Syphilis infection in HIV-positive men can cause greater increases in HIV viral levels and bigger drops in CD4-cell counts than in HIV-positive men not also coinfected with the sexually transmitted disease, according to a study in the October 21 edition of the journal AIDS. The researchers also say their findings show that HIV-positive men coinfected with syphilis are potentially more infectious than other HIV-positive men and could be more easily spreading the virus to others because of their higher HIV viral loads.
Researchers in San Francisco analyzed the health records of 52 HIV-positive men also diagnosed with primary or secondary syphilis between early 2001 and spring 2004. Most of the men had received antibiotic treatment for their syphilis infections, and the drugs were successful in curing the STD in all but two of the men. A total of 36 men had their HIV viral levels measured before and after syphilis infection. The researchers noted that viral levels were significantly higher among many of the men after being diagnosed with primary syphilis, and even higher in those diagnosed with secondary syphilis. Of 26 men who had a detectable HIV viral level before being infected with syphilis, half experienced significant elevations in HIV viral loads. Of the 10 men who had undetectable HIV viral levels while on antiretroviral therapy before being diagnosed with syphilis, two developed detectable viral levels after being infected with syphilis. HIV viral levels did not decrease significantly after syphilis was successfully treated, the researchers report.
The researchers also looked at the effect of syphilis infection on CD4-cell levels. Thirty-one men had CD4-cell measurements taken before and after being coinfected with syphilis. A mean drop of 62 cells was recorded among the men after syphilis infection. Decreases were even steeper for men whose syphilis advanced from the primary to secondary disease stage before being treated. CD4-cell counts rebounded by an average of 33 cells after successful syphilis treatment, still well below presyphilis levels.
The researchers conclude that their data show syphilis infection speeds HIV disease progression by elevating HIV viral levels and lowering immune cell counts. They call for larger studies to confirm their findings, but say their results suggest that integrated public health campaigns are needed to address the spread of the two STDs.