A novel adenovirus of Western lowland gorillas (Gorilla gorilla gorilla)
© Wevers et al; licensee BioMed Central Ltd. 2010
Received: 1 September 2010
Accepted: 5 November 2010
Published: 5 November 2010
Adenoviruses (AdV) broadly infect vertebrate hosts including a variety of primates. We identified a novel AdV in the feces of captive gorillas by isolation in cell culture, electron microscopy and PCR. From the supernatants of infected cultures we amplified DNA polymerase (DPOL), preterminal protein (pTP) and hexon gene sequences with generic pan primate AdV PCR assays. The sequences in-between were amplified by long-distance PCRs of 2 - 10 kb length, resulting in a final sequence of 15.6 kb. Phylogenetic analysis placed the novel gorilla AdV into a cluster of primate AdVs belonging to the species Human adenovirus B (HAdV-B). Depending on the analyzed gene, its position within the cluster was variable. To further elucidate its origin, feces samples of wild gorillas were analyzed. AdV hexon sequences were detected which are indicative for three distinct and novel gorilla HAdV-B viruses, among them a virus nearly identical to the novel AdV isolated from captive gorillas. This shows that the discovered virus is a member of a group of HAdV-B viruses that naturally infect gorillas. The mixed phylogenetic clusters of gorilla, chimpanzee, bonobo and human AdVs within the HAdV-B species indicate that host switches may have been a component of the evolution of human and non-human primate HAdV-B viruses.
Adenoviruses are non-enveloped icosahedral double-stranded DNA viruses that infect fish, amphibians, reptiles, birds and mammals . Human adenoviruses (HAdV) are categorized into seven species (HAdV-A to HAdV-G) . Each species includes a distinct number of serotypes . In addition, intra-species shuffling of penton base, fiber and hexon genes by recombination has been frequently observed [4–6]. Simian adenoviruses have been discovered in monkeys and great apes [7–11]. They are very similar to HAdV, and most of them can be grouped into corresponding HAdV species or the newly established species Simian adenovirus A (SAdV-A).
In 2008, a group of Western lowland gorillas (Gorilla gorilla gorilla) suffered from prolonged diarrhea and self-limiting respiratory disease in the Zoological gardens of Münster, Germany. To isolate viral agents potentially responsible for the symptoms, fecal samples were suspended in phosphate-buffered saline, sterile filtered and cultured on MRC-5 cells and A549 cells. After eight days of culture, a cytopathogenic effect was observed. The culture supernatant was examined by electron microscopy, and virus-like structures were detected their size and general structure being consistent with that of adenoviruses (Additional Figure 1).
Primers for amplification of DPOL, pTP and hexon gene sequences
Name of primer
Specific primers for long-distance PCR
Primers specific for AdV species B
Adenoviruses, accession numbers and hosts
GenBank accession number
HAdV-B of this study
Gorilla gorilla adenovirus B7
Western lowland gorilla
Gorilla gorilla adenovirus B8
Western lowland gorilla
Gorilla gorilla adenovirus B9
Western lowland gorilla
Gorilla gorilla adenovirus B10
Western lowland gorilla
Simian adenovirus 21
Simian adenovirus 27.1
Simian adenovirus 27.2
Simian adenovirus 28.1
Simian adenovirus 28.2
Simian adenovirus 29
Simian adenovirus 32
Simian adenovirus 33
Simian adenovirus 35.1
Simian adenovirus 35.2
Simian adenovirus 41.1
Simian adenovirus 41.2
Simian adenovirus 46
Simian adenovirus 47
Human adenovirus B3
Human adenovirus B7
Human adenovirus B11
Human adenovirus B14
Human adenovirus B16
Human adenovirus B21
Human adenovirus B34
Human adenovirus B35
Human adenovirus B50
To acquire extended sequence information of GgorAdV-B7, three additional nested PCR assays were designed (Table 1) targeting the preterminal protein (pTP) and two conserved regions at the 5'- and 3'-end of the hexon gene (Figure 1). PCRs were performed as described above, except that elongation at 72°C was for 1 min. With each primer set products of the expected size were obtained. BLAST analysis of their sequences also revealed a HAdV-B-like virus (not shown). To prove that the DPOL, pTP and hexon sequences originate from the same virus, we connected them with long-distance (LD) PCRs (Figure 1) using the TaKaRa-EX PCR system according to the instructions of the manufacturer (Takara Bio Inc., Otsu, Japan). The LD primer pairs are listed with their annealing temperatures in Table 1. Three overlapping PCR products were generated and sequenced by primer walking. A final contiguous sequence of 15637 bp was obtained spanning the genes DPOL, pTP and 52 k, the genes encoding the AdV proteins pIIIa, III (penton base), pVII, V, pX and pVI, and the hexon gene of GgorAdV-B7 (Figure 1).
The remarkably close relatedness of GgorAdV-B7 to chimpanzee AdVs (SAdV-29 and 35.1) prompted us to investigate whether gorillas naturally host GgorAdV-B7. For this purpose, we examined wild Western lowland gorillas (Gorilla. g. gorilla) from Gabon and additional captive gorillas. Fecal samples were collected from 19 individuals in a remote area with little human presence in Loango National Park, Gabon. They originated from fresh nest sites or were freshly found on gorilla paths . Samples were collected using single-use gloves and preserved by drying over silica. DNA was extracted following a previously described method . In addition, ten necropsy samples (spleen, liver, pancreas, lymph node, tonsil, lung, kidney, urine) and one plasma sample were collected from four deceased captive gorillas in the Zoological gardens of Berlin as well as six fecal samples from three captive gorillas in the Zoological gardens of Münster, Germany. To test for the presence of HAdV-B viruses, we set up a nested PCR (PCR Hex-loop2; Table 1) which targets flanking sequences of a hyper variable region (loop 2) in the hexon gene (Figure 1) and amplifies 380 bp. The primers were deduced from HAdV-B sequences only and not degenerated. A total of 36 gorilla samples were screened. AdV DNA was only detected in feces (5/19 wild gorilla samples and 4/6 captive gorilla samples). In total, 9/25 fecal samples were PCR-positive (36%), and the products sequenced. Most importantly, a virus apparently identical to GgorAdV-B7 was identified in a wild gorilla from Gabon. Three additional HAdV-B viruses were also detected. Two were without close similarities to any published AdV sequence. The third one was nearly identical to the gorilla AdVs SAdV-27.2 and SAdV-47, which had been originally isolated from captive individuals . They were tentatively named GgorAdV-B8, -B9 and -B10.
Taken together, these observations cannot be explained by co-speciation. Rather, they are in line with recombination and host switching. Such events have been previously discussed to be involved in the evolution of human AdV, because intra-species shuffling of penton base, fiber and hexon genes has been frequently observed [4–6]. In addition, a recombinant between viruses of the sub-clades HAdV-B1 and HAdV-B2 has been isolated from a captive chimpanzee . Here, a close similarity of GgorAdV-B7 to SAdV-29 (complete sequence, excluding hexon loops) and to SAdV-35.1 (hexon loops) was observed (Figure 2). However, since in the loop region the nucleic acid identity between GgorAdV-B7 and SAdV-35.1 was well below 100%, it is unlikely that the existing AdVs are parent viruses in a recent recombination event giving rise to GgorAdV-B7. Rather, a more ancient one with subsequent genetic drift may have been involved or recombination with an unknown AdV, as suggested for HAdV-A18 .
Shuffling of genes by recombination between AdVs that naturally infect different host species (e.g., great ape and human AdVs) but under certain conditions co-infect the same host, may be an additional mechanism by which AdVs exchange genetic information. This could occur in places where contacts between humans and apes are frequent like in zoos and animal facilities. In addition, people who are involved in hunting primates and preparation of bush meat  are at risk to be infected. So far, infections of humans with non-human primate (NHP) AdVs have not been observed. Nevertheless, antibodies with specificity for chimpanzee HAdV-C viruses have been detected in humans from Sub-Saharan Africa and were significantly less frequent in people from the United States of America and Thailand . In addition, the species HAdV-E comprises only one human serotype but more than 12 great ape serotypes. Therefore, the human HAdV-E was thought to be the result of a zoonotic transmission from chimpanzees to humans . The gorilla AdV described in the present study (GgorAdV-B7) is highly similar to chimpanzee AdVs. Thus, a transmission event between chimpanzees and gorillas was possibly involved which is further indication for the potential of AdVs to jump between closely related hosts.
Very little is known about the pathogenic properties of NHP-AdV. GgorAdV-B7 was originally discovered in a group of gorillas suffering from prolonged diarrhea and self-limiting respiratory infection. Since human species B AdV have been linked to respiratory diseases [22–24], an etiological association of GgorAdV-B7 with the observed respiratory symptoms is possible. However, recent studies reported the frequent shedding of AdVs in the feces of healthy captive chimpanzees and gorillas [12, 25]. Therefore, further investigations are needed.
Knowledge about the spectrum of AdV in wild great apes in general  is very limited. Specifically from wild gorillas, no information has been published. Although examining only a small set of samples, our findings show that AdV infecting captive gorillas can readily be found in wild animals (GgorAdV-B7; GgorAdV-B8). This is a good example of how humans may be brought into contact with new pathogens, not only locally through bushmeat hunting in regions where NHP live naturally, but also in other regions of the world where NHP are housed in zoos.
The high variety of known and novel HAdV-B viruses in great apes calls for larger studies to understand the diversity of AdVs currently circulating in African NHP as well as in local human populations. It is justified to assume that such studies will improve our insight into the zoonotic potential of adenoviruses and possibly answer the intriguing question whether AdVs of non-human primates have already contributed to the human "adeno-virosphere".
The sequences reported in this study were deposited in GenBank under the accession numbers listed in Table 2.
We thank Michael Laue for electron microscopic analysis. The technical assistance of Sonja Liebmann and Cornelia Walter is kindly acknowledged. We thank the Agence Nationale des Parcs Nationaux (ANPN) and the Centre National de la Recherche Scientifique et Technique (CENAREST) of Gabon for permission to conduct research in Loango National Park. We also thank the Société pour la Conservation et le Développement (SCD) and Wildlife Conservation Society (WCS) for financial and logistical support. For sample collection from wild gorilla, we thank L. Rabanal, L. Mackaga, E. R. Guizard, N. Tagg, B. Graw, E. Fairet, M. Gregoire, L. Rankin and the other field assistants of the Loango Ape project. For DNA extraction and identification of individual samples from wild gorilla we thank M. Arandjelovic and L. Vigilant from the Max-Planck-Institute for Evolutionary Anthropology, Leipzig.
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