Norovirus GII.4 antibodies in breast milk and serum samples: their role preventing virus-like particles binding to their receptors.
BACKGROUND
Norovirus GII.4 genotype is a leading cause of nonbacterial gastroenteritis in infants. Effective vaccines against noroviruses are not yet available, enhancing the interest of the protection mechanisms elicited by breast milk that may contain norovirus-specific antibodies and histo-blood group antigens. The aims of our study were to analyze norovirus GII.4-specific antibodies in breast milk and serum and to assess their blocking activity on recombinant norovirus virus-like particles (VLPs) binding to saliva.


METHODS
Mature milk and serum from 108 mothers were analyzed for specific IgA to norovirus GII.4-2006b and for their blocking activity on the binding of norovirus GII.4-2006b VLPs to fucosyltransferase FUT2-positive and negative saliva. Norovirus GII.4-2006b-specific IgG antibodies were also analyzed in serum samples.


RESULTS
Higher specific IgA titers were detected in mature milk (75%) than in serum samples (62%), showing a correlation between both results (ρ = 0.427, P = 0.000). However, only 56.3% of the serum samples contained norovirus-specific IgG. Almost all mature milk samples (99.1%) inhibited the binding of norovirus VLPs to FUT2-negative saliva; however, only 25% did so to FUT2-positive saliva (P = 0.000). Ninety percent of serum samples inhibited the binding of norovirus VLPs to FUT2-negative saliva.


CONCLUSIONS
Breast milk inhibits norovirus GII.4-2006b VLPs binding to receptors in saliva, and anti-norovirus IgA antibodies are only partly responsible for this activity. The FUT2 status of the receptor seems to be a strong predictor of this effect, but more studies to ascertain the participation of histo-blood group antigens in the protection against norovirus infections elicited by breast milk are required.
From the *Department of Pediatrics and †Department of Microbiology, School of Medicine, University of Valencia, Hospital Clínico Universitario de Valencia, Spain.
Parisá
P
Khodayar-Pardo
Cecilia
C
Martínez-Costa
Noelia
N
Carmona-Vicente
Javier
J
Buesa
D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000032:analysis / Q000097:blood / Q000276:immunology*; D017250:Caliciviridae Infections / Q000276:immunology* / Q000821:virology; D005260:Female; D005759:Gastroenteritis / Q000276:immunology / Q000821:virology; D006801:Humans; D007118:Immunoassay; D007070:Immunoglobulin A / Q000032:analysis / Q000097:blood / Q000276:immunology*; D008895:Milk, Human / Q000737:chemistry / Q000276:immunology* / Q000821:virology*; D029322:Norovirus / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D012463:Saliva / Q000737:chemistry / Q000276:immunology / Q000821:virology; D053585:Virus Attachment; D055815:Young Adult
D000914:Antibodies, Viral; D007070:Immunoglobulin A