Leukocyte adhesion deficiency (LAD) is a rare autosomal recessive disorder characterized by immunodeficiency resulting in recurrent infections.

The classic descriptions of LAD included recurrent bacterial infections, defects in neutrophil adhesion, and a delay in umbilical cord sloughing.

Infections such as omphalitis, pneumonia, gingivitis, and peritonitis are common and often life-threatening due to the infant's inability to properly destroy the invading pathogens.

The main function of these proteins is to allow neutrophils to make their way out of the blood stream and into the infected tissues by adhering to different ligands expressed by the endothelium, e.g. ICAM-1.

[citation needed] Although patients can receive intensive antibiotherapy and even granulocyte transfusions from healthy donors, the only current curative therapy is the hematopoietic stem cell transplant.

Both foamyviral and lentiviral vectors expressing the human ITGB2 gene under the control of different promoters have been developed and have been tested so far in preclinical LAD-I models (such as CD18-deficient mice and canine leukocyte adhesion deficiency-affected dogs).