Trachoma: Protective and Pathogenic Ocular Immune Responses to Chlamydia trachomatis

Abstract

Trachoma, caused by Chlamydia trachomatis (Ct), is the leading infectious blinding disease worldwide. Chronic conjunctival inflammation develops in childhood and leads to eyelid scarring and blindness in adulthood. The immune response to Ct provides only partial protection against re-infection, which can be frequent. Moreover, the immune response is central to the development of scarring pathology, leading to loss of vision. Here we review the current literature on both protective and pathological immune responses in trachoma. The resolution of Ct infection in animal models is IFNγ-dependent, involving Th1 cells, but whether this is the case in human ocular infection still needs to be confirmed. An increasing number of studies indicate that innate immune responses arising from the epithelium and other innate immune cells, along with changes in matrix metalloproteinase activity, are important in the development of tissue damage and scarring. Current trachoma control measures, which are centred on repeated mass antibiotic treatment of populations, are logistically challenging and have the potential to drive antimicrobial resistance. A trachoma vaccine would offer significant advantages. However, limited understanding of the mechanisms of both protective immunity and immunopathology to Ct remain barriers to vaccine development.

Making connections: snapshots of chlamydial type III secretion systems in contact with host membranes

“…Chlamydiae cause disease in humans and other animals, and in particular Chlamydia 18 trachomatis remains the leading bacterial agent of sexually transmitted disease 19 worldwide, while ocular infections cause blinding trachoma, which is designated as a 20 neglected tropical disease by the World Health Organisation [3]. Studying 21…”

Tracoma: de lo básico a lo clínico

“…Se afecta la conjuntiva tarsal, más gravemente la superior; al examen físico se evidencia un engrosamiento folicular y papilar de las glándulas por la acumulación subepitelial de células linfoides y cuerpos elementales (32,34). Estas se observan como pequeños puntos blancos o amarillos, que una vez resueltos dejan depresiones patognomónicas conocidas como pozos de Hebert y, en algunas ocasiones, pannus corneal (7,29,35). La fase activa más grave genera engrosamiento y edema de la conjuntiva (36).…”

“…Si se llega a la opacidad corneal se produce ceguera irreversible. Las infecciones a repetición aumentan el riesgo de ocasionar cicatrices conjuntivales (29,31). No hay manifestaciones en otras partes del cuerpo (31).…”

Trachoma as cause of blindness: literature review

“…Trachoma is the result of a complex interaction between chlamydia infection and the immune res-ponse occurring over many years [22]. It begins in the form of follicular conjunctivitis (active follicular trachoma), with papillary hypertrophy and inflammatory cells infiltrating the conjunctiva (lymphocytes, macrophages, neutrophils, and plasma cells) punctuated by lymphoid follicles (B cells surrounded by a mantle of T0 cells ) [23], which extends throughout the conjunctiva, especially in the upper tarsal conjunctiva.…”