Vaccine strategies to protect against Trachoma tested in humans

Researchers from Statens Serum Institut (SSI) and Imperial College London have completed a clinical phase I trial, testing different vaccine strategies for immunity against ocular Chlamydia infections (Trachoma). The clinical trial was in part funded by EU’s Horizon2020 programme. The results are published in Lancet Infectious Diseases.

The results show that it is possible to supplement a traditional intramuscular vaccine (‘prime’) with a mucosal ocular administration (in eye drops) of the vaccine antigen (‘pull’), to direct immunity to the eye. In particular, the production of the antibody IgA in the eye was increased.

”As the eye enjoys a special status called immune privilege, it is a challenge to generate an immune response in this location via traditional parenteral vaccination. This trial teaches us that by using a prime/pull strategy, immunity can be induced in the eye. This is an important result, and it bodes well for vaccines against eye infections, such as Trachoma. Furthermore, this ‘prime/pull’ strategy could possibly also be applicable to other mucosal sites”

The vaccine is safe, and all participants developed an immune response against the vaccine

The clinical trial, was a phase 1, double-blind, randomised, placebo-controlled trial at the National Institute for Health Research, Imperial Clinical Research Facility, London, UK. Participants were healthy men and non-pregnant women aged 18 to 45 years. All vaccinated participants receiving the vaccine seroconverted, and those that also received a mucosal ocular pull, generated neutralising antibodies in both the systemic (blood) and ocular (tears) compartment.

“We envision a future chlamydia vaccine that is able to protect against both urogenital infections and possibly ocular infections and are in the process of developing such a vaccine, now that this trial has demonstrated how such a vaccine is to be administered in order to be both safe and immunogenic”, says Jes Dietrich.

FACTS ABOUT Trachoma

• Trachoma is a disease of the eye caused by infection with the bacterium Chlamydia trachomatis.
• It is a public health problem in 42 countries, and is responsible for the blindness or visual impairment of about 1.9 million people.
• Blindness from trachoma is irreversible.
• 125 million people live in trachoma endemic areas and are at risk of trachoma blindness.
• WHO SAFE program (Surgery Antibiotics Facial, Environmental) program is designed to reduce and eliminate disease. The SAFE program was initiated in early 1990 with the goal of eradicating trachoma by 2020, which was unsuccessful.
• Currently routine screening and mass antibiotic treatment has not been able to eradicate ocular infections. An effective Chlamydia vaccine would be able to significantly change the landscape for trachoma.