Courtney Harry S, Hasty David L, Dale James B
Veterans Affairs Medical Center and Department of Medicine, University of Tennessee, Memphis, Tennessee 38104, USA.
Infect Immun. 2003 Sep;71(9):5097-103. doi: 10.1128/IAI.71.9.5097-5103.2003.
Serum opacity factor (SOF) is a protein expressed by Streptococcus pyogenes that opacifies mammalian serum. SOF is also a virulence factor of S. pyogenes, but it has not been previously shown to elicit a protective immune response. Herein, we report that SOF evokes bactericidal antibodies against S. pyogenes in humans, rabbits, and mice. Rabbit antiserum against purified recombinant SOF2 opsonized SOF-positive M type 2, 4, and 28 S. pyogenes in human blood but had no effect on SOF-negative M type 5 S. pyogenes. Furthermore, affinity-purified human antibodies against SOF2 also opsonized SOF-positive streptococci. A combination of antisera against M2 and SOF2 proteins was dramatically more effective in killing streptococci than either antiserum alone, indicating that antibodies against SOF2 enhance the opsonic efficiency of M protein antibodies. Mice tolerated an intravenous injection of 100 microg of SOF without overt signs of toxicity, and immunization with SOF protected mice against challenge infections with M type 2 S. pyogenes. These data indicate that SOF evokes opsonic antibodies that may protect against infections by SOF-positive serotypes of group A streptococci and suggest that different serotypes of SOF have common epitopes that may be useful vaccine candidates to protect against group A streptococcal infections.
血清混浊因子（SOF）是化脓性链球菌表达的一种可使哺乳动物血清变混浊的蛋白质。SOF也是化脓性链球菌的一种毒力因子，但此前尚未证明它能引发保护性免疫反应。在此，我们报告SOF能在人、兔和小鼠体内诱发针对化脓性链球菌的杀菌抗体。抗纯化重组SOF2的兔抗血清可调理人血中SOF阳性的2型、4型和28型化脓性链球菌，但对SOF阴性的5型化脓性链球菌无作用。此外，亲和纯化的抗SOF2人抗体也能调理SOF阳性的链球菌。抗M2和SOF2蛋白的抗血清组合在杀死链球菌方面比单独使用任何一种抗血清都显著有效，这表明抗SOF2抗体可提高M蛋白抗体的调理效率。小鼠能耐受静脉注射100微克SOF且无明显毒性迹象，用SOF免疫可保护小鼠免受2型化脓性链球菌的攻击感染。这些数据表明，SOF能诱发调理抗体，可能对A组链球菌SOF阳性血清型感染起到保护作用，并提示不同血清型的SOF具有共同表位，可能是预防A组链球菌感染的有用候选疫苗。
