Influence of mite growth culture phases on the biological standardization of allergenic extracts.

House dust mites are a well known cause of asthma and other respiratory allergies. In order to improve the standardization of allergenic extracts for diagnosis and immunotherapy, it is important to determine the frequency and concentration of the components, both the major and the minor allergens during the growth period of the mite population. In a previous paper we demonstrated that the laboratory cultures of Dermatophagoides pteronyssinus and Dermatophogoides farinae exhibited three well differentiated growth phases: latency, exponential growth, and death of the culture. Biological standardization of extracts from the two mite species were carried out by skin prick tests in a group of 20 patients, using different concentrations of the extracts at the three growth phases. The patient sera were also studied by means of the RAST technique to determine the levels of specific IgE for each phase. The extracts produced from the exponential growth phase of the cultures revealed six times more relative allergenic activity in in vivo studies, and average RAST values were approximately three times higher than those extracts from latency and death phases. The reproducibility of the extract production method was assessed by comparing different batches obtained in similar conditions. The results showed batch-to-batch homogeneity allergenic activity. In conclusion, it was demonstrated that extracts obtained from cultures with the highest concentration of live mites (maximum growth phase) render the best diagnostic results in vivo and in vitro.