Daniela Mateus

Objectives: This study aimed to investigated the role of Giardia extracellular vesicles (EVs) in intercellular communication and to evaluated their potential as vaccine candidates. Methods: The immunomodulatory effects of Giardia EVs were assessed in mouse macrophages and human monocyte-derived dendritic cells (Mo-DCs), with a particular focus on key inflammatory signaling pathways. In vivo immunogenicity was evaluated following EV administration, and the antigenic composition of EV cargo was characterized by proteomic analysis. Results: Giardia EVs activated pro-inflammatory signaling pathways in mouse macrphages, including SAPK/JNK, ERK1/2, and NF-κB. This activation was associated with IκB-α degradation and nuclear translocation of p65. Furthermore, EV stimulation significantly upregulated the expression of pro-inflammatory genes, including Il1β, Il6, Il4, Ptgs2, Nos2, and Tnf, with log₂ fold changes ranging from 3.9 to 15.8. Consistently, EVs increased iNOS protein expression (28–45%) and nitrite production (9.6–12.3-fold). In human Mo-DCs, Giardia EVs promoted cellular maturation, as evidenced by increased expression of MHC-II, CD80, and CD86, and enhanced T-cell proliferation with a Th1-skewed profile. In vivo immunization induced antigen-specific antibody responses, with IgG subclass distribution indicative of a balanced Th1/Th2 response. Proteomic analysis identified immunoreactive EV-associated proteins, including elongation factor 1-alpha, α-7.3 giardin, tubulin, and variant surface proteins (VSPs), which are well-established antigens in Giardia infection, with prominent bands observed at approximately 22 kDa and 50 kDa. Conclusions: Collectively, these findings demonstrate that Giardia EVs modulate innate immune responses in vitro, elicit antigen-specific humoral immunity in vivo, and contain conserved immunogenic proteins. These properties support their potential as a promising cell-free vaccine platform against giardiasis.

In this study, we investigated the role of Giardia EVs in cellular communication and their potential as vaccine candidates. Our findings revealed that Giardia EVs activate pro-inflammatory signalling cascades, including SAPK/JNK and ERK1/ERK2, as well as the NF-kB pathway, resulting in IκB-α degradation and p65 translocation to the nucleus, in mouse macrophages. Moreover, Giardia EVs increased the expression of genes encoding pro-inflammatory molecules, such as Il1β, Il6, Il4, Ptgs2, Nos2, and Tnf. Interestingly, Giardia EVs enhanced the maturation status of human Mo-DCs and significantly increased T-cell proliferation with a Th1 profile. Immunization studies demonstrated that Giardia EVs elicited antigen-specific antibodies, with IgG subclasses indicating a balance Th1/ Th2 response. Mass spectrometry analysis identified EV proteins (22 KDa and 50 KDa) that bind to serum antibodies of immunized mice including elongation factor 1-alpha, Alpha-7.3 giardin, tubulin, and Variant Surface Proteins (VSP), known antigenic proteins in Giardia infections. Overall, our results indicated that Giardia EVs modulate innate immune cells in vitro, induce antibody-based immune response in vivo, and contain conserved immunogenic proteins. Consequently, Giardia EVs hold promise as a cell-free vaccine candidate for giardiasis.

Dendritic cells (DCs) are the most specialized and proficient antigen-presenting cells. They bridge innate and adaptive immunity and display a powerful capacity to prime antigen-specific T cells. The interaction of DCs with the receptor-binding domain of the spike (S) protein from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a pivotal step to induce effective immunity against the S protein-based vaccination protocols, as well as the SARS-CoV-2 virus. Herein, we describe the cellular and molecular events triggered by virus-like particles (VLPs) containing the receptor-binding motif from the SARS-CoV-2 spike protein in human monocyte-derived dendritic cells, or, as controls, in the presence of the Toll-like receptors (TLR)3 and TLR7/8 agonists, comprehending the events of dendritic cell maturation and their crosstalk with T cells. The results demonstrated that VLPs boosted the expression of major histocompatibility complex molecules and co-stimulatory receptors of DCs, indicating their maturation. Furthermore, DCs’ interaction with VLPs promoted the activation of the NF-kB pathway, a very important intracellular signalling pathway responsible for triggering the expression and secretion of proinflammatory cytokines. Additionally, co-culture of DCs with T cells triggered CD4⁺ (mainly CD4⁺Tbet⁺) and CD8⁺ T cell proliferation. Our results suggested that VLPs increase cellular immunity, involving DC maturation and T cell polarization towards a type 1 T cells profile. By providing deeper insight into the mechanisms of activation and regulation of the immune system by DCs, these findings will enable the design of effective vaccines against SARS-CoV-2.

The novel coronavirus disease 2019 (Covid‐19) first appeared in Wuhan and has so far killed more than four million people worldwide. Men are more affected than women by Covid‐19, but the cellular and molecular mechanisms behind these differences are largely unknown. One plausible explanation is that differences in sex hormones could partially account for this distinct prevalence in both sexes. Accordingly, several papers have reported a protective role of 17β‐estradiol during Covid‐19, which might help explain why women appear less likely to die from Covid‐19 than men. 17β‐estradiol is the predominant and most biologically active endogenous estrogen, which signals through estrogen receptor α, estrogen receptor β, and G protein‐coupled estrogen receptor 1. These receptors are expressed in mature cells from the innate and the adaptive immune system, particularly on dendritic cells (DCs), suggesting that estrogens could modulate their effector functions. DCs are the most specialized and proficient antigen‐presenting cells, acting at the interface of innate and adaptive immunity with a powerful capacity to prime antigen‐specific naive CD8+ T cells. DCs are richly abundant in the lung where they respond to viral infection. A relative increase of mature DCs in broncho‐alveolar lavage fluids from Covid‐19 patients has already been reported. Here we will describe how SARS‐CoV‐2 acts on DCs, the role of estrogen on DC immunobiology, summarise the impact of sex hormones on the immune response against Covid‐19, and explore clinical trials regarding Covid‐19