Alberto García-Lozano

CD4+ T cells are major players in the immune response against several diseases; including AIDS, leishmaniasis, tuberculosis, influenza and cancer. Their activation has been successfully achieved by administering antigen coupled with antibodies, against DC-specific receptors in combination with adjuvants. Unfortunately, most of the adjuvants used so far in experimental models are unsuitable for human use. Therefore, human DC-targeted vaccination awaits the description of potent, yet nontoxic adjuvants. The nontoxic cholera B subunit (CTB) can be safely used in humans and it has the potential to activate CD4+ T cell responses. However, it remains unclear whether CTB can promote DC activation and can act as an adjuvant for DC-targeted antigens. Here, we evaluated the CTB’s capacity to activate DCs and CD4+ T cell responses, and to generate long-lasting protective immunity. Intradermal (i.d.) administration of CTB promoted late and prolonged activation and accumulation of skin and lymphoid-resident DCs. When CTB was co-administered with anti-DEC205-OVA, it promoted CD4+ T cell expansion, differentiation, and infiltration to peripheral nonlymphoid tissues, i.e., the skin, lungs and intestine. Indeed, CTB promoted a polyfunctional CD4+ T cell response, including the priming of Th1 and Th17 cells, as well as resident memory T (RM) cell differentiation in peripheral nonlymphoid tissues. It is worth noting that CTB together with a DC-targeted antigen promoted local and systemic protection against experimental melanoma and murine rotavirus. We conclude that CTB administered i.d. can be used as an adjuvant to DC-targeted antigens for the induction of broad CD4+ T cell responses as well as for promoting long-lasting protective immunity.

Sporotrichosis is a chronic subcutaneous mycosis caused by the Sporothrix schenckii (S. schenckii) species complex and it is considered an emerging opportunistic infection in countries with tropical and subtropical climates. The host’s immune response has a main role in the development of this disease. However, it is unknown the features of the memory cellular immune response that could protect against the infection. Our results show that i.d. immunization in the ears of mice with inactivated S. schenckii conidia (iC) combined with the cholera toxin (CT) induces a cellular immune response mediated by circulating memory CD4+ T cells, which mainly produce interleukin 17 (IL-17). These cells mediate a strong delayed-type hypersensitivity (DTH) reaction. Systemic and local protection against S. schenckii was mediated by circulating CD4+ T cells. In contrast, the infection induces a potent immune response in the skin mediated by CD4+ T cells, which have an effector phenotype that preferentially produce interferon gamma (IFN-γ) and mediate a transitory DTH reaction. Our findings prove the potential value of the CT as a potent skin adjuvant when combined with fungal antigens, and they also have important implications for our better understanding of the differences between the memory immune response induced by the skin immunization and those induced by the infection; this knowledge enhances our understanding of how a protective immune response against a S. schenckii infection is developed.

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.

Background: Bacterial lysates are known to modulate the immune response against respiratory infections. However, the effects of the commercial bacterial lysate Pulmonarom® on dendritic cells—particularly human monocyte-derived dendritic cells (moDCs)—have not been studied. Additionally, limited data are available on the expression of Toll-like receptors (TLRs) and cytokines following stimulation with bacterial lysates. Methods: Human monocytes were isolated from buffy coats and differentiated into moDCs. Pulmonarom® was lyophilized, quantified, and used to stimulate moDCs. Ultrastructural changes were evaluated using transmission electron microscopy. The expression of TLRs and selected cytokines was analyzed by flow cytometry. Results: Pulmonarom® stimulation induced morphological changes in moDCs, including an increased number of dendrites and lysosomes. It also led to the upregulation of MHC class II molecules and TLRs 2, 3, 6, and 7. Additionally, the production of IL-4, IL-6, IL-8, and MCP-1 was significantly increased. Conclusions: Pulmonarom® promotes moDC maturation, characterized by enhanced antigen presentation capabilities and lysosomal activity, along with increased expression of specific TLRs and cytokines. These features suggest a trained immunity phenotype in moDCs, potentially improving their ability to initiate adaptive immune responses against respiratory pathogens. To our knowledge, this is the first study to investigate the immunomodulatory effects of Pulmonarom® on human moDCs, providing novel insights into its potential as an immunotherapeutic adjuvant.

Background Evidence shows bacterial lysates may participate in the immune response against respiratory infections. However, few studies have been conducted on dendritic cells, and, to our knowledge, none on human dendritic cells, and few have analyzed certain TLRs and cytokines. Materials and Methods Monocytes were obtained from the buffy coat and subsequently differentiated into dendritic cells (moDCs). The protein of commercial bacterial lysate Pulmonarom® was lyophilized and quantified. Ultrastructural changes induced by Pulmonarom® were evaluated in moDC by electron microscopy, and the expression of TLRs and some cytokines in these cells was evaluated by flow cytometry. Results Pulmonarom®-stimulated moDCs showed increased numbers of dendrites and the presence of lysosomes; they also showed increased expression of MHC-II and TLRs 2, 3, 6, and 7, IL-4, IL-6, IL-8, and MCP-1. Major conclusions The effects of Pulmonarom® on moDC correlate with an increased capacity to mobilize to lymph nodes and present antigens, initiating an effective adaptive immune response. Lysosomal activity and maturation of moDC, increased expression of TLR2, TLR3, TLR6, and TLR7 receptors, and increased production of the cytokines IL-8, MCP-1, IL-6, and IL-4, indicate a training process in moDC after their activation with Pulmonarom® bacterial lysate. This suggests that Pulmonarom® could enhance responses against viruses and bacteria by activating moDC. To our knowledge, this is the first study to address the effect of Pulmonarom® on one of the most important cells orchestrating the innate and acquired immune responses.