The CCR5Δ32 allele is not a major predisposing factor for severe H1N1pdm09 infection

Background: Host genetic factors are thought to modulated the severity of disease caused by infection with the 2009 H1N1 pandemic influenza virus (H1N1pdm09). The human CCR5 gene encodes a cytokine receptor important for cell-mediated immune response against H1N1pdm09. A 32-bp polymorphic deletion in the coding sequence of CCR5, the so-called CCR5Δ32 allele, segregates in populations of European ancestry with a frequency of 8-15%. A high proportion of CCR5Δ32 heterozygotes was reported in a sample of white Canadian critically-ill H1N1pdm09 infected subjects, suggesting an association with disease severity. Methods. We recruited 29 H1N1pdm09 infected subjects from Southern Europe (mostly Italians) with a wide clinical spectrum of disease symptoms; the sample included 7 subjects who developed acute respiratory distress syndrome requiring extracorporeal membrane oxygenation. The CCR5Δ32 variant was genotyped in all subjects. Results: The CCR5Δ32 allele was found in one single subject, who developed a very mild form and was not hospitalized. Conclusions: The CCR5Δ32 allele was not found to be associated with the risk of H1N1pdm09 infection or with a severe disease course.