AUTHOR=Xu Xiaobai , Negandhi Jaina , Min Weixian , Tsui Michael , Post Martin , Harrison Robert V. , Grunebaum Eyal
TITLE=Early Enzyme Replacement Therapy Improves Hearing and Immune Defects in Adenosine Deaminase Deficient-Mice
JOURNAL=Frontiers in Immunology
VOLUME=10
YEAR=2019
URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2019.00416
DOI=10.3389/fimmu.2019.00416
ISSN=1664-3224
ABSTRACT=Background: Inherited defects in adenosine deaminase (ADA) cause severe immune deficiency, which can be corrected by ADA enzyme replacement therapy (ERT). Additionally, ADA-deficient patients suffer from hearing impairment. We hypothesized that ADA-deficient (–/–) mice also exhibit hearing abnormalities and that ERT from an early age will improve the hearing and immune defects in these mice.
Methods: Auditory brainstem evoked responses, organ weights, thymocytes numbers, and subpopulations, lymphocytes in peripheral blood as well as T lymphocytes in spleen were analyzed in ADA–/– and ADA-proficient littermate post-partum (pp). The cochlea was visualized by scanning electron microscopy (SEM). The effects of polyethylene glycol conjugated ADA (PEG-ADA) ERT or 40% oxygen initiated at 7 days pp on the hearing and immune abnormalities were assessed.
Results: Markedly abnormal hearing thresholds responses were found in ADA–/– mice at low and medium tone frequencies. SEM demonstrated extensive damage to the cochlear hair cells of ADA–/– mice, which were splayed, short or missing, correlating with the hearing deficits. The hearing defects were not reversed when hypoxia in ADA–/– mice was corrected. Progressive immune abnormalities were detected in ADA–/– mice from 4 days pp, initially affecting the thymus followed by peripheral lymphocytes and T cells in the spleen. ERT initiated at 7 days pp significantly improved the hearing of ADA–/– mice as well as the number of thymocytes and T lymphocytes, although not all normalized.
Conclusions: ADA deficiency is associated with hearing deficits and damage to cochlear hair cells. Early initiation of ERT improves the hearing and immune abnormalities.