Immune and airway effects of house dust mite aeroallergen exposures during postnatal development of the infant rhesus monkey

Background The effect of chronic environmental aeroallergen exposure on the immune system and airways has not been experimentally defined in very young children. Objective The purpose of this study was to determine the immunophenotype of peripheral blood and airway leucocytes in the newborn rhesus macaque monkey, following recurrent aerosol exposure to house dust mite (HDM) (Dermatophagoides farinae). Methods A regimen of HDM aerosolization was initiated for 2 h per day, three times per week, starting when rhesus macaque monkeys were 1 week of age. All monkeys were inoculated with diptheria, tetanus, and acellular pertussis vaccine at 5 weeks of age to simulate human infant vaccination schedules. Results Following 8 weeks of HDM aeroallergen exposure, infant monkeys exhibited a significant reduction in the total peripheral blood lymphocyte numbers and a decreased frequency of peripheral blood CD4(+) T lymphocytes with a CD45RA(-)'memory' immunophenotype. Lavage CD4(+) T lymphocytes from HDM-exposed monkeys showed elevated expression of CD25, as well as an increase in CD45RA(-)/CD62L(-)/CD11a(high) immunophenotype. Eosinophils were more abundant within airways of HDM-exposed monkeys, accumulating maximally within the trachea. Conclusion These data demonstrate the development of immunological responses following chronic inhalation of a common environmental allergen during postnatal maturation in the non-human primate.