First, be sure to uncheck the box that states “Show only frequently occurring alleles” since the allele in question might actually be available. Second, select IEDB recommended as the prediction method. Some of the methods available have been trained on a limited set of alleles and thus will not make alleles outside of that set available for the user to specify. If the allele still does not appear, it means that insufficient experimental data exist to train the machine learning algorithms. You can get a sense of this by running a query for the host species and allele in the IEDB. Click the search button on the home page to get to the results page. You can then specify the host species and the allele of interest. As new data are added to the IEDB, the prediction methods are periodically updated, so the number of available alleles will expand over time.