Identification of new pathogens in the intraocular fluid of patients with uveitis

Uveitis in mouse and man

Uveitis is underappreciated as a sight-threatening cause of blindness. There are two broad causative classes of uveitis: infectious and non-infectious. Non-infectious uveitis is considered a prototypical autoimmune disorder based mainly on data from experimental models in the mouse. Several different experimental models exist that reflect the different types of uveitis in man (anterior, intermediate, and posterior uveitis). These models have demonstrated that uveitis is predominantly a Th1/Th17 mediated disease, although innate immune cells play a significant role both in induction of disease and in tissue damage. Most experimental models of uveitis rely on activation of the innate immune system by use of adjuvants that activate a range of pathogen recognition receptors (PRRs). This begs the question of the underlying role of initial and/or persistent infection, including latent infection, in immune-mediated uveitis in which active infection cannot be demonstrated. This further raises the possibility of pathogenic mechanisms such as antigenic cross-reactivity and molecular mimicry. Alternatively, residual/latent antigen from infectious agents may act as "endogenous" adjuvants for induction of immune reactions to damaged/altered self antigen, suggesting a commonality in pathogenesis for both infectious and non-infectious uveitis in man.

Viral ocular manifestations: a broad overview

The viruses able to affect the eye are taxonomically diverse, ranging from double-stranded DNA viruses, to single stranded RNA viruses, to retroviruses. Any part of the eye may be affected, frequently producing blepharitis, conjunctivitis, keratitis, uveitis, cataract and retinitis. The more common ocular viral infections include the Herpesviruses such as HSV-1, VZV and CMV. The HIV pandemic is placing a serious burden on ophthalmology clinics, particularly in sub-Saharan Africa as the number of viral ocular diseases is increasing. In particular, CMV retinitis is becoming more prevalent where antiretroviral therapy is not available and is replaced by immune-recovery uveitis where antiretrovirals are given. This review aims to improve knowledge of the common viral ocular diseases, their diagnosis and management, as well as the fairly uncommon viral ocular diseases that may also cause considerable morbidity.

Viral anterior uveitis

PURPOSE OF REVIEW

With improvements in molecular diagnostics tests, viruses are increasingly being found to be associated with what was previously described as idiopathic anterior uveitis. This review presents the clinical features of viral anterior uveitis.

RECENT FINDINGS

Herpes simplex virus/varicella zoster virus (HSV/VZV) are important causes of anterior uveitis, but other viruses including cytomegalovirus (CMV) and rubella are also found in a significant number of cases. The various viral anterior uveitides have similar features and should be suspected in eyes with diffuse, fine, stellate keratic precipitates, iris atrophy or ocular hypertension. Acyclovir remains the mainstay of therapy in HSV/VZV infections. CMV responds to ganciclovir, but the relapse rate is high and prolonged therapy may be required. Cataract and glaucoma are the main complications of viral anterior uveitis requiring appropriate management.

SUMMARY

There is considerable overlap between clinical manifestations of the different viral anterior uveitides as well noninfectious hypertensive anterior uveitis syndromes. Hence, corticosteroids should be used with caution in these eyes if virus diagnostic tests are not available.