Gandhi M J, Boyd M R, Yi L, Yang G G, Vyas G N
Department of Laboratory Medicine, University of California, San Francisco, USA.
Dev Biol (Basel). 2000;102:141-8.
Cyanovirin-N (CV-N) is a novel anti-HIV protein isolated and characterized from a cyanobacterium Nostoc ellipsosporum. CV-N protein is a single 101 amino acid chain containing two intrachain disulphide bonds and considerable internal sequence duplication, but no significant homology to previously described proteins or to the transcription products of known nucleotide sequences. In solution, CV-N exists largely as a beta-sheet protein with internal two-fold pseudosymmetry. CV-N irreversibly inactivates diverse laboratory strains, primary isolates and clades of HIV-1, as well as strains of HIV-2 and simian immunodeficiency virus (SIV). CV-N binds with extremely high affinity to highly conserved binding site(s) on the viral envelope glycoprotein gp120, preventing virus-to-cell fusion, viral entry and infection of cells. The CV-N binding site appears to overlap, but is not identical with, the unique carbohydrate-dependent epitope 2G12, and may lie predominantly within an immunologically "silent" region of gp120. CV-N is undergoing preclinical development for topical anti-HIV prophylactic (e.g., microbicidal) applications to prevent sexual transmission of HIV. Since CV-N may be immunogenic in humans, methods for using CV-N for ex vivo inactivation of HIV in blood, plasma, or putative vaccines preferably would allow for its exclusion from biologicals for parenteral use. To explore this concept we biotinylated CV-N (bCV-N) and coupled it to streptavidin coated magnetic beads to provide a product which we termed sessile CV-N (sCV-N). When reacted with a laboratory strain and a primary isolate of HIV- 1, the sCV-N completely inactivated 100 TCID50 of the virus. However RT-PCR of the viral extracts indicated that only a fraction of the virus was removed by the sCV-N, leaving behind a relatively larger fraction of non-infectious virus in the supernatant which we designated as replication incompetent virions (RIV). It would be worthwhile investigating the role of RIV as a putative HIV vaccine.
氰胍蛋白-N（CV-N）是一种从蓝藻椭圆念珠藻中分离并鉴定出的新型抗HIV蛋白。CV-N蛋白是一条由101个氨基酸组成的单链，含有两条链内二硫键以及大量内部序列重复，但与先前描述的蛋白或已知核苷酸序列的转录产物没有显著同源性。在溶液中，CV-N主要以具有内部双重假对称的β-折叠蛋白形式存在。CV-N能不可逆地使多种HIV-1实验室菌株、原代分离株和分支失活，以及HIV-2菌株和猴免疫缺陷病毒（SIV）失活。CV-N以极高的亲和力与病毒包膜糖蛋白gp120上高度保守的结合位点结合，阻止病毒与细胞融合、病毒进入及细胞感染。CV-N的结合位点似乎与独特的碳水化合物依赖性表位2G12重叠，但并不相同，且可能主要位于gp120的免疫“沉默”区域内。CV-N正在进行临床前开发，用于局部抗HIV预防（如杀微生物剂）应用，以预防HIV的性传播。由于CV-N在人类中可能具有免疫原性，将CV-N用于血液、血浆或推定疫苗中HIV的体外灭活的方法，最好能使其不被用于肠胃外使用的生物制品中。为了探索这一概念，我们将CV-N生物素化（bCV-N）并将其偶联到包被链霉亲和素的磁珠上，得到一种我们称为固定CV-N（sCV-N）的产物。当与HIV-1的一种实验室菌株和一种原代分离株反应时，sCV-N能完全灭活100个TCID50的病毒。然而，病毒提取物的逆转录聚合酶链反应（RT-PCR）表明，sCV-N仅去除了一部分病毒，上清液中留下了相对较大比例的无感染性病毒，我们将其指定为复制无能力病毒粒子（RIV）。研究RIV作为推定HIV疫苗的作用将是值得的。
