Active immunization with a structurally aggregated PD-L1 antigen breaks T and B immune tolerance in non-human primates and exhibits in vivo anti-tumoral effects in immunocompetent mouse tumor models.

Despite the clinical success of the programmed death ligand 1 (PD-L1) blocking therapy in cancer treatment, only a subset of patients exhibits durable responses, therefore further exploration of other immunotherapeutic alternatives are needed. This paper reported the development of the PKPD-L1Vac vaccine, a new protein vaccine candidate that uses aluminum phosphate as an adjuvant and as an antigen the extracellular domain of human PD-L1 fused to a 47 amino-terminal portion of the LpdA protein from N. meningitides (PKPD-L1). The PKPD-L1 antigen has different physical and biological characteristics than those found in the natural molecule and in others PD-L1 vaccine candidates. The quimeric protein has a reduced binding capacity to the PD-1 and CD80 receptors to decrease their pro-tumoral activity. Besides, the distinctive feature of the PKPD-L1 polypeptide to be structurally aggregated could be desirable for its immunogenic properties. PKPD-L1Vac elicited anti-PD-L1-specific IgG antibodies and T lymphocyte-mediated immunity in mice and non-human primates. The vaccine administration demonstrated antitumor activity on CT-26 and B16-F10 primary tumor models in mice. Moreover, the immunization with PKPD-L1Vac increased the tumor-infiltrating lymphocytes and decreased the proportion of CD3+CD8+PD1+high anergic T cells in CT-26 tumor tissues, suggesting that the vaccine may remodel the tumor microenvironment. In summary, the PKPD-L1Vac vaccine exhibits very promising preclinical results and deserves to move forward to a phase I clinical trial.

Dengue virus identification by transmission electron microscopy and molecular methods in fatal dengue hemorrhagic fever.

Dengue virus is the most significant virus transmitted by arthropods worldwide and may cause a potentially fatal systemic disease named dengue hemorrhagic fever. In this work, dengue virus serotype 4 was detected in the tissues of one fatal dengue hemorrhagic fever case using electron immunomicroscopy and molecular methods. This is the first report of dengue virus polypeptides findings by electron immunomicroscopy in human samples. In addition, not-previously-documented virus-like particles visualized in spleen, hepatic, brain, and pulmonary tissues from a dengue case are discussed.

Efecto adverso en la calidad proteica de los alimentos de dietas con alto contenido de fibra dietaria / Adverse effect on the food protein quality of diets high in dietary fiber

Modern diet tends to change eating habits and there is a tendency to consume more processed foods. These changes in eating habits towards more consumption of processed food, and the recognized benefic effects of dietary fiber by consumers, tend to increase the number of "high fiber" foods in the market. Although the beneficial effects of dietary fiber on human health is widely recognized, this increased consumption of dietary fiber may also have adverse effects on digestion, absorption and utilization offood proteins. Research in the past has shown that the consumption of high dietary fiber diets have an adverse effect on certain indicators of protein quality. Therefore it becomes very important to study the physicochemical properties of the various sources of dietary fiber, as well as the presence of other factors, associated to the fibrous fraction, in their possible negative influence on the protein quality of rich dietary fiber diets.

La dieta moderna cambia los hábitos alimenticios y existe una tendencia al consumo de alimentos más procesados. El cambio de hábito alimentario hacia alimentos más procesados tiende a incrementar, algunas veces por propósitos publicitarios, aquellos alimentos procesados "altos en fibra". Si bien los efectos benéficos de la fibra dietética a la salud humana son ampliamente reconocidos, este aumento en el consumo de fibra dietética puede también tener efectos adversos en la digestión, absorción y utilización de la proteína de los alimentos. En las investigaciones revisadas se obtuvo que el consumo de dietas altas en fibra dietética tiene efecto adverso en ciertos indicadores de calidad proteica, por lo que la inclusión de fuentes proteicas con altos contenidos de fibra impone la necesidad de estudiar las características físico-químicas de la fibra dietética, así como la presencia de factores que pudieran unirse a la fracción fibrosa e influir negativamente en la calidad proteica.

Characterization of the HCV core virus-like particles produced in the methylotrophic yeast Pichia pastoris.

Little is known about the mechanism of hepatitis C virion assembly. So the capacity of the entire Hepatitis C virus core protein (HCcAg) produced in Pichia pastoris to form particles either in its native soluble state or after detergent treatment of HCcAg associated to cell debris were studied. Size exclusion chromatography suggested that HCcAg assembled into high molecular weight structures. HCcAg was also specifically recognized by a serum from a chronic HCV carrier patient. This antigen migrated with buoyant density values similar to those obtained for native nucleocapsid particles from infected patients when analyzed using sucrose density gradient centrifugation. The analysis by electron microscopy of purified HCcAg showed aggregates resembling virus-like particles (VLPs) with an average diameter of 30 nm. These results indicated that the HCcAg obtained from P. pastoris assembled into VLPs resembling HCV nucleocapsid particles in a mature stage. Such HCcAg aggregates characterized here could be a valuable tool to elucidate the mechanisms of HCV nucleocapsid assembly.

Plasmid DNA-recombinant Opc protein complexes for nasal DNA immunization.

The nasal mucosa may provide a simple, non-invasive route to deliver DNA encoding genes that stimulate a specific immune response. Based on this, a new approach using pCMVbeta-gal plasmid DNA complexed to the Opc meningococcal outer membrane protein was assayed for. Optimal conditions of interaction were established between recombinant Opc protein and pCMVbeta-gal plasmid DNA. Complexes were fully characterized by electrophoresis analysis, DNAse resistance assay and transmission electron microscopy. DNA-protein complexes were also evaluated in in vitro transfection experiments. After the characterisation of complexes, Balb/c mice were intranasal (i.n.) and intramuscularly (i.m.) immunized. The humoral immune response against beta-galactosidase was measured by ELISA. The proliferative response in the spleen lymph nodes was also measured. Complexes administered by i.n. route induced both systemic and mucosal antibody responses. This behavior was not observed with the naked DNA. Finally, a lymphoproliferative response specific to beta-galactosidase induced by DNA-protein complexes was also detected.

Assembly of truncated HCV core antigen into virus-like particles in Escherichia coli.

Core protein is one of the most conserved and immunogenic of the hepatitis C virus proteins. Several pieces of experimental evidence suggest its ability for formation of virus like particles alone or in association with other viral proteins in mammalian or yeast cells with great similarity to those detected in patient sera and liver extract. In this work we report an Escherichia coli-derived truncated hepatitis C core protein that is able to aggregate. SDS-PAGE and size exclusion chromatography patterns bring to mind the aggregation of monomers of recombinant protein Co.120. The Co.120 protein migrated with buoyant density of 1.28 g/cm(3) when analyzed using CsCl density gradient centrifugation. Spherical structures with an average diameter of 30 nm were observed using electron microscopy. We report here that VLPs are generated when the first 120 aa of HCV core protein are expressed in E. coli.

Ultrastructural and immunocytochemical evidences of core-particle formation in the methylotrophic Pichia pastoris yeast when expressing HCV structural proteins (core-E1).

Particulate antigens of the Hepatitis C virus (HCV) are reported for the first time by transmission electron microscopy in Pichia pastoris. The yeast was cloned to express the first 339 NH2-terminal amino acids of the HCV polyprotein (C-E1.339 polypeptide). The C-E1.339 polypeptide covers the putative 191 aa of the core protein (aa 1-191) and 148 aa of the E1 envelope antigen (aa 192-339). Virus-like particles (VLP) with diameters ranging from 20 nm to 30 nm were specifically observed in those cells expressing the HCV polyprotein. The VLP appeared along the membrane of the endoplasmic reticulum, but were fundamentally localized in vacuoles, either free or inside autophagic bodies. Clustered particles, chains of particles, high-density reticular structures, and crystalloid bodies were also detected, the last one being an orderly arrangement of particles with 20 nm diameters. The crystal-associated particles are well differentiated from the intracellular VLP because of their uniform size and shape. We argue that membrane components are retained in the architecture of the VLP, conferring to this particle certain heterogeneity. Both kinds of particles, the VLP formed after treatment with NP-40 and the crystal-associated particles, were core protein-positives. Whether they reflect mature HCV nucleocapsid or intermediary states in the viral nucleocapsid morphogenesis remains unknown. We conclude that, like mammalian cell lines, the P. pastoris yeast could be an appropriate host for the analysis of HCV polyprotein processing and, eventually, virus assembly.

Ultrastructural and immunocytochemical characteristics of hepatocytes from hepatitis B virus infected chimpanzees.

Liver tissue samples from four chimpanzees submitted to viral challenge in order to test a recombinant anti-hepatitis B virus vaccine, were studied by electron microscopy. The vaccinated monkeys showed no evidences of acute viral hepatitis (AVH), demonstrating the protection against an infective viral dose; on the contrary, the non-vaccinated chimps developed signs of AVH in hepatocytes such as: different size and shape, slight dilatation of the rough endoplasmic reticulum, disappearance of the mitochondrial crests, broadening of the normal space between the membranes of the nuclear coating and presence of laminar bodies and cytoplasmic vacuoles. Furthermore, the presence of the hepatitis B virus surface (HBV) antigen was confirmed in non-vaccinated monkeys using immunocytochemical techniques. Transmission electron microscopy and immunocytochemical analysis corroborated the protective effect of the recombinant vaccine against the HBV in the vaccinated animals.