Dirofilaria immitis: proteases produced by third- and fourth-stage larvae

Area of Science:

• Parasitology
• Biochemistry
• Dermatology

Background:

• Cutaneous extracellular matrix (ECM) is vital for skin structure and integrity.
• Dirofilaria immitis larvae (L3 and L4) must degrade ECM for tissue migration and development.
• The enzymatic activity of D. immitis larvae on ECM is not fully understood.

Purpose of the Study:

• To investigate if Dirofilaria immitis larvae secrete active proteases capable of degrading cutaneous ECM.
• To characterize the types and activity of proteases secreted by L3 and L4 larvae.
• To correlate protease activity with larval molting and ECM degradation.

Main Methods:

• Utilized a model of cutaneous extracellular matrix.
• Incubated third-stage (L3) and fourth-stage (L4) Dirofilaria immitis larvae with the ECM model for 72 hours.
• Analyzed ECM degradation, focusing on collagen, glycoprotein, and elastin components.
• Characterized larval proteases using synthetic substrates and protease inhibitors.
• Separated proteases by size-exclusion chromatography.

Main Results:

• L3 larvae degraded 24% of the total ECM, while L4 larvae degraded 10%.
• Molting L3 larvae showed a significant increase in ECM degradation, particularly collagen (62% vs 35% by L4).
• Cysteine proteases and metalloproteases were identified in larval extracts and secretions.
• Metalloprotease activity was higher in molting L3, while cysteine protease activity was present in both L3 and L4.
• Metalloprotease molecular weight was estimated at 49-54 kDa, and cysteine protease at 34-39 kDa.

Conclusions:

• Dirofilaria immitis larvae secrete active proteases, including cysteine and metalloproteases.
• These proteases degrade key components of the cutaneous extracellular matrix.
• Larval proteases likely play a role in both ECM degradation and the molting process.