Immune activation caused by infection with syphilis can stimulate latent reservoirs of HIV and cause viral load to rebound to low levels, according to a case report published in the September 26th edition of AIDS. Syphilis should be considered as a cause of low-level rebound in patients with previously undetectable viral load, say the investigators.
The case concerned a 28 year old gay men who had had maintained an undetectable viral load for 18 months after starting HAART. However, low level HIV viral load (ranging from 64 copies/mL to 741 copies/mL) was detected on three instances at four weekly intervals in the summer of 2001. Without a change in HIV treatment regimen the man’s viral load then became undetectable again and has remained so for 17 months.
Coinciding with the low rebound in viral load, the patient reported low-grade fevers after several unprotected casual sexual contacts. Syphilis was diagnosed and the man received appropriate antibiotic therapy.
The patient’s recent sexual history led the investigators to speculate that the man had been superinfected with another strain of HIV, causing his viral load to rebound. However, tests conclusively revealed that the virus the man was initially infected with was the same as that detected during the man’s viral rebound.
Attention then shifted to resistance as a possible cause of the viral rebound. Clonal sequencing of the protease and reverse transcriptase regions were performed, but no resistance-conferring mutations in either region were detected.
Having ruled out these two possibilities, levels of proviral HIV DNA were measured in peripheral blood mononuclear cells. Levels of proviral DNA fell sharply during the period of the patient’s low-level rebound.
The investigators concluded that the man’s short-term, low-level rebound may have originated from activated reservoirs of previously infected cells, with the activation caused by infection with syphilis.
”This observation” conclude the investigators, “suggests that efforts should be made to study apparent causes of virological failure carefully before a particular regimen is abandoned.”
Further information on this website
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Syphilis - factsheet
Padte N et al. Sustained viremia during highly active antiretroviral therapy with accelerated proviral DNA decay in the setting of infection with syphilis. AIDS 17: 2143 – 2145, 2003.