Human antibodies to pneumococcal surface protein A in health and disease.
BACKGROUND
Diseases caused by Streptococcus pneumoniae have a high impact in young children whose ability to mount antibodies to capsular polysaccharides is impaired. Pneumococcal surface protein A (PspA) is a potential vaccine candidate for this age group.


METHODS
We used Western blot analysis and enzyme immunoassay to study human sera of healthy adults from Alabama (n = 20) and from Finland (n = 21), healthy children from Finland (n = 20) and ill children from Finland, those with pneumococcal invasive infection (n = 26) and those with nonpneumococcal invasive infection (n = 26).


RESULTS
Human antibodies to PspA exhibited strong cross-reactivity among different pneumococcal strains. The geometric mean titer of IgG antibody to PspA in sera from 21 healthy adults was 4,040, from ten 3-year-old healthy children 1,080 and from ten 2-month-old healthy children 1,650. The geometric mean titer of PspA antibody of acute phase sera of children with invasive pneumococcal disease was 140, significantly (P < 0.001) lower than the respective value, 1,020, for children with infection caused by other bacteria.


CONCLUSIONS
We demonstrate for the first time the existence of antibodies to PspA in human sera in health and disease. The findings in ill children suggest that antibodies to PspA might play a role in protection against pneumococcal disease.
Virolainen
A
A
University of Alabama at Birmingham, USA. anni.virolainen@helsinki.fi
Russell
W
W
Crain
M J
MJ
Rapola
S
S
Käyhty
H
H
Briles
D E
DE
D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood*; D001426:Bacterial Proteins / Q000276:immunology*; D015153:Blotting, Western; D002675:Child, Preschool; D003429:Cross Reactions; D005387:Finland; D006801:Humans; D007124:Immunoenzyme Techniques; D007223:Infant; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology*
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; C051592:pneumococcal surface protein A