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Clin. Vaccine Immunol. doi:10.1128/CVI.00221-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Antibodies Specific for the High Molecular Weight Adhesion Proteins of Nontypable Haemophilus influenzae are Opsonophagocytic for both Homologous and Heterologous Strains

Department of Pediatrics, Saint Louis University School of Medicine; and the Pediatric Research Institute, Cardinal Glennon Children's Hospital, Saint Louis, Missouri 63104

^* To whom correspondence should be addressed. Email: barenksj{at}slu.edu.

	Abstract

The HMW1/HMW2-like adhesion proteins of nontypable Haemophilus influenzae (NTHi) are expressed by 75% of NTHi. Antibodies directed against these proteins are opsonophagocytic in vitro and are protective in an animal model of infection. The objective of the present study was to determine the opsonophagocytic activity of high-titer anti-HMW1/HMW2 immune sera against both homologous and heterologous NTHi strains. Chinchillas were immunized with purified HMW1/HMW2-like proteins from five prototype NTHi. Serum opsonophagocytic activity was monitored in an assay that uses human promyelocytic cell line, HL-60, as the source of phagocytic cells. Preimmune sera did not demonstrate opsonophagocytic killing of any strains. In contrast, the immune sera demonstrated killing of the five homologous NTHi strains at titers ranging from 1:320 to 1:640. The immune sera also demonstrated killing of eight heterologous NTHi strains that express HMW1/HMW2-like proteins at titers ranging from 0 to 1:640. Killing of heterologous strains sometimes demonstrated a prozone phenomenon. None of the immune sera killed NTHi strains that did not express HMW1/HMW2-like proteins. Adsorption of immune sera with HMW1/HMW2-like proteins purified from either homologous or heterologous NTHi strains eliminated opsonophagocytic killing of homologous strains in most cases. These data demonstrate that antibodies produced following immunization with the HMW1/HMW2-like proteins are opsonophagocytic for both homologous and heterologous NTHi and strongly suggest that common epitopes recognized by functionally-active antibodies exist on the HMW1/HMW2-like proteins of unrelated NTHi. The results argue for the continued investigation of the HMW1/HMW2-like proteins as potential vaccine candidates for prevention of NTHi disease.