Determinación del genotipo del virus de la hepatitis B y detección de mutaciones de resistencia al tratamiento con lamivudina

The emergence of YMDD mutants precedes biochemical flare by 19 weeks in lamivudine-treated chronic hepatitis B patients: an opportunity for therapy reevaluation

Given the loss of therapeutic efficacy associated with the development of resistance to lamivudine (LMV) and the availability of new alternative treatments for chronic hepatitis B patients, early detection of viral genotypic resistance could allow the clinician to consider therapy modification before viral breakthrough and biochemical relapse occur. To this end, 28 LMV-treated patients (44 +/- 12 years; 24 men), on their first therapy schedule, were monitored monthly at four Brazilian centers for the emergence of drug resistance using the reverse hybridization-based INNO-LiPA HBV DR assay and occasionally sequencing (two cases). Positive viral responses (HBV DNA clearance) after 6, 12, and 18 months of therapy were achieved by 57, 68, and 53% of patients, while biochemical responses (serum alanine aminotransferase normalization) were observed in 82, 82, and 53% of cases. All viral breakthrough cases (N = 8) were related to the emergence of YMDD variants observed in 7, 21, and 35% of patients at 6, 12, and 18 months, respectively. The emergence of these variants was not associated with viral genotype, HBeAg expression status, or pretreatment serum alanine aminotransferase levels. The detection of resistance-associated mutations was observed before the corresponding biochemical flare (41 +/- 14 and 60 +/- 15 weeks) in the same individuals. Then, if highly sensitive LMV drug resistance testing is carried out at frequent and regular intervals, the relatively long period (19 +/- 2 weeks) between the emergence of viral resistance and the onset of biochemical relapse can provide clinicians with ample time to re-evaluate drug therapy.

Genotypic resistance to lamivudine among hepatitis B virus isolates in Mexico

BACKGROUND

Drug resistance of hepatitis B virus (HBV) is an increasing clinical problem. Resistance to lamivudine in HBV isolates in Mexico has been poorly explored.

OBJECTIVES

To characterize the mutation patterns associated with genotypic resistance to lamivudine and their prevalence among HBV isolates in Mexico.

MATERIAL AND METHODS

Thirty-nine Mexican HBV isolates were analysed by PCR and line probe assay for detection of genetic variants in the polymerase open reading frame domains B and C (INNO-LiPA HBV DR; INNOGENETICS N. V., Ghent, Belgium). This assay detects wild-type and mutations at codons 180, 204 and 207 of the HBV polymerase gene, and at codon positions 171, 172, 195, 196, 198 and 199 of the HBV surface antigen (HBsAg). HBV isolates were obtained from HBsAg-positive serum samples of 15 chronic hepatitis patients, two haemodialysis patients with chronic HBV carriage, 20 men found positive for HBsAg when seeking HIV testing and two AIDS patients with chronic HBV infection. None of the participants had received antiviral therapy.

RESULTS

Overall, HBV wild-type was found in 37 (94.9%) out of the 39 isolates studied. Two (5.1%) out of the 39 isolates showed mixed wild-type and mutant populations. These mutations occurred in isolates from one hepatitis patient and one haemodialysis patient. The isolate from the hepatitis patient showed a double mutation at codon positions 180 (L180M) and 204 (M204V), thus a 2.6% prevalence of genotypic resistance to lamivudine was found. The isolate from the haemodialysis patient showed a single mutation at codon position 180 (L180M). The two HBV mutant isolates were further analysed for genotype and both isolates were genotype H.

CONCLUSIONS

HBV genotypic resistance to lamivudine exists in Mexican isolates. The results highlight the importance of testing for HBV resistance before treatment and have implications for a more rational use of drugs.