Swine influenza virus antibodies in humans, western Europe, 2009

Abstract

Serologic studies for swine influenza viruses (SIVs) in humans with occupational exposure to swine have been reported from the Americas but not from Europe. We compared levels of neutralizing antibodies against 3 influenza viruses--pandemic (H1N1) 2009, an avian-like enzootic subtype H1N1 SIV, and a 2007-08 seasonal subtype H1N1--in 211 persons with swine contact and 224 matched controls in Luxembourg. Persons whose profession involved contact with swine had more neutralizing antibodies against SIV and pandemic (H1N1) 2009 virus than did the controls. Controls also had antibodies against these viruses although exposure to them was unlikely. Antibodies against SIV and pandemic (H1N1) 2009 virus correlated with each other but not with seasonal subtype H1N1 virus. Sequential exposure to variants of seasonal influenza (H1N1) viruses may have increased chances for serologic cross-reactivity with antigenically distinct viruses. Further studies are needed to determine the extent to which serologic responses correlate with infection.

Figure

Geometric mean titers (>10) of antibodies against pandemic (H1N1) 2009 virus, seasonal influenza (H1N1) virus, and swine influenza virus of swine workers (A, B, C) and controls (D). Each symbol represents titer of 1 person; only persons with positive results (>10) for at least 1 of the 2 viruses of the panel are shown. Trend lines are shown; R² values were R²>0.01 for panels A, B, and D and R² = 0.5 for panel C.