Effect of gammaglobulin on pneumococcal otitis media in the rat

Immunization and protection in pneumococcal otitis media studied in a rat model

The recent and growing problem of bacterial resistance to common antibiotics has generated great interest in different methods for prevention of infections. The treatment of the pathogens causing upper airway infections and especially acute otitis media (AOM) is especially interesting in this context because these infections are a common cause of prescription of antibiotics all over the world. Both in AOM and recurrent AOM, Streptococcus pneumoniae, the most frequently occurring bacterium is isolated in 30-50% of all AOM attacks. In the last decade, multiresistant S. pneumoniae have emerged as a major problem. Thus, it is important to explore possibilities that immunization may protect against pneumococcal OM. In a well-defined animal model using Sprague-Dawley rats, we have investigated the effects of different routes of immunization with different antigens and whole cells. Together with otomicroscopical evaluation of middle ear (ME) status, samples for bacterial cultivation as well as for studies of histopathological changes have been collected. Antibody titers have been followed during and after pneumococcal AOM by an enzyme-linked immunosorbent assay (ELISA) method.

Active immunisation and resistance to experimental acute pneumococcal otitis media

The middle ear mucosal system and the humoral systemic immune factors are the two immunological systems whose involvement in the defence against acute otitis media (AOM) have been most intensively studied. However, their respective importance and their mutual influence is not clear. In the present study, a rat model for pneumococcal AOM was used to further elucidate the involvement of systemic immunity in protection against pneumococcal AOM. Six groups of male Sprague-Dawley rats were immunised with pneumococcal vaccine (PneumovaxRN) or live pneumococci (type 3) via one of three different routes: intraperitoneally, into the gastrointestinal tract (GIT) or into the right middle ear. A subsequent middle ear challenge (re-challenge in one group) with the same pneumococcal strain was performed after 4 days to 8 weeks in the different groups. Systemic immunity was found to be triggered, not only by systemic immunisation, but also by antigenic stimulation of the mucosa in the middle ear and in the GIT. In all groups but that immunised in the GIT, no new peak of specific IgG antibody response was demonstrated in serum after middle ear challenge/re-challenge. In contrast, half of the rats immunised in the GIT showed such a response not only after the inoculation into the GIT but also after a later performed middle ear challenge. Though a faster resolution of pus from the middle ear was observed in rats from all but one group, a significant reduction in the number of rats who developed AOM occurred exclusively among those rats that had previously manifested serological response to immunisation in the GIT.

Nasopharyngeal bacterial flora in otitis prone children treated with immunoglobulin

The present study was undertaken to evaluate possible beneficial effects of regularly given, long term immunoglobulin prophylaxis of children below 2 years of age with recurrent acute otitis media (RAOM). The nasopharyngeal bacterial flora and the frequency of acute otitis media (AOM) and secretory otitis media SOM were studied. Every second of 44 children with 3 or more periods of AOM during the last year received immunoglobulin intramuscularly (Gammaglobulin Kabi 165 mg/l, 0.45 ml/kg b.w.) every third week for 6 months, while the other 22 children served as controls. All children were followed for 12 months. Immunoglobulin prophylaxis neither influenced the nasopharyngeal flora, nor the frequency of AOM or SOM periods. Children with AOM or SOM more often harbored bacterial pathogens in their nasopharynx than children with normal middle ear status. Also, the immunoglobulin prophylaxis did not influence the increased frequency of bacterial pathogens in the nasopharynx of children attending public day care or family day care as compared to those taken care of at home.

Experimental recurrent pneumococcal otitis media. Protection and serum antibodies

To elucidate immune mechanisms in otitis media, middle ear infection was induced in 12 rats by intratympanic inoculation of Streptococcus pneumoniae type 3, either the ipsilateral or the contralateral middle ear being re-challenged 4 weeks later. Otomicroscopy inspection confirmed the presence of acute otitis media (AOM) in all rats after the first challenge. After re-challenge, protection against AOM was noted both in the ipsilateral and contralateral ears. Serum antibody concentrations increased after the initial challenge, reaching a maximum at 4-7 days, but had decreased to pre-immune levels at re-challenge, after which no new increase was noted. Serum IgG-antibodies to pneumococcal type 3-polysaccharide were triggered following the initial induction of unilateral pneumococcal AOM, but mucosal immune mechanisms are argued to be a more probable explanation of the ipsilateral protection seen after re-challenge.