International Immunology, Vol. 11, No. 4, 569-576,
April 1999
© 1999 Japanese Society for Immunology
Functional analysis of IgA antibodies specific for a conserved epitope within the M protein of group A streptococci from Australian Aboriginal endemic communities
Molecular Immunology Laboratory and CRC for Vaccine Technology, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, Queensland 4029, Australia
1 Menzies School of Health Research, Casuarina, NT 0810, Australia
2 Department of Microbiology, University of Melbourne, Parkville, Victoria 3052, Australia
3 Centre for Statistics, University of Queensland, St Lucia, Queensland 4067, Australia
Correspondence to: M. F. Good
The mucosa is one of the initial sites of group A streptococcal (GAS) infection and salivary IgA (sIgA) is thought to be critical to immunity. However, the target epitopes of sIgA and the function of sIgA in GAS immunity, in particular the role of accessory cells and complement, is largely unknown. We studied the aquisition and the function of sIgA specific for a conserved region epitope, p145 (sequence: LRRDLDASREAKKQVEKALE) of the M protein. Peptide 145-specific sIgA is highly prevalent within an Aboriginal population living in an area endemic for GAS and acquisition of p145-specific sIgA increases with age, consistent with a role for such antibodies in immunity to GAS. Human sIgA and IgG specific for p145 were affinity purified and shown to opsonize M5 GAS in vitro. Opsonization could be specifically inhibited by the addition of free p145 to the antibodies during assay. Opsonization of GAS was totally dependent on the presence of both complement and polymorphonuclear leukocytes, and, moreover, affinity-purified p145-specific sIgA was shown to fix complement in the presence of M5 GAS. These data show that mucosal IgA to this conserved region peptide within the M protein has an important role in human immunity against GAS and may be useful in a broad-based cross-protective anti-streptococcal vaccine.
Keywords: rheumatic fever, vaccine
Transmitting editor: S. H. Kaufmann
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