Neonatal immune response predicts viral illness

Newborns with a decreased innate response to viruses have more viral respiratory infections in their first year of life than infants with a stronger immune response, a new study reports.

Researchers cultured monocytes in cord blood samples obtained in the delivery room from 82 newborns enrolled in the Urban Environment and Childhood Asthma study, inoculated the samples with respiratory syncytial virus (RSV), and evaluated production of IFNG (the gene encoding interferon-γ) and CCL5 mRNA 24 hours later to assess immune response. They then monitored the infants for frequency of acute respiratory illness every 3 months during the first year of life and assessed respiratory viruses in nasal lavage samples at the time of illness.

Antiviral responses varied widely in the cord blood samples. Children whose cord blood monocytes showed decreased production of IFNG (but not CCL5)in response to RSV infection had significantly more frequent upper-respiratory infections and greater prevalence of ear and sinus infections, pneumonias, and respiratory-related hospitalizations than children with a more robust immune response.

These results suggest that it is possible to identify individual variations in the innate immune response to respiratory tract viruses even at birth and predict susceptibility to acute respiratory illness on the basis of these differences during the first year of life.

The finding was unexpected in light of previous opinion, which held that IFNG expression occurred only in lymphoid cells, not monocytes. The study supports the hypothesis that enhancing the body's IFN-γ monocytes may help protect against viral infection, including seasonal influenza.

The researchers note that the results of their study are in line with previous observations that production of interferon-γ decreases in response to RSV in peripheral blood monocytes from older children and adults with allergic asthma, suggesting that an inadequate antiviral defense in infancy may persist into later life.

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