Valere Kimyata, Lu Wuyuan, Chang Theresa L
Department of Microbiology and Molecular Genetics, Rutgers University, New Jersey Medical School, Newark, NJ 07103, USA.
Institute of Human Virology, University of Maryland School of Medicine, Baltimore, MD 21250, USA.
Viruses. 2017 Aug 29;9(9):244. doi: 10.3390/v9090244.
Defensins are antimicrobial peptides important for mucosal innate immunity. They exhibit a broad spectrum of activity against bacteria, viruses, and fungi. Levels of α-defensins are elevated at the genital mucosa of individuals with sexually transmitted infections (STIs). Somewhat paradoxically, human α-defensin 5 and 6 (HD5 and HD6) promote human immunodeficiency virus (HIV) infectivity, and contribute to STI-mediated enhancement of HIV infection in vitro. Specific amino acid residues of HD5 and HD6 that are crucial for antimicrobial activities have been characterized previously; however, the key determinants of defensins responsible for enhancement of HIV infectivity are not known. Here, we have identified residues of HD5 and HD6 that are required for enhancement of HIV attachment and infection. Most of these residues are involved in hydrophobicity and self-association of defensins. Specifically, we found that mutant defensins L16A-HD5, E21me-HD5, L26A-HD5, Y27A-HD5, F2A-HD6, H27W-HD6, and F29A-HD6 significantly lost their ability to promote HIV attachment and infection. L29A mutation also reduced HIV infection-enhancing activity of HD5. Additionally, a number of mutations in charged residues variably affected the profile of HIV attachment and infectivity. One HD5 charged mutation, R28A, notably resulted in a 34-48% loss of enhanced HIV infectivity and attachment. These results indicate that defensin determinants that maintain high-ordered amphipathic structure are crucial for HIV enhancing activity. In a comparative analysis of the mutant defensins, we found that for some defensin mutants enhancement of HIV infectivity was associated with the reverse transcription step, suggesting a novel, HIV attachment-independent, mechanism of defensin-mediated HIV enhancement.
防御素是对黏膜固有免疫很重要的抗菌肽。它们对细菌、病毒和真菌表现出广谱活性。在性传播感染（STIs）患者的生殖黏膜中，α-防御素水平会升高。有点矛盾的是，人类α-防御素5和6（HD5和HD6）会促进人类免疫缺陷病毒（HIV）的感染性，并在体外导致性传播感染介导的HIV感染增强。HD5和HD6中对抗菌活性至关重要的特定氨基酸残基先前已得到表征；然而，负责增强HIV感染性的防御素的关键决定因素尚不清楚。在这里，我们确定了HD5和HD6中增强HIV附着和感染所需的残基。这些残基中的大多数都参与了防御素的疏水性和自我缔合。具体而言，我们发现突变防御素L16A-HD5、E21me-HD5、L26A-HD5、Y27A-HD5、F2A-HD6、H27W-HD6和F29A-HD6显著丧失了促进HIV附着和感染的能力。L29A突变也降低了HD5增强HIV感染的活性。此外，带电残基中的一些突变对HIV附着和感染性的影响各不相同。一个HD5带电突变R28A尤其导致增强的HIV感染性和附着能力丧失34-48%。这些结果表明，维持高阶两亲结构的防御素决定因素对HIV增强活性至关重要。在对突变防御素的比较分析中，我们发现对于一些防御素突变体，HIV感染性的增强与逆转录步骤相关，这表明防御素介导的HIV增强存在一种新的、不依赖HIV附着的机制。
