Polymorphisms in the retinoic acid-1 like-receptor family of genes and their association with clinical outcome of dengue virus infection

Identification of genetic variants associated with dengue or West Nile virus disease: a systematic review and meta-analysis

BACKGROUND

Dengue and West Nile viruses are highly cross-reactive and have numerous parallels in geography, potential vector host (Aedes family of mosquitoes), and initial symptoms of infection. While the vast majority (> 80%) of both dengue and West Nile virus infections result in asymptomatic infections, a minority of individuals experience symptomatic infection and an even smaller proportion develop severe disease. The mechanisms by which these infections lead to severe disease in a subset of infected individuals is incompletely understood, but individual host differences including genetic factors and immune responses have been proposed. We sought to identify genetic risk factors that are associated with more severe disease outcomes for both viruses in order to shed light on possible shared mechanisms of resistance and potential therapeutic interventions.

METHODS

We applied a search strategy using four major databases (Medline, PubMed, Embase, and Global Health) to find all known genetic associations identified to date with dengue or West Nile virus disease. Here we present a review of our findings and a meta-analysis of genetic variants identified.

RESULTS

We found genetic variations that are significantly associated with infections of these viruses. In particular we found variation within the OAS1 (meta-OR = 0.83, 95% CI: 0.69-1.00) and CCR5 (meta-OR = 1.29, 95% CI: 1.08-1.53) genes is significantly associated with West Nile virus disease, while variation within MICB (meta-OR = 2.35, 95% CI: 1.68-3.29), PLCE1 (meta-OR = 0.55, 95% CI: 0.42-0.71), MBL2 (meta-OR = 1.54, 95% CI: 1.02-2.31), and IFN-γ (meta-OR = 2.48, 95% CI: 1.30-4.71), is associated with dengue disease.

CONCLUSIONS

Despite substantial heterogeneity in populations studied, genes examined, and methodology, significant associations with genetic variants were found across studies within both diseases. These gene associations suggest a key role for immune mechanisms in susceptibility to severe disease. Further research is needed to elucidate the role of these genes in disease pathogenesis and may reveal additional genetic factors associated with disease severity.

Host genetics and dengue fever

Dengue is a major worldwide problem in tropical and subtropical areas; it is caused by four different viral serotypes, and it can manifest as asymptomatic, mild, or severe. Many factors interact to determine the severity of the disease, including the genetic profile of the infected patient. However, the mechanisms that lead to severe disease and eventually death have not been determined, and a great challenge is the early identification of patients who are more likely to progress to a worse health condition. Studies performed in regions with cyclic outbreaks such as Cuba, Brazil, and Colombia have demonstrated that African ancestry confers protection against severe dengue. Highlighting the host genetics as an important factor in infectious diseases, a large number of association studies between genetic polymorphisms and dengue outcomes have been published in the last two decades. The most widely used approach involves case-control studies with candidate genes, such as the HLA locus and genes for receptors, cytokines, and other immune mediators. Additionally, a Genome-Wide Association Study (GWAS) identified SNPs associated with African ethnicity that had not previously been identified in case-control studies. Despite the increasing number of publications in America, Africa, and Asia, the results are quite controversial, and a meta-analysis is needed to assess the consensus among the studies. SNPs in the MICB, TNF, CD209, FcγRIIA, TPSAB1, CLEC5A, IL10 and PLCE1 genes are associated with the risk or protection of severe dengue, and the findings have been replicated in different populations. A thorough understanding of the viral, human genetic, and immunological mechanisms of dengue and how they interact is essential for effectively preventing dengue, but also managing and treating patients.