HIV and Syphilis Coinfection

Question

I have been HIV positive for 20+ years. I am generally doing well - my viral load is undetectable and my CD4 count is in the high 400s. However, I had syphilis back in the 1990s, and it hasn't seemed to go away. Upon itial diagnosis, I was treated with Benzathine PCN 2.4 million units IM for 3 weeks. My titers went down, but quickly came back up. I then was treated with ceftriaxone for 3 weeks. My titers have gone up and down repeatedly since I initially contracted syphilis. I have had no sexual contact, so I don't suspect reinfection. What exactly does the syphilis titer measure? Is it like an HIV viral load? Or, does it measure your body's response in some way? I have had the RPR test as well as follow-up FTA-ABS and the VDRL. My latest titers jumped from 128 to 2048. I am regularly tested (both for syphilis and HIV) every 3 months - even though I'm not sexually active. My doctor says that I will always show reactive to syphilis. However, these fluctuating titers have us both confused. I just had a retest and if the results are still high, I am going to have a lumbar puncture and an ECG. My doctor says that some HIV positive people have a problem clearing the bacterium Treponema Pallidum and that it can cause fluctuating titers. Does this mean I have tertiary or neurosyphilis? If the titers are still high my doctor wants to put me back on IV antibiotics (twice daily). He says that aqueous PCN G is difficult to obtain and that he will probably go back to ceftriaxone and possibly an oral antibiotic in combination. I'm just stumped by these lab results. How can I be doing so well against HIV but have problems with a little bacterium? Any light you could shed on this would be greatly appreciated. Thanks for all that you and everyone else at The Body do. It's a great resource.

Answer

You don't indicate what your CD4 count and HIV viral load is. The CDRL and FTA will always be positive. The RPR qualitative test will always be positive. The quantitative RPR should be 1 or 2 after successful treatment. If the RPR titer is has gone from 128 to 1024, this indicates active infection somewhere. A lumbar puncture is required and prolonged IV treatment (preferably with PCN G) is the treatment of choice.