Clinical

Philippine HBV isolate may be a new subgenotype C6

Last Updated: 2009-07-10 17:15:05 -0400 (Reuters Health)

NEW YORK (Reuters Health) - A new isolate of hepatitis B virus (HBV) from the Philippines fulfills all criteria for a new subgenotype C6, researchers report in the June issue of the Journal of Medical Virology.

Dr. Stephan Schaefer of the University of Rostock, Germany, and colleagues observe that HBV genotypes and subgenotypes show distinct geographical prevalence, and introduction of a virus into new genetic environments leads to adaptation causing genetic segregation.

The researchers analyzed 28 serum samples from asymptomatic HBV carriers from the Philippines. Fifteen patients had genotype B, 5 had genotype C2, 4 had genotype D, 2 had A1 and 2 patients were infected dually with HBV genotypes B and D.

The distribution was similar to that observed in a previous study. However, further analysis showed that 1 of the isolates (Ph105) formed a separate clade in genotype C. It did not belong to one of the known subgenotypes.

The team notes that a threshold of 4% is usually used to differentiate subgenotypes from each other. The proposed new subgenotype was closest to subgenotype C2, with a 4.1% difference in nucleotide substitutions over the whole genome.

"We assume," the authors conclude, "that the proposed Philippine C6 isolate evolved from C2 after being brought into a new genetic environment."

"Currently," they add, "further efforts are being undertaken to identify other isolates of C6 in the Philippines."

J Med Virol 2009;81:983-987.