Evolutionary biology of human hepatitis viruses

Abstract

Hepatitis viruses are major threats to human health. During the last decade, highly diverse viruses related to human hepatitis viruses were found in animals other than primates. Herein, we describe both surprising conservation and striking differences of the unique biological properties and infection patterns of human hepatitis viruses and their animal homologues, including transmission routes, liver tropism, oncogenesis, chronicity, pathogenesis and envelopment. We discuss the potential for translation of newly discovered hepatitis viruses into preclinical animal models for drug testing, studies on pathogenesis and vaccine development. Finally, we re-evaluate the evolutionary origins of human hepatitis viruses and discuss the past and present zoonotic potential of their animal homologues.

Keywords: Evolution; Hepatitis; Homologues; Virus; Zoonotic.

Graphical abstract

Fig. 1

Selected milestones in hepatitis virus research. References include for HAV,, , , , , , , , , for HBV,, , , , , , , , , , , , , , for HCV,, , , , , , , , , , , , , , , for HDV, , , , , , , and for HEV., , , , , , , , , , , , , Due to space constraints, only selected milestones are shown. Animal pictograms represent host orders in which distinct hepatitis viruses were detected. DAA, direct-acting antiviral; HAV, hepatitis A virus; HBV, hepatitis B virus; HCV, hepatitis C virus; HDV, hepatitis delta virus; HEV, hepatitis E virus; miR-122, micro RNA-122; NRTI, nucleoside reverse transcriptase inhibitor; NTCP, sodium taurocholate co-transporting polypeptide; RBV, ribavirin.

Fig. 2

Virus particles and genome characteristics of human hepatitis viruses. C, core protein; CP, capsid protein; E, envelope protein; HAV, hepatitis A virus; HBV, hepatitis B virus; HCV, hepatitis C virus; HDV, hepatitis delta virus; HEV, hepatitis E virus; Hel, Helicase; HVR, hypervariable region; IRES, Internal ribosomal entry site; LHBs, large surface protein; L-HDAg, large hepatitis delta antigen; MHBs, medium surface protein; MeT, methyltransferase; NS, non-structural protein; ORF, open reading frame; PCP, papain-like cysteine protease; Pol, polymerase; RdRp, RNA-dependent RNA polymerase; S, surface protein; SHBs, small surface protein; S-HDAg, small hepatitis delta antigen; VP, viral protein; X, X-domain/ADP-ribose-binding module. Important secondary structures are depicted below genomes.

Fig. 3

Hepatitis virus homologues in non-human hosts. (A) Simplified phylogenetic tree of mammalian orders, Aves, Reptilia, Amphibia, Osteichthyes, Condrichthyes, and Insecta (Phylogeny adapted from[196], [239]). Squares indicate orders for which homologues of human hepatitis viruses were found; black, same virus genus as human representative; grey, viruses distantly related to human hepatitis viruses. Host taxa for which no homologous hepatitis viruses were found are shown without pictograms and are coloured in grey. Numbers next to nodes show approximate time of divergence in million years according to., (B) GenBank entries of human hepatitis viruses and their homologues per mammalian host order given in percent of all entries of the search term. Host orders with less than 0.1% of entries are summarised as others. Host orders with less than 0.5% of entries are magnified 10-fold to the right. GenBank search terms and final entries per mammalian host taxon were: for HAV (January 17, 2018): “Hepatovirus [Organism] AND host [All Fields]”, Human, n = 3,186, Rodentia, n = 90, Eulipotyphla, n = 49, Chiroptera, n = 32, NHP, n = 6, Scandentia, n = 1, and Carnivora, n = 1; for HBV (January 19, 2018): “Hepadnaviridae [Organism] AND host [All Fields]”, Human, n = 68,867, NHP, n = 156, Aves, n = 87, Chiroptera, n = 73, Rodents, n = 25 and Cetartiodactyla, n = 10; for HCV (January 18, 2018): “Hepacivirus [Organism] AND host [All Fields]”, Human, n = 132,645, NHP, n = 491, Perissodactyla, n = 456, Rodentia, n = 182, Carnivora, n = 25, Cetartiodactyla, n = 18 and Chiroptera, n = 12; for HDV (January 17, 2018): “Deltavirus [Organism] AND host [All Fields]”, Human, n = 912; for HEV (January 17, 2018): “Hepeviridae [Organism] AND host [All Fields]”, Human, n = 7,601, Cetartiodactyla, n = 3,152, Lagomorpha, n = 456, Rodentia, n = 316, Aves, n = 155, Carnivora, n = 76, Non-human primates, n = 16, Chiroptera, n = 10, Scandentia, n = 2, Eulipotyphla, n = 1 and Perissodactyla, n = 1. (C) Patristic distance (maximum percentage pairwise amino acid distance) per host order calculated in MEGA7 using translation alignments generated in Geneious 9.1.8. HAV: A GenBank search with the term “Hepatovirus” was performed on January 18, 2018, and all sequences longer than 6,000 nucleotides were selected. Duplicates, cell culture-adapted strains, or viruses isolated from experimentally infected animals were excluded from the dataset. Sorting according to host orders resulted in: Human, n = 101, NHP, n = 5, Chiroptera, n = 4, Rodentia, n = 7 and Eulipotyphla, n = 5 sequences for translation alignments of complete polyproteins. Non-homologous regions (px/3A) were subsequently deleted. For HBV, HCV and HDV, GenBank searches as performed for 3B were used. HBV: All sequences with complete polymerase CDS from non-human hosts were selected. Complete polymerase CDS of reference sequences from and the capuchin monkey hepatitis B virus (CMHBV, Acc. No. KY703886) were used. Sorting according to host orders resulted in Human, n = 37, NHP, n = 92, Chiroptera, n = 60 and Rodentia, n = 5 sequences. HCV: All sequences with complete polyprotein CDS from non-human hosts were selected. Complete polyprotein CDS of reference sequences from (https://hcv.lanl.gov/components/sequence/HCV/search/searchi.html) and GBV-B (Acc. No. NC001655) were used. Sorting according to host orders resulted in Human, n = 178, NHP, n = 4, Chiroptera, n = 5, Rodentia, n = 15, Perissodactyla, n = 19, Cetartiodactyla, n = 10 sequences. HDV: Sequences with complete HDAg CDS were selected resulting in a total of 158 human-derived sequences. HEV: A GenBank search with the term “Hepeviridae” was performed on January 25, 2018, and all sequences longer than 6,000 nucleotides were selected. Duplicates, cell culture-adapted strains, or viruses isolated from experimentally infected animals were excluded from the dataset. Sorting according to host orders resulted in Human, n = 165, Chiroptera, n = 3, Rodentia, n = 18, Cetartiodactyla, n = 93, Aves, n = 11, Carnivora, n = 13 and Lagomorpha, n = 17 sequences. CDS, coding sequences; HAV, hepatitis A virus; HBV, hepatitis B virus; HCV, hepatitis C virus; HDV, hepatitis delta virus; HEV, hepatitis E virus; NHP, non-human primates. Bars are coloured according to host taxon.

Fig. 4

Phylogenetic relationships of human hepatitis viruses and their vertebrate homologues. Phylogenies are based on amino acid alignments for hepatoviruses, hepaciviruses, deltaviruses, and hepeviruses and a nucleotide alignment for hepadnaviruses generated using MAFFT in Geneious 9.1.8. Phylogenies were generated using a WAG substitution model (for amino acid sequences) or an HKY substitution model (for nucleotide sequences) excluding all ambiguous data or gaps. Hepadnavirus and deltavirus phylogenies were generated using a Maximum Likelihood algorithm and 1,000 bootstrap replicates in MEGA7. For all other virus genera, Bayesian phylogenies were generated using MrBayes V3.1. Outgroups were: Hepatoviruses, Avian encephalomyelitis virus, accession number (Acc. No.) NC003990; Hepadnaviruses, Bluegill hepadnavirus, Acc. No. NC030445; Hepaciviruses, Wenling shark virus, Acc. No. KR902729; Hepeviruses, Piscihepevirus, Acc. No. HQ731075. The deltavirus phylogeny was calculated without an outgroup. Bayesian phylogenies were run for 2 million generations, sampled every 100 steps. After an exclusion of 5,000 of the total 20,000 trees as burn-in, final trees were annotated with TreeAnnotator from the BEAST package and visualised with FigTree. Bayesian posterior probability support of grouping above 0.9 or bootstrap support above 90% is highlighted by filled circles at nodes. The scale bar indicates genetic distance. Animal pictograms are coloured according to their host taxa: Black and red, Primates; Orange, Rodentia; Light green, Lagomorpha; Pink, Scandentia; Yellow, Perissodactyla; Light brown, Eulipotyphla; Light blue, Chiroptera; Dark blue, Carnivora; Dark green, Cetartiodactyla; Grey, Marsupialia; Turquois, Aves; Dark brown, Reptilia. (A) For hepatoviruses, the complete P1 domain was used. Acc. No. of representative sequences were: M59286, KT452691, KT877158, KT452714, KT452730, KR703607, KT452742, KT452735, AB279735, AB279732, AY644670, AY644676, AF268396, AB020564, D00924, KT452685, KT452658, MG181943. (B) For hepadnaviruses, complete genomes were used. Acc. No. of representative sequences were: MH307930 NC024444, FN594748, EU594434, AB032432, FJ798097, FM209516, LT992443, AF193863, FM209514, GU563556, AB194951, AB368296, FJ899779, AB036920, AB516393, AF046996, NC24445, NC004107, AB486012, FJ023659. (C) For hepaciviruses, domains encoding the structural proteins C-E1-E2-p7 were used. Acc. No. of representative sequences were: KC411777, JQ434004, D00944, GU814265, M62321, Y12083, Y13184, D17763, EF108306, KC796074, KC411806, KC796077, U22304, KJ950938, KC551800, KP641127. (D) For deltaviruses, complete S-HDAg coding regions were used. Acc. No. of representative sequences were: X04451, X60193, L22063, AF018077, AJ584848, AJ584847, AJ584844, AJ584849, MH988742, MH824555. (E) For hepeviruses, complete ORF 2 sequences encoding the viral capsid were used. Acc. No. of representative sequences were: AB197673, DQ279091, AB573435, AF082843, AP003430, KJ013415, KJ496143, KT818608, KX387865, AB602441, M73218, M74506, KF951328, KR905549 GU345042, AY535004, JQ001749. Gt, Genotype; HAV, hepatitis A virus; HBV, hepatitis B virus; HCV, hepatitis C virus; HDV, hepatitis delta virus; HEV, hepatitis E virus; ORF, open-reading frame; S-HDAg, small form HDV antigen.

Fig. 5

Global distribution of hepatitis virus genotypes. Distribution of the most prevalent genotypes were adapted and simplified from for HAV, from, for HBV, from, for HCV, from for HDV and from for HEV. NHP genotypes are shown as pictograms and represent HAV genotype 5 in Africa, HAV genotypes 4 and 6 in Asia, Chimpanzee HBV and Gorilla HBV in Africa and Orangutan HBV and Gibbon HBV genotypes in Asia., HAV, hepatitis A virus; HBV, hepatitis B virus; HCV, hepatitis C virus; HDV, hepatitis delta virus; HEV, hepatitis E virus; NHP, non-human primate.

Fig. 6

Evolutionary origins of hepatitis viruses. (A) Evolutionary origins, ancestors and sources of human infections. Animal pictograms represent host taxa. (B) Hypotheses for the evolution of hepatitis-like viruses among diverse animals. Black lines, simplified bilateria phylogeny from including selected taxa. Black pictograms, animal taxa comprising hosts of hepatitis viruses and related viruses. Grey pictograms, representatives of selected animal taxa. From bottom to top: phylum Nematoda, superphylum Lophotrochozoa, phylum Echinodermata. Blue lines: hypothesised virus evolution. Gt, genotype; HAV, hepatitis A virus; HBV, hepatitis B virus; HCV, hepatitis C virus; HDV, hepatitis delta virus; HEV, hepatitis E virus.