Immune response induced by standard and fractional doses of 17DD yellow fever vaccine.

The re-emergence of yellow fever (YF) urged new mass vaccination campaigns and, in 2017, the World Health Organization approved the use of the fractional dose (FD) of the YF vaccine due to stock shortage. In an observational cross-sectional investigation, we have assessed viremia, antibodies, soluble mediators and effector and memory T and B-cells induced by primary vaccination of volunteers with FD and standard dose (SD). Similar viremia and levels of antibodies and soluble markers were induced early after immunization. However, a faster decrease in the latter was observed after SD. The FD led to a sustained expansion of helper T-cells and an increased expression of activation markers on T-cells early after vaccination. Although with different kinetics, expansion of plasma cells was induced upon SD and FD immunization. Integrative analysis reveals that FD induces a more complex network involving follicular helper T cells and B-cells than SD. Our findings substantiate that FD can replace SD inducing robust correlates of protective immune response against YF.

Impacts of the COVID-19 pandemic on immunization with pneumococcal vaccines in children and older adults in Brazil.

The COVID-19 pandemic has profoundly impacted individuals, resulting in long-lasting consequences. One of the effects has been a decline in vaccine adherence attributed to physical distancing measures, potentially contributing to the resurgence of preventable diseases, and posing diagnostic challenges. Consequently, monitoring immunization rates becomes crucial as an indicator for health promotion campaigns and to mitigate the strain on healthcare systems. This study aims to assess the effects of the COVID-19 pandemic on immunization with pneumococcal vaccines in children and older adults in Brazil from 2018 to 2021. Data was collected from the Department of Informatics of the Unified Health System, focusing on the number of doses administered and vaccination coverage with pneumococcal vaccines across the country. A total of 21,780,450 doses were administered, with a decline of 19.97% in vaccine coverage throughout the evaluation period. An overall negative trend was observed in the time series analysis for all states in Brazil. However, not all showed a statistically significant change associated with the pandemic. Therefore, it is essential for states that experienced a decline in vaccination rates during the COVID-19 pandemic to closely monitor changes in pneumococcal vaccination. Failure in the process may lead to an increase in pneumococcal infections and place an additional burden on the healthcare system.

Disrupted Iron Metabolism and Mortality during Co-infection with Malaria and an Intestinal Gram-Negative Extracellular Pathogen.

Individuals with malaria exhibit increased morbidity and mortality when infected with Gram-negative (Gr-) bacteria. To explore this experimentally, we performed co-infection of mice with Plasmodium chabaudi and Citrobacter rodentium, an extracellular Gr- bacterial pathogen that infects the large intestine. While single infections are controlled effectively, co-infection results in enhanced virulence that is characterized by prolonged systemic bacterial persistence and high mortality. Mortality in co-infected mice is associated with disrupted iron metabolism, elevated levels of plasma heme, and increased mitochondrial reactive oxygen species (ROS) production by phagocytes. In addition, iron acquisition by the bacterium plays a key role in pathogenesis because co-infection with a mutant C. rodentium strain lacking a critical iron acquisition pathway does not cause mortality. These results indicate that disrupted iron metabolism may drive mortality during co-infection with C. rodentium and P. chabaudi by both altering host immune responses and facilitating bacterial persistence.

Putative biomarkers for early diagnosis and prognosis of congenital ocular toxoplasmosis.

In the present study we have evaluated the performance of several immunological biomarkers for early diagnosis and prognosis of congenital toxoplasmosis. Our results showed that ex vivo serum levels of CXCL9, and the frequencies of circulating CD4+CD25+ T-cells and T. gondii-specific IFN-γ+CD4+ T-cells measured 30-45 days after birth presented high accuracy to distinguish T. gondii-infected infants from healthy age-matched controls (Global Accuracy/AUC = 0.9; 0.9 and 0.8, respectively). Of note was the enhanced performance (Accuracy = 96%) achieved by using a combined stepwise analysis of CD4+CD25+ T-cells and CXCL9. In addition, high global accuracy (AUC = 0.9) with elevated sensitivity (Se = 98%) was also reached by using the total frequency of in vitro IFN-γ-producing T. gondii-specific T-cells (∑ IFN-γ+ CD4+ & CD8+) as a biomarker of congenital toxoplasmosis. Furthermore, the analysis of in vitro T. gondii-specific IL5+CD4+ T-cells and IFN-γ+NK-cells displayed a high accuracy for early prognosis of ocular lesion in infant with congenital toxoplasmosis (Global Accuracy/AUC = 0.8 and 0.9, respectively). Together, these findings support the relevance of employing the elements of the cell-mediated immune response as biomarkers with potential to endorse early diagnosis and prognosis of congenital ocular toxoplasmosis to contribute for a precise clinical management and effective therapeutic intervention.

Effect of the expression of CD62P and thrombin generation on patients using central venous catheters for hemodialysis.

The formation of thrombi in medical devices that come into contact with blood is a common cause of increased morbidity and mortality. Prolonged use of central venous catheters (CVCs) may cause high infection rates or compromise CVC patency due to thrombus development. In this study, we sought insights into possible changes in the hemostatic system during prolonged use of inserted CVCs for hemodialysis by assessing platelets by CD62P and CD41a expression and the potential for thrombin generation (TG). This study included patients with chronic renal failure who were undergoing hemodialysis three times a week using a CVC, and healthy subjects as controls. The participants were distributed into three groups: Group 1: clinically and laboratorially healthy individuals matched by sex and age to the patients (controls); Group II: patients who had completed 1 month of CVC insertion; and Group III: the same patients after they had completed 4 months of CVC insertion. Platelet activation analysis and TG evaluation were performed using blood samples obtained through two different accesses, that is, through a peripheral vein and directly from the CVC lumen. The data showed platelet activation and an increase in the generation of thrombin, particularly after 4 months of CVC use. The results also indicated that insertion of the catheter into the blood stream stimulated the intrinsic rather than the extrinsic pathway. Taken together, the data showed a direct relationship between the use of CVCs in hemodialysis patients and a state of hypercoagulability, most likely associated with endothelial damage and the contact of the medical device with blood components such as platelets and coagulation factors.

Blockade of CTLA-4 promotes the development of effector CD8+ T lymphocytes and the therapeutic effect of vaccination with an attenuated protozoan expressing NY-ESO-1.

The development of cancer immunotherapy has long been a challenge. Here, we report that prophylactic vaccination with a highly attenuated Trypanosoma cruzi strain expressing NY-ESO-1 (CL-14-NY-ESO-1) induces both effector memory and effector CD8(+) T lymphocytes that efficiently prevent tumor development. However, the therapeutic effect of such a vaccine is limited. We also demonstrate that blockade of Cytotoxic T Lymphocyte Antigen 4 (CTLA-4) during vaccination enhances the frequency of NY-ESO-1-specific effector CD8(+) T cells producing IFN-γ and promotes lymphocyte migration to the tumor infiltrate. As a result, therapy with CL-14-NY-ESO-1 together with anti-CTLA-4 is highly effective in controlling the development of an established melanoma.

Oxidized multiwalled carbon nanotubes as antigen delivery system to promote superior CD8(+) T cell response and protection against cancer.

Properties like high interfacial area with cellular membranes, unique ability to incorporate multiple functionalization, as well as compatibility and transport in biological fluids make carbon nanotubes (CNTs) useful for a variety of therapeutic and drug-delivery applications. Here we used a totally synthetic hybrid supramolecule as an anticancer vaccine formulation. This complex structure comprises CNTs as delivery system for the Cancer Testis Antigen named NY-ESO-1, allied to a synthetic Toll-Like Receptor agonist. The CNT constructs were rapidly internalized into dendritic cells, both in vitro and in vivo, and served as an intracellular antigen depot. This property favored the induction of strong CD4(+) T as well as CD8(+) T cell-mediated immune responses against the NY-ESO-1. Importantly, the vaccination significantly delayed the tumor development and prolonged the mice survival, highlighting the potential application of CNTs as a vaccine delivery system to provide superior immunogenicity and strong protection against cancer.

Vaccination using recombinants influenza and adenoviruses encoding amastigote surface protein-2 are highly effective on protection against Trypanosoma cruzi infection.

In the present study we evaluated the protection raised by immunization with recombinant influenza viruses carrying sequences coding for polypeptides corresponding to medial and carboxi-terminal moieties of Trypanosoma cruzi ´s amastigote surface protein 2 (ASP2). Those viruses were used in sequential immunization with recombinant adenovirus (heterologous prime-boost immunization protocol) encoding the complete sequence of ASP2 (Ad-ASP2) in two mouse strains (C57BL/6 and C3H/He). The CD8 effector response elicited by this protocol was comparable to that observed in mice immunized twice with Ad-ASP2 and more robust than that observed in mice that were immunized once with Ad-ASP2. Whereas a single immunization with Ad-ASP2 sufficed to completely protect C57BL/6 mice, a higher survival rate was observed in C3H/He mice that were primed with recombinant influenza virus and boosted with Ad-ASP2 after being challenged with T. cruzi. Analyzing the phenotype of CD8+ T cells obtained from spleen of vaccinated C3H/He mice we observed that heterologous prime-boost immunization protocol elicited more CD8+ T cells specific for the immunodominant epitope as well as a higher number of CD8+ T cells producing TNF-α and IFN-γ and a higher mobilization of surface marker CD107a. Taken together, our results suggest that immunodominant subpopulations of CD8+ T elicited after immunization could be directly related to degree of protection achieved by different immunization protocols using different viral vectors. Overall, these results demonstrated the usefulness of recombinant influenza viruses in immunization protocols against Chagas Disease.