Association of Single Nucleotide Polymorphisms in Surfactant Protein A and D with Otitis Media.
Barnett, C. M. E. (2007). Association of Single Nucleotide Polymorphisms in Surfactant Protein A and D with Otitis Media. (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from http://hdl.handle.net/10289/2338
Permanent Research Commons link: http://hdl.handle.net/10289/2338
Otitis Media is one of the most common childhood diseases. Recurrent acute otitis media RAOM is characterized by repeated episodes of inflammation of the middle ear in conjunction with middle ear fluid, and often with an inflamed or bulging eardrum. Defective clearance by the Eustachian tube results in mucus build-up and is characteristic of otitis media with effusion (OME). Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, respiratory syncytial virus, and rhinovirus are the most common contributors to otitis media pathogenesis. In New Zealand, OME has been implicated with conductive hearing loss in childhood and has been shown to significantly impact on speech and language development. New Zealand Māori and Polynesian children have displayed significantly higher hearing test failure rates than European-Caucasian children. The collectins, Surfactant Protein (SP)-A and -D are encoded by three genes (SP-A1, SP-A2, and SP-D) and are host defense proteins present in the middle ear and Eustachian tube. Single nucleotide polymorphisms (SNPs) in SP-A1 and SP-A2 have been associated with increased or decreased susceptibility to otitis media, meningococcal disease, and range of respiratory diseases. Using allele-specific primers and real-time PCR with SYBR Green I melting curve analysis, four groups of individuals were genotyped for eleven SP-A1, SP-A2, and SP-D SNPs: European-Caucasian individuals with RAOM/OME; New Zealand Māori/Polynesian individuals with RAOM/OME; individuals with meningococcal disease; and a control group. The computer program, Haploview, was employed to perform χ2 analyses and identify statistically significant associations of alleles/haplotypes with RAOM/OME or meningococcal disease. In the European-Caucasian population, two SP-A1 alleles, one SP-A2 allele, and four haplotypes (CGAGC, 1A3, 1A9, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). Conversely, haplotypes 6A2 and 1A2 were found to be protective against susceptibility to RAOM/OME (P lt; 0.05). In New Zealand Māori and Polynesian individuals, two SP-A1 alleles, three SP-A2 alleles, one SP-D allele, and four haplotypes (6A8, 6A10, 1A3, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). An additional four haplotypes (6A2, 1A0, 1A2, and TA) were determined to be protective against susceptibility to RAOM/OME (P lt; 0.05). However, protective SPA1/SPA2/SPD haplotype 6A2-1A0-TA was significantly under-represented in the New Zealand Māori and Polynesian population (P lt; 0.05). A single allele and haplotype were associated with increased risk of meningococcal disease (P lt; 0.05). The findings of this study confirm that specific genetic variants of SP-A and SP-D are associated with either increased or decreased risk of developing RAOM and/or OME. Furthermore, it was demonstrated that New Zealand Māori and Polynesian individuals appear to exhibit more haplotypes susceptible to RAOM/OME. This may provide a partial explanation for the higher RAOM/OME-related failure rates of hearing tests in New Zealand Māori and Polynesian children. However, there are numerous socio-economic and environmental factors that also contribute to otitis media pathogenesis which were not considered in this study. The effects of the SP-A1, SP-A2, and SP-D alleles and haplotypes on the bacterial/viral binding efficiencies of SP-A and SP-D need to be investigated by further research, using a large population, to confirm the association with susceptibility or resistance with RAOM/OME.
The University of Waikato
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