New natural variants of hepatitis B virus among Amerindians from Argentina with mainly occult infections.

Hepatitis B virus infection is frequent among Amerindians. In Argentina HBV genotypes A, B, C, D, E, F and H were described in different populations, while some cases of occult hepatitis B infection (OBI) were reported in human immunodeficiency virus (HIV) coinfected patients.To determine the prevalence, genetic diversity of HBV and to analyze the deduced amino acid sequence of both S and viral polymerase (P) genes among Amerindians of Argentina.A cross-sectional study including 561 individuals belonging to distinct ethnic groups, the Mbyá-guaraní (MG), the Kolla (K), the Sagua-Huarpe (SH) and the Wichi (W) was performed.The prevalence of HBsAg was 1.7% and 1.4% for the MG and SH, respectively, while anti-HBc was detected in all communities. HBV DNA of S/P and preCore-Core genomic regions were amplified by nested polymerase chain reaction in 59 reactive samples for anti-HBc total Ig and/or HBsAg. Of them, thirteen exhibited detectable HBV DNA, eleven of which were identified as OBI. Genotype F was predominant in the MG community with co-circulation of subgenotypes F4, F1b, A2 and D3, while subgenotype C2 prevailed within the SH community. All cases exhibited the polymorphism rtL217R within the RT domain associated to resistance to adefovir. Mutations rtD206E and rtV207I associated with lamivudine resistance were found in two MG and three SH respectively. Other new substitutions were described within the P sequence.This study shows for the first time the predominance of OBI, HBV subgenotypes and natural variants in Amerindians from Argentina.