Variants in the TNFA, IL6 and IFNG genes are associated with the dengue severity in a sample from Colombian population

No Association Between Interleukin 6 and Inducible Nitric Oxide Synthase Polymorphisms and Dengue Infection: A Case-Control Study

BACKGROUND

Dengue is a life-threatening disease. The factors that lead to severe cases are not completely understood. The host immune system is involved in the response to infections and plays an important role in dengue infection. IL-6 and iNOS are components of the immune system and genetic polymorphisms in these genes may be involved in dengue virus infection. The study aimed to investigate the association of genetic polymorphisms in the IL6 and iNOS genes and dengue.

METHODS

We performed a case-control study using 60 dengue-infected individuals and 119 healthy controls. Polymorphisms in the IL6 (T15A) and iNOS (-1173CT) genes were amplified by Real-Time PCR. Statistical analyses were performed using BioEstat 5.0.

RESULTS

We identified that the frequency of T/A genotype of IL6 was higher in dengue fever patients and C/T genotype of iNOS was higher in dengue hemorrhagic fever patients, however, no association was found between these polymorphisms and dengue.

CONCLUSION

Polymorphisms in iNOS and IL6 were not associated with dengue infection.

Dengue, Severity Paradox, and Socioeconomic Distribution Among Afro-Colombians

BACKGROUND

The clinical presentation of dengue ranges from self-limited mild illness to severe forms, including death. African ancestry is often described as protective against dengue severity. However, in the Latin American context, African ancestry has been associated with increased mortality. This "severity paradox" has been hypothesized as resulting from confounding or heterogeneity by socioeconomic status (SES). However, few systematic analyses have been conducted to investigate the presence and nature of the disparity paradox.

METHODS

We fit Bayesian hierarchical spatiotemporal models using individual-level surveillance data from Cali, Colombia (2012-2017), to assess the overall morbidity and severity burden of notified dengue. We fitted overall and ethnic-specific models to assess the presence of heterogeneity by SES across and within ethnic groups (Afro-Colombian vs. non-Afro-Colombians), conducting sensitivity analyses to account for potential underreporting.

RESULTS

Our study included 65,402 dengue cases and 13,732 (21%) hospitalizations. Overall notified dengue incidence rates did not vary across ethnic groups. Severity risk was higher among Afro-Colombians (risk ratio [RR] = 1.16; 95% Credible Interval [95% CrI] = 1.08, 1.24) but after accounting for underreporting by ethnicity this association was nearly null (RR = 1.02; 95% CrI = 0.97, 1.07). Subsidized health insurance and low-SES were associated with increased overall dengue rates and severity.

CONCLUSION

The paradoxically increased severity among Afro-Colombians can be attributed to differential health-seeking behaviors and reporting among Afro-Colombians. Such differential reporting can be understood as a type of intersectionality between SES, insurance scheme, and ethnicity that requires a quantitative assessment in future studies.

What is the association between the IL6-174 G > C (rs1800795) polymorphism and the risk of dengue? Evidence from a meta-analysis

The association of polymorphisms in genes responsible for immunological mediators with dengue allows the identification of certain genetic alterations that increase or decrease the development risk of the disease. A few number of studies that correlate the interleukin 6-174 G > C (IL6-174 G > C) polymorphism (rs1800795) with dengue. However, there is an inconsistency on the polymorphism influence on the disease which motivated this meta-analysis. So, this study aimed to evaluate the rs1800795 polymorphism with protection or susceptibility for development of dengue. A search of the literature was performed for studies published before 05 September 2020 in various databases. Calculations of Odds Ratio (OR) with 95% of Confidence Intervals (CI) and heterogeneity (I²) were assessed and publication bias was done by Begg' and Egger's test. The value of P < 0.05 was considered as significant. As results, five case-control studies were identified and included in the results. The analysis showed that the heterozygous genotype has a protective role against dengue without warning signs (DWOS) (OR = 0.57, p = 0.001), as well as the polymorphic C allele (OR = 0.77, p = 0.04). When unifying the data from the included studies, the GG genotype was more prevalent among individuals with dengue with warning signs (DWWS) when compared to the control group (p = 0.0221). GC genotype was more prevalent in the control group than in the DWWS group (p = 0.0119). Therefore, in our study we observed that the GC genotype and the C allele have a protective role against DWOS. Since this polymorphism is associated with low IL-6 expression, thus it is expected that there will be a decreased pro-inflammatory response. However, more studies regarding this thematic are necessary to have a consensus about this polymorphism and dengue.

Activation of an Effective Immune Response after Yellow Fever Vaccination Is Associated with the Genetic Background and Early Response of IFN-γ and CLEC5A

The yellow fever vaccine (YF17DD) is highly effective with a single injection conferring protection for at least 10 years. The YF17DD induces polyvalent responses, with a TH1/TH2 CD4⁺ profile, robust T CD8⁺ responses, and synthesis of interferon-gamma (IFN-γ), culminating in high titers of neutralizing antibodies. Furthermore, C-type lectin domain containing 5A (CLEC5A) has been implicated in innate outcomes in other flaviviral infections. Here, we conducted a follow-up study in volunteers immunized with YF17DD, investigating the humoral response, cellular phenotypes, gene expression, and single nucleotide polymorphisms (SNPs) of IFNG and CLEC5A, to clarify the role of these factors in early response after vaccination. Activation of CLEC5A⁺ monocytes occurred five days after vaccination (DAV). Following, seven DAV data showed activation of CD4⁺ and CD8⁺T cells together with early positive correlations between type II IFN and genes of innate antiviral response (STAT1, STAT2, IRF7, IRF9, OAS1, and RNASEL) as well as antibody levels. Furthermore, individuals with genotypes rs2430561 AT/AA, rs2069718 AG/AA (IFNG), and rs13237944 AC/AA (CLEC5A), exhibited higher expression of IFNG and CLEC5A, respectively. Together, we demonstrated that early IFN-γ and CLEC5A responses, associated with rs2430561, rs2069718, and rs13237944 genotypes, may be key mechanisms in the long-lasting immunity elicited by YF17DD.