McNeely T B, Shugars D C, Rosendahl M, Tucker C, Eisenberg S P, Wahl S M
Laboratory of Immunology, National Institute of Dental Research, National Institutes of Health, Bethesda, MD, USA.
Blood. 1997 Aug 1;90(3):1141-9.
Infection of monocytes with human immunodeficiency virus type 1(Ba-L) (HIV-1(Ba-L)) is significantly inhibited by treatment with the serine protease inhibitor, secretory leukocyte protease inhibitor (SLPI). SLPI does not appear to act on virus directly, but rather the inhibitory activity is most likely due to interaction with the host cell. The current study was initiated to investigate how SLPI interacts with monocytes to inhibit infection. SLPI was found to bind to monocytes with high affinity to a single class of receptor sites (approximately 7,000 receptors per monocyte, K(D) = 3.6 nmol/L). The putative SLPI receptor was identified as a surface protein with a molecular weight of 55 +/- 5 kD. A well-characterized function of SLPI is inhibition of neutrophil elastase and cathepsin G. However, two SLPI mutants (or muteins) that contain single amino acid substitutions and exhibit greatly reduced protease inhibitory activity still bound to monocytes and retained anti-HIV-1 activity. SLPI consists of two domains, of which the C-terminal domain contains the protease inhibiting region. However, when tested independently, neither domain had potent anti-HIV-1 activity. SLPI binding neither prevented virus binding to monocytes nor attenuated the infectivity of any virus progeny that escaped inhibition by SLPI. A polymerase chain reaction (PCR)-based assay for newly generated viral DNA demonstrated that SLPI blocks at or before viral DNA synthesis. Therefore, it most likely inhibits a step of viral infection that occurs after virus binding but before reverse transcription. Taken together, the unique antiviral activity of SLPI, which may be independent of its previously characterized antiprotease activity, appears to reside in disruption of the viral infection process soon after virus binding.
用丝氨酸蛋白酶抑制剂分泌型白细胞蛋白酶抑制剂（SLPI）处理可显著抑制1型人类免疫缺陷病毒（Ba-L株）（HIV-1(Ba-L)）对单核细胞的感染。SLPI似乎并非直接作用于病毒，其抑制活性很可能归因于与宿主细胞的相互作用。启动本研究以探究SLPI如何与单核细胞相互作用来抑制感染。发现SLPI以高亲和力与单核细胞上一类单一的受体位点结合（每个单核细胞约有7000个受体，解离常数K(D)=3.6 nmol/L）。推测的SLPI受体被鉴定为一种分子量为55±5 kD的表面蛋白。SLPI一个已明确的功能是抑制中性粒细胞弹性蛋白酶和组织蛋白酶G。然而，两个含有单个氨基酸取代且蛋白酶抑制活性大幅降低的SLPI突变体（或突变蛋白）仍能与单核细胞结合并保留抗HIV-1活性。SLPI由两个结构域组成，其中C端结构域包含蛋白酶抑制区域。然而，单独测试时，这两个结构域均无强大的抗HIV-1活性。SLPI的结合既不能阻止病毒与单核细胞的结合，也不能减弱任何逃脱SLPI抑制的病毒子代的感染性。一种基于聚合酶链反应（PCR）的新生成病毒DNA检测方法表明，SLPI在病毒DNA合成时或之前发挥阻断作用。因此，它很可能抑制病毒感染过程中发生在病毒结合之后但逆转录之前的某个步骤。综上所述，SLPI独特的抗病毒活性可能独立于其先前已明确的抗蛋白酶活性，似乎在于病毒结合后不久对病毒感染过程的破坏。
