Nonspecific Effects of Infant Vaccines Make Children More Resistant to SARS-CoV-2 Infection.

A myriad of reasons, or a combination of them, have been alluded to in order to explain the lower susceptibility of children to SARS-CoV-2 infection and the development of severe forms of COVID-19. This document explores an additional factor, still little addressed in the medical literature related to the matter: nonspecific resistance to SARS-CoV-2 that could be generated by vaccines administered during childhood. The analysis carried out allows one to conclude that a group of vaccines administered during childhood is associated with a lower incidence and severity of SARS-CoV-2 infection among pediatric ages. Looking from an epidemiological perspective, this conclusion must be taken into consideration in order to ensure greater rationality in the design and implementation of prevention and control actions, including the administration of the COVID-19 vaccine, for these ages.

The regarding the call to explore the unexpected low severity of COVID-19 in Sub-Saharan Africa.

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OSBPL10, RXRA and lipid metabolism confer African-ancestry protection against dengue haemorrhagic fever in admixed Cubans.

Ethnic groups can display differential genetic susceptibility to infectious diseases. The arthropod-born viral dengue disease is one such disease, with empirical and limited genetic evidence showing that African ancestry may be protective against the haemorrhagic phenotype. Global ancestry analysis based on high-throughput genotyping in admixed populations can be used to test this hypothesis, while admixture mapping can map candidate protective genes. A Cuban dengue fever cohort was genotyped using a 2.5 million SNP chip. Global ancestry was ascertained through ADMIXTURE and used in a fine-matched corrected association study, while local ancestry was inferred by the RFMix algorithm. The expression of candidate genes was evaluated by RT-PCR in a Cuban dengue patient cohort and gene set enrichment analysis was performed in a Thai dengue transcriptome. OSBPL10 and RXRA candidate genes were identified, with most significant SNPs placed in inferred weak enhancers, promoters and lncRNAs. OSBPL10 had significantly lower expression in Africans than Europeans, while for RXRA several SNPs may differentially regulate its transcription between Africans and Europeans. Their expression was confirmed to change through dengue disease progression in Cuban patients and to vary with disease severity in a Thai transcriptome dataset. These genes interact in the LXR/RXR activation pathway that integrates lipid metabolism and immune functions, being a key player in dengue virus entrance into cells, its replication therein and in cytokine production. Knockdown of OSBPL10 expression in THP-1 cells by two shRNAs followed by DENV2 infection tests led to a significant reduction in DENV replication, being a direct functional proof that the lower OSBPL10 expression profile in Africans protects this ancestry against dengue disease.

Role of CC chemokine receptor 1 and two of its ligands in human dengue infection. Three approaches under the Cuban situation.

Any of the four dengue serotypes can cause a severe disease, partly due to systemic inflammation orchestrated by mediators like cytokines and chemokines. We addressed the role of CCR1 and its ligands CCL3/MIP-1α and CCL5/RANTES in dengue infection using three different approaches: an ex vivo model exploring memory immune response in subjects with a well characterized dengue immune background, an in vivo study in patients with primary or secondary dengue infection, and an approach in fatal dengue. CCR1 and CCL3/MIP-1α gene expression showed differences after homotypic and heterotypic challenge according to dengue immune background of subjects, in correspondence with previous observations in Cuban dengue outbreaks. CCL5/RANTES gene expression was higher after homotypic challenge. CCR1 and CCL3/MIP-1α gene expression was higher in patients with secondary infection during critical days of the dengue disease, while the increase in RANTES expression started earlier than the observed for CCR1 and CCL3/MIP-1α. CCR1 and CCL3/MIP-1α gene expression was as high in brain as in spleen tissue from necropsy. Our results confirm the strong influence of previous immunity in subsequent dengue infections, and confer a possible pathogenic role to CCR1 and CCL3/MIP-1α in dengue disease and a possible protective role for CCL5/RANTES, probably through CCR5 interaction.

[Low-affinity Fcγ receptor IIa gene polymorphism and dengue bleeding disorder]. / Polimorfismo del receptor FcγRIIa y su posible relación con las manifestaciones clínicas del dengue.

INTRODUCTION: The pathophysiological changes that determine the severity of dengue are still not well known, therefore it is important to study the probable relationship with the host genetic. METHODS: We analyzed the possible association between the FcγRIIa polymorphism and clinical signs in individuals who suffered dengue infection in 2006, using contingency tables. RESULTS: We found that bleeding was significantly associated to FcγRIIa H/H131 genotype (80%). CONCLUSION: Our results suggest that in clinical dengue infection the bleeding could be associated to FcγRIIa H/H131 genotype.

Variation in inflammatory/regulatory cytokines in secondary, tertiary, and quaternary challenges with dengue virus.

Secondary heterologous dengue infection is a risk factor for severe disease manifestations because of the immune-enhancement phenomenon. Succeeding clinical infections are seldom reported, and the clinical course of tertiary and quaternary dengue infections is not clear. Cuba represents a unique environment to study tertiary/quaternary dengue infections in a population with known clinical and serologic dengue markers and no dengue endemicity. We took advantage of this exceptional epidemiologic condition to study the effect of primary, secondary, tertiary, and quaternary dengue infection exposure on the expression of pro-inflammatory and regulatory cytokines, critical in dengue infection pathogenesis, by using a dengue infection ex vivo model. Whereas secondary exposure induced a high cytokine response, we found a significantly lower expression of tumor necrosis factor-α, interferon-γ, interleukin-10, and tumor growth factor-ß after tertiary and quaternary infectious challenge. Significant differences in expression of the cytokines were seen between the dengue immune profiles, suggesting that the sequence in which the immune system encounters serotypes may be important in determining the nature of the immune response to subsequent infections.

Association of MICA and MICB alleles with symptomatic dengue infection.

Dengue viruses (DV) are one of the most important arthropod-borne viral diseases in the developing world. DV can cause syndromes that are either self-limiting or severe. Allelic variants of human leukocyte antigen (HLA) genes have been demonstrated to be associated with disease susceptibility. Here we report the association of nonclassical HLA class I MICA-MICB genes with disease outcome during DV infection. A sequencing-based typing method and genotyping of MICA and MICB in a well-characterized group of Cuban individuals with dengue hemorrhagic fever (DHF), dengue fever (DF), or asymptomatic dengue infection (ADI) was performed. Statistical analysis revealed a tendency for MICA*008 and MICB*008 to associate with susceptibility to illness when symptomatic versus asymptomatic cases (odds ratio [OR] = 2.1, p(v) = 0.03, and OR = 10.4, p = 0.0096, respectively) were compared. Surprisingly, a stronger association of both allelic forms was observed for the DF patients compared with the ADI group (MICA*008, OR = 5.2, p = 0.0001; and MICB*008, OR = 13.2, p = 0.0025) rather than the severe cases. Major histocompatibility class I-related gene-related natural killer cells and/or γδ and αß T-cell activation might regulate the development of symptomatic DF and DHF.

Long-term persistence of clinical symptoms in dengue-infected persons and its association with immunological disorders.

OBJECTIVES: The acute manifestations of dengue are well known. The clinical symptoms that present during the convalescent phase of infection are less well characterized, but may be autoimmune-based. This study was undertaken to determine the prevalence of persistent clinical symptoms among individuals infected during the 2006 Cuban epidemic and to evaluate the immunological and genetic factors associated with their occurrence. METHODS: In 2008, clinical data and blood samples were collected from a random sample of adult individuals diagnosed during the 2006 epidemic with dengue fever (DF, n=68), dengue hemorrhagic fever (DHF, n=29), or an asymptomatic infection (AI, n=42). The presence of persistent symptoms was evaluated in all individuals and a psychological assessment was performed. IgG titers and the Fc receptor (FcR) were also evaluated. The following autoimmune markers were assessed in a subset (n=26) of symptomatic individuals: complement factors C3/C4, rheumatoid factor (RF), C-reactive protein (CRP), antinuclear antibodies (ANA), and immune complex (IC). RESULTS: Over half (55/97) the individuals with a prior of diagnosis of DF or DHF had persistent clinical symptoms in the 2 years following infection. The sequelae were unrelated to the initial diagnosis and were more common among women (44/55). No symptoms were reported in the AI group and all study participants had normal mental and cognitive function. Persistent clinical symptoms were associated with HH polymorphic variant (p=0.027) and high IgG titer (p=0.041). Autoimmune marker alterations were common (20/26) in the subset of symptomatic individuals evaluated. CONCLUSIONS: Clinical sequelae after recovery from an acute dengue virus infection are common in the 2 years following infection. The results obtained in this study suggest that persistent symptoms are associated with alterations in some immunological parameters and FcγRIIa gene polymorphism. This could suggest an autoimmune-based disturbance.

Tumor necrosis factor-alpha, transforming growth factor-ß1, and interleukin-10 gene polymorphisms: implication in protection or susceptibility to dengue hemorrhagic fever.

Dengue virus infection has emerged as one of the most important arthropod-borne viral diseases. Some dengue infected individuals develop the severe, life-threatening form of the disease, dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). Host genetic factors may be relevant and may predispose some individuals to the severe illness. Human leukocyte antigen (HLA), FcγR, tumor necrosis factor (TNF)-α, and dendritic cell-specific intracellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), among others genes have been associated with the pathogenesis of dengue. Little is known, however, about the predictive value of cytokine genotypes for the clinical outcome of dengue infection. In this study, the TNF-α, interleukin (IL)-6, interferon (IFN)-γ, IL-10 and transforming growth factor (TGF)-ß1 gene single nucleotide polymorphisms (SNP) were studied by polymerase chain reaction-sequence-specific primer in a group of individuals with the antecedent of DHF during a secondary infection in the sequence dengue 1/dengue 2. A control group was also included. TNF-α (-308) A allele and IL-10 (-1082/-819/-592) ACC/ATA haplotype were significantly associated with DHF. TNF-α (-308) GG and TGF-ß1 (c25) GG genotypes were associated with protection. Our results suggest that genetic predisposition to a high TNF-α production and a low IL-10 production seems to increase the susceptibility to DHF during a secondary dengue 2 infection, whereas TGF-ß1 high producers might be protected for developing DHF.

Asymptomatic dengue infection in a Cuban population confirms the protective role of the RR variant of the FcgammaRIIa polymorphism.

The role of human Fcgamma receptors (FcgammaR) has been recognized considerably over the last years. These receptors vary in their affinity for IgG subclasses and the intracellular signals elicited by them. Allelic variants of FcgammaR genes may influence the biological phagocyte activity, accounting for an inherited pre-disposition to disease. The specific FcgammaRIIa (CD32) contains a polymorphic variant (H/R131) that has been associated to a reduced risk for developing dengue hemorrhagic fever (DHF). Here, we investigated the role of this polymorphism in a very well-characterized group of Cuban individuals with antecedents of DHF, dengue fever (DF), or subclinical dengue infection. The HH131 genotype was significantly associated with dengue disease, either DF (*P = 0.016; odds ratio = 4.425; 95% confidence interval = 1.10-20.52) or DHF (P = 0.00018; odds ratio = 10.56; 95% confidence interval = 2.33-54.64) with respect to the subclinical infection.

Secondary heterologous dengue infection risk: Disequilibrium between immune regulation and inflammation?

Increased serum levels of cytokines released by cells of the immune response have been detected in patients suffering from dengue disease. Likewise, secondary infections by a different dengue virus serotype result in a highest risk of development of the severe dengue disease. Both findings suggest that the memory immune response is one of the key players in the pathogenesis of this disease. Here we take advantage of the particular Cuban epidemiological situation in dengue to analyze a broad spectrum of cell-mediated immune response mediators at mRNA and protein level. Evidences for a regulatory immune pattern in homologous (TGF-beta, IL-10) vs. pro-inflammatory pattern (IFN-gamma, TNF-alpha) in heterologous dengue virus re-challenge were found, suggesting a possible association with the higher incidence of severe dengue cases in the latter case.

Producción ex vivo de TNFa y óxido nítrico por células sanguíneas en presencia de virus dengue / TNFa and nitric oxide ex vivo production by blood cells due to dengue virus

Objetivo: niveles elevados de TNFa se han vinculado al desarrollo de la forma clínica severa de la infección por dengue. La producción de óxido nítrico parece estar disminuida en casos con fiebre hemorrágica del dengue al comparar con la fiebre dengue, sin embargo, no se conoce el papel de estos mediadores en una infección terciaria por el virus. Métodos: la capacidad de las células sanguíneas de individuos con antecedentes de infección por dengue de producir TNFa y óxido nítrico al ser cultivadas con un serotipo diferente del virus en una infección terciaria ex vivo, fue medida en los sobrenadantes de cultivo mediante el empleo de un estuche ELISA comercial y el test de Griess, respectivamente. Resultados: la estimulación con virus dengue indujo la liberación de altos y variables niveles de TNFa en el sobrenadante de células de sangre total de los individuos estudiados, apoyando el posible papel del TNFa en la patogénesis de una infección terciaria sintomática por dengue. La síntesis de óxido nítrico, en las condiciones experimentales estudiadas, no difirió entre casos con historia de fiebre dengue y fiebre hemorrágica del dengue, al parecer estaba algo inhibida en presencia de anticuerpos heterotípicos. Conclusiones: los niveles diferenciales de síntesis de TNFa entre individuos pudieran tener implicaciones en el desarrollo de una infección natural terciaria por dengue.

Objective: High TNFa levels have been associated with the development of severe forms of dengue virus infection. The NO production seems to be lower in dengue hemorrhagic fever cases compared to dengue fever cases. However, the role of those mediators in the tertiary dengue infection has not been discovered yet. Methods: The ability of whole blood cells from individuals with a history of dengue infection of producing TNFa and Nitric oxide (NO) when cultured with a different serotype of dengue virus mimicking an ex vivo tertiary infection, was measured in the culture supernatants by using a standard ELISA kit and Griess test, respectively. Results: Dengue virus stimulation induced the release of very high and variable TNFa levels in whole blood cells supernatant, thus supporting the possible role of this cytokine in the pathogenesis of a symptomatic tertiary dengue infection. In these experimental conditions, there was no difference in the NO synthesis between DF and DHF cases, showing an apparent inhibition due to heterotypic antibodies. Conclusions: The dispersion of TNFa levels among individuals could have some effects on the development of a tertiary natural dengue infection.

Niveles de óxido nítrico en monos Macacus irus inoculados con virus dengue / Serum nitric oxide in Macacus irus monkeys inoculated with dengue virus

Objetivo: partiendo de que los anticuerpos preexistentes en la infección secundaria por dengue suprimen la acción de moléculas con acciones antivirales como el óxido nítrico, se determinó el comportamiento de esa molécula en suero de monos Macacus irus inoculados con virus dengue 2 como infección primaria y en monos con una infección secuencial dengue 4-dengue2. Métodos: los niveles de óxido nítrico referidos como niveles de nitritos fueron detectados mediante la reacción de Griess. Resultados: los niveles máximos de óxido nítrico se detectaron en los animales que sufrieron una infección primaria a partir del séptimo día posinoculación, a diferencia de los monos con infección secundaria en que no se obtuvieron niveles mayores de 100 µM. Conclusiones: al parecer existe una asociación entre la infección secundaria y la inhibición de la producción del óxido nítrico.

Objective: To determine the action of nitric Oxide (NO) in serum samples of dengue 2 inoculated Macacus irus monkeys as primary infection and in dengue 4 -dengue 2 inoculated monkeys as secondary infection, taking into account that preexisting antibodies in secondary dengue infection elicit the action of antiviral molecules such as nitric oxide. Methods: NO levels referred as nitrite levels were detected by Griess colorimetric reaction. Results: The highest nitric oxide levels were detected in those animals with primary infection seven days after inoculation monkeys whereas those monkeys with secondary infection did not show NO levels over 100 µM. Conclusions: Our results suggest that there seems to be a relationship between secondary infection and NO production inhibition.

Dengue y fiebre hemorrágica del dengue, un problema de salud mundial / Dengue and dengue hemorrhagic fever: a worldwide health problem

Desde épocas tan remotas como 1635 y 1699, el dengue ha sido considerado la enfermedad viral transmitida por mosquitos de mayor importancia médica. Dada la importancia de esta entidad al nivel mundial y particularmente para la región de las Américas, se hizo necesaria la búsqueda de una solución inmediata para abortar el desarrollo de la forma grave de la enfermedad. En este estudio se presentó una actualización del tema en aspectos tan importantes como: el espectro clínico de la enfermedad, las características del agente etiológico y los mecanismos inmunopatogénicos que tienen lugar en su interacción con el hospedero.

Since remote times as early as 1635 and 1699, dengue has been considered as the most important mosquito-borne viral disease. Given the significance of this disease worldwide, particularly in the Americas, it was necessary to look for an immediate solution to hinder the development of the most serious dengue variant. This study covered a review about some important aspects like clinical spectrum of the disease, the characteristics of the etiologic agent, and the immunopathogenic mechanisms that interact with the host.

HLA-A, -B, -C, and -DRB1 allele frequencies in Cuban individuals with antecedents of dengue 2 disease: advantages of the Cuban population for HLA studies of dengue virus infection.

Dengue virus infection has emerged as one of the most important arthropod-borne diseases. In some dengue-infected individual, the disease progresses to its severe, life-threatening form, dengue hemorrhagic fever (DHF). Host genetic factors may be relevant and predispose some individuals to the severe dengue disease. The unique history of dengue outbreaks in Cuba is extremely advantageous for genetic studies of dengue disease resistance or susceptibility. Consequently, samples collected from 120 healthy individuals that developed dengue fever (DF) and DHF during the 1997 dengue 2 outbreak in the Santiago de Cuba municipality were HLA genotyped using polymerase chain reaction-sequence-specific primers. Polymorphism at the human leukocyte antigen (HLA) class I loci was significantly associated with DHF disease susceptibility, but polymorphism in the HLA-DRB1 was associated with protection. Amino acid peptides present in the poly-protein of the dengue 2 Jamaica strain, which are able to bind to the HLA class I and class II allotypes associated with susceptibility to or protection against the dengue clinical disease, respectively, were predicted using the BIMAS and SYFPEITHI predictive algorithms of peptide/MHC interaction.

[Dengue and dengue hemorrhagic fever: research priorities]. / El dengue y el dengue hemorrágico: prioridades de investigación.

Dengue is one of the most important infectious diseases in tropical and subtropical countries. At present, the only strategy available to reduce the incidence of dengue is vector control. The World Health Organization and the Pan American Health Organization have called on all nations to take the needed steps to help diminish the burden of this disease and its medical and socioeconomic impact. It is hoped that it will be possible to reverse the increase in dengue and help control its spread through a coordinated, effective international response, along with epidemiological, clinical, and virological research that brings together the most advanced methods and techniques. This piece summarizes the most up-to-date information on dengue, analyzes current epidemiologic trends in the Region of the Americas, discusses the main global and Western Hemisphere initiatives to control the disease, and presents the main areas of research that should be developed in the immediate future.

El dengue y el dengue hemorrágico: prioridades de investigación / Dengue and dengue hemorrhagic fever: research priorities

Dengue is one of the most important infectious diseases in tropical and subtropical countries. At present, the only strategy available to reduce the incidence of dengue is vector control. The World Health Organization and the Pan American Health Organization have called on all nations to take the needed steps to help diminish the burden of this disease and its medical and socioeconomic impact. It is hoped that it will be possible to reverse the increase in dengue and help control its spread through a coordinated, effective international response, along with epidemiological, clinical, and virological research that brings together the most advanced methods and techniques. This piece summarizes the most up-to-date information on dengue, analyzes current epidemiologic trends in the Region of the Americas, discusses the main global and Western Hemisphere initiatives to control the disease, and presents the main areas of research that should be developed in the immediate future.

IL-10 levels in Dengue patients: some findings from the exceptional epidemiological conditions in Cuba.

The pathogenesis associated with Dengue haemorrhagic fever, has yet to be fully elucidated, with no definitive in vivo evidence. The exceptional epidemiological circumstances in Cuba allow the evaluation of different mediators in a well-defined situation. In the present study, we describe the determination of levels of IL-12, IL-10 and RANTES in the sera of Cuban patients hospitalised with Dengue fever or Dengue haemorrhagic fever. The results showed that levels of serum IL-10 were higher in patients than controls, and those patients with secondary infections had consistently higher levels. All the Dengue haemorrhagic fever patients had increased levels of IL-10. In contrast, levels of IL-12 did not differ between patients and controls. Finally, RANTES serum levels detected in patients were lower than those observed in the controls. The association of increased levels of IL-10 in Dengue patients with a sequential infection suggests a possible role of this cytokine in the pathogenesis of Dengue disease.

[Detection of lymphoproliferative response in monkeys innoculated with dengue 4 virus]. / Detección de respuesta linfoproliferativa en monos inoculados con virus dengue 4.

A group of 6 Cynomolgus monkeys was immunized with dengue 4 virus (H247 standard strain). 60 days after innoculation the cellular proliferation against the same serotype as well as against hetereologous serotypes 1 and 2 was measured. A proliferative response predominantly of the specific serotype and some cross reactivity were detected. These results showed a behavior of primates similar in some extent to that of human beings and mice regarding the specific serotype and cross serotype response to dengue virus.