A High Variability of Mixed Infections and Recent Recombinations of Hepatitis B Virus in Laos

In Lao PDR, where more than 8 % of the population are chronic carriers of HBsAg, multiple genotypes and subgenotypes cocirculate and are prone to generate recombinant viruses. Phylogenetic analyses of multiple clones per donor revealed mixed infections of subgenotypes B1, B2, B4, C1, C5, I1 and I2 in almost 6 % of HBsAg positive rejected blood donors. Recombination analyses and distance calculations furthermore showed that about 65 % (17/26) of the mixed infected donors showed recombinations in the S-gene alone, involving the predominant genotypes B and C. These results suggest that, at least in Laos, hepatitis B virus (HBV) mixed infections lead to frequent recombinations. In many donors with recombinant strains, the recombinant fragment and a non-recombinant strain of the same genotype co-existed (127/185 analysed recombinant fragments). For a large proportion of these (60/127), the most closely related known virus was found, although not always exclusively, in the same donor. Recombinant virus strains are largely distinct. This is reflected in an unexpected diversity in recombination breakpoints and the relatively rare recombinations with identical recombination patterns of the same genotypes in different donors. Recent recombination events would explain the limited spread of each of the recombinants. Using a published mutation rate of 4.2610 25 mutations per site and year, the observed minimum genetic distances of 0–0.60 % between parent strain and recombinant fragment would correspond to 0–71 years of evolution from a most recent common ancestor (MRCA). Thus several lines of evidence are suggestive of recen

Possible New Hepatitis B Virus Genotype, Southeast Asia

We conducted a phylogenetic analysis of 19 hepatitis B virus strains from Laos that belonged to 2 subgenotypes of a new genotype I. This emerging new genotype likely developed outside Southeast Asia and is now found in mixed infections and in recombinations with local strains in a geographically confined region

Sub-/genotypes in HBV mixed infections in Lao PDR.

<p>*n/a: not applicable.</p

Number of donors suspected to be mixed infected with at least 2 sub-/genotypes of HBV, Lao PDR.

<p>Number of donors suspected to be mixed infected with at least 2 sub-/genotypes of HBV, Lao PDR.</p

Phylogenetic clustering of selected HBV/B subgenotype B3, B5, B7 and B8 strains from GenBank and selected genotype B strains from Laos.

<p>Non-subgenotypable clones are indicated by red diamonds. Scale bar indicates nucleotide substitutions per site.</p

Phylogenetic clustering and recombination patterns of recombinant strains.

<p>Colour codes indicate genotypes B and C (red and yellow) involved in the recombination and regions homologous between at least 2 genotypes (grey). Recombinant strains from this study (red) or detected in previously published strains (green) are indicated by diamonds.</p