Experimental recurrent otitis media induced by Haemophilus influenzae: protection and serum antibodies.
OBJECTIVE
To study whether acute otitis media caused by encapsulated or nontypeable Haemophilus influenzae confers cross-reactive protective immunity in an animal model system and to explore the possible involvement of various humoral specific antibodies in protection.


METHODS
Rats were intrabullarly challenged with H influenzae type b and two different nontypeable H influenzae strains. One month after the initial infection, the animals were rechallenged ipsilaterally or contralaterally with either a homologous or heterologous strain, and the susceptibility to reinfection was investigated by otomicroscopy.


RESULTS
The animals challenged and rechallenged with the type b strain were well-protected ipsilaterally and contralaterally, while the protection after homologous rechallenge with a nontypeable strain was partial in the ipsilateral ear and very poor in the contralateral ear. Middle ears previously infected with a nontypeable strain remained fully susceptible to infections with heterologous strains, but there was an indication of cross-protection in the animal groups where the first episode of acute otitis media was caused by type b and the second by a nontypeable strain. Using the Western blot technique and an enzyme linked immunosorbant assay, the serological response to different outer membrane proteins, especially protein D, of H influenzae during and after middle ear infection were investigated. The serological response from the type b infected animals were generally more distinct, while the antibody levels against protein D were lower in these groups compared with the groups infected with nontypeable strains.


CONCLUSIONS
These data indicate that H influenzae type-b-induced experimental otitis media results in a better protection than a nontypeable-induced, and H influenzae b confers a cross protection.
Melhus
A
A
Department of Medical Microbiology, Lund University, Malmö General Hospital, Sweden.
Hermansson
A
A
Akkoyunlu
M
M
Forsgren
A
A
Prellner
K
K
D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis / Q000097:blood*; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology; D001426:Bacterial Proteins; D015153:Blotting, Western; D002352:Carrier Proteins / Q000276:immunology; D003429:Cross Reactions; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D004797:Enzyme-Linked Immunosorbent Assay; D006192:Haemophilus Infections / Q000276:immunology*; D006193:Haemophilus influenzae / Q000145:classification / Q000276:immunology*; D007114:Immunization; D007072:Immunoglobulin D / Q000276:immunology; D008074:Lipoproteins / Q000276:immunology; D008297:Male; D008853:Microscopy; D010033:Otitis Media / Q000276:immunology* / Q000382:microbiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012008:Recurrence; D012703:Serotyping
D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D007072:Immunoglobulin D; D008074:Lipoproteins; C067989:glpQ protein, Haemophilus influenzae