Schistosoma haematobium: experimental infection in capuchin monkey, Cebus apella

A novel hepatitis B virus species discovered in capuchin monkeys sheds new light on the evolution of primate hepadnaviruses

BACKGROUND & AIMS

All known hepatitis B virus (HBV) genotypes occur in humans and hominoid Old World non-human primates (NHPs). The divergent woolly monkey HBV (WMHBV) forms another orthohepadnavirus species. The evolutionary origins of HBV are unclear.

METHODS

We analysed sera from 124 Brazilian monkeys collected during 2012-2016 for hepadnaviruses using molecular and serological tools, and conducted evolutionary analyses.

RESULTS

We identified a novel orthohepadnavirus species in capuchin monkeys (capuchin monkey hepatitis B virus [CMHBV]). We found CMHBV-specific antibodies in five animals and high CMHBV concentrations in one animal. Non-inflammatory, probably chronic infection was consistent with an intact preCore domain, low genetic variability, core deletions in deep sequencing, and no elevated liver enzymes. Cross-reactivity of antisera against surface antigens suggested antigenic relatedness of HBV, CMHBV, and WMHBV. Infection-determining CMHBV surface peptides bound to the human HBV receptor (human sodium taurocholate co-transporting polypeptide), but preferentially interacted with the capuchin monkey receptor homologue. CMHBV and WMHBV pseudotypes infected human hepatoma cells via the human sodium taurocholate co-transporting polypeptide, and were poorly neutralised by HBV vaccine-derived antibodies, suggesting that cross-species infections may be possible. Ancestral state reconstructions and sequence distance comparisons associated HBV with humans, whereas primate hepadnaviruses as a whole were projected to NHP ancestors. Co-phylogenetic analyses yielded evidence for co-speciation of hepadnaviruses and New World NHP. Bayesian hypothesis testing yielded strong support for an association of the HBV stem lineage with hominoid ancestors. Neither CMHBV nor WMHBV was likely the ancestor of the divergent human HBV genotypes F/H found in American natives.

CONCLUSIONS

Our data suggest ancestral co-speciation of hepadnaviruses and NHP, and an Old World origin of the divergent HBV genotypes F/H. The identification of a novel primate hepadnavirus offers new perspectives for urgently needed animal models of chronic hepatitis B.

LAY SUMMARY

The origins of HBV are unclear. The new orthohepadnavirus species from Brazilian capuchin monkeys resembled HBV in elicited infection patterns and could infect human liver cells using the same receptor as HBV. Evolutionary analyses suggested that primate HBV-related viruses might have emerged in African ancestors of New World monkeys millions of years ago. HBV was associated with hominoid primates, including humans and apes, suggesting evolutionary origins of HBV before the formation of modern humans. HBV genotypes found in American natives were divergent from those found in American monkeys, and likely introduced along prehistoric human migration. Our results elucidate the evolutionary origins and dispersal of primate HBV, identify a new orthohepadnavirus reservoir, and enable new perspectives for animal models of hepatitis B.

Pathology of Schistosoma haematobium infection in the capuchin monkey (Cebus apella)

Capuchin monkeys exposed to 500-2000 Schistosoma haematobium cercariae were followed for up to 6 1/2 years after infection. Worm burdens decreased as infections became more chronic and decreasing numbers of eggs and active circumoval lesions were found in the bladder and elsewhere. Nodular and hyperplastic epithelial lesions of the urinary bladder were not seen during the first year of infection but occurred in 30% of monkeys examined 1-2 years after infection and in 23% of those examined between the second and third years; they were present in only 3% of monkeys studied 3-6 1/2 years after infection. These epithelial proliferative lesions were located near foci of egg deposition and occurred in the monkeys with the most intense active lesions in the bladder. The lesions regressed in animals followed sequentially. The lesions thus appear not to be neoplastic. Obstructive lesions of the ureter accompanied by hydronephrosis were present in a few animals. The obstructive uropathy did not appear to cause significant morbidity. Mortality was substantial among infected monkeys at most intervals after infection but was rare among uninfected controls.

Comparison of the infectivity and pathogenicity of six species of African schistosomes and their hybrids. 2. Baboons

The behaviour of six species of African schistosomes and their hybrids has been compared qualitatively and quantitatively in baboons, with a view to finding a schistosome of high infectivity but low pathogenicity to the baboon for use in heterologous immunity experiments. This study, which includes the first comparative study of the pathogenicity of these six species in primates, is complementary to earlier studies in rodents in which these schistosomes and their hybrids were compared in terms of egg morphology, snail infectivity, and infectivity and pathogenicity. In rodents, statistically significant differences were detected in the behaviour of each pair of sibling species with regard to percentage worm recovery, rate of egg production and percentage distribution of the eggs in the tissues, and the hybrids also differed significantly from their “parental” species.

Even greater differences were found in baboons. For example, although all the strains studied produced mature egg-laying adults in rodents, no worms, eggs, or histopathological changes resulted from exposure of baboons to S. rodhaini or S. bovis. With regard to prepatent period, S. mansoni was the shortest (5–6 weeks), S. haematobium the longest (12–14 weeks), while S. mattheei and S. intercalatum occupied intermediate positions (7–9 weeks). The hybrids all matured in 7–9 weeks except the S. bovis/S. mattheei hybrid (11–16 weeks). S. haematobium similarly had a much longer maturation time in rodents. Complete or partial “self-cure” occurred in 3 baboons but was not observed in rodents. The percentage worm recovery of S. mansoni was higher than for the S. mansoni/S. rodhaini hybrids while with the S. haematobium group of species, worm recovery was highest with S. mattheei followed by S. intercalatum and S. haematobium, the same order as in rodents. With the S. haematobium-group hybrids, worm recovery was generally high except with the S. bovis/S. haematobiuun hybrid.