Monitoring syphilis and HIV infection

Most cases of congenital syphilis and HIV infections occur in high-risk populations. Testing high-risk groups for infection with either pathogen is essential to reduce the risk of more severe disease and to prevent transmission. The aim of EU-funded project 'Assured point-of-care device for syphilis and HIV in pregnant women and new born' (PREVENTIT) is to develop a simple diagnostic tool for simultaneous diagnose of HIV and syphilis infections.

The concept of the assay combines the principle of ELISA with a lateral flow assay using a visually detectable label or strong fluorescent dye for digital read-out. Advantages and characteristics of the assay device have to meet the ASSURED (affordable, sensitive, specific, user-friendly, rapid and robust, equipment free, deliverable) criteria for use at the point-of-care.

Syphilis and HIV-1 antigens have been selected and used as capture probes for use in the multi-analyte assay format. Selected antigens were conjugated to colloidal gold to obtain detection probes for visual reading and to different fluorophores to function as probes for automatic read-out with an optical reader. Assay conditions were optimised and standard operation procedures defined. Diagnostic accuracy is currently being assessed by validation against an extended panel of serum samples from patients with syphilis and/or HIV infection.

Assay conditions for multi-analyte testing on a solid matrix and for automatic detection using fluorophores conjugates are being investigated and optimised. A prototype disposable device using colloidal gold-labelled detection probes for visual reading is being tested in the laboratory evaluation study. This device will be further adjusted to perform the different incubation, wash and reading steps.

Currently, testing of high-risk groups for HIV and syphilis infections is not part of routine practices. The introduction of a simple and affordable combination assay for the detection of HIV and syphilis infection is expected to drastically reduce the incidence of congenital transmission to newborns.