Megraud F, Gamon L B, McGarrity G J
Infect Immun. 1983 Dec;42(3):1168-75. doi: 10.1128/iai.42.3.1168-1175.1983.
Spiroplasma mirum (suckling mouse cataract agent) was studied in an epithelial cell line AG-4676, derived from rabbit eye lens. Rabbit eye lens is a natural target tissue of S. mirum infection. The organism grew rapidly in this cell line, reaching titers of 10(7) to 10(9) color change units per ml at 7 days after infection. This is the same level as that achieved in SP-4 medium designed specifically for S. mirum. No lag period was apparent in growth in AG-4676. S. mirum did not grow in Dulbecco minimal essential medium-10% fetal bovine serum, the medium for AG-4676, indicating the need for cells or a cellular product. S. mirum-infected AG-4676 cells exhibited vacuolization and granulation and an increase in polynucleation compared with uninfected controls (36/100 versus 14/100, P less than 0.001). Infection significantly decreased the growth rate of AG-4676, especially late in the growth cycle. In a representative experiment, growth of AG-4676 at 11 days was reduced from 9 X 10(5) to 2 X 10(4) cells by S. mirum infection. S. mirum grew to high titers in conditioned medium of AG-4676, obtained from cell-free supernatants of 1- to 5-day-old AG-4676 cultures. This growth promotion was not due to osmotic conditioning of the medium. Preliminary characterization of this growth promotion substance showed it to be active after 0.22-micron filtration, heating at 56 degrees C for 30 min, freezing and thawing, and dilution at 10(-1) but not 10(-2). AG-4676-propagated S. mirum produced death or cataracts in suckling Wistar rats at the same frequency (55/60, 91.7%) as SP-4-propagated organisms (60/65, 92.3%).
微小螺旋体（乳鼠白内障病原体）在源自兔眼晶状体的上皮细胞系AG - 4676中进行了研究。兔眼晶状体是微小螺旋体感染的天然靶组织。该病原体在这个细胞系中生长迅速，感染后7天每毫升达到10⁷至10⁹个颜色变化单位的滴度。这与专门为微小螺旋体设计的SP - 4培养基中达到的水平相同。在AG - 4676中的生长没有明显的滞后期。微小螺旋体在AG - 4676的培养基（杜尔贝科最低必需培养基 - 10%胎牛血清）中不生长，这表明需要细胞或细胞产物。与未感染的对照相比，感染微小螺旋体的AG - 4676细胞表现出空泡化和颗粒化以及多核化增加（36/100对14/100，P小于0.001）。感染显著降低了AG - 4676的生长速率，尤其是在生长周期后期。在一个代表性实验中，微小螺旋体感染使AG - 4676在11天时的生长从9×10⁵个细胞减少到2×10⁴个细胞。微小螺旋体在AG - 4676的条件培养基中生长至高滴度，该条件培养基取自1至5日龄AG - 4676培养物的无细胞上清液。这种生长促进不是由于培养基的渗透调节。这种生长促进物质的初步特性表明，它在经过0.22微米过滤、56℃加热30分钟、冻融以及10⁻¹而非10⁻²稀释后仍具有活性。在乳鼠Wistar大鼠中，AG - 4676传代的微小螺旋体导致死亡或白内障的频率（55/60，91.7%）与SP - 4传代的病原体（60/65，92.3%）相同。
