RESUMEN
The immune state of wild animals is largely unknown. Knowing this and what affects it is important in understanding how infection and disease affects wild animals. The immune state of wild animals is also important in understanding the biology of their pathogens, which is directly relevant to explaining pathogen spillover among species, including to humans. The paucity of knowledge about wild animals' immune state is in stark contrast to our exquisitely detailed understanding of the immunobiology of laboratory animals. Making an immune response is costly, and many factors (such as age, sex, infection status, and body condition) have individually been shown to constrain or promote immune responses. But, whether or not these factors affect immune responses and immune state in wild animals, their relative importance, and how they interact (or do not) are unknown. Here, we have investigated the immune ecology of wild house mice-the same species as the laboratory mouse-as an example of a wild mammal, characterising their adaptive humoral, adaptive cellular, and innate immune state. Firstly, we show how immune variation is structured among mouse populations, finding that there can be extensive immune discordance among neighbouring populations. Secondly, we identify the principal factors that underlie the immunological differences among mice, showing that body condition promotes and age constrains individuals' immune state, while factors such as microparasite infection and season are comparatively unimportant. By applying a multifactorial analysis to an immune system-wide analysis, our results bring a new and unified understanding of the immunobiology of a wild mammal.
Asunto(s)
Inmunidad Adaptativa , Infestaciones por Pulgas/inmunología , Inmunidad Humoral , Inmunidad Innata , Infecciones por Nematodos/inmunología , Infestaciones por Garrapatas/inmunología , Animales , Animales Salvajes , Variación Biológica Poblacional/inmunología , Células Dendríticas/citología , Células Dendríticas/inmunología , Ecología , Femenino , Infestaciones por Pulgas/parasitología , Variación Genética/inmunología , Interacciones Huésped-Parásitos/inmunología , Linfocitos/clasificación , Linfocitos/citología , Linfocitos/inmunología , Masculino , Ratones , Análisis Multivariante , Infecciones por Nematodos/parasitología , Estaciones del Año , Infestaciones por Garrapatas/parasitología , Reino UnidoRESUMEN
The resolution of malaria infection is dependent on a balance between proinflammatory and regulatory immune responses. While early effector T cell responses are required for limiting parasitemia, these responses need to be switched off by regulatory mechanisms in a timely manner to avoid immune-mediated tissue damage. Interleukin-10 receptor (IL-10R) signaling is considered to be a vital component of regulatory responses, although its role in host resistance to severe immune pathology during acute malaria infections is not fully understood. In this study, we have determined the contribution of IL-10R signaling to the regulation of immune responses during Plasmodium berghei ANKA-induced experimental cerebral malaria (ECM). We show that antibody-mediated blockade of the IL-10R during P. berghei ANKA infection in ECM-resistant BALB/c mice leads to amplified T cell activation, higher serum gamma interferon (IFN-γ) concentrations, enhanced intravascular accumulation of both parasitized red blood cells and CD8+ T cells to the brain, and an increased incidence of ECM. Importantly, the pathogenic effects of IL-10R blockade during P. berghei ANKA infection were reversible by depletion of T cells and neutralization of IFN-γ. Our findings underscore the importance of IL-10R signaling in preventing T-cell- and cytokine-mediated pathology during potentially lethal malaria infections.
Asunto(s)
Linfocitos T CD8-positivos/inmunología , Interferón gamma/sangre , Malaria Cerebral/inmunología , Plasmodium berghei/inmunología , Receptores de Interleucina-10/inmunología , Animales , Anticuerpos Bloqueadores/administración & dosificación , Anticuerpos Neutralizantes/administración & dosificación , Encéfalo/patología , Linfocitos T CD8-positivos/efectos de los fármacos , Eritrocitos/efectos de los fármacos , Eritrocitos/parasitología , Femenino , Hígado/patología , Activación de Linfocitos/inmunología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Parasitemia/inmunología , Receptores de Interleucina-10/antagonistas & inhibidores , Transducción de SeñalRESUMEN
It is well established that IFN-γ is required for the development of experimental cerebral malaria (ECM) during Plasmodium berghei ANKA infection of C57BL/6 mice. However, the temporal and tissue-specific cellular sources of IFN-γ during P. berghei ANKA infection have not been investigated, and it is not known whether IFN-γ production by a single cell type in isolation can induce cerebral pathology. In this study, using IFN-γ reporter mice, we show that NK cells dominate the IFN-γ response during the early stages of infection in the brain, but not in the spleen, before being replaced by CD4(+) and CD8(+) T cells. Importantly, we demonstrate that IFN-γ-producing CD4(+) T cells, but not innate or CD8(+) T cells, can promote the development of ECM in normally resistant IFN-γ(-/-) mice infected with P. berghei ANKA. Adoptively transferred wild-type CD4(+) T cells accumulate within the spleen, lung, and brain of IFN-γ(-/-) mice and induce ECM through active IFN-γ secretion, which increases the accumulation of endogenous IFN-γ(-/-) CD8(+) T cells within the brain. Depletion of endogenous IFN-γ(-/-) CD8(+) T cells abrogates the ability of wild-type CD4(+) T cells to promote ECM. Finally, we show that IFN-γ production, specifically by CD4(+) T cells, is sufficient to induce expression of CXCL9 and CXCL10 within the brain, providing a mechanistic basis for the enhanced CD8(+) T cell accumulation. To our knowledge, these observations demonstrate, for the first time, the importance of and pathways by which IFN-γ-producing CD4(+) T cells promote the development of ECM during P. berghei ANKA infection.
Asunto(s)
Encéfalo/inmunología , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/patología , Linfocitos T CD8-positivos/inmunología , Movimiento Celular/inmunología , Interferón gamma/biosíntesis , Malaria Cerebral/inmunología , Malaria Cerebral/patología , Traslado Adoptivo , Animales , Encéfalo/parasitología , Encéfalo/patología , Linfocitos T CD4-Positivos/metabolismo , Linfocitos T CD8-positivos/patología , Movimiento Celular/genética , Modelos Animales de Enfermedad , Femenino , Predisposición Genética a la Enfermedad/genética , Inmunidad Innata/genética , Interferón gamma/deficiencia , Interferón gamma/genética , Malaria Cerebral/parasitología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Plasmodium berghei/inmunologíaRESUMEN
RTS,S/AS01, a vaccine targeting pre-erythrocytic stages of Plasmodium falciparum, is undergoing clinical trials. We report an analysis of cellular immune response to component Ags of RTS,S-hepatitis B surface Ag (HBs) and P. falciparum circumsporozoite (CS) protein-among Tanzanian children in a phase IIb RTS,S/AS01(E) trial. RTS,S/AS01 (E) vaccinees make stronger T cell IFN-γ, CD69, and CD25 responses to HBs peptides than do controls, indicating that RTS,S boosts pre-existing HBs responses. T cell CD69 and CD25 responses to CS and CS-specific secreted IL-2 were augmented by RTS,S vaccination. Importantly, more than 50% of peptide-induced IFN-γ(+) lymphocytes were NK cells, and the magnitude of the NK cell CD69 response to HBs peptides correlated with secreted IL-2 concentration. CD69 and CD25 expression and IL-2 secretion may represent sensitive markers of RTS,S-induced, CS-specific T cells. The potential for T cell-derived IL-2 to augment NK cell activation in RTS,S-vaccinated individuals, and the relevance of this for protection, needs to be explored further.
Asunto(s)
Epítopos/inmunología , Interleucina-2/metabolismo , Células Asesinas Naturales/inmunología , Células Asesinas Naturales/metabolismo , Vacunas contra la Malaria/administración & dosificación , Biomarcadores/metabolismo , Células Cultivadas , Humanos , Lactante , Kenia , Células Asesinas Naturales/parasitología , Activación de Linfocitos/inmunología , Vacunas contra la Malaria/inmunología , Plasmodium falciparum/inmunología , Proteínas Protozoarias/administración & dosificación , Proteínas Protozoarias/inmunología , Proteínas Protozoarias/metabolismo , Subgrupos de Linfocitos T/inmunología , Subgrupos de Linfocitos T/metabolismo , Subgrupos de Linfocitos T/parasitología , TanzaníaRESUMEN
The Philippines is a high-incidence country for tuberculosis, with the increasing prevalence of multi- (MDR-TB) and extensively-drug (XDR-TB) resistant Mycobacterium tuberculosis strains posing difficulties to disease control. Understanding the genetic diversity of circulating strains can provide insights into underlying drug resistance mutations and transmission dynamics, thereby assisting the design of diagnostic tools, including those using next generation sequencing (NGS) platforms. By analysing genome sequencing data of 732 isolates from Philippines drug-resistance survey collections spanning from 2011 to 2019, we found that the majority belonged to lineages L1 (531/732; 72.5%) and L4 (European-American; n = 174; 23.8%), with the Manila strain (L1.2.1.2.1) being the most prominent (475/531). Approximately two-thirds of isolates were found to be at least MDR-TB (483/732; 66.0%), and potential XDR-TB genotypic resistance was observed (3/732; 0.4%), highlighting an emerging problem in the country. Genotypic resistance was highly concordant with laboratory drug susceptibility testing. By finding isolates with (near-)identical genomic variation, five major clusters containing a total of 114 isolates were identified: all containing either L1 or L4 isolates with at least MDR-TB resistance and spanning multiple years of collection. Closer inspection of clusters revealed transmission in prisons, some involving isolates with XDR-TB, and mutations linked to third-line drug bedaquiline. We have also identified previously unreported mutations linked to resistance for isoniazid, rifampicin, ethambutol, and fluoroquinolones. Overall, this study provides important insights into the genetic diversity, transmission and circulating drug resistance mutations of M. tuberculosis in the Philippines, thereby informing clinical and surveillance decision-making, which is increasingly using NGS platforms.
Asunto(s)
Antituberculosos , Mutación , Mycobacterium tuberculosis , Tuberculosis Resistente a Múltiples Medicamentos , Secuenciación Completa del Genoma , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/efectos de los fármacos , Mycobacterium tuberculosis/aislamiento & purificación , Filipinas/epidemiología , Humanos , Secuenciación Completa del Genoma/métodos , Tuberculosis Resistente a Múltiples Medicamentos/microbiología , Tuberculosis Resistente a Múltiples Medicamentos/epidemiología , Tuberculosis Resistente a Múltiples Medicamentos/transmisión , Antituberculosos/farmacología , Tuberculosis Extensivamente Resistente a Drogas/microbiología , Tuberculosis Extensivamente Resistente a Drogas/epidemiología , Genoma Bacteriano , Farmacorresistencia Bacteriana Múltiple/genética , Genotipo , Filogenia , Pruebas de Sensibilidad MicrobianaRESUMEN
Immunity to malaria is widely believed to wane in the absence of reinfection, but direct evidence for the presence or absence of durable immunological memory to malaria is limited. Here, we analysed malaria-specific CD4+ T cell responses of individuals living in an area of low malaria transmission in northern Thailand, who had had a documented clinical attack of P. falciparum and/or P. vivax in the past 6 years. CD4+ T cell effector memory (CD45RO+) IFN-γ (24 hours ex vivo restimulation) and cultured IL-10 (6 day secretion into culture supernatant) responses to malaria schizont antigens were detected only in malaria-exposed subjects and were more prominent in subjects with long-lived antibodies or memory B cells specific to malaria antigens. The number of IFN-γ-producing effector memory T cells declined significantly over the 12 months of the study, and with time since last documented malaria infection, with an estimated half life of the response of 3.3 (95% CI 1.9-10.3) years. In sharp contrast, IL-10 responses were sustained for many years after last known malaria infection with no significant decline over at least 6 years. The observations have clear implications for understanding the immunoepidemiology of naturally acquired malaria infections and for malaria vaccine development.
Asunto(s)
Linfocitos T CD4-Positivos/metabolismo , Memoria Inmunológica/fisiología , Interferón gamma/metabolismo , Interleucina-10/metabolismo , Malaria/inmunología , Adulto , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/fisiología , Células Cultivadas , Enfermedades Endémicas , Femenino , Geografía , Humanos , Malaria/epidemiología , Malaria/metabolismo , Masculino , Persona de Mediana Edad , Tailandia/epidemiología , Factores de Tiempo , Adulto JovenRESUMEN
IFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Interferón gamma/inmunología , Activación de Linfocitos/inmunología , Malaria/inmunología , Plasmodium berghei/inmunología , Animales , Movimiento Celular/inmunología , Separación Celular , Citometría de Flujo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The integration of next-generation sequencing into the identification and characterization of resistant and virulent strains as well as the routine surveillance of foodborne pathogens such as Salmonella enterica have not yet been accomplished in the Philippines. This study investigated the antimicrobial profiles, virulence, and susceptibility of the 105 S. enterica isolates from swine and chicken samples obtained from slaughterhouses and public wet markets in Metropolitan Manila using whole-genome sequence analysis. Four predominant serovars were identified in genotypic serotyping, namely, Infantis (26.7%), Anatum (19.1%), Rissen (18.1%), and London (13.3%). Phenotypic antimicrobial resistance (AMR) profiling revealed that 65% of the isolates were resistant to at least one antibiotic, 37% were multidrug resistant (MDR), and 57% were extended-spectrum ß-lactamase producers. Bioinformatic analysis revealed that isolates had resistance genes and plasmids belonging to the Col and Inc plasmid families that confer resistance against tetracycline (64%), sulfonamide (56%), and streptomycin (56%). Further analyses revealed the presence of 155 virulence genes, 42 of which were serovar-specific. The virulence genes primarily code for host immune system modulators, iron acquisition enzyme complexes, host cell invasion proteins, as well as proteins that allow intracellular and intramacrophage survival. This study showed that virulent MDR S. enterica and several phenotypic and genotypic AMR patterns were present in the food chain. It serves as a foundation to understand the current AMR status in the Philippines food chain and to prompt the creation of preventative measures and efficient treatments against foodborne pathogens.
RESUMEN
Resistance to several prevalent infectious diseases requires both cellular and humoral immune responses. T cell immunity is initiated by mature dendritic cells (DCs) in lymphoid organs, whereas humoral responses to most antigens require further collaboration between primed, antigen-specific helper T cells and naive or memory B cells. To determine whether antigens delivered to DCs in lymphoid organs induce T cell help for antibody responses, we targeted a carrier protein, ovalbumin (OVA), to DCs in the presence of a maturation stimulus and assayed for antibodies to a hapten, (4-hydroxy-3-nitrophenyl) acetyl (NP), after boosting with OVA-NP. A single DC-targeted immunization elicited long-lived T cell helper responses to the carrier protein, leading to large numbers of antibody-secreting cells and high titers of high-affinity antihapten immunoglobulin Gs. Small doses of DC-targeted OVA induced higher titers and a broader spectrum of anti-NP antibody isotypes than large doses of OVA in alum adjuvant. Similar results were obtained when the circumsporozoite protein of Plasmodium yoelii was delivered to DCs. We conclude that antigen targeting to DCs combined with a maturation stimulus produces broad-based and long-lived T cell help for humoral immune responses.
Asunto(s)
Formación de Anticuerpos/inmunología , Presentación de Antígeno/inmunología , Linfocitos B/inmunología , Células Dendríticas/inmunología , Linfocitos T/inmunología , Adyuvantes Inmunológicos/administración & dosificación , Compuestos de Alumbre/administración & dosificación , Animales , Formación de Anticuerpos/efectos de los fármacos , Presentación de Antígeno/efectos de los fármacos , Pollos , Haptenos/inmunología , Humanos , Inmunización/métodos , Inmunoglobulina G/inmunología , Memoria Inmunológica/efectos de los fármacos , Memoria Inmunológica/inmunología , Ratones , Ratones Endogámicos BALB C , Ovalbúmina/inmunología , Plasmodium yoelii/inmunología , Proteínas Protozoarias/inmunologíaRESUMEN
There is considerable debate as to the nature of the primary parasite-derived moieties that activate innate pro-inflammatory responses during malaria infection. Microparticles (MPs), which are produced by numerous cell types following vesiculation of the cellular membrane as a consequence of cell death or immune-activation, exert strong pro-inflammatory activity in other disease states. Here we demonstrate that MPs, derived from the plasma of malaria infected mice, but not naive mice, induce potent activation of macrophages in vitro as measured by CD40 up-regulation and TNF production. In vitro, these MPs induced significantly higher levels of macrophage activation than intact infected red blood cells. Immunofluorescence staining revealed that MPs contained significant amounts of parasite material indicating that they are derived primarily from infected red blood cells rather than platelets or endothelial cells. MP driven macrophage activation was completely abolished in the absence of MyD88 and TLR-4 signalling. Similar levels of immunogenic MPs were produced in WT and in TNF(-/-), IFN-gamma(-/-), IL-12(-/-) and RAG-1(-/-) malaria-infected mice, but were not produced in mice injected with LPS, showing that inflammation is not required for the production of MPs during malaria infection. This study therefore establishes parasitized red blood cell-derived MPs as a major inducer of systemic inflammation during malaria infection, raising important questions about their role in severe disease and in the generation of adaptive immune responses.
Asunto(s)
Micropartículas Derivadas de Células/inmunología , Eritrocitos/parasitología , Inflamación/inmunología , Activación de Macrófagos/inmunología , Malaria/inmunología , Animales , Antígenos CD40/inmunología , Separación Celular , Micropartículas Derivadas de Células/parasitología , Micropartículas Derivadas de Células/ultraestructura , Ensayo de Inmunoadsorción Enzimática , Eritrocitos/inmunología , Femenino , Citometría de Flujo , Técnica del Anticuerpo Fluorescente , Interacciones Huésped-Parásitos/inmunología , Inflamación/parasitología , Macrófagos/inmunología , Macrófagos/parasitología , Malaria/parasitología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microscopía Electrónica de Rastreo , Plasmodium berghei/inmunología , Factor de Necrosis Tumoral alfa/inmunologíaRESUMEN
Successful resolution of malaria infection requires induction of proinflammatory immune responses that facilitate parasite clearance; however, failure to regulate this inflammation leads to immune-mediated pathology. The pathways that maintain this immunological balance during malaria infection remain poorly defined. In this study, we demonstrate that IL-27R-deficient (WSX-1(-/-)) mice are highly susceptible to Plasmodium berghei NK65 infection, developing exacerbated Th1-mediated immune responses, which, despite highly efficient parasite clearance, lead directly to severe liver pathology. Depletion of CD4(+) T cells---but not CD8(+) T cells---prevented liver pathology in infected WSX-1(-/-) mice. Although WSX-1 signaling was required for optimal IL-10 production by CD4(+) T cells, administration of rIL-10 failed to ameliorate liver damage in WSX-1(-/-) mice, indicating that additional, IL-10-independent, protective pathways are modulated by IL-27R signaling during malaria infection. These data are the first to demonstrate the essential role of IL-27R signaling in regulating effector T cell function during malaria infection and reveal a novel pathway that might be amenable to manipulation by drugs or vaccines.
Asunto(s)
Malaria/inmunología , Receptores de Citocinas/inmunología , Transducción de Señal/inmunología , Células TH1/inmunología , Animales , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/patología , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/patología , Citocinas/genética , Citocinas/inmunología , Citocinas/metabolismo , Ensayo de Inmunoadsorción Enzimática , Femenino , Citometría de Flujo , Interferón gamma/sangre , Interleucina-10/genética , Interleucina-10/inmunología , Interleucina-17/sangre , Hígado/inmunología , Hígado/parasitología , Hígado/patología , Recuento de Linfocitos , Malaria/sangre , Malaria/parasitología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Parasitemia/sangre , Parasitemia/inmunología , Plasmodium berghei/inmunología , Receptores de Citocinas/genética , Receptores de Citocinas/fisiología , Receptores de Interleucina , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/genética , Transducción de Señal/fisiología , Células TH1/metabolismoRESUMEN
IL-4 receptor (IL-4R)-deficient CD8+ T cells specific for the circumsporozoite protein of Plasmodium yoelii develop a severely impaired memory response after priming with parasites. Memory CD8+ T cells lacking the IL-4R are unable to establish a stable population residing in nonlymphoid organs, although they develop normally in lymphoid organs. Because memory cells from nonlymphoid organs disappear shortly after immunization, the protective antiparasitic activity of this T cell response also is lost. These results demonstrate that IL-4/IL-4R interactions on CD8+ T cells play a critical role in modulating the development and tissue distribution of memory cells induced by parasite immunization. They also indicate that memory cells residing in nonlymphoid tissues are critical for protective immunity against malaria parasites.
Asunto(s)
Inmunidad Celular , Memoria Inmunológica , Malaria/inmunología , Plasmodium yoelii/inmunología , Proteínas Protozoarias/inmunología , Receptores de Interleucina-4/inmunología , Animales , Linfocitos T CD8-positivos , Diferenciación Celular/inmunología , Interleucina-4/inmunología , Malaria/parasitología , Malaria/prevención & control , Vacunas contra la Malaria/inmunología , Ratones , Ratones Endogámicos BALB C , Ratones Transgénicos , Receptores de Interleucina-4/genética , VacunaciónRESUMEN
The immune function of wild animals has been rather little studied. Wild animals' immune function may differ from that of laboratory bred animals because of their different environments. This idea follows from the concept of resource partitioning in which animals distribute scarce resources to all aspects of life, including to costly immune responses. A logical extension of this idea is that there may be substantial interindividual variation in the immune function of wild animals. To begin to investigate this, we compared the immune function of a laboratory bred mouse strain (C57BL/6, a widely used mouse strain that makes potent immune responses) and wild caught Mus musculus. We found that by most measures of immune function, the wild caught mice had greater immune function. Specifically, wild mice had greater concentrations and more avid antigen-specific IgG responses, as well as higher concentrations of total IgG and IgE, compared with those laboratory bred mice. Moreover, flow cytometric analysis showed a comparatively greater overall level of activation of the cells of the immune system in wild mice. Lastly, we observed that immune function was substantially more variable among wild caught mice than among the laboratory bred mice. The next research challenge is to understand which aspects of an individual animal's life determine its immune function.
Asunto(s)
Inmunidad Celular , Inmunidad Humoral , Ratones Endogámicos C57BL/inmunología , Ratones/inmunología , Animales , Animales Salvajes/inmunología , Afinidad de Anticuerpos , Antígenos/inmunología , Femenino , Hemocianinas/inmunología , Inmunoglobulina E/sangre , Inmunoglobulina G/sangre , Leucocitos/inmunología , Masculino , Nematodos , Infecciones por Nematodos/inmunología , Bazo/citología , Bazo/inmunologíaRESUMEN
Plasmodium sporozoites, the infective stage of the malaria parasite transmitted by mosquitoes, migrate through several hepatocytes before infecting a final one. Migration through hepatocytes occurs by breaching their plasma membranes, and final infection takes place with the formation of a vacuole around the sporozoite. Once in the liver, sporozoites have already reached their target cells, making migration through hepatocytes prior to infection seem unnecessary. Here we show that this migration is required for infection of hepatocytes. Migration through host cells, but not passive contact with hepatocytes, induces the exocytosis of sporozoite apical organelles, a prerequisite for infection with formation of a vacuole. Sporozoite activation induced by migration through host cells is an essential step of Plasmodium life cycle.
Asunto(s)
Hepatocitos/parasitología , Plasmodium/fisiología , Animales , Línea Celular , Exocitosis , Ratones , Ratones Endogámicos BALB CRESUMEN
CD4+ T cells are crucial to the development of CD8+ T cell responses against hepatocytes infected with malaria parasites. In the absence of CD4+ T cells, CD8+ T cells initiate a seemingly normal differentiation and proliferation during the first few days after immunization. However, this response fails to develop further and is reduced by more than 90%, compared to that observed in the presence of CD4+ T cells. We report here that interleukin-4 (IL-4) secreted by CD4+ T cells is essential to the full development of this CD8+ T cell response. This is the first demonstration that IL-4 is a mediator of CD4/CD8 cross-talk leading to the development of immunity against an infectious pathogen.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Interleucina-4/metabolismo , Malaria/inmunología , Animales , Antígenos CD4/inmunología , Linfocitos T CD4-Positivos/citología , Linfocitos T CD8-positivos/citología , Diferenciación Celular/inmunología , Hepatocitos/inmunología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Plasmodium yoeliiRESUMEN
Despite many decades of research to develop a malaria vaccine, only one vaccine candidate has been explored in pivotal phase III clinical trials. This candidate subunit vaccine consists of a portion of a single Plasmodium antigen, circumsporozoite protein (CSP). This antigen was initially identified in the murine malaria model and shown to contain an immunodominant and protective CD8+ T cell epitope specific to the H-2K d (BALB/c)-restricted genetic background. A high-content screen for CD8+ epitopes in the H2K b /D b (C57BL/6)-restricted genetic background, identified two distinct dominant epitopes. In this study, we present a characterization of one corresponding antigen, the Plasmodium sporozoite-specific protein S20. Plasmodium berghei S20 knockout sporozoites and liver stages developed normally in vitro and in vivo. This potent infectivity of s20(-) sporozoites permitted comparative analysis of knockout and wild-type parasites in cell-based vaccination. Protective immunity of irradiation-arrested s20(-) sporozoites in single, double and triple immunizations was similar to irradiated unaltered sporozoites in homologous challenge experiments. These findings demonstrate the presence of an immunogenic Plasmodium pre-erythrocytic determinant, which is not essential for eliciting protection. Although S20 is not needed for colonization of the mammalian host and for initiation of a blood infection, it is conserved amongst Plasmodium species. Malarial parasites express conserved, immunogenic proteins that are not required to establish infection but might play potential roles in diverting cellular immune responses.
RESUMEN
The outcome of malaria infection is determined, in part, by the balance of pro-inflammatory and regulatory immune responses. Failure to develop an effective pro-inflammatory response can lead to unrestricted parasite replication, whilst failure to regulate this response leads to the development of severe immunopathology. IL-10 and TGF-beta are known to be important components of the regulatory response, but the cellular source of these cytokines is still unknown. Here we have examined the role of natural and adaptive regulatory T cells in the control of malaria infection and find that classical CD4+CD25(hi) (and Foxp3+) regulatory T cells do not significantly influence the outcome of infections with the lethal (17XL) strain of Plasmodium yoelii (PyL). In contrast, we find that adaptive IL-10-producing, CD4+ T cells (which are CD25-, Foxp3-, and CD127- and do not produce Th1, Th2, or Th17 associated cytokines) that are generated during both PyL and non-lethal P. yoelii 17X (PyNL) infections are able to down-regulate pro-inflammatory responses and impede parasite clearance. In summary, we have identified a population of induced Foxp3- regulatory (Tr1) T cells, characterised by production of IL-10 and down regulation of IL-7Ralpha, that modulates the inflammatory response to malaria.
Asunto(s)
Antígenos CD4/metabolismo , Factores de Transcripción Forkhead/metabolismo , Interleucina-10/metabolismo , Subunidad alfa del Receptor de Interleucina-2/metabolismo , Subunidad alfa del Receptor de Interleucina-7/metabolismo , Malaria/inmunología , Plasmodium yoelii/inmunología , Linfocitos T Reguladores/inmunología , Animales , Citocinas/metabolismo , Modelos Animales de Enfermedad , Regulación hacia Abajo , Interacciones Huésped-Parásitos , Malaria/parasitología , Ratones , Plasmodium yoelii/patogenicidad , Ratas , Receptores de Interleucina-7/metabolismoRESUMEN
Cerebral malaria is a life-threatening complication of malaria infection. The pathogenesis of cerebral malaria is poorly defined and progress in understanding the condition is severely hampered by the inability to study in detail, ante-mortem, the parasitological and immunological events within the brain that lead to the onset of clinical symptoms. Experimental murine models have been used to investigate the sequence of events that lead to cerebral malaria, but there is significant debate on the merits of these models and whether their study is relevant to human disease. Here we review the current understanding of the parasitological and immunological events leading to human and experimental cerebral malaria, and explain why we believe that studies with experimental models of CM are crucial to define the pathogenesis of the condition.
Asunto(s)
Encéfalo/parasitología , Modelos Animales de Enfermedad , Eritrocitos/parasitología , Malaria Cerebral/parasitología , Plasmodium/crecimiento & desarrollo , Animales , Encéfalo/inmunología , Eritrocitos/inmunología , Humanos , Malaria Cerebral/inmunología , RatonesRESUMEN
BACKGROUND: Human ovale malaria is caused by the two closely related species, Plasmodium ovale curtisi and P. ovale wallikeri. Both species are known to relapse from quiescent hepatic forms months or years after the primary infection occurred. Although some studies have succeeded in establishing mosquito transmission for ovale malaria, none have specifically described transmission and human hepatocyte infection of both sibling species. METHODS: Here we describe a simplified protocol for successful transmission of both P. ovale curtisi and P. ovale wallikeri to Anopheles coluzzii mosquitoes and streamlined monitoring of infection using sensitive parasite DNA detection, by loop-activated amplification, in blood-fed mosquitoes. RESULTS: In one experimental infection with P. ovale curtisi and one with P. ovale wallikeri, viable sporozoites were isolated from mosquito salivary glands and used to successfully infect cultured human hepatocytes. CONCLUSIONS: This protocol provides a method for the utilisation of pretreatment clinical blood samples from ovale malaria patients, collected in EDTA, for mosquito infection studies and generation of the hepatic life cycle stages of P. ovale curtisi and P. ovale wallikeri. We also demonstrate the utility of loop-activated amplification as a rapid and sensitive alternative to dissection for estimating the prevalence of infection in Anopheles mosquitoes fed with Plasmodium-infected blood.
Asunto(s)
Anopheles/parasitología , Hepatocitos/parasitología , Malaria/transmisión , Plasmodium ovale , Animales , Línea Celular , ADN Protozoario , Femenino , Humanos , Estadios del Ciclo de Vida , Malaria/parasitología , Técnicas de Diagnóstico Molecular , Técnicas de Amplificación de Ácido Nucleico , Plasmodium ovale/fisiología , Esporozoítos/fisiologíaRESUMEN
The Philippines has a high incidence of tuberculosis disease (TB), with an increasing prevalence of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) strains making its control difficult. Although the M. tuberculosis "Manila" ancient lineage 1 strain-type is thought to be prevalent in the country, with evidence of export to others, little is known about the genetic diversity of circulating strains. By whole genome sequencing (WGS) 178 isolates from the Philippines National Drug Resistance Survey, we found the majority (143/178; 80.3%) belonged to the lineage 1 Manila clade, with the minority belonging to lineages 4 (European-American; n = 33) and 2 (East Asian; n = 2). A high proportion were found to be multidrug-resistant (34/178; 19.1%), established through highly concordant laboratory drug susceptibility testing and in silico prediction methods. Some MDR-TB isolates had near identical genomic variation, providing potential evidence of transmission. By placing the Philippine isolates within a phylogeny of global M. tuberculosis (n > 17,000), we established that they are genetically similar to those observed outside the country, including a clade of Manila-like strain-types in Thailand. An analysis of the phylogeny revealed a set of ~200 SNPs that are specific for the Manila strain-type, and a subset can be used within a molecular barcode. Sixty-eight mutations known to be associated with 10 anti-TB drug resistance were identified in the Philippine strains, and all have been observed in other populations. Whilst nine putative streptomycin resistance conferring markers in gid (8) and rrs (1) genes appear to be novel and with functional consequences. Overall, this study provides an important baseline characterisation of M. tuberculosis genetic diversity for the Philippines, and will fill a gap in global datasets and aid the development of a nation-wide database for epidemiological studies and clinical decision making. Further, by establishing a molecular barcode for detecting Manila strains it will assist with the design of diagnostic tools for disease control activities.