Immunologic hypo- or non-responder in natural dengue virus infection

Inapparent dengue virus infection among students in Mandalay, Myanmar

BACKGROUND

A school- and laboratory-based cross-sectional descriptive study was conducted to find out the burden of inapparent dengue virus (DENV) infection in Mandalay where DENV is endemic and there is circulation of all four DENV serotypes.

METHODS

A total of 420 students who had no history of fever and visited the hospital within 6 months were recruited from three monastic schools. Serum samples were collected and the DENV genome was checked by conventional one-step RT-PCR and anti-DENV IgM and IgG antibodies were determined. Inapparent dengue (DEN) infection is defined as individuals who were either RT-PCR-positive or anti-DENV IgM-positive with no clinical manifestations or mild symptoms, and which are not linked to a visit to a healthcare provider.

RESULTS

Among 420 students, 38 students (9.0%, 95% CI, 6.4 to 12.2) were confirmed as recent inapparent DEN infection. The DENV serotype-1 was detected in six students. Thirty-one out of 38 (81.6%) laboratory-confirmed inapparent DEN-infected students had primary infections and seven (18.4%) had secondary infections.

CONCLUSION

This study explored the prevalence of inapparent DEN infection rate in urban monastic schools in Mandalay and showed that the rate of primary infection among inapparent DENV-infected children was high.

Use of Animal Models in Studying Roles of Antibodies and Their Secretion Cells in Dengue Vaccine Development

The cardinal feature of adaptive immunity is its ability to form memory responses that can be rapidly recalled to contain pathogens upon reencountering. Conferring a robust memory immune response to an infection is a key feature for a successful vaccination program. The plasmablasts are cells that not only can secret non-neutralizing antibodies but also can secrete the specific antibodies essential to neutralize and inactivate the invading pathogens. Dengue has been recognized as one of the most important vector-borne human viral diseases globally. Currently, supportive care with vigilant monitoring is the standard practice since there is as yet no approved therapeutic modality to treat dengue. Even though the approved vaccine has become available, its low efficacy with the potential to cause harm is the major hurdle to promote the widespread usage of the vaccine. Despite the decades of research on dengue, the major challenge in dengue vaccine development is the absence of suitable experimental animal models that reflect the pathological features and clinical symptoms, as seen in humans. Dengue is transmitted by the bite of mosquitoes carrying infectious dengue virus (DENV), which has four distinct serotypes. Recently, cases resulting from unconventional transmission routes, such as blood transfusion, organs as well as stem cells and bone marrow transplantations, and mother-to-infant vertical transmission, have been reported, suggesting an alternate route of DENV transmission exists in nature. This review discusses issues and challenges needing to be resolved to develop an effective dengue vaccine. Development of a robust and reliable dengue animal model that can reflect not only dynamic human clinical symptoms but also can answer around why preexisting neutralizing antibodies do not confer protection upon re-infection and immune protection marker for dengue vaccine efficacy evaluation.

[Dengue fever : Symptoms, epidemiology, entomology, pathogen diagnosis and prevention]

Dengueinfektionen gehören zu den häufigsten Ursachen fieberhafter Erkrankungen im tropischen Umfeld. Die Infektion wird durch ein Flavivirus verursacht, das durch Aedes-Moskitos übertragen wird. Hauptüberträger für Dengueviren sind die weltweit in den Tropen verbreiteten Aedes-aegypti-Stechmücken. Da diese einerseits tagaktiv und andererseits sog. „container breeder“ sind, bedarf es besonderer Vorbeugungs- und Bekämpfungsmaßnahmen. Die Schwere der Symptomatik variiert und kann vom milden grippeähnlichen klinischen Bild bis hin zu schweren Hämorrhagien und Schock reichen. Zu den häufigsten Symptomen bei Reisenden gehören Fieber, Muskelschmerzen, Kopfschmerzen und Hautausschlag. Zur Diagnostik kommen, in Abhängigkeit vom Stadium der Infektion, patientennah einsetzbare Schnellteste oder – in der virämischen Phase – molekulare Erregerdirektnachweise infrage. Die serologische Diagnostik ist aufgrund von serologischen Kreuzreaktionen mit anderen Flaviviren hinsichtlich ihrer Interpretation anspruchsvoll.

Is Empirical Research on Periodization Trustworthy? A Comprehensive Review of Conceptual and Methodological Issues

Periodization is a core concept in training. Recently, systematic reviews and meta-analyses have attempted to provide a comprehensive overview of the topic, but theoretical criticisms have arisen with regard to how such research has been conducted. The purpose of the study was to review comprehensively the conceptual and methodological issues surrounding empirical research on periodization in training with human subjects. A search was conducted late in February 2016 on Academic Search Complete, CINAHL Plus, MedicLatina, MEDLINE, PsycINFO, PubMed, Scielo, Scopus, SPORTDiscus and Web of Science. Forty-two randomized or randomized controlled trials were retrieved. Problems emerged in three domains: (a) Conceptually, periodization and variation were applied differently in research, while no empirical research tested predictions concerning direction, timing or magnitude of the adaptations; (b) Study design: More than 95% of papers investigated the 'physical' factor (mainly strength). Research on long-term effects was absent (no study lasted more than nine months). Controlling for confounding factors such as nutrition, supplementation and medication was largely ignored; (c) Data analysis was biased as dispersion in responsiveness was ignored when discussing the findings. Overall, research on periodization fails to analyze the conceptual premises proposed by these approaches.

Biomarkers of severe dengue disease - a review

Dengue virus infection presents a wide spectrum of manifestations including asymptomatic condition, dengue fever (DF), or severe forms, such as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) in affected individuals. The early prediction of severe dengue in patients without any warning signs who may later develop severe DHF is very important to choose appropriate intensive supportive therapy since available vaccines for immunization are yet to be approved. Severe dengue responses include T and B cell activation and apoptosis, cytokine storm, hematologic disorders and complement activation. Cytokines, complement and other unidentified factors may transiently act on the endothelium and alter normal fluid barrier function of the endothelial cells and cause plasma leakage. In this review, the host factors such as activated immune and endothelial cells and their products which can be utilized as biomarkers for severe dengue disease are discussed.

Role of cognitive parameters in dengue hemorrhagic fever and dengue shock syndrome

Dengue is becoming recognized as one of the most important vector-borne human diseases. It is predominant in tropical and subtropical zones but its geographical distribution is progressively expanding, making it an escalating global health problem of today. Dengue presents with spectrum of clinical manifestations, ranging from asymptomatic, undifferentiated mild fever, dengue fever (DF), to dengue hemorrhagic fever (DHF) with or without shock (DSS), a life-threatening illness characterized by plasma leakage due to increased vascular permeability. Currently, there are no antiviral modalities or vaccines available to treat and prevent dengue. Supportive care with close monitoring is the standard clinical practice. The mechanisms leading to DHF/DSS remains poorly understood. Multiple factors have been attributed to the pathological mechanism, but only a couple of these hypotheses are popular in scientific circles. The current discussion focuses on underappreciated factors, temperature, natural IgM, and endotoxin, which may be critical components playing roles in dengue pathogenesis.

Can non-human primates serve as models for investigating dengue disease pathogenesis?

Dengue Virus (DV) infects between 50 and 100 million people globally, with public health costs totaling in the billions. It is the causative agent of dengue fever (DF) and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), vector-borne diseases that initially predominated in the tropics. Due to the expansion of its mosquito vector, Aedes spp., DV is increasingly becoming a global problem. Infected individuals may present with a wide spectrum of symptoms, spanning from a mild febrile to a life-threatening illness, which may include thrombocytopenia, leucopenia, hepatomegaly, hemorrhaging, plasma leakage and shock. Deciphering the underlining mechanisms responsible for these symptoms has been hindered by the limited availability of animal models that can induce classic human pathology. Currently, several permissive non-human primate (NHP) species and mouse breeds susceptible to adapted DV strains are available. Though virus replication occurs in these animals, none of them recapitulate the cardinal features of human symptomatology, with disease only occasionally observed in NHPs. Recently our group established a DV serotype 2 intravenous infection model with the Indian rhesus macaque, which reliably produced cutaneous hemorrhages after primary virus exposure. Further manipulation of experimental parameters (virus strain, immune cell expansion, depletion, etc.) can refine this model and expand its relevance to human DF. Future goals include applying this model to elucidate the role of pre-existing immunity upon secondary infection and immunopathogenesis. Of note, virus titers in primates in vivo and in vitro, even with our model, have been consistently 1000-fold lower than those found in humans. We submit that an improved model, capable of demonstrating severe pathogenesis may only be achieved with higher virus loads. Nonetheless, our DV coagulopathy disease model is valuable for the study of select pathomechanisms and testing DV drug and vaccine candidates.