Detection and characterization of circulating microvesicles containing Shiga toxin type 2 in a rat model of Hemolytic Uremic Syndrome.

Shiga toxin producing Escherichia coli (STEC) are foodborne pathogens that release Shiga toxin (Stx), virulence factor responsible for the development of Hemolytic Uremic Syndrome (HUS). Stx causes endothelial cell damage, which leads to platelets deposition and thrombi formation within the microvasculature. It has been described that Stx activates blood cells and induces the shedding of proinflammatory and prothrombotic microvesicles (MVs) containing the toxin. In this sense, it has been postulated that MVs containing Stx2 (MVs-Stx2+) can contribute to the physiopathology of HUS, allowing Stx2 to reach the target organs while evading the immune system. In this work, we propose that circulating MVs-Stx2+ can be a potential biomarker for the diagnosis and prognosis of STEC infections and HUS progression. We developed a rat HUS model by the intraperitoneal injection of a sublethal dose of Stx2 and observed: decrease in body weight, increase of creatinine and urea levels, decrease of creatinine clearance and histological renal damages. After characterization of renal damages, we investigated circulating total MVs and MVs-Stx2+ by flow cytometry at different times after Stx2 injection. Additionally, we evaluated the correlation of biochemical parameters such as creatinine and urea in plasma with MVs-Stx2+. As a result, we found a significant circulation of MVs-Stx2+ at 72 and 96 h after Stx2 injection, nevertheless no correlation with creatinine and urea plasma levels were detected. Our results suggest that MVs-Stx2+ may be an additional biomarker for the characterization and diagnosis of HUS progression. A further analysis is required in order to validate MVs-Stx2+ as biomarker of the disease.

Humoral response and neutralising capacity at 6 months post-vaccination against COVID-19 among institutionalised older adults in Argentina.

The COVID-19 pandemic has particularly affected older adults residing in nursing homes, resulting in high rates of hospitalisation and death. Here, we evaluated the longitudinal humoral response and neutralising capacity in plasma samples of volunteers vaccinated with different platforms (Sputnik V, BBIBP-CorV, and AZD1222). A cohort of 851 participants, mean age 83 (60-103 years), from the province of Buenos Aires, Argentina were included. Sequential plasma samples were taken at different time points after vaccination. After completing the vaccination schedule, infection-naïve volunteers who received either Sputnik V or AZD1222 exhibited significantly higher specific anti-Spike IgG titers than those who received BBIBP-CorV. Strong correlation between anti-Spike IgG titers and neutralising activity levels was evidenced at all times studied (rho=0.7 a 0.9). Previous exposure to SARS-CoV-2 and age <80 years were both associated with higher specific antibody levels. No differences in neutralising capacity were observed for the infection-naïve participants in either gender or age group. Similar to anti-Spike IgG titers, neutralising capacity decreased 3 to 9-fold at 6 months after initial vaccination for all platforms. Neutralising capacity against Omicron was between 10-58 fold lower compared to ancestral B.1 for all vaccine platforms at 21 days post dose 2 and 180 days post dose 1. This work provides evidence about the humoral response and neutralising capacity elicited by vaccination of a vulnerable elderly population. This data could be useful for pandemic management in defining public health policies, highlighting the need to apply reinforcements after a complete vaccination schedule.

Immunogenicity and reactogenicity of heterologous immunization against SARS CoV-2 using Sputnik V, ChAdOx1-S, BBIBP-CorV, Ad5-nCoV, and mRNA-1273.

Heterologous vaccination against coronavirus disease 2019 (COVID-19) provides a rational strategy to rapidly increase vaccination coverage in many regions of the world. Although data regarding messenger RNA (mRNA) and ChAdOx1 vaccine combinations are available, there is limited information about the combination of these platforms with other vaccines widely used in developing countries, such as BBIBP-CorV and Sputnik V. Here, we assess the immunogenicity and reactogenicity of 15 vaccine combinations in 1,314 participants. We evaluate immunoglobulin G (IgG) anti-spike response and virus neutralizing titers and observe that a number of heterologous vaccine combinations are equivalent or superior to homologous schemes. For all cohorts in this study, the highest antibody response is induced by mRNA-1273 as the second dose. No serious adverse events are detected in any of the schedules analyzed. Our observations provide rational support for the use of different vaccine combinations to achieve wide vaccine coverage in the shortest possible time.

Longitudinal Study after Sputnik V Vaccination Shows Durable SARS-CoV-2 Neutralizing Antibodies and Reduced Viral Variant Escape to Neutralization over Time.

Recent studies have shown a temporal increase in the neutralizing antibody potency and breadth to SARS-CoV-2 variants in coronavirus disease 2019 (COVID-19) convalescent individuals. Here, we examined longitudinal antibody responses and viral neutralizing capacity to the B.1 lineage virus (Wuhan related), to variants of concern (VOC; Alpha, Beta, Gamma, and Delta), and to a local variant of interest (VOI; Lambda) in volunteers receiving the Sputnik V vaccine in Argentina. Longitudinal serum samples (N = 536) collected from 118 volunteers obtained between January and October 2021 were used. The analysis indicates that while anti-spike IgG levels significantly wane over time, the neutralizing capacity for the Wuhan-related lineages of SARS-CoV-2 and VOC is maintained within 6 months of vaccination. In addition, an improved antibody cross-neutralizing ability for circulating variants of concern (Beta and Gamma) was observed over time postvaccination. The viral variants that displayed higher escape to neutralizing antibodies with respect to the original virus (Beta and Gamma variants) were the ones showing the largest increase in susceptibility to neutralization over time after vaccination. Our observations indicate that serum neutralizing antibodies are maintained for at least 6 months and show a reduction of VOC escape to neutralizing antibodies over time after vaccination. IMPORTANCE Vaccines have been produced in record time for SARS-CoV-2, offering the possibility of halting the global pandemic. However, inequalities in vaccine accessibility in different regions of the world create a need to increase international cooperation. Sputnik V is a recombinant adenovirus-based vaccine that has been widely used in Argentina and other developing countries, but limited information is available about its elicited immune responses. Here, we examined longitudinal antibody levels and viral neutralizing capacity elicited by Sputnik V vaccination. Using a cohort of 118 volunteers, we found that while anti-spike antibodies wane over time, the neutralizing capacity to viral variants of concern and local variants of interest is maintained within 4 months of vaccination. In addition, we observed an increased cross-neutralization activity over time for the Beta and Gamma variants. This study provides valuable information about the immune response generated by a vaccine platform used in many parts of the world.

Anti-inflammatory Role of Galectin-8 During Trypanosoma cruzi Chronic Infection.

Galectins are animal lectins with high affinity for ß-galactosides that drive the immune response through several mechanisms. In particular, the role of galectin-8 (Gal-8) in inflammation remains controversial. To analyze its role in a chronic inflammatory environment, we studied a murine model of Trypanosoma cruzi infection. The parasite induces alterations that lead to the development of chronic cardiomyopathy and/or megaviscera in 30% of infected patients. The strong cardiac inflammation along with fibrosis leads to cardiomyopathy, the most relevant consequence of Chagas disease. By analyzing infected wild-type (iWT) and Gal-8-deficient (iGal-8KO) C57BL/6J mice at the chronic phase (4-5 months post-infection), we observed that the lack of Gal-8 favored a generalized increase in heart, skeletal muscle, and liver inflammation associated with extensive fibrosis, unrelated to tissue parasite loads. Remarkably, increased frequencies of neutrophils and macrophages were observed within cardiac iGal-8KO tissue by flow cytometry. It has been proposed that Gal-8, as well as other galectins, induces the surface expression of the inner molecule phosphatidylserine on activated neutrophils, which serves as an "eat-me" signal for macrophages, favoring viable neutrophil removal and tissue injury protection, a process known as preaparesis. We found that the increased neutrophil rates could be associated with the absence of Gal-8-dependent preaparesis, leading to a diminished neutrophil-clearing capability in macrophages. Thus, our results support that Gal-8 exerts an anti-inflammatory role in chronic T. cruzi infection.

Inactive trans-Sialidase Expression in iTS-null Trypanosoma cruzi Generates Virulent Trypomastigotes.

Disclosing virulence factors from pathogens is required to better understand the pathogenic mechanisms involved in their interaction with the host. In the case of Trypanosoma cruzi several molecules are associated with virulence. Among them, the trans-sialidase (TS) has arisen as one of particular relevance due to its effect on the immune system and involvement in the interaction/invasion of the host cells. The presence of conserved genes encoding for an inactive TS (iTS) isoform is puzzlingly restricted to the genome of parasites from the Discrete Typing Units TcII, TcV, and TcVI, which include highly virulent strains. Previous in vitro results using recombinant iTS support that this isoform could play a different or complementary pathogenic role to that of the enzymatically active protein. However, direct evidence involving iTS in in vivo pathogenesis and invasion is still lacking. Here we faced this challenge by transfecting iTS-null parasites with a recombinant gene that allowed us to follow its expression and association with pathological events. We found that iTS expression improves parasite invasion of host cells and increases their in vivo virulence for mice as shown by histopathologic findings in heart and skeletal muscle.

Astrocyte Apoptosis and HIV Replication Are Modulated in Host Cells Coinfected with Trypanosoma cruzi.

The protozoan Trypanosoma cruzi is the etiological agent of Chagas disease. In immunosuppressed individuals, as it occurs in the coinfection with human immunodeficiency virus (HIV), the central nervous system may be affected. In this regard, reactivation of Chagas disease is severe and often lethal, and it accounts for meningoencephalitis. Astrocytes play a crucial role in the environment maintenance of healthy neurons; however, they can host HIV and T. cruzi. In this report, human astrocytes were infected in vitro with both genetically modified-pathogens to express alternative fluorophore. As evidenced by fluorescence microscopy and flow cytometry, HIV and T. cruzi coexist in the same astrocyte, likely favoring reciprocal interactions. In this context, lower rates of cell death were observed in both T. cruzi monoinfected-astrocytes and HIV-T. cruzi coinfection in comparison with those infected only with HIV. The level of HIV replication is significantly diminished under T. cruzi coinfection, but without affecting the infectivity of the HIV progeny. This interference with viral replication appears to be related to the T. cruzi multiplication rate or its increased intracellular presence but does not require their intracellular cohabitation or infected cell-to-cell contact. Among several Th1/Th2/Th17 profile-related cytokines, only IL-6 was overexpressed in HIV-T. cruzi coinfection exhibiting its cytoprotective role. This study demonstrates that T. cruzi and HIV are able to coinfect astrocytes thus altering viral replication and apoptosis.

DTU I isolates of Trypanosoma cruzi induce upregulation of Galectin-3 in murine myocarditis and fibrosis.

Chagas heart disease is a major public concern since 30% of infected patients develop cardiac alterations. The relationship between Trypanosoma cruzi discrete typing units (DTUs) and the biological properties exhibited by the parasite population has yet to be elucidated. In this study, we analysed the expression of α-smooth muscle actin (α-SMA) and galectin-3 (Gal-3) associated with cardiac extracellular matrix (ECM) remodelling a murine chronic cardiomyopathy induced by Tc I genotypes. We found the induction of myocarditis was associated with the upregulation of Col I, α-SMA, Gal-3, IFN-γ and IL-13, as analysed by q-PCR. In myocardial areas of fibrosis, the intensity of myocarditis and significant ECM remodelling correlated with the presence of Col I-, Gal-3- and α-SMA-positive cells. These results are promising for the further efforts to evaluate the relevance of Gal-3 in Chagas heart disease, since this galectin was proposed as a prognosis marker in heart failure patients.