Over a third of HIV-positive individuals coinfected with hepatitis B virus (HBV), who received 3TC, a drug which is active against both viruses, as part of their HAART regimen, have HBV which is 3TC resistant, according to a small Australian study published in the July 15th edition of AIDS.
The Australian investigators also found that all the patients with 3TC resistant HBV had detectable hepatitis B and HIV viral loads, and had HIV mutations indicative of 3TC resistance.
Investigators in Melbourne conducted a retrospective study involving 33 HIV and HBV coinfected patients who received at least six months of 3TC therapy between 1995 and 2001. The investigators wished to establish the prevalence of 3TC resistant HBV; risk factors for 3TC resistance; and the HBV gene mutations associated with resistance.
Patients’ demographic and clinical data was obtained from hospital notes, and stored serum samples were tested for 3TC resistance. The patients had an average age of 39 years, all but one were men, mean CD4 cell count was 318 cells/mm3, and average HIV viral load was 2,800 copies/mL. 3TC therapy had been used for an average of 28 months.
Three groups of patients were identified by the investigators. Group one (eleven patients) had HBV replication, but no 3TC resistance; group two (13 patients) had HBV viral replication, with 3TC resistance mutations; and, group 3 (nine individuals) had no evidence of HBV replication or 3TC resistance.
There were no statistical demographic differences between the three groups or in CD4 cell count or HIV viral load, although the patients with 3TC resistance all had a detectable HIV viral load and HIV resistance mutations characteristic of 3TC resistance.
The HBV viral load was also higher in patients with 3TC resistant HBV than either of the other two groups (p=0.0056). Individuals with 3TC resistance had higher alanine aminotransferase (ALT) levels than patients in group one, who in turn had higher ALT levels than those in group three (p
Mutations in HBV polymerase were detected at rtV172L, rtL180M and rtM204V in the 3TC resistant patients. These resistance mutations have been shown in laboratory tests to be transmittable, even to individuals who have been successfully vaccinated against HBV.
The investigators conclude that 39% of HIV and HBV coinfected patients treated with 3TC as part of their HAART regimen have 3TC resistant HBV. These patients had significantly higher HBV viral loads and ALT levels. The investigators also noted that the resistance mutations that occurred in the 3TC resistant patients could be potentially transmittable to individuals who had been vaccinated against HBV.
Further information on this website
Hepatitis B - overview
Hepatitis B - factsheet
BHIVA guidelines on the treatment of HIV/HBV coinfection
HIV and hepatitis - booklet in the information for HIV-positive people
3TC - overview
Cooley L et al. Prevalence and characterization of lamivudine-resistant hepatitis B virus mutations in HIV-HBV co-infected individuals. AIDS 17: 1649 – 1657, 2003.