Binding and Neutralizing Capacity of Respiratory Syncytial Virus (RSV)-Specific Recombinant IgG Against RSV in Human Milk, Gastric and Intestinal Fluids from Infants.

Veronique Demers-Mathieu,Brian P Scottoline,David C Dallas,Jiraporn Lueangsakulthai,Yunyao Qu

doi:10.3390/nu12071904

Veronique Demers-Mathieu, Brian P Scottoline + Show 3 more

Open Access

https://doi.org/10.3390/nu12071904

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Abstract

Oral administration of pathogen-specific recombinant antibodies may help to prevent infant gastrointestinal (GI) pathogen infection; however, to neutralize an infectious agent, these antibodies must resist degradation in the GI tract. Palivizumab, a recombinant antibody specific for the respiratory syncytial virus (RSV), was used as a model for pathogen-specific IgG in human milk. The aim was to compare the remaining binding capacity of palivizumab in milk between three mothers after exposure to an in vitro model of infant gastrointestinal digestion (gastric and duodenal fluids) using ELISA. The neutralizing capacity of palivizumab in pooled human milk, gastric contents, and stools from preterm infants was also evaluated for blocking RSV with green fluorescent protein (RSV-GFP) infection in Hep-2 cells using confocal and inverted microscopy and flow cytometry. The reduction of palivizumab binding capacity in human milk and digested samples was slightly different between mothers. Overall, palivizumab decreased 50% after simulated gastric digestion with pepsin and 62% after simulated intestinal digestion with pancreatin. Palivizumab (2–8 μg/mL) in human milk or stool samples blocked RSV (3.4 × 104 FFU/mL) infection (no syncytia formation on Hep-2 cells) by microscopy. Syncytia formation was detected on Hep-2 cells when RSV was incubated in gastric contents or virus medium with 2–4 μg/mL of palivizumab, but no infection was observed at 8 μg/mL. No fluorescence (absence of infected cells) was detected when palivizumab (100 μg/mL) was incubated in human milk or medium with RSV-GFP (1.1 × 105 FFU/mL), whereas fluorescence increased with the reduced concentration of palivizumab using flow cytometry. These results suggest that undigested and digested matrices could change the binding and neutralizing capacity of viral pathogen-specific antibodies.

Highlights

Respiratory syncytial virus (RSV) can induce severe infections in preterm infants, such as pneumonia or bronchiolitis [1]
While human milk Secretory IgA (SIgA) is likely to stay on the surface of the intestinal mucosa, human milk immunoglobulin G (IgG) may potentially be absorbed in the gut to reach the bloodstream, enabling interaction with other immune components to protect against systemic pathogen invasion
Palivizumab in human milk incubated at 37 ◦ C reduced 19.1% after 30 min (p = 0.026), 19.8% after 60 min (p = 0.022), and ~24–25% (p = 0.004) after 90 and 120 min (Figure 2B)

Summary

Introduction

Respiratory syncytial virus (RSV) can induce severe infections in preterm infants, such as pneumonia or bronchiolitis [1]. This viral infection can lead to serious complications, re-hospitalization, and death. Immunoglobulin G (IgG) is the most abundant antibody in the blood and efficiently interacts with the immune cells to activate the immune responses (opsonization) when pathogens have entered the bloodstream [4]. While human milk SIgA is likely to stay on the surface of the intestinal mucosa, human milk IgG may potentially be absorbed in the gut to reach the bloodstream, enabling interaction with other immune components to protect against systemic pathogen invasion

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