Protective Role of Pre-F Antibodies Against RSV Acute Respiratory Infection

Serum antibodies against the pre-fusion respiratory syncytial virus fusion protein (pre-F) may be a correlate of protection against RSV acute respiratory infection.

Serum antibodies against the pre-fusion respiratory syncytial virus (RSV) fusion protein (pre-F) may be a correlate of protection against acute RSV infection, according to study data published in The Journal of Infectious Diseases.

To investigate the potential protective role of breast milk RSV-specific antibodies, collections from mother-infant pairs of breast milk at 1, 3, and 6 months postpartum along with mid-nasal swabs during episodes of infant illness were obtained. A total of 174 infants with and without acute RSV infection were matched 1:1 according to risk factors for disease and breast milk was measured for pre-F IgA and IgG antibody levels.

Median breast milk concentration of pre-F IgG antibodies before illness was lower in mothers of the infants with acute RSV infection than without (1.4, interquartile range [IQR] 1.1-1.6 log10 ng/mL and 1.5; IQR: 1.3-1.8 log10 ng/mL, respectively [P =.001]). No differences in median concentrations were found in pre-F IgA levels in cases vs controls (1.7, IQR: 0.0-2.2 log10 ng/mL and 1.7; IQR: 1.2-2.2 log10 ng/mL, respectively [P =.58]).

The study did not measure pre-F antibodies in the serum of mothers or in the cord blood. In addition, no blood was drawn from infants making further study of the children impossible. It is therefore possible that serum pre-F antibody titres in women and their children are actually responsible for protective effects. Future work will need to replicate these results in a larger group from a different population with longer follow-up time. Further, it is possible that “the protective effect of breast milk pre-F specific antibodies against respiratory disease may have been underestimated because antibodies against all pre-F epitopes were measured, which include less potent RSV-neutralizing or non-neutralizing antibodies.”

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Investigators concluded that the study provides evidence of a potential protective role from pre-F IgG antibodies in breastmilk against RSV-confirmed acute respiratory infection during the first months of life. And induction of these antibodies in breastmilk could be a potential mechanism of protection for maternal RSV vaccine candidates.


Mazur NI, Horsley N, Englund JA, et al. Breast milk prefusion F IgG as a correlate of protection against respiratory syncytial virus acute respiratory illness [published online August 10 2018]. J Infect Dis. doi:10.1093/infdis/jiy477