Background
The impact of a first episode of syphilis on the course of subsequent episodes in people living with HIV (PLH) is somehow controversial and of clinical interest.
Methods
Prospective cohort study of 348 episodes of syphilis observed in 175 PLH with regular follow up (12.5 person-years) in a HIV Unit in a tertiary hospital. Syphilis testing was routinely performed every 6-12 months in all the cases, and unscheduled visits were included in case of suspicion of syphilis or other sexually transmitted diseases.
Results
At the first diagnosis, median age was 48 years, predominantly were male (99%), nadir CD4+ count was 303 cells/μL, and 99% were receiving suppressive antiretroviral therapy. Of note, a fall in CD4+ count (-10 cells/μL) and CD4/CD8 ratio (-0.04) was observed at the diagnosis of syphilis. During median follow up of 35 months (3.6 person-years), nearly half of included PLH had more than 1 syphilis episode (two, 91, 26%; three or more, 82 PLH, 24% of episodes of syphilis). The form of presentation changes according to number of episodes (primary syphilis from 17 to 9%; secondary syphilis from 17% at the first, to 8% at those with a third episode). However, the proportion of individuals whose 1st episode was early latent stage was similar, probably related to the close follow up. Also, serological presentation was similar according to successive episodes (median RPR 1/32 from the 1st to 3rd episode, but with a trend to higher RPR titer subsequently), as well as the decrease in the CD4+ count (-9 vs -11 cells/μ in 1st and 2nd), CD4/CD8 ratio, time to initial serological response (5.5 vs 5.9 months), or time to negativization of RPR titer (with a trend to decrease, 19 vs 16 vs 12 months; p=0.12). Of note, the rate of serofast status was similar in subsequent episodes (37% vs 46% vs 50%) whereas the time of persistence in the serofast status was significantly shorter in the third or successive episodes (p=0.012, log-rank).
Conclusions
A previous episode of syphilis could change the clinical picture of successive episodes, but importantly it does not alter the serological presentation and outcome of subsequent infections with T. pallidum. A shorter time of persistence of serofast status reinforce the role of immunity in this outcome.