Sulfated polysaccharides block chlamydia infection in vitro, but do not protect mice from vaginal inoculation

There is considerable interest in developing a vaginal product that women could use to protect themselves from sexually transmitted pathogens, including chlamydia. It has been suggested that sulfated polysaccharides would be effective in a prophylactic product because they have been shown to block infection of cultured cells by sexually transmitted pathogens, including chlamydia. In order to compare in vitro findings with animals, we placed sulfated polysaccharides into the vaginae of mice prior to inoculation with chlamydia. The surfactant nonoxynol 9 (N9) was used as a positive control as it has been previously shown to protect mice from infection by chlamydia. In this study, N9 also protected the mice from infection. However, sulfated polysaccharides which had been shown to be efficacious in vitro did not block infection.