MMP2 and myeloid sarcoma: Moreover, increased levels of the matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) have been detected in HSV-1 latently-infected CNS, which could contribute to the degradation of the surrounding extracellular matrix and cell surface proteins leading to a partial breakdown of the blood-brain barrier (BBB), which plays an important role in MS (16, 17).