Pal Sukumar, Peterson Ellena M, de la Maza Luis M
Department of Pathology, Medical Sciences, Room D440, University of California-Irvine, Irvine, CA 92697-4800, USA.
Infect Immun. 2004 Jul;72(7):4210-6. doi: 10.1128/IAI.72.7.4210-4216.2004.
The lack of an experimental model has significantly limited the understanding of the pathogenesis of Chlamydia trachomatis infections in males. In an attempt to establish a model using the natural route of infection, we inoculated male mice in the meatus urethra. To establish the 50% infectious dose (ID(50)), C3H/HeN (H-2(k)) male mice were inoculated in the meatus urethra with doses ranging from 10(1) to 10(7) inclusion-forming units (IFU) of C. trachomatis mouse pneumonitis biovar (MoPn) and were euthanized at 10 days postinfection (p.i.). Approximately 50% of the animals inoculated with 5 x 10(4) IFU had positive cultures of the urethra, urinary bladder, epididymides, and/or testes. Subsequently, to characterize the course of the infection, a group of animals was inoculated with 10(6) IFU/mouse (20 times the ID(50)). Positive cultures from the urethra, urinary bladder, epididymides, and testes were obtained from the animals. The infection peaked in the first 2 weeks p.i. and subsequently declined over the 7 weeks of observation. C. trachomatis-specific antibodies were first detected in serum by 2 weeks p.i. and rose over the period of observation. The titers of immunoglobulin G2a (IgG2a) were 16-fold higher than those of IgG1. A lymphoproliferative assay using splenocytes and local lymph nodes showed a strong cell-mediated immune response. Levels of gamma interferon were significantly higher than those of interleukin-4 in the supernatants from stimulated lymphocytes. An acute inflammatory infiltrate consisting of polymorphonuclear leukocytes was detected in the urethra at 1 week p.i. At 3 weeks p.i., a mixed acute and chronic inflammatory infiltrate was observed in the urethra that by 5 to 6 weeks was mainly composed of mononuclear cells. Similar findings were also observed in the urinary bladder, although the inflammatory infiltrate was delayed by approximately a week relative to that in the urethra. Sections of the epididymides showed a focal acute inflammatory infiltrate at 2 weeks p.i. Immunohistochemical staining demonstrated multiple chlamydial inclusions in the epithelium of the urethra and urinary bladder. No chlamydial inclusions were observed in the epididymides or testes. In conclusion, inoculation of male mice in the meatus urethra with C. trachomatis MoPn results in an infection of the genitourinary tract that closely parallels that described in humans. This model should help to characterize the pathogenesis of chlamydial infections in males and to test therapeutic and preventive measures.
缺乏实验模型严重限制了对男性沙眼衣原体感染发病机制的理解。为了尝试建立一种利用自然感染途径的模型，我们将雄性小鼠接种于尿道开口处。为确定50%感染剂量（ID50），将C3H/HeN（H-2(k)）雄性小鼠在尿道开口处接种101至107个沙眼衣原体小鼠肺炎生物变种（MoPn）的包涵体形成单位（IFU），并在感染后10天（p.i.）实施安乐死。接种5×104 IFU的动物中约50%尿道、膀胱、附睾和/或睾丸培养呈阳性。随后，为了描述感染过程，一组动物接种106 IFU/小鼠（ID50的20倍）。从这些动物身上获得了尿道、膀胱、附睾和睾丸的阳性培养物。感染在感染后前2周达到高峰，随后在7周的观察期内下降。沙眼衣原体特异性抗体在感染后2周首次在血清中检测到，并在观察期内上升。免疫球蛋白G2a（IgG2a）的滴度比IgG1高16倍。使用脾细胞和局部淋巴结进行的淋巴细胞增殖试验显示出强烈的细胞介导免疫反应。刺激淋巴细胞上清液中γ干扰素水平显著高于白细胞介素-4水平。感染后1周在尿道检测到由多形核白细胞组成的急性炎性浸润。感染后3周，在尿道观察到急性和慢性混合性炎性浸润，到5至6周时主要由单核细胞组成。在膀胱中也观察到类似结果，尽管炎性浸润相对于尿道延迟约1周。附睾切片在感染后2周显示局灶性急性炎性浸润。免疫组织化学染色显示尿道和膀胱上皮中有多个衣原体包涵体。在附睾或睾丸中未观察到衣原体包涵体。总之，将沙眼衣原体MoPn接种于雄性小鼠尿道开口处会导致泌尿生殖道感染，这与人类描述的感染情况非常相似。该模型应有助于描述男性衣原体感染的发病机制，并测试治疗和预防措施。
