Background and aims RSV is the main pathogen associated to hospitalisation for respiratory infections in infants. Prematurity, congenital heart disease and chronic lung disease are known risk factors for severe RSV infection. However, most infants that require hospitalisation do not have known risk factors. The identification of new markers of disease susceptibility is important in order to develop novel preventive measures. Natural killer cells are an essential component of the innate immune system and constitute one of the first lines of defense against viral infections. We analysed the KIR genotype in a group of infants with RSV infection requiring hospitalisation to assess whether this trait influences the risk of severe infection.

Methods Thirty-five infants without underlying conditions who required hospitalisation for RSV infection were included in this analysis. Oral swabs were used to collect samples for DNA extraction and the KIR genotype was determined by detection of the presence or absence of each of the KIR genes. Genotype frequencies were compared to a group of 300 healthy donors from the same hospital. In addition, characteristics of infants with AA and Bx genotypes were compared.

Results KIR AA/Bx genotype frequencies in infants with RSV infection (34.3% and 65.7%) were similar to those of the comparison group (34% and 66%). There were no significant differences in age, intensive care unit admissions, hospitalisation duration, or condition on discharge between infants with AA and Bx genotypes.

Conclusions Our results suggest that the KIR genotype does not influence the risk of developing severe RSV infection.