforcement and maintenance of intestinal homeostasis.

The ability of the immune system to respond to different pathogens throughout life requires the constant production and selection of T cells in the thymus. This immune organ is very sensitive to age, infectious processes and nutrition disorders (obesity and malnutrition). Several studies have shown that the incorporation of some probiotic bacteria or probiotic fermented milk in the diet has beneficial effects, not only at the intestinal level but also on distant mucosal tissues, improving the architecture of the thymus in a malnutrition model. The aim of the present study was to determine whether supplementation with the probiotic strain Lactobacillus casei CRL 431 and/or its cell wall could improve body weight, intestinal microbiota and thymus structure and function in both obese and aging mice. We evaluated probiotic administration to BALB/c mice in 2 experimental mouse models: obesity and senescence, including mice of different ages (21, 28, 45, 90 and 180 days). Changes in thymus size and histology were recorded. T-lymphocyte population and cytokine production were also determined. The consumption of probiotics improved the cortical/medullary ratio, the production and regulation of cytokines and the recovery of mature T-lymphocyte populations of the thymus in obese and old mice. Probiotic incorporation into the diet could not only modulate the immune system but also lead to thymus function recovery, thus improving quality of life.

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a global pandemic with dramatic health and socioeconomic consequences. The Coronavirus Disease 2019 (COVID-19) challenges health systems to quickly respond by developing new diagnostic strategies that contribute to identify infected individuals, monitor infections, perform contact-tracing, and limit the spread of the virus. In this brief report, we developed a highly sensitive, specific, and precise “In-House” ELISA to correctly discriminate previously SARS-CoV-2-infected and non-infected individuals and study population seroprevalence. Among 758 individuals evaluated for anti-SARS-CoV-2 serology in the province of Tucumán, Argentina, we found a weak correlation between antibodies elicited against the RBD, the receptor-binding domain of the Spike protein, and the nucleocapsid (N) antigens of this virus. Additionally, we detected mild levels of anti-RBD IgG antibodies in 33.6% of individuals diagnosed with COVID-19, while only 19% showed sufficient antibody titers to be considered as plasma donors. No differences in IgG anti-RBD titers were found between women and men, neither in between different age groups ranging from 18 to 60. Surprisingly, individuals from a high altitude village displayed elevated and longer lasting anti-RBD titers compared to those from a lower altitude city. To our knowledge, this is the first report correlating altitude with increased humoral immune response against SARS-CoV-2 infection.

Probiotics have been associated with a variety of health benefits. They can act as adjuvant to enhance specific immune response. Bacterial cell wall (CW) molecules are key structures that interact with host receptors promoting probiotic effects. The adjuvant capacity underlying this sub-cellular fraction purified from Lactobacillus casei CRL431 and L. paracasei CNCMI-1518 remains to be characterized. We interrogated the molecular and cellular events after oral feeding with probiotic-derived CW in addition to heat-inactivated Salmonella Typhimurium and their subsequent protective capacity against S. Typhimurium challenge. Intact probiotic bacteria were orally administered for comparison. We find that previous oral feeding with probiotics or their sub-cellular fraction reduce bacterial burden in spleen and liver after Salmonella challenge. Antibody responses after pathogen challenge were negligible, characterized by not major changes in the antibody-mediated phagocytic activity, and in the levels of total and Salmonella-specific intestinal sIgA and serum IgG, respectively. Conversely, the beneficial effect of probiotic-derived CW after S. Typhimurium challenge were ascribed to a Th1-type cell-mediated immunity which was characterized by augmentation of the delayed-type hypersensitivity response. The cell-mediated immunity associated with the oral feeding with probiotic-derived CW was accompanied with a Th1-cell polarizing cytokines, distinguished by increase IFN-γ/IL-4 ratio. Similar results were observed with the intact probiotics. Our study identified molecular events associated with the oral administration of sub-cellular structures derived from probiotics and their adjuvant capacity to exert immune modulatory function.

We hypothesized that in individuals with previous SARS-CoV-2 infection, the first vaccine dose would work as a booster, eliciting a faster and more intense immune response. We herein describe antibody responses to the first and second doses of Gam-COVID-Vac (SPUTNIK V) vaccine in health personnel of Tucumán, Argentina, with previous COVID-19 and compared it with uninfected personnel. Individuals with anti-SARS-CoV-2 titers at baseline showed significantly higher responses to the first dose than people with no prior history of disease (p One-Sentence Summary First vaccine dose in subjects with prior COVID19 elicits a higher antibody response than two doses in uninfected individuals

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) first reported in Wuhan has caused a global pandemic with dramatic health and socioeconomic consequences. The Coronavirus Disease 2019 (COVID-19) associated represents a challenge for health systems that had to quickly respond developing new diagnostic and therapeutic strategies. In the present work, we developed an “ In House ” ELISA with high sensitivity (92.2 %), specificity (100%) and precision (93.9%), with an area under the ROC curve (AUC) of 0.991, rendering the assay as an excellent serological test to correctly discriminate between SARS-COv-2 infected and non-infected individuals and study population seroprevalence. Among 758 patients evaluated for SARS-CoV-2 diagnosis in the province of Tucumán, Argentina, we found a Pearson correlation coefficient of 0.5048 between antibodies elicited against the RBD and the nucleocapsid (N) antigen. Additionally, 33.6% of individuals diagnosed with COVID-19 displayed mild levels of RBD-IgG antibodies, while 19% of the patients showed high antibody titers. Interestingly, patients with SARS-COV-2 infection over 60 years old elicited significantly higher levels of IgG antibodies against RBD compared to younger ones, while no difference was found between women and men. Surprisingly, individuals from a high altitude village displayed statistically significant higher and longer lasting anti-RBD antibodies compared to those from a city at a lower altitude, suggesting that a hypobaric hypoxia-adapted mechanism may act as a protective factor for COVID-19. To our knowledge, this is the first report correlating altitude with increased humoral immune response against SARS-Cov-2 infection.

This study is based on our previous research showing that commercial probiotic fermented milk (PFM) intake mitigates respiratory allergy development to ovalbumin (OVA) in adult mice (6-weeks old) increasing specific immunoglobulin (Ig)G2a and interferon (IFN)-γ rather than IgE. The aim was to determine if PFM exerts a protective effect when an allergy model is induced 5 days after weaning and whether the mechanisms involved are similar to those previously reported. Before inducing allergy, a group of 21-day old BALB/c mice received PFM for 10 days to analyse the impact on intestinal epithelial cells (IECs) activation. Two more groups received PFM for 5 days and were sensitised with OVA; only one group continued taking PFM until the end of the experiment. Sensitisation scheme: 3 OVA injections 1% in phosphate buffered saline (PBS) plus 7 days OVA aerosol exposure and re-stimulus 15 days later. The contents of specific- IgE, IgG, total-secretory-IgA and Th1/Th2 balance in serum, bronchoalveolar lavage (BAL) and gut were measured at 7 and 15 days post-sensitisation (dPS) and 2 days post-re-stimulus (2dPR). Treg cells in lungs were also quantified. Results were compared with normal and sensitised controls. PFM induced mild activation of IECs increasing monocyte chemoattractant protein-1 (MCP-1 or CCL2) and interleukin (IL)-6 production. In sensitised mice, PFM controlled the response inducing IgG rather than IgE at 7 and 15-dPS and 2dPR (60 days old). Th1-balance (IFN-γ) was favoured by PFM in lungs at 7 dPS with low levels of IL-10 released to regulate the response. Total-S-IgA increased in lungs and gut; however, PFM intake did not affect Treg cells in lungs. PFM maintains controlled stimulation of the immune cells involved in Th1 response, favouring IgG at the respiratory mucosal site. Although the effect was not as strong as that reported previously, PFM promoted maturation and activation of gut immune cells preserving intestinal homeostasis and lung immune response.

Background: The gastrointestinal tract is one of the most microbiologically active ecosystems that plays a crucial role in the working of the mucosal immune system (MIS). In this ecosystem, the consumed probiotics stimulate the immune system and induce a network of signals mediated by the whole bacteria or their cell wall structure. This review is aimed at describing the immunological mechanisms of probiotics and their beneficial effects on the host. Summary: Once administered, oral probiotic bacteria interact with the intestinal epithelial cells (IECs) or immune cells associated with the lamina propria, through Toll-like receptors, and induce the production of different cytokines or chemokines. Macrophage chemoattractant protein 1, produced by the IECs, sends signals to other immune cells leading to the activation of the MIS, characterized by an increase in immunoglobulin A⁺ cells of the intestine, bronchus and mammary glands, and the activation of T cells. Specifically, probiotics activate regulatory T cells that release IL-10. Interestingly, probiotics reinforce the intestinal barrier by an increase of the mucins, the tight junction proteins and the Goblet and Paneth cells. Another proposed mechanism of probiotics is the modulation of intestinal microbiota by maintaining the balance and suppressing the growth of potential pathogenic bacteria in the gut. Furthermore, it has been demonstrated that long-term probiotics consumption does not affect the intestinal homeostasis. The viability of probiotics is crucial in the interaction with IECs and macrophages favoring, mainly, the innate immune response. Macrophages and Dendritic cells (DCs) play an important role in this immune response without inducing an inflammatory pattern, just a slight increase in the cellularity of the lamina propria. Besides, as part of the machinery that probiotics activate to protect against different pathogens, an increase in the microbicidal activity of peritoneal and spleen macrophages has been reported. In malnutrition models, such as undernourishment and obesity, probiotic was able to increase the intestinal and systemic immune response. Furthermore, probiotics contribute to recover the histology of both the intestine and the thymus damaged in these conditions. Probiotic bacteria are emerging as a safe and natural strategy for allergy prevention and treatment. Different mechanisms such as the generation of cytokines from activated pro-T-helper type 1, which favor the production of IgG instead of IgE, have been proposed. Key Messages: Probiotic bacteria, their cell walls or probiotic fermented milk have significant effects on the functionality of the mucosal and systemic immune systems through the activation of multiple immune mechanisms.

The huge amount of intestinal bacteria represents a continuing threat to the intestinal barrier. To meet this challenge, gut epithelial cells produce antimicrobial peptides (AMP) that act at the forefront of innate immunity. We explore whether this antimicrobial activity and Paneth cells, the main intestinal cell responsible of AMP production, are influenced by probiotics administration, to avoid the imbalance of intestinal microbiota and preserve intestinal barrier. Administration of Lactobacillus casei CRL 431 (Lc 431) and L. paracasei CNCM I-1518 (Lp 1518) to 42 days old mice, increases the number of Paneth cells on small intestine, and the antimicrobial activity against the pathogens Staphylococcus aureus and Salmonella Typhimurium in the intestinal fluids. Specifically, strong damage of the bacterial cell with leakage of cytoplasmic content, and cellular fragmentation were observed in S. Typhimurium and S. aureus. Even more important, probiotics increase the antimicrobial activity of the intestinal fluids at the different ages, from weaning (21 days old) to old age (180 days old). Intestinal antimicrobial activity stimulated by oral probiotics, do not influence significantly the composition of total anaerobic bacteria, lactobacilli and enterobacteria in the large intestine, at any age analyzed. This result, together with the antimicrobial activity observed against the same probiotic bacteria; endorse the regular consumption of probiotics without adverse effect on the intestinal homeostasis in healthy individuals. We demonstrate that oral probiotics increase intestinal antimicrobial activity and Paneth cells in order to strengthen epithelial barrier against pathogens. This effect would be another important mechanism by which probiotics protect the host mainly against infectious diseases.