Respiratory syncytial virus-neutralizing serum antibody titers in infants following palivizumab prophylaxis with an abbreviated dosing regimen.

Jennifer Claydon,Amitava Sur,Allison Callejas,Mihoko Ladd,Eddie Kwan,Stuart E Turvey,Alfonso Solimano,Richard Taylor,Pascal M Lavoie,Nico Marr,Charles J Russell

doi:10.1371/journal.pone.0176152

Abstract

BackgroundMonthly injections of palivizumab during the respiratory syncytial virus (RSV) season in at-risk infants reduces RSV-associated hospitalizations. However, the additive effect of naturally acquired immunity remains unclear. The objective of this study was to assess total neutralizing serum antibodies (NAb) against RSV in at-risk infants who had received an abbreviated course of palivizumab prophylaxis.MethodsSerum samples were collected from infants enrolled in the RSV Immunoprophylaxis Program in British Columbia, Canada over 2 consecutive RSV seasons (2013 to 2015). Infants in this program had received an abbreviated course of palivizumab in accordance with the provincial guidelines. Data were compared to adults and infants less than 12 months of age who did not receive palivizumab. Anti-RSV NAb titers were measured using an RSV microneutralization assay.FindingsInfants who received palivizumab had anti-RSV NAb titers at the end of the RSV season that persisted beyond what is expected from the pharmacokinetics of palivizumab alone. Moreover, 54% of the control infants who did not receive palivizumab and all tested adults had protective anti-RSV NAb titers.ConclusionsBased on our observations, we hypothesize that naturally acquired NAb provide additive protection, which may significantly reduce the need for additional doses of palivizumab in infants at risk of severe RSV infections.

Highlights

Respiratory syncytial virus (RSV) is the main cause of lower respiratory tract infections and hospitalization among infants and young children, and is responsible for up to 200,000 fatalities in these age groups each year, worldwide [1]
We hypothesize that naturally acquired neutralizing serum antibodies (NAb) provide additive protection, which may significantly reduce the need for additional doses of palivizumab in infants at risk of severe respiratory syncytial virus (RSV) infections
We recently reported hospitalization rates among at–risk infants in British Columbia (BC), Canada, who received an abbreviated palivizumab regimen of 3 or 4 doses during an RSV season that were comparable to historical controls treated under a 5-dose regimen [4]

Summary

Introduction

Respiratory syncytial virus (RSV) is the main cause of lower respiratory tract infections and hospitalization among infants and young children, and is responsible for up to 200,000 fatalities in these age groups each year, worldwide [1]. We recently reported hospitalization rates among at–risk infants in British Columbia (BC), Canada, who received an abbreviated palivizumab regimen of 3 or 4 doses during an RSV season that were comparable to historical controls treated under a 5-dose regimen [4] It remained unclear whether natural anti-RSV neutralizing antibodies (NAb) contributed to the protection of these infants who received an abbreviated palivizumab dosing schedule. Previous studies have demonstrated associations between the seasonal variation of maternally derived antiRSV NAb and the seasonal pattern of RSV hospitalizations in infants at the population level [7], as well as between breast feeding and lower risk for RSV hospitalizations in a case-control cohort [8] These observations further indicate that maternally-derived antibodies contribute to the protection of infants during the course of primary RSV infection. The objective of this study was to assess total neutralizing serum antibodies (NAb) against RSV in at-risk infants who had received an abbreviated course of palivizumab prophylaxis

Objectives

Methods

Results

Conclusion