How is "Influenza Severity" encoded by the genome?
Chances are all of us have experienced some type of flu symptoms in our lifetime. But the particular strain of flu— A/H1N1pdm09 virus has had a global impact. But while some get incredibly sick, others may have mild symptoms, and the variety in the severity for individuals remains unknown.
What is known, is that in severe cases the presence of high systemic levels of T helper (Th)1 and Th17 cytokines, also identified as hypercytokinemia, has been reported as a characteristic, as well as host genetic variations that affect cytokine production.
A study was carried out among 246 patients infected with the virus to discover how influenza develops and its severity among different people. The functional single nucleotide polymorphisms (SNPs) in the TNFA gene, the IFNG gene, the IL10 gene, and the CCL2 gene were studied because these genes encode for proinflammatory and anti-inflammatory cytokines associated with disease severity. Based on the data from case history sheets, study subjects were classified into those with mild disease or severe disease based on the presence of severe acute respiratory illness (SARI). As per the World Health Organization definition, patients with influenza-like illness and shortness of breath or difficulty in breathing and requiring hospital admission are considered SARI patients and considered severe cases. Among the cases, 129 had mild disease, whereas 117 had severe disease. There were 27 fatal cases. When the genotype frequencies were compared between the mild and severe cases, patients with AA genotype were more likely to show severe symptoms than patients with GA and GG genotypes.
Scientists believe this could be because IL10 production is typically higher in the G allele, which could help reduce inflammation. It also reports an association between SNPs in IL10 genes and disease severity for the first time in an Indian population. Further studies in different populations with larger sample sizes investigating the association of SNPs in cytokine genes and cytokine levels with influenza virus-infected subjects may help understand SNPs' role in determining disease severity and might help determine the variation in disease outcomes.
If you would like to know more about this research, you can read the study here:
https://pubmed.ncbi.nlm.nih.gov/30475169/
Are you interested in learning more about your genetic tendency for influenza severity? You can log in to your Genomelink TRAITS to see this new genetic trait.
