Theories about evolutionary origins of human hepatitis B virus in primates and humans

Abstract

Introduction: The human hepatitis B virus causes acute and chronic hepatitis and is considered one of the most serious human health issues by the World Health Organization, causing thousands of deaths per year. There are similar viruses belonging to the Hepadnaviridae family that infect non-human primates and other mammals as well as some birds. The majority of non-human primate virus isolates were phylogenetically close to the human hepatitis B virus, but like the human genotypes, the origins of these viruses remain controversial. However, there is a possibility that human hepatitis B virus originated in primates. Knowing whether these viruses might be common to humans and primates is crucial in order to reduce the risk to humans.

Objective: To review the existing knowledge about the evolutionary origins of viruses of the Hepadnaviridae family in primates.

Methods: This review was done by reading several articles that provide information about the Hepadnaviridae virus family in non-human primates and humans and the possible origins and evolution of these viruses.

Results: The evolutionary origin of viruses of the Hepadnaviridae family in primates has been dated back to several thousand years; however, recent analyses of genomic fossils of avihepadnaviruses integrated into the genomes of several avian species have suggested a much older origin of this genus.

Conclusion: Some hypotheses about the evolutionary origins of human hepatitis B virus have been debated since the '90s. One theory suggested a New World origin because of the phylogenetic co-segregation between some New World human hepatitis B virus genotypes F and H and woolly monkey human hepatitis B virus in basal sister-relationship to the Old World non-human primates and human hepatitis B virus variants. Another theory suggests an Old World origin of human hepatitis B virus, and that it would have been spread following prehistoric human migrations over 100,000 years ago. A third theory suggests a co-speciation of human hepatitis B virus in non-human primate hosts because of the proximity between the phylogeny of Old and New World non-human primate and their human hepatitis B virus variants. The importance of further research, related to the subject in South American wild fauna, is paramount and highly relevant for understanding the origin of human hepatitis B virus.

Keywords: Evolutionary origins; Hepadnaviridae; Hepatitis B virus; Non-human primates.

Fig. 1

(A) Geographical distribution of publication relating to non-human primates which were detected with some HBV genotype. Sample animals are listed by genera in Table 1. (B) The evolutionary history was inferred by Neighbor–Joining method. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown above the branches. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the p-distance method and are in the units of number of base difference per site. All positions containing gaps and missing data were eliminated. There were a total of 3167 positions in the final dataset. evolutionary analyses were conducted in MEGAS.

Fig. 2

In green and yellow, the geographic distribution of non-human primates, , , . In yellow, Brazil which has large range of species and subspecies of neotropical non-human primates in the wild fauna, representing approximately 21% of the group in the world.,