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Paper of the Month October 2011

A live-attenuated chlamydial vaccine protects against trachoma in nonhuman primates

J. Exp. Med. Vol. 208 No. 11, 2217-2223


Laszlo Kari, William M. Whitmire, Norma Olivares-Zavaleta, Morgan M. Goheen, Lacey D. Taylor, John H. Carlson, Gail L. Sturdevant, Chunxue Lu, Lauren E. Bakios, Linnell B. Randall,Michael J. Parnell, Guangming Zhong, and Harlan D. Caldwell


Blinding trachoma is an ancient neglected tropical disease caused by Chlamydia trachomatis for which a vaccine is needed. We describe a live-attenuated vaccine that is safe and efficacious in preventing trachoma in nonhuman primates, a model with excellent predictive value for humans. Cynomolgus macaques infected ocularly with a trachoma strain deficient for the 7.5-kb conserved plasmid presented with short-lived infections that resolved spontaneously without ocular pathology. Multiple infections with the attenuated plasmid-deficient strain produced no inflammatory ocular pathology but induced an anti-chlamydial immune response. Macaques vaccinated with the attenuated strain were either solidly or partially protected after challenge with virulent plasmid-bearing organisms. Partially protected macaques shed markedly less infectious organisms than controls. Immune correlates of protective immunity were not identified, but we did detect a correlation between MHC class II alleles and solid versus partial protection. Epidemiological models of trachoma control indicate that a vaccine with this degree of efficacy would significantly reduce the prevalence of infection and rates of reinfection, known risk factors which drive blinding disease.