Multifaceted mechanisms of HIV-1 entry inhibition by human α-defensin.
The human neutrophil peptide 1 (HNP-1) is known to block the human immunodeficiency virus type 1 (HIV-1) infection, but the mechanism of inhibition is poorly understood. We examined the effect of HNP-1 on HIV-1 entry and fusion and found that, surprisingly, this α-defensin inhibited multiple steps of virus entry, including: (i) Env binding to CD4 and coreceptors; (ii) refolding of Env into the final 6-helix bundle structure; and (iii) productive HIV-1 uptake but not internalization of endocytic markers. Despite its lectin-like properties, HNP-1 could bind to Env, CD4, and other host proteins in a glycan- and serum-independent manner, whereas the fusion inhibitory activity was greatly attenuated in the presence of human or bovine serum. This demonstrates that binding of α-defensin to molecules involved in HIV-1 fusion is necessary but not sufficient for blocking the virus entry. We therefore propose that oligomeric forms of defensin, which may be disrupted by serum, contribute to the anti-HIV-1 activity perhaps through cross-linking virus and/or host glycoproteins. This notion is supported by the ability of HNP-1 to reduce the mobile fraction of CD4 and coreceptors in the plasma membrane and to precipitate a core subdomain of Env in solution. The ability of HNP-1 to block HIV-1 uptake without interfering with constitutive endocytosis suggests a novel mechanism for broad activity against this and other viruses that enter cells through endocytic pathways.
Division of Pediatric Infectious Diseases, Emory University Children's Center, Atlanta, Georgia 30322, USA.
Lusine H
LH
Demirkhanyan
Mariana
M
Marin
Sergi
S
Padilla-Parra
Changyou
C
Zhan
Kosuke
K
Miyauchi
Maikha
M
Jean-Baptiste
Gennadiy
G
Novitskiy
Wuyuan
W
Lu
Gregory B
GB
Melikyan
D000818:Animals; D015704:CD4 Antigens / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis; D057809:HEK293 Cells; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D011485:Protein Binding; D055503:Protein Multimerization; D053586:Virus Internalization; D023084:alpha-Defensins / Q000235:genetics / Q000378:metabolism*; D054299:env Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
D015704:CD4 Antigens; D023084:alpha-Defensins; D054299:env Gene Products, Human Immunodeficiency Virus; C406413:human neutrophil peptide 1