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In this study, we assessed the potential synergistic effect of the Erns RNase activity and the poly-U insertion in the 3′ untranslated region (UTR) of the low-virulence classical swine fever virus (CSFV) isolate Pinar de Rio (PdR) in innate and adaptive immunity regulation and its relationship with classical swine fever (CSF) pathogenesis in pigs. We knocked out the Erns RNase activity of PdR and replaced the long polyuridine sequence of the 3′ UTR with 5 uridines found typically at this position, resulting in a double mutant, vPdR-H30K-5U. This mutant induced severe CSF in 5-day-old piglets and 3-week-old pigs, with higher lethality in the newborn (89.5%) than in the older (33.3%) pigs. However, the viremia and viral excretion were surprisingly low, while the virus load was high in the tonsils. Only alpha interferon (IFN-α) and interleukin 12 (IL-12) were highly and consistently elevated in the two groups. Additionally, high IL-8 levels were found in the newborn but not in the older pigs. This points toward a role of these cytokines in the CSF outcome, with age-related differences. The disproportional activation of innate immunity might limit systemic viral spread from the tonsils and increase virus clearance, inducing strong cytokine-mediated symptoms. Infection with vPdR-H30K-5U resulted in poor neutralizing antibody responses compared with results obtained previously with the parent and RNase knockout PdR. This study shows for the first time the synergistic effect of the 3′ UTR and the Erns RNase function in regulating innate immunity against CSFV, favoring virus replication in target tissue and thus contributing to disease severity. IMPORTANCE CSF is one of the most relevant viral epizootic diseases of swine, with high economic and sanitary impact. Systematic stamping out of infected herds with and without vaccination has permitted regional virus eradication. However, the causative agent, CSFV, persists in certain areas of the world, leading to disease reemergence. Nowadays, low- and moderate-virulence strains that could induce unapparent CSF forms are prevalent, posing a challenge for disease eradication. Here, we show for the first time the synergistic role of lacking the Erns RNase activity and the 3′ UTR polyuridine insertion from a low-virulence CSFV isolate in innate immunity disproportional activation. This might limit systemic viral spread to the tonsils and increase virus clearance, inducing strong cytokine-mediated symptoms, thus contributing to disease severity. These results highlight the role played by the Erns RNase activity and the 3′ UTR in CSFV pathogenesis, providing new perspectives for novel diagnostic tools and vaccine strategies. info:eu-repo/semantics/publishedVersion

Numerous pathogens can affect cellular homeostasis and organelle dynamics. Hepatitis C virus (HCV) triggers Golgi fragmentation through the immunity-related GTPase M (IRGM), a resident Golgi protein, to enhance its lipid supply for replication., Hepatitis C virus (HCV) infection triggers Golgi fragmentation through the Golgi-resident protein immunity-related GTPase M (IRGM). Here, we report the roles of NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) and ASC (apoptosis-associated speck-like protein containing a caspase activation and recruitment domain [CARD]), two inflammasome components, in the initial events leading to this fragmentation. We show that ASC resides at the Golgi with IRGM at homeostasis. Upon infection, ASC dissociates from both IRGM and the Golgi and associates with HCV-induced NLRP3. NLRP3 silencing inhibits Golgi fragmentation. ASC silencing disrupts the Golgi structure in both control and infected cells and reduces the localization of IRGM at the Golgi. IRGM depletion in the ASC-silenced cells cannot totally restore the Golgi structure. These data highlight a role for ASC, upstream of the formation of the inflammasome, in regulating IRGM through its control on the Golgi. A similar mechanism occurs in response to nigericin treatment, but not in cells infected with another member of the Flaviviridae family, Zika virus (ZIKV). We propose a model for a newly ascribed function of the inflammasome components in Golgi structural remodeling during certain stimuli. IMPORTANCE Numerous pathogens can affect cellular homeostasis and organelle dynamics. Hepatitis C virus (HCV) triggers Golgi fragmentation through the immunity-related GTPase M (IRGM), a resident Golgi protein, to enhance its lipid supply for replication. Here, we reveal the role of the inflammasome components NLRP3 and ASC in this process, thus uncovering a new interplay between effectors of inflammation and viral infection or stress. We show that the inflammasome component ASC resides at the Golgi under homeostasis and associates with IRGM. Upon HCV infection, ASC is recruited to NLRP3 and dissociates from IRGM, causing Golgi fragmentation. Our results uncover that aside from their known function in the inflammation response, these host defense regulators also ensure the maintenance of intact intracellular structure in homeostasis, while their activation relieves factors leading to Golgi remodeling.

La peste porcina clásica (PPC) es una enfermedad viral altamente contagiosa de cerdos domésticos y salvajes, incluida en la lista de enfermedades de declaración obligatoria a la Organización Mundial de Sanidad Animal. El agente causal, el virus PPC (VPPC), pertenece al género Pestivirus, familia Flaviviridae. A pesar de los grandes esfuerzos dirigidos a controlar y erradicar la PPC, continúa siendo una de las enfermedades más importantes para la sanidad animal y la industria porcina en todo el mundo. La circulación y la importancia intrínseca de cepas de VPPC de baja y moderada virulencia en las regiones endémicas ha sido objeto de discusión en los últimos años. Varios trabajos han demostrado el papel de cepas de baja virulencia en el nacimiento de lechones persistentemente infectados (PI) con el VPPC. No obstante, los mecanismos involucrados en este tipo de infecciones por VPPC no son bien conocidos, y los estudios existentes datan de hace 40 años. Por otro lado, la posible generación de persistencia viral después de la infección postnatal con VPPC era todavía una cuestión a resolver. Esta tesis demuestra la capacidad de cepas de VPPC de baja y moderada virulencia de inducir persistencia vírica de forma postnatal en cerdo doméstico y salvaje. Para ello, cerditos recién nacidos fueron inoculados de forma intranasal con el VPPC. Durante seis semanas, estos lechones permanecieron aparentemente sanos, a pesar de no generar respuesta inmunológica celular ni humoral específica para VPPC. Se demostró viremia permanente y alta carga de virus en todas las muestras de tejido, secreciones y excreciones de los animales persistentemente infectados (PI), hasta el fin del estudio. Además, se demostró la ineficacia de la vacunación de cerdos PI, de seis semanas de edad, los cuales no generaron respuesta de IFN de tipo I ni de tipo II, ni de anticuerpos durante 21 días tras la vacunación con una vacuna viva atenuada de VPPC (la C-strain). La falta de detección del ARN vacunal mediante RT-qPCR específica en sangre, excreciones y tejidos, incluyendo la tonsila, sugirió la ausencia de replicación del virus vacunal en los animales PI y un posible fenómeno de interferencia viral. Finalmente, jabalíes de seis semanas de vida con infección persistente de VPPC (primera infección) fueron inoculados con una cepa de alta virulencia de VPPC (segunda infección o superinfección). Los jabalíes PI no desarrollaron signos clínicos y mostraron alta carga del virus primario, causante de la persistencia, en todas las muestras analizadas. Por el contrario, el virus secundario no fue detectado ni por RT-qPCR ni por secuenciación, demostrando así el fenómeno de exclusión de la superinfección (ESI). La ausencia de una respuesta de IFN de tipo I y II y de anticuerpos respaldó los resultados previos de los estudios de esta tesis. Estos hallazgos demostraron por primera vez la capacidad del VPPC para inducir ESI in vivo, en cerdos con infección persistente. El fenómeno ESI probablemente explicaría la falta de respuesta de los animales con infección persistente después de la vacunación con la vacuna viva atenuada. Considerando la existencia de cepas de virulencia baja a moderada y su capacidad para producir formas de infección persistente, los resultados aquí presentados pueden tener potenciales repercusiones epidemiológicas, especialmente en el contexto endémico. Es importante destacar que los animales persistentemente infectados pasarían desapercibidos bajo control serológico, dada la ausencia de respuesta de anticuerpos específicos. Esta tesis doctoral ha contribuido a la comprensión de la patogénesis producida por el VPPC, que depende no sólo de la virulencia de la cepa sino también de la interacción virus-huésped, y abre nuevas líneas de investigación para comprender los mecanismos subyacentes que conducen a la generación de inmunotolerancia y persistencia del VPPC., Classical swine fever (CSF) is a highly contagious viral disease of domestic and wild pigs, included in the list of diseases notifiable to the World Organisation for Animal Health. The causative agent, CSF virus (CSFV), belongs to the Pestivirus genus, Flaviviridae family. Over the last century, great efforts have been directed towards the control and eradication of CSF, which today remains one of the most important diseases for animal health and in the pig industry worldwide. The circulation and intrinsic importance of low and moderate virulence strains in the endemic regions has been extensively described. Also, it has been shown the role of these type of viral strains in the generation of “the pregnant carrier sow syndrome” and persistent infection of piglets after trans-placental transmission. However, the mechanisms involved in this form of CSFV infections are not well known, and the existing studies date over 40 years ago. By contrast, the possible generation of viral persistence after postnatal infection of pigs is still a question to resolve. Against this background, this thesis has demonstrated the capacity of low and moderate virulence CSFV strains to produce postnatal persistent infection early after birth. To this end, newborn piglets were inoculated intranasally with CSFV. During six weeks, these piglets remained apparently healthy, although they were not able to generate detectable CSFV specific humoral nor cellular immune responses, maintaining high virus load in blood, organs and body secretions and excretions. In addition, it has been demonstrated the ineffectiveness of vaccination of six-week-old PI pigs, which were unable to elicit a detectable innate immune response, in terms of IFN type-I production, as well as acquired immune responses (i.e. IFN type-II and antibodies) following vaccination with a CSFV live attenuated vaccine (C-strain). The RNA of the vaccine could not be detected by a specific RT-qPCR in any of the samples analysed after vaccination, including the tonsil, suggesting a superinfection exclusion (SIE) phenomenon between the persistently infecting virus (primary infection) and the CSFV vaccine strain (secondary infection). Finally, six-week-old wild boars with CSFV persistent infection (first infection) were inoculated with a CSFV strain of high virulence (second infection or superinfection). PI wild boars did not develop clinical signs and showed a high load of the primary virus, causing persistence, in all samples analysed. In contrast, the secondary virus was not detected by either RT-qPCR or sequence analyses, thus demonstrating the phenomenon of superinfection exclusion (SIE). The lack of innate and acquired immune responses supported the previous studies from this thesis. In addition, in vitro assays with the PBMCs isolated ex vivo from persistently infected animals, a well-known target for the CSFV viral replication, further corroborated the CSFV SIE phenomenon. These findings demonstrated for the first time the ability of CSFV to induce SIE in vivo, in swine with persistent infection. The SIE phenomenon would likely explain the unresponsiveness of animals with persistent infection after vaccination with the live attenuated vaccine. Considering the existence of CSFV strains of low and moderate virulence and their ability to produce persistent infection forms, the results showed here may have potential epidemiological repercussions, especially in the endemic context. Importantly, persistently infected animals would remain unnoticed under serological control, given the absence of specific antibody response. This doctoral thesis has contributed to the understanding of the pathogenesis of CSFV infection, which depends not only on the virulence of the strain but also on the virus-host interaction, and opens new lines of research to understand the immunological bases and of viral pathogenesis for the generation of immunotolerance and persistence, hitherto unknown.

Proyecto Fin de Grado-Universidad Pontificia de Salamanca, Facultad de Ciencias Humanas y Sociales, 2012, Las rutinas infantiles se fundamentan en la vida cotidiana como fuente de aprendizaje diario y continuo. La vida cotidiana es el soporte del aprendizaje de las acciones cotidianas y de las rutinas, inevitables para el bienestar y referencia de los niños/as. La vida cotidiana ha de estar estructurada espacial y temporalmente ya que el entorno resulta ser, en definitiva, el medio en el que los escolares desarrollan su actividad, la cual es esencialmente lúdica. Lo que se pretende al organizar de esta manera su día a día es que el alumno desarrolle habilidades y estrategias necesarias y que sea capaz de regular su propia actividad. Se muestra aquí un programa que bien podría utilizarse en cualquier aula de infantil.

Classical swine fever (CSF) causes major losses in pig farming, with various degrees of disease severity. Efficient live attenuated vaccines against classical swine fever virus (CSFV) are used routinely in endemic countries. However, despite intensive vaccination programs in these areas for more than 20 years, CSF has not been eradicated. Molecular epidemiology studies in these regions suggests that the virus circulating in the field has evolved under the positive selection pressure exerted by the immune response to the vaccine, leading to new attenuated viral variants. Recent work by our group demonstrated that a high proportion of persistently infected piglets can be generated by early postnatal infection with low and moderately virulent CSFV strains. Here, we studied the immune response to a hog cholera lapinised virus vaccine (HCLV), C-strain, in six-week-old persistently infected pigs following post-natal infection. CSFV-negative pigs were vaccinated as controls. The humoral and interferon gamma responses as well as the CSFV RNA loads were monitored for 21 days post-vaccination. No vaccine viral RNA was detected in the serum samples and tonsils from CSFV postnatally persistently infected pigs for 21 days post-vaccination. Furthermore, no E2-specific antibody response or neutralising antibody titres were shown in CSFV persistently infected vaccinated animals. Likewise, no of IFN-gamma producing cell response against CSFV or PHA was observed. To our knowledge, this is the first report demonstrating the absence of a response to vaccination in CSFV persistently infected pigs.

Zika virus (ZIKV) infection can cause developmental and neurological defects and represents a threat for human health. Type I/III interferon responses control ZIKV infection and pathological processes, yet the virus has evolved various mechanisms to defeat these host responses. Here, we established a pipeline to delineate at high-resolution the genetic evolution of ZIKV in a controlled host cell environment. We uncovered that serially passaged ZIKV acquired increased infectivity, defined as the probability for one virus to initiate infection, and simultaneously developed a resistance to TLR3-induced restriction. We built a mathematical model that suggests that the increased infectivity is due to a reduced time-lag between infection and viral replication. We found that this adaptation is cell-type specific, suggesting that different cell environments may drive viral evolution along different routes. Deep-sequencing of ZIKV quasi-species pinpointed mutations whose increased frequencies temporally coincide with the acquisition of the adapted phenotype. We functionally validated a point-mutation in ZIKV envelope (E) protein recapitulating the adapted phenotype. Its positioning on the E structure suggests a putative function in protein refolding/stability. Altogether, our results uncovered ZIKV adaptations to the cell environment leading to an accelerated replication onset coupled with resistance to TLR3-induced antiviral response. Our work provides insights into viral escape mechanisms and interactions with host cell and can serve as a framework to study other viruses.