HIV is a double stranded virus, means it has two strands to integrate into the host chromosome.
Lets say it infects a developing T/B cell, one of the chromosomes in the cell gets excluded because it produces a faulty TCR/IG epitope that binds it too tightly to self antigens, this would effectively kill the integrated provirus in the excluded chromosome.
But, HIV has got ways to get around this, the second copy integrates into the homolog (we all have homologs remember?) , so HIV cant be defeated by allelic exclusion.