Scabies mite inactivated serine protease paralogs inhibit the human complement system

Area of Science:

• Parasitology
• Immunology
• Molecular Biology

Background:

• Scabies, caused by Sarcoptes scabiei, affects 300 million globally, necessitating new treatments.
• Scabies mite-inactivated protease paralogs (SMIPPs) are secreted into the mite's gut and feces.
• Mites feed on host proteins and plasma, encountering host defense mechanisms.

Purpose of the Study:

• To investigate the function of SMIPPs in the context of host immune interactions.
• To determine if SMIPPs can modulate the human complement system.

Main Methods:

• Recombinant expression of two SMIPPs.
• Assays to test SMIPP inhibition of the three human complement pathways.
• Binding studies of SMIPPs to complement components (C1q, mannose-binding lectin, properdin).
• Immunohistochemical staining of mite gut tissue.

Main Results:

• Two SMIPPs inhibited all three human complement pathways.
• SMIPPs bound to C1q, mannose-binding lectin, and properdin, preventing complement initiation.
• SMIPPs prevented alternative pathway convertase assembly but did not dissociate existing ones.
• C1q was detected in the mite gut.

Conclusions:

• SMIPPs likely protect scabies mites from complement-mediated damage in their gut.
• SMIPPs contribute to a favorable environment for mite survival and feeding.
• SMIPPs represent potential targets for novel anti-scabies therapies.