Short Communication: Transmission of Hepatitis B Viruses with Lamivudine Resistance Mutations in Newly Diagnosed HIV Individuals

C hronic hepatitis B virus (HBV) infection currently affects 5–10% of individuals with HIV infection in developed countries, despite the fact that HBV vaccination is widely available and is successful in preventing HBV infection. ^1,2 Due to shared routes of infection, persons at high risk for HIV infection are particularly prone to acquire HBV. ³ Coinfection with HIV alters the natural history of chronic hepatitis B with faster progression to liver cirrhosis and liver-related death. ⁴ Based on these facts, most current guidelines recommend considering HBV therapy in all HIV/HBV-coinfected individuals. ^{2,5 –8} For those who require HIV treatment, experts uniformly advise prescribing regimens dually active against both HIV and HBV. In asymptomatic HIV/HBV-coinfected patients with high CD4 counts and no current need for HIV therapy, anti-HBV treatment with either interferon or adefovir might be considered. ^2,7 Alternatively, earlier initiation of antiretroviral therapy, including agents active against HBV, may be recommended in these patients. ^{2,5 –7}

Drug resistance testing is currently examined in all HIV individuals in Western countries before initiating antiretroviral therapy, based on a reported prevalence of transmission of drug-resistant HIV of around 10% ^{9 –11} and the demonstration of impaired treatment response when antiretroviral drugs are used empirically in patients with acquired drug-resistant strains. ¹² Similar information for HBV infection is still scarce, but recent reports have emphasized that the rate of primary drug resistance mutations among drug-naive chronic hepatitis B-monoinfected patients may be around 8% in Western countries ¹³ and that patients infected with HBV-resistant strains may be prone to subsequent treatment failure. ¹⁴ In almost all cases, lamivudine resistance mutations are the ones recognized. However, it should be noted that lamivudine-resistant HBV strains display cross-resistance to emtricitabine, telbivudine, and to a lesser extent entecavir. ¹⁵ Little is known about the rate of transmission of HBV-resistant strains among HIV patients, in whom lamivudine has been widely used for more than a decade. The aim of this study was to analyze the rate of HBV drug resistance mutations in a group of HIV/HBV-coinfected drug-naive patients.

Plasma samples from all individuals newly diagnosed with HIV-1 infection at several HIV clinics located in the Madrid urban area between January 2000 and December 2008 and who had been sent to Hospital Carlos III for baseline HIV drug resistance testing were identified. All specimens were further tested for HBV serum antigen (HBsAg) using a commercial enzyme immunoassay. In HBsAg⁺ patients, HBV-DNA and HBV drug resistance mutations were further investigated in plasma specimens. A commercial line probe assay, INNO-LiPA (Innogenetics, Ghent, Belgium), was used for screening of HBV drug resistance mutations. The sensitivity of this hybridization technique for recognizing drug-resistant mutations in HBV is better than for bulk sequencing, as 10% of viral genomes carrying drug-resistant changes can be recognized. ¹⁶ Data from medical records were further reviewed to obtain epidemiological and other relevant information.

Samples from 1519 newly diagnosed HIV-1 individuals were analyzed during the study period. HBsAg was positive in 65 (4.3%). The main characteristics of the study population are recorded in Table 1. HIV/HBV-coinfected patients had a mean age of 34 years and 85% were male. Although Spaniards represented 42% of HBsAg⁺ patients, 18% were from Latin America, 18% from Africa, and 6% from other European countries. Most HIV/HBV-coinfected individuals were homosexual men (50.5%), while 23% had been infected by heterosexual contact and only 1.5% through intravenous drug use. All HIV/HBV-coinfected patients were HBV viremic.

Drug resistance genotyping could be tested in 55 specimens from HBsAg⁺ patients. There was not enough volume for testing the remaining 10 subjects. The most frequent HBV genotypes were A (40%) and D (13.3%). Two of the 55 subjects (3.6%) carried rtM204V in HBV, a mutation that typically confers lamivudine resistance. No other HBV drug resistance changes were found in these cases. These two individuals were immigrants and men who admitted to having sex with men. One was a 34-year-old male originally from the Dominican Republic who carried an HBV genotype D strain. Another was a 28-year-old male born in Morocco but living in Spain for the last 20 years; he carried HBV genotype A. Both patients were infected by HIV subtype B. The diagnosis of HIV and HBV infections in these two individuals had been made in 2003 and 2007, respectively. Interestingly, none of them carried drug resistance mutations in HIV, despite having 11% of the prevalence of any HIV drug resistance mutations in recent HIV-infected persons in Spain. ¹⁷ Both subjects confirmed that they had never been exposed to lamivudine or any other oral antiviral agents.

The prevalence of serum HBsAg⁺ among HIV-infected persons worldwide varies from 5% to 20%, mainly based on geographic region and risk group category. ^1,18,19 The overall prevalence of HBsAg⁺ among newly diagnosed HIV individuals in Madrid was 4.3%, which is slightly lower but in agreement with figures from other Western European countries. ¹ The prevalence of HBV drug resistance in this drug-naive HIV population was 3.6%. The recognition of drug-resistant HBV strains in coinfected patients emphasizes the occurrence of transmission of drug-resistant HBV variants within the HIV population. Given that HBV-resistant variants may depict a diminished response to antiviral therapy, our observation may have major public health implications. To the best of our knowledge, our results represent the first report documenting potential transmission of lamivudine-resistant HBV among HIV patients in Spain, an event described only as single cases in France ²⁰ and more recently in the United Kingdom. ²¹

Lamivudine is an oral cytosine analogue with both anti-HIV and anti-HBV activities. It was the first nucleoside analogue approved for the treatment of chronic hepatitis B. Lamivudine monotherapy has been widely used for more than a decade in chronic hepatitis B patients worldwide. Although it provides a significant suppression of HBV replication, improvement in liver enzymes, and amelioration of histological damage in many patients, ⁸ selection of resistance is a major drawback and the reason why lamivudine is currently no longer recommended as monotherapy against HBV. ⁸ The risk for selecting resistance using lamivudine monotherapy in HBV is even more accentuated in HIV-coinfected patients. ²² In this regard, given the widespread use of lamivudine as an antiretroviral agent, the HIV/HBV-coinfected population should be considered as particularly prone to select and transmit lamivudine-resistant HBV strains. ²³

It should be noted that no drug resistance mutations in HIV were seen in the two HIV/HBV-coinfected individuals with drug-resistant HBV variants identified in our study. Two different considerations may account for this observation. First, these patients could have acquired HIV and HBV at different time points, since the HBV source was a subject carrying lamivudine-resistant HBV. On the other hand, our patients might have been exposed to both HIV and HBV at the same time from the same source, who might have been exposed to and failed lamivudine treatment. Hypothetically the sources would carry lamivudine-resistant HIV and HBV strains, but only the mutant HBV might have persisted for long periods in the newly infected persons. This may occur given the different dynamics of selection and disappearance of YMDD resistance mutations in HIV and HBV, being faster in the former. ²⁴

No mutations associated with HBV resistance to other antiviral drugs (adefovir, tenofovir, etc.) were recognized in our series. This observation could be attributed to several facts. On one hand, adefovir is very rarely used among HIV/HBV-coinfected individuals, ²⁵ some of whom could have been the source of infection for our study population. With respect to tenofovir, the current evidence is that mutation rtA194T, which was originally reported in a few HIV/HBV-coinfected individuals showing detectable HBV viremia despite being treated with the drug, ²⁶ is only rarely seen. Moreover, most drug-resistant associated changes in HBV significantly impair viral fitness, ²⁷ halting the opportunity for efficient HBV transmission. Finally, we cannot exclude the possibility than if much more sensitive methods were used, such as allele-specific PCR assays or pyrosequencing, a greater number of individuals in our series would have been recognized as carrying drug-resistant HBV mutations. Studies are currently ongoing to test this hypothesis.

In summary, baseline drug resistance testing in HBV might be warranted in newly diagnosed HIV/HBV coinfected patients. Further surveillance studies assessing the rate of primary HBV drug resistance in larger populations of HIV/HBV coinfected patients are required to confirm these results. Moreover, a cost-benefit assessment of baseline HBV drug resistance testing in clinical practice must be performed, especially for HIV/HBV-coinfected individuals. The recognition of lamivudine-resistant HBV in antiretroviral-naive coinfected patients may have important implications in the selection of first-line antiretroviral therapy.