Extracellular vesicles derived from antigen-presenting cells pulsed with foot and mouth virus vaccine-antigens act as carriers of viral proteins and stimulate B cell response.

Foot and mouth disease (FMD) is a highly contagious infection caused by FMD-virus (FMDV) that affects livestock worldwide with significant economic impact. The main strategy for the control is vaccination with FMDV chemically inactivated with binary ethylenimine (FMDVi). In FMDV infection and vaccination, B cell response plays a major role by providing neutralizing/protective antibodies in animal models and natural hosts. Extracellular vesicles (EVs) and small EVs (sEVs) such as exosomes are important in cellular communication. EVs secreted by antigen-presenting cells (APC) like dendritic cells (DCs) participate in the activation of B and T cells through the presentation of native antigen membrane-associated to B cells or by transferring MHC-peptide complexes to T cells and even complete antigens from DCs. In this study, we demonstrate for the first time that APC activated with the FMDVi O1 Campos vaccine-antigens secrete EVs expressing viral proteins/peptides that could stimulate FMDV-specific immune response. The secretion of EVs-FMDVi is a time-dependent process and can only be isolated within the first 24 h post-activation. These vesicles express classical EVs markers (CD9, CD81, and CD63), along with immunoregulatory molecules (MHC-II and CD86). With an average size of 155 nm, they belong to the category of EVs. Studies conducted in vitro have demonstrated that EVs-FMDVi express antigens that can stimulate a specific B cell response against FMDV, including both marginal zone B cells (MZB) and follicular B cells (FoB). These vesicles can also indirectly or directly affect T cells, indicating that they express both B and T epitopes. Additionally, lymphocyte expansion induced by EVs-FMDVi is greater in splenocytes that have previously encountered viral antigens in vivo. The present study sheds light on the role of EVs derived from APC in regulating the adaptive immunity against FMDV. This novel insight contributes to our current understanding of the immune mechanisms triggered by APC during the antiviral immune response. Furthermore, these findings may have practical implications for the development of new vaccine platforms, providing a rational basis for the design of more effective vaccines against FMDV and other viral diseases.

Therapeutic effects of Salmonella typhi in a mouse model of T-cell lymphoma.

In this study, we assessed the effectiveness of a live, attenuated Salmonella enterica serovar Typhi (S. Typhi) vaccine strain as a cancer immunotherapy in a mouse model of metastatic T-cell lymphoma. EL4 tumor-bearing C57BL/6J mice immunized with S. Typhi strain CVD 915, by injection into the tumor and the draining lymph node areas, displayed a significant decrease in tumor growth, a reduction in the mitotic index (MI) of tumors, a delayed development of palpable lymph node metastases and most importantly improved survival, compared to untreated mice. Besides, complete tumor regression was achieved in a small number of bacteria-treated mice. A successful therapeutic response associated with a significant reduction of tumor mass was evident as early as 5 days after treatment. The administration of Salmonella to tumor-bearing mice promoted early cellular infiltration (mainly neutrophils) within the tumor, and was accompanied by a decreased intratumoral interleukin 10 production as well as by leukocyte expansion in tumor draining lymph nodes. A tumor-specific memory immune response was induced in most of cured animals, as evidenced by the lack of tumor growth after a rechallenge with the same tumor. EL4 cells cultured with live Salmonella failed to proliferate and underwent apoptosis in a dose-dependent, time-dependent, and contact-dependent manner. To our knowledge, these results demonstrate for the first time the efficacy of a S. Typhi vaccine strain as an oncolytic and immunotherapeutic agent against a highly malignant tumor and support the use of S. Typhi-based vaccine strains in cancer therapy.

Baculovirus capsid display potentiates OVA cytotoxic and innate immune responses.

Baculoviruses (BV) are DNA viruses that are pathogenic for insects. Although BV infect a range of mammalian cell types, they do not replicate in these cells. Indeed, the potential effects of these insect viruses on the immune responses of mammals are only just beginning to be studied. We show in this paper that a recombinant Autographa californica multiple nuclear polyhedrosis virus carrying a fragment of ovalbumin (OVA) on the VP39 capsid protein (BV-OVA) has the capacity to act as an adjuvant and vector of antigens in mice, thereby promoting specific CD4 and cytotoxic T cell responses against OVA. BV also induced in vivo maturation of dendritic cells and the production of inflammatory cytokines, thus promoting innate and adaptive immune responses. The OVA-specific response induced by BV-OVA was strong enough to reject a challenge with OVA-expressing melanoma cells (MO5 cells) and effectively prolonged survival of MO5 bearing mice. All these findings, together with the absence of pre-existing immunity to BV in humans and the lack of viral gene expression in mammalian cells, make BV a candidate for vaccination.

A novel Salmonella Typhi-based immunotherapy promotes tumor killing via an antitumor Th1-type cellular immune response and neutrophil activation in a mouse model of breast cancer.

We investigated the use of a live, attenuated Salmonella enterica serovar Typhi vaccine strain as an antitumor immunotherapy. Mice bearing a subcutaneous tumor (LM3 mammary adenocarcinoma) were immunized on three occasions with S. Typhi strain CVD 915 by injection into the tumor, the peritumoral tissue and the draining lymph node areas; this procedure was termed Salmonella multiple treatment (Salmonella MT). Tumor-bearing mice subjected to the Salmonella MT exhibited reduced tumor growth, prolonged survival and reduced incidence of lung metastases, compared to untreated mice. We examined the mechanisms mediating this effect and found that Salmonella MT promoted an antitumor Th1-type response characterized by increased frequencies of IFN-γ-secreting CD4(+) T and CD8(+) T cells with reduction of regulatory T cells in tumor draining lymph nodes. The main cells infiltrating bacteria-treated tumors were activated neutrophils, which can exert an antitumor effect through the secretion of TNF-α. These results demonstrate for the first time the efficacy of an attenuated S. Typhi vaccine strain as a cancer immunotherapeutic agent. By potentiating the host antitumor immune response, this approach could be a powerful adjunct tool for cancer therapy.

Caracterizacion inmunobiologica de la leucemia murina LB y la linea celular LBC / Immunobiological characterization of the murine LB leukemia and the LBC cell line

El tumor LB se originó como una leucemia linfoide de origen espontáneo. No es inmunogénico y crece rápidamente en el huésped singeneico infiltrando hígado, bazo y ganglíos linfáticos. A partir del tumor original se obtuvo la línea en cultivo LBC, que crece en suspensión, no requiere del agregado de factores de crecimiento y presenta un número modal de cromosomas igual al patrón normal de ratón. La caracterización fenotípica de las células LB y de la línea en cultivo demostró que ambos tipos celulares están constituídos por linfocitos T, CD3-, CD25+, gp 70-, J22d.2+, que expresan antígenos del CMH de clase I pero no de clase II, CD8+, y CD4- en el tumor original pero CD4+ en la línea celular. Esta última fue capaz de inducir una respuesta inmune en el huésped singeneico, mediada por anticuerpos que reaccionaron contra componentesde peso molecular 14, 16 y 27 kDa presentes en las células tumorales y en timocitos pero no en ganglios normales, y por células citotóxicas, efectivas para retardar el tiempo de muerte de los ratones desafiados con el tumor original LB. Por ELISA se pudo comprobar la presencia de receptor soluble de IL-2 en los sueros, ascitis y sobrenadantes de células LB en cultivo, responsable del efecto inhibitorio de la proliferación tumoral. Las células fueron estimuladas por agregado de IL-2 e inhibidas en presencia de un anticuerpo monoclonal específico para IL-2, demostrando la funcionalidad del receptor. Por RT-PCR se puso en evidencia la presencia de ARNn de IL-2 en las células tumorales, confirmando que éstas sintetizan IL-2. Se realizó una triple transfección de las células LBC con los genes que codificam para las cadenas alpha y beta de las moléculas I-A(d) y el gen pSV2-Neo, que confiere resistÛncia al antibiótico Genetecín, y se obtuvieron 3 clones positivos para I-A(d). Por inoculación de estas células se generaron linfocitos T citotóxicos que fueron efectivos para impedir o retrasar significativamente el desarrollo tumoral. En función de estos resultados postulamos que la expresión de antígenos de clase II sobre la superfície celular le confiere a la célula tumoral la capacidad para actuar como célula presentadora de antígenos, generando una respuesta anti-tumoral más eficiente. (AU)

Caracterizacion inmunobiologica de la leucemia murina LB y la linea celular LBC / Immunobiological characterization of the murine LB leukemia and the LBC cell line

El tumor LB se originó como una leucemia linfoide de origen espontáneo. No es inmunogénico y crece rápidamente en el huésped singeneico infiltrando hígado, bazo y ganglíos linfáticos. A partir del tumor original se obtuvo la línea en cultivo LBC, que crece en suspensión, no requiere del agregado de factores de crecimiento y presenta un número modal de cromosomas igual al patrón normal de ratón. La caracterización fenotípica de las células LB y de la línea en cultivo demostró que ambos tipos celulares están constituídos por linfocitos T, CD3-, CD25+, gp 70-, J22d.2+, que expresan antígenos del CMH de clase I pero no de clase II, CD8+, y CD4- en el tumor original pero CD4+ en la línea celular. Esta última fue capaz de inducir una respuesta inmune en el huésped singeneico, mediada por anticuerpos que reaccionaron contra componentesde peso molecular 14, 16 y 27 kDa presentes en las células tumorales y en timocitos pero no en ganglios normales, y por células citotóxicas, efectivas para retardar el tiempo de muerte de los ratones desafiados con el tumor original LB. Por ELISA se pudo comprobar la presencia de receptor soluble de IL-2 en los sueros, ascitis y sobrenadantes de células LB en cultivo, responsable del efecto inhibitorio de la proliferación tumoral. Las células fueron estimuladas por agregado de IL-2 e inhibidas en presencia de un anticuerpo monoclonal específico para IL-2, demostrando la funcionalidad del receptor. Por RT-PCR se puso en evidencia la presencia de ARNn de IL-2 en las células tumorales, confirmando que éstas sintetizan IL-2. Se realizó una triple transfección de las células LBC con los genes que codificam para las cadenas alpha y beta de las moléculas I-A(d) y el gen pSV2-Neo, que confiere resistência al antibiótico Genetecín, y se obtuvieron 3 clones positivos para I-A(d). Por inoculación de estas células se generaron linfocitos T citotóxicos que fueron efectivos para impedir o retrasar significativamente el desarrollo tumoral. En función de estos resultados postulamos que la expresión de antígenos de clase II sobre la superfície celular le confiere a la célula tumoral la capacidad para actuar como célula presentadora de antígenos, generando una respuesta anti-tumoral más eficiente.