An NAD+ Phosphorylase Toxin Triggers Mycobacterium tuberculosis Cell Death.

Toxin-antitoxin (TA) systems regulate fundamental cellular processes in bacteria and represent potential therapeutic targets. We report a new RES-Xre TA system in multiple human pathogens, including Mycobacterium tuberculosis. The toxin, MbcT, is bactericidal unless neutralized by its antitoxin MbcA. To investigate the mechanism, we solved the 1.8 Å-resolution crystal structure of the MbcTA complex. We found that MbcT resembles secreted NAD+-dependent bacterial exotoxins, such as diphtheria toxin. Indeed, MbcT catalyzes NAD+ degradation in vitro and in vivo. Unexpectedly, the reaction is stimulated by inorganic phosphate, and our data reveal that MbcT is a NAD+ phosphorylase. In the absence of MbcA, MbcT triggers rapid M. tuberculosis cell death, which reduces mycobacterial survival in macrophages and prolongs the survival of infected mice. Our study expands the molecular activities employed by bacterial TA modules and uncovers a new class of enzymes that could be exploited to treat tuberculosis and other infectious diseases.

Structure of the Mycobacterium tuberculosis type VII secretion system chaperone EspG5 in complex with PE25-PPE41 dimer.

The growth or virulence of Mycobacterium tuberculosis bacilli depends on homologous type VII secretion systems, ESX-1, ESX-3 and ESX-5, which export a number of protein effectors across membranes to the bacterial surface and environment. PE and PPE proteins represent two large families of highly polymorphic proteins that are secreted by these ESX systems. Recently, it was shown that these proteins require system-specific cytoplasmic chaperones for secretion. Here, we report the crystal structure of M. tuberculosis ESX-5-secreted PE25-PPE41 heterodimer in complex with the cytoplasmic chaperone EspG(5). EspG(5) represents a novel fold that is unrelated to previously characterized secretion chaperones. Functional analysis of the EspG(5) -binding region uncovered a hydrophobic patch on PPE41 that promotes dimer aggregation, and the chaperone effectively abolishes this process. We show that PPE41 contains a characteristic chaperone-binding sequence, the hh motif, which is highly conserved among ESX-1-, ESX-3- and ESX-5-specific PPE proteins. Disrupting the interaction between EspG(5) and three different PPE target proteins by introducing different point mutations generally affected protein secretion. We further demonstrate that the EspG(5) chaperone plays an important role in the ESX secretion mechanism by keeping aggregation-prone PE-PPE proteins in their soluble state.

The Landscape of Neutralizing Monoclonal Antibodies (nAbs) for Treatment and Prevention of COVID-19.

Purpose: After nearly 3 years of the COVID-19 pandemic, even though a vast body of knowledge and products (including vaccines and treatments) have been developed and disseminated, the virus is still evolving and new variants arising. Consequently, thousands of lives continue to be lost. Neutralizing monoclonal antibodies (nAbs) are promising drugs that emerged to treat SARS-CoV-2. In the uncertainty of the current situation, there is the question of whether organizations should continue to invest in this technology. To help decision-making in scientifical and pharmaceutical organizations, it is of major importance to monitor the development of products and technologies. Therefore, the aim of this study is analyze the landscape of nAbs for COVID-19. Methods: The scenario of 473 biotherapeutics focusing on nAbs was evaluated using foresight techniques and a review of literature. Data were obtained from structured and semi-structured databases and processed for treatment, cleaning, consistency, validation, and enrichment. Results: We identified 227 nAbs and performed an extensive literature review of 16 nAbs in late clinical development, including development technologies, responses to variants of concern (VOCs), manufacturing, and clinical aspects. Conclusions: Even though the emergence of new VOCs is a threat to the effectiveness of this treatment, demanding constant genomic surveillance, the use of nAbs to treat and prevent COVID-19 will probably continue to be relevant due to excellent safety profiles and the possibility of immediate immunity transfer, especially in patients showing inadequate immunological response to vaccination. Therefore, we suggest that organizations should keep investing in improvements in this technology.

Structural Variability of EspG Chaperones from Mycobacterial ESX-1, ESX-3, and ESX-5 Type VII Secretion Systems.

Type VII secretion systems (ESX) are responsible for transport of multiple proteins in mycobacteria. How different ESX systems achieve specific secretion of cognate substrates remains elusive. In the ESX systems, the cytoplasmic chaperone EspG forms complexes with heterodimeric PE-PPE substrates that are secreted from the cells or remain associated with the cell surface. Here we report the crystal structure of the EspG1 chaperone from the ESX-1 system determined using a fusion strategy with T4 lysozyme. EspG1 adopts a quasi 2-fold symmetric structure that consists of a central ß-sheet and two α-helical bundles. In addition, we describe the structures of EspG3 chaperones from four different crystal forms. Alternate conformations of the putative PE-PPE binding site are revealed by comparison of the available EspG3 structures. Analysis of EspG1, EspG3, and EspG5 chaperones using small-angle X-ray scattering reveals that EspG1 and EspG3 chaperones form dimers in solution, which we observed in several of our crystal forms. Finally, we propose a model of the ESX-3 specific EspG3-PE5-PPE4 complex based on the small-angle X-ray scattering analysis.

The homopentameric chlorite dismutase from Magnetospirillum sp.

Chlorite dismutase (Cld) is a b-type heme containing enzyme that catalyzes the reduction of chlorite into chloride plus dioxygen. This enzyme has gained attention because it can be used in the development of bioremediation processes, biosensors, and controlled dioxygen production. In the present work, Cld was purified from Magnetospirillum sp. cells cultured anaerobically with acetate/perchlorate until stationary phase. Biochemical, spectroscopic and X-ray crystallography methods showed that Cld from Magnetospirillum sp. is a ~140 kDa homopentamer comprising ~27.8 kDa monomers. Preliminary X-ray crystallography studies confirmed the quaternary structure and the presence of one b-type heme per monomer. The EPR spectroscopic signature of the as-purified Cld samples is affected by the buffer composition used during the purification. Potassium phosphate buffer is the only buffer that affected neither the spectral nor the kinetic properties of Cld. Kinetic studies in solution revealed that Cld from Magnetospirillum sp. decomposes chlorite at high turnover rates with optimal pH6.0. A temperature below 10 °C is required to avoid enzyme inactivation due to cofactor bleaching during turnover, and to achieve full substrate consumption. Cld kinetic parameters were not affected when kinetic assays were performed in the presence of air or under argon atmosphere, but chloride is a weak mixed inhibitor that modifies the EPR signal of as-prepared samples.

Ligand Binding to Chlorite Dismutase from Magnetospirillum sp.

Chlorite dismutase (Cld) catalyzes the reduction of chlorite to chloride and dioxygen. Here, the ligand binding to Cld of Magnetospirillum sp. (MaCld) is investigated with X-ray crystallography and electron paramagnetic resonance (EPR). EPR reveals a large heterogeneity in the structure of wild-type MaCld, showing a variety of low- and high-spin ferric heme forms. Addition of an axial ligand, such as azide or imidazole, removes this heterogeneity almost entirely. This is in line with the two high resolution crystal structures of MaCld obtained in the presence of azide and thiocyanate that show the coordination of the ligands to the heme iron. The crystal structure of the MaCld-azide complex reveals a single well-defined orientation of the azide molecule in the heme pocket. EPR shows, however, a pH-dependent heme structure, probably due to acid-base transitions of the surrounding amino-acid residues stabilizing azide. For the azide and imidazole complex of MaCld, the hyperfine and nuclear quadrupole interactions with the close-by (14)N and (1)H nuclei are determined using pulsed EPR. These values are compared to the corresponding data for the low-spin forms observed in the ferric wild-type MaCld and to existing EPR data on azide and imidazole complexes of other heme proteins.

A case of yellow fever vaccine-associated viscerotropic disease in Ecuador.

We report the first case of viscerotropic syndrome in Ecuador. Because of similarities between yellow fever and viscerotropic syndrome, the incidence of this recently described complication of vaccination with the 17D yellow fever vaccine is not known. There is a large population in South America that is considered at risk for possible reemergence of urban yellow fever. Knowledge of potentially fatal complications of yellow fever vaccine should temper decisions to vaccinate populations where the disease is not endemic.

Sepsis por Vibrio vulnificus: reporte de dos casos en ciudades de altura en el Ecuador / Vibrio vulnificus sepsis: report of two cases in high altitude cities from Ecuador

La infección por Vibrio vulnifcus está generalmente relacionada con el contacto de heridas con agua de mar y el consumo de mariscos bivalvos. No se han publicado hasta la fecha casos causados por Vibrio vulnifcus en el Ecuador. Presentación de los casos Se describen dos casos de sepsis fatal. El primer caso fue un hombre de 69 años, residente en Ibarra (2220 m.s.n.m.), que tenía como enfermedad de base diabetes mellitus tipo 2, artritis reumatoide y hepatopatía. El segundo fue un hombre de 26 años, residente en Quito (2800 m.s.n.m.), con antecedente de anemia aplásica bajo tratamiento. Ambos pacientes ingresaron febriles y presentaron un deterioro rápidamente progresivo, sin respuesta al manejo de soporte y antibiótico-terapia en cuidados intensivos, falleciendo en menos de 48 horas posteriores a su ingreso. En los hemocultivos se identifcó la presencia de Vibrio vulnifcus. Conclusión El reporte de estos casos pone en alerta la presencia de esta bacteria como causa de sepsis en pacientes con factores de riesgo. El reconocimiento oportuno del cuadro clínico, el tratamiento de soporte, terapia antibiótica y un equipo multidisciplinario, son pilares fundamentales en el manejo de este tipo de infecciones.

Vibrio vulnifcus infection usually is related to the contact of wounds with seawater and bivalve shellfsh consumption. Non-cases has been published of this infection in Ecuador. Case Report Two cases of septic shock are described. The frst case was a man (69 years old) from Ibarra city (2220 m.s.l.) who had diabetes mellitus, rheumatoid arthritis and liver disease. The second case was a man (26 years old) resident in Quito city (2800 m.s.l.) with a history of treated aplastic anemia. Both patients were admitted febrile and showed a fast and progressive deterioration, without response to support management and antibiotic therapy in the intensive care unit. They died within 48 hours after admission. Blood cultures were positive for Vibrio vulnifcus. Conclusion The report of these cases must put on alert for the presence of this bacterium as a cause of sepsis in patients with risk factors. Early recognition of clinical data, the supportive management, antibiotic therapy and a multidisciplinary team are essentials for the outcome.

Revisión del tratamiento del embarazo ectópico sobre cicatriz de cesárea previa. Una localización poco habitual / Review of the treatment of ectopic pregnancy in a previous cesarean section scar. A unusual location

La gestación implantada sobre cicatriz de cesárea previa es una forma poco habitual de embarazo ectópico, pero cuya incidencia ha aumentado en los últimos años en relación con las técnicas de reproducción asistida. Precisa de un diagnóstico temprano para poder minimizar las posibles complicaciones que pueden ocurrir (metrorragia, hemoperitoneo, rotura uterina,..). Disponemos de diferentes opciones diagnósticas y terapéuticas que revisaremos en este trabajo y que elegiremos en función de las características individuales de cada paciente (AU)

The pregnancy implanted on cesarean scar is a rare form of ectopic pregnancy, but whose incidence has increased in recent years in relation to assisted reproduction techniques. Accurate early diagnosis is needed in order to minimize the possible complications that can occur (metrorrhagia, hemoperitoneum, uterine rupture,..). We have different diagnostic and treatment options that will be reviewed in this paper and we will choose based on the individual characteristics of each patient (AU)

Oxigenoterapia / Oxygen therapy

Oxígeno es la única droga en el manejo de pacientes con la enfermedad pulmonar obstructiva crónica que podría prolongar la vida. Es esencial que sepamos las indicaciones para administrarla, los efectos adversos, y como se debe prescribirla en una forma correcta dependiendo del contexto clínico en que se encuentra. Este artículo describe las indicaciones y el uso de oxígeno como una droga crítica en el contexto más grande de reanimación respiratoria.

Toxoplasmosis cerebral

Presentamos una revisión de la literatura sobre la toxoplasmosis en general y principalmente los efectos a nivel del sistema nervioso central, a propósito del caso de un paciente diagnosticado y tratado en nuestro hospital, se describe el caso clínico, estudios complementarios, para relievar el cuadro polimorfo de presentación y que puede confundir con otras afecciones del sistema nervioso central.

Sepsis por leptospira: a propósito de un caso / Sepsis by leptospira: to proposito of a case

Analiza que las manifestaciones clínicas de leptospirosis son usualmente benignas. Se presenta el caso clínico de un paciente joven, sin antecedentes de vivir en una zona epidemiológicamente relacionada con esta patología, quien desarrollo sépsis y fallo multiorgánico secundario a infección por leptospira. Se incluye una revisión bibliográfica acerca de esta entidad patológica.