Adenovirus Infections in African Humans and Wild Non-Human Primates: Great Diversity and Cross-Species Transmission

Respiratory adenovirus infections in children: a focus on Africa

PURPOSE OF REVIEW

Lower respiratory tract infections (LRTIs) are an important cause of child morbidity and mortality globally, especially in children under the age of 5 years in Africa. Respiratory viruses, including human adenoviruses (HAdVs), are common causes of LRTIs in children. This review aims to shed light on the epidemiology, clinical manifestations, sequelae, and treatment options specific to adenovirus respiratory infections in African children.

RECENT FINDINGS

Recent evidence has challenged the perception that adenovirus is a negligible cause of LRTIs. Studies show HAdV emerging as the third most common viral pathogen in fatal pneumonias among under-5 children in low-income and middle-income African countries, contributing to 5.5% of all pneumonia deaths and ranking second in hospital-associated viral pneumonia deaths. Predominant HAdV serotypes associated with disease differ by country and region, and have changed over time. Risk factors for increased disease severity and long-term respiratory sequelae in previously healthy African children with HAdV LRTIs are not well established.

SUMMARY

Although respiratory viruses, including HAdV, are recognized contributors to LRTIs, the prevalence and impact of adenovirus infections have been under-recognized and understated. Available data suggests that African children, particularly those under 5 years old, are at risk of severe sequelae from respiratory HAdV infections. Long-term sequelae, including bronchiectasis and postinfectious bronchiolitis obliterans, further underscore the significant impact of HAdV infections. However, the scarcity of comprehensive data hampers our understanding of the extent of the impact of HAdV infections on child lung health in Africa. We recommend scaled-up HAdV surveillance, ensuring its consistent inclusion in population-level LRTI assessments, and expanded and equitable access to diagnostics for early recognition of African children at risk of developing chronic sequelae and death. Enhanced understanding of adenovirus epidemiology and clinical outcomes and the availability of therapeutic options are essential for informed public health strategies and clinical care.

An optimised protocol for the expression and purification of adenovirus core protein VII

Adenovirus protein VII (pVII) is a highly basic core protein, bearing resemblance to mammalian histones. Despite its diverse functions, a comprehensive understanding of its structural intricacies and the mechanisms underlying its functions remain elusive, primarily due to the complexity of producing a good amount of soluble pVII. This study aimed to optimise the expression and purification of recombinant pVII from four different adenoviruses with a simple vector construct. This study successfully determined the optimal conditions for efficiently purifying pVII across four adenovirus species, revealing the differential preference for bacterial expression systems. The One Shot BL21 Star (DE3) proved favourable over Rosetta 2 (DE3) pLysS with consistent levels of expression between IPTG-induced and auto-induction. We demonstrated that combining chemical and mechanical cell lysis is possible and highly effective. Other noteworthy benefits were observed in using RNase during sample processing. The addition of RNase has significantly improved the quality and quantity of the purified protein as confirmed by chromatographic and western blot analyses. These findings established a solid groundwork for pVII purification methodologies and carry the significant potential to assist in unveiling the core structure of pVII, its arrangement within the core, DNA condensation intricacies, and potential pathways for nuclear transport.

Isolation of a recombinant simian adenovirus encoding the human adenovirus G52 hexon suggests a simian origin for human adenovirus G52

Human adenoviruses (HAdVs) are causative agents of morbidity and mortality throughout the world. These double-stranded DNA viruses are phylogenetically classified into seven different species (A-G). HAdV-G52, originally isolated in 2008 from a patient presenting with gastroenteritis, is the sole human-derived member of species G. Phylogenetic analysis previously suggested that HAdV-G52 may have a simian origin, indicating a potential zoonotic spillover into humans. However, evidence of HAdV-G52 in either human or simian populations has not been reported since. Here, we describe the isolation and in vitro characterization of rhesus (rh)AdV-69, a novel simian AdV with clear evidence of recombination with HAdV-G52, from the stool of a rhesus macaque. Specifically, the rhAdV-69 hexon capsid protein is 100% identical to that of HAdV-G52, whereas the remainder of the genome is most similar to rhAdV-55, sharing 95.36% nucleic acid identity. A second recombination event with an unknown adenovirus (AdV) is evident at the short fiber gene. From the same sample, we also isolated a second, highly related recombinant AdV (rhAdV-68) that harbors a distinct hexon gene but nearly identical backbone compared to rhAdV-69. In vitro, rhAdV-68 and rhAdV-69 demonstrate comparable growth kinetics and tropisms in human cell lines, nonhuman cell lines, and human enteroids. Furthermore, we show that coinfection of highly related AdVs is not unique to this sample since we also isolated coinfecting rhAdVs from two additional rhesus macaque stool samples. Our data collectively contribute to elucidating the origins of HAdV-G52 and provide insights into the frequency of coinfections and subsequent recombination in AdV evolution.IMPORTANCEUnderstanding the host origins of adenoviruses (AdVs) is critical for public health as transmission of viruses from animals to humans can lead to emergent viruses. Recombination between animal and human AdVs can also produce emergent viruses. HAdV-G52 is the only human-derived member of the HAdV G species. It has been suggested that HAdV-G52 has a simian origin. Here, we isolated from a rhesus macaque, a novel rhAdV, rhAdV-69, that encodes a hexon protein that is 100% identical to that of HAdV-G52. This observation suggests that HAdV-G52 may indeed have a simian origin. We also isolated a highly related rhAdV, differing only in the hexon gene, from the same rhesus macaque stool sample as rhAdV-69, illustrating the potential for co-infection of closely related AdVs and recombination at the hexon gene. Furthermore, our study highlights the critical role of whole-genome sequencing in understanding AdV evolution and monitoring the emergence of pathogenic AdVs.

Detection and Molecular Characterization of Adenoviruses in Captive and Free-Roaming African Green Monkeys (Chlorocebus sabaeus): Evidence for Possible Recombination and Cross-Species Transmission

In the present study, 31 samples (12 fecal, 9 nasal and 10 rectal swabs) from 28/92 (30.43%, 10 captive and 18 free-roaming African green monkeys (AGMs, Chlorocebus sabaeus)) apparently healthy AGMs in the Caribbean Island of St. Kitts tested positive for adenoviruses (AdVs) by DNA-dependent DNA polymerase (pol)-, or hexon-based screening PCR assays. Based on analysis of partial deduced amino acid sequences of Pol- and hexon- of nine AGM AdVs, at least two AdV genetic variants (group-I: seven AdVs with a Simian mastadenovirus-F (SAdV-F)/SAdV-18-like Pol and hexon, and group-II: two AdVs with a SAdV-F/SAdV-18-like Pol and a Human mastadenovirus-F (HAdV-F)/HAdV-40-like hexon) were identified, which was corroborated by analysis of the nearly complete putative Pol, complete hexon, and partial penton base sequences of a representative group-I (strain KNA-08975), and -II (KNA-S6) AdV. SAdV-F-like AdVs were reported for the first time in free-roaming non-human primates (NHPs) and after ~six decades from captive NHPs. Molecular characterization of KNA-S6 (and the other group-II AdV) indicated possible recombination and cross-species transmission events involving SAdV-F-like and HAdV-F-like viruses, corroborating the hypothesis that the evolutionary pathways of HAdVs and SAdVs are intermingled, complicated by recombination and inter-species transmission events, especially between related AdV species, such as HAdV-F and SAdV-F. To our knowledge, this is the first report on detection and molecular characterization of AdVs in AGMs.

Molecular characterisation of human adenoviruses associated with respiratory infections in Uganda

Human adenoviruses (HAdV) are a diverse group of viruses causing a broad range of infections of the respiratory, urogenital and gastrointestinal tracts and keratoconjunctivitis. There are seven species of human adenoviruses with 113 genotypes which may contain multiple genetic variants. This study characterised respiratory human adenoviruses and associated factors in samples collected from selected hospitals in Uganda. A total of 2,298 nasopharyngeal samples were collected between the period of 2008 to 2016 from patients seeking health care at tertiary hospitals for influenza-like illness. They were screened by polymerase chain reaction (PCR) to determine the prevalence of HAdV. HAdV was cultured in A549 cell lines and the hexon gene was sequenced for genotyping. Of the 2,298 samples tested, 225 (9.8%) were adenovirus-positive by PCR. Age was found to be significantly associated with HAdV infections (p = 0.028) with 98% (220/225) of the positives in children aged 5 years and below and none in adults above 25 years of age. The sequenced isolates belonged to species HAdV-B and HAdV-C with most isolates identified as genotype B3. The results showed a high prevalence and genetic diversity in respiratory HAdV circulating in Ugandan population. Deeper genomic characterization based on whole genome sequencing may be necessary to further elucidate possible transmission and impact of current adenovirus-vectored vaccines in Africa.

Characterization of monkey adenoviruses with three fiber genes

Although the occurrence of three fiber genes in monkey adenoviruses had already been described, the relatedness of the "extra" fibers have not yet been discussed. Here we report the genome analysis of two simian adenovirus (SAdV) serotypes from Old World monkeys and the phylogenetic analysis of the multiple fiber genes found in these and related AdVs. One of the newly sequenced serotypes (SAdV-2), isolated from a rhesus macaque (Macaca mulatta), was classified into species Human mastadenovirus G (HAdV-G), while the other serotype (SAdV-17), originating from a grivet (Chlorocebus aethiops), classified to Simian mastadenovirus F (SAdV-F). We identified unique features in the gene content of these SAdVs compared to those typical for other members of the genus Mastadenovirus. Namely, in the E1B region of SAdV-2, the 19K gene was replaced by an ITR repetition and a copy of the E4 ORF1 gene. Among the 37 genes in both SAdVs, three genes of different lengths, predicted to code for the cellular attachment proteins (the fibers), were found. These proteins exhibit high diversity. Yet, phylogenetic calculations of their conserved parts could reveal the probable evolutionary steps leading to the multiple-fibered contemporary HAdV and SAdV species. Seemingly, there existed (a) common ancestor(s) with two fiber genes for the lineages of the AdVs in species SAdV-B, -E, -F and HAdV-F, alongside a double-fibered ancestor for today's SAdV-C and HAdV-G, which later diverged into descendants forming today's species. Additionally, some HAdV-G members picked up a third fiber gene either to the left-hand or to the in-between position from the existing two. A SAdV-F progenitor also obtained a third copy to the middle, as observed in SAdV-17. The existence of three fiber genes in these contemporary AdVs brings novel possibilities for the design of optimised AdV-based vectors with potential multiple target binding abilities.

Epidemiological investigations of diarrhea in children in Praia city, Cape Verde

Introduction

Diarrheal disease is a major cause of infant mortality and morbidity in Africa and results primarily from contaminated food and water sources, but its prevalence predictors in Cape Verde are not completely known. For this reason, this study aimed to identify the etiological agents of diarrhea in Cape Verdean children and assess its associated risk factors.

Methods

A survey questionnaire was used, and a total of 105 stool samples from children with diarrhea aged 0-12 years at the Central Hospital of Praia (Santiago, Cape Verde) were analyzed. The analyses were carried out using Biofire FilmArray Gastrointestinal Panels. Possible risk factors for these pathogens were analyzed using logistic regression, chi-square tests, or Fisher's exact test.

Results

Among the bacteria, enteroaggregative Escherichia coli (45.71%; 95% CI: 36.71-56.70), enteropathogenic E. coli (40%; 95% CI: 30.56-50.02), Shigella/enteroinvasive E. coli (29.52%; 95% CI: 21.02-39.22), E. coli enterotoxigenic (12.38%; 95% CI: 6.76-20.24), Campylobacter sp. (10.48%; 95% CI: 5.35-1.97), Vibrio sp. (4.76%; 95% CI: 1.56-10.76), Clostridioides difficile (3.81%; 95% CI: 1.05-9.47), Vibrio cholerae (2.86%; 0.59-8.12), Shiga-like toxin-producing E. coli (2.86%; 0.59-8.12) and Salmonella sp. (0.95%; 0.02-5.19) were identified; four viruses, Rotavirus A (28.57%; 95% CI: 20.18-38.21), Sapovirus I. II. IV and V (11.43%; 95% CI: 6.05-19.11), Norovirus GI.GII (6.67%; 95% CI: 2.72-13.25) and Adenovirus F 40.41 (6.67%; 95% CI: 2.72-13.25) were also observed. All the pathogens detected in this study were found in coinfections. Significant associations with risk factors were found; specifically, having a bathroom at home reduced the risk of Campylobacter sp., having animals at home increased the risk of Shigella/EIEC infection, and drinking bottled water reduced the risk of Sapovirus infection.

Discussion

From the findings of this study, it can be concluded that, in Cape Verde, there is a high prevalence and diversity of pathogens among children. Our results could help to establish an adequate diagnosis and effective treatments for diarrheal disease.

CELO Fiber1 Knob Is a Promising Candidate to Modify the Tropism of Adenoviral Vectors

Fowl adenovirus 4 (FAdV-4) has the potential to be constructed as a gene transfer vector for human gene therapy or vaccine development to avoid the pre-existing immunity to human adenoviruses. To enhance the transduction of FAdV-4 to human cells, CELO fiber1 knob (CF1K) was chosen to replace the fiber2 knob in FAdV-4 to generate recombinant virus F2CF1K-CG. The original FAdV4-CG virus transduced 4% human 293 or 1% HEp-2 cells at the multiplicity of infection of 1000 viral particles per cell. In contrast, F2CF1K-CG could transduce 98% 293 or 60% HEp-2 cells under the same conditions. Prokaryotically expressed CF1K protein blocked 50% transduction of F2CF1K-CG to 293 cells at a concentration of 1.3 µg/mL while it only slightly inhibited the infection of human adenovirus 5 (HAdV-5), suggesting CF1K could bind to human cells in a manner different from HAdV-5 fiber. The incorporation of CF1K had no negative effect on the growth of FAdV-4 in the packaging cells. In addition, CF1K-pseudotyped HAdV-41 could transduce HEp-2 and A549 cells more efficiently. These data indicated that CF1K had the priority to be considered when there is a need to modify adenovirus tropism.

Adenovirus in fishery harbours and identification of contamination sources

Adenoviruses (AdVs) are a major cause of clinical infections and have been proposed as indicators of water quality. However, quantitative data on the environmental prevalence of AdVs is lacking. We investigated the prevalence, distribution, seasonal occurrence, quantity, and genotype of AdVs in 13 fishing harbours in Taiwan. AdVs in the water samples were isolated by membrane filtration and the AdV DNA was extracted. Next, AdVs were detected using nested polymerase chain reaction. Genotyping and phylogenetic analysis were performed to identify various AdV genotypes present in the water samples. The F species human AdV (HAdV) serotype 41 (63.6%) and C species porcine AdV (PAdV) serotype 5 (33.3%) were more prevalent than the other serotypes. The prevalence of AdVs was highest in the fall, followed by in the spring and summer. Among the fishing harbours, the highest detection rate of AdVs was observed in Yenpudongang in all seasons. However, Puoziliao was the only site at which AdVs were not detected during the study period. AdV detection at sampling sites may be correlated with sewage and livestock wastewater discharge via outflow of nearby rivers to fishing ports. Statistical analysis (Mann-Whitney U test) based on data from water quality indicators revealed that the presence of AdVs was significantly associated with the heterotrophic plate count, pH, and salinity. Human and swine population data from nearby local townships and river/drainage basins were collected from the Taiwan Central Government's website. The data were analyzed using Spearman's rank correlation coefficient to determine the relationship between the prevalence of AdVs, HAdVs, and PAdVs in fishing harbours, and microbial water quality indicators. Statistical evidence indicated that the detection levels of HAdVs and PAdVs in fishing harbours were mainly associated with human and swine populations in the corresponding river/drainage basin, respectively. Additionally, the swine population in the river/drainage basin was positively correlated with microbial water quality indicators.

A host non-coding RNA, nc886, plays a pro-viral role by promoting virus trafficking to the nucleus

Elucidation of the interplay between viruses and host cells is crucial for taming viruses to benefit human health. Cancer therapy using adenovirus, called oncolytic virotherapy, is a promising treatment option but is not robust in all patients. In addition, inefficient replication of human adenovirus in mouse hampered the development of an in vivo model for preclinical evaluation of therapeutically engineered adenovirus. nc886 is a human non-coding RNA that suppresses Protein Kinase R (PKR), an antiviral protein. In this study, we have found that nc886 greatly promotes adenoviral gene expression and replication. Remarkably, the stimulatory effect of nc886 is not dependent on its function to inhibit PKR. Rather, nc886 facilitates the nuclear entry of adenovirus via modulating the kinesin pathway. nc886 is not conserved in mouse and, when xenogeneically expressed in mouse cells, promotes adenovirus replication. Our investigation has discovered a novel mechanism of how a host ncRNA plays a pro-adenoviral role. Given that nc886 expression is silenced in a subset of cancer cells, our study highlights that oncolytic virotherapy might be inefficient in those cells. Furthermore, our findings open future possibilities of harnessing nc886 to improve the efficacy of oncolytic adenovirus and to construct nc886-expressing transgenic mice as an animal model.

Animal Models in Human Adenovirus Research

Simple Summary

Animal models are widely used to study various aspects of human diseases and disorders. Likewise, they are indispensable for preclinical testing of medicals and vaccines. Human adenovirus infections are usually self-limiting, and can cause mild respiratory symptoms with fever, eye infection or gastrointestinal symptoms, but occasional local outbreaks with severe disease courses have been reported. In addition, adenovirus infections pose a serious risk for children and patients with a weakened immune system. Human adenovirus research in animal models to study adenovirus-induced disease and tumor development started in the 1950s. Various animal species have been tested for their susceptibility to human adenovirus infection since then, and some have been shown to mimic key characteristics of the infection in humans, including persistent infection. Furthermore, some rodent species have been found to develop tumors upon human adenovirus infection. Our review summarizes the current knowledge on animal models in human adenovirus research, describing the pros and cons along with important findings and future perspectives.

Abstract

Human adenovirus (HAdV) infections cause a wide variety of clinical symptoms, ranging from mild upper respiratory tract disease to lethal outcomes, particularly in immunocompromised individuals. To date, neither widely available vaccines nor approved antiadenoviral compounds are available to efficiently deal with HAdV infections. Thus, there is a need to thoroughly understand HAdV-induced disease, and for the development and preclinical evaluation of HAdV therapeutics and/or vaccines, and consequently for suitable standardizable in vitro systems and animal models. Current animal models to study HAdV pathogenesis, persistence, and tumorigenesis include rodents such as Syrian hamsters, mice, and cotton rats, as well as rabbits. In addition, a few recent studies on other species, such as pigs and tree shrews, reported promising data. These models mimic (aspects of) HAdV-induced pathological changes in humans and, although they are relevant, an ideal HAdV animal model has yet to be developed. This review summarizes the available animal models of HAdV infection with comprehensive descriptions of virus-induced pathogenesis in different animal species. We also elaborate on rodent HAdV animal models and how they contributed to insights into adenovirus-induced cell transformation and cancer.

What is the risk of a deadly adenovirus pandemic?

Many of us had refresher courses in virology, immunology, and epidemiology in 2020, and we were reminded of the fact that Homo sapiens, the wiliest predator on the planet, has been hunting everything that moves for millennia. These repeated interspecies contacts inherently lead to recurrent zoonosis (nonhuman to human) and anthroponosis (human to nonhuman). Given the accelerating changes in our ecosystems since the neolithic revolution, it was not surprising to see a virus that spreads via aerosolization and liquid droplets cause a pandemic in a few months. The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic begs the question—which viruses could cause a global threat? In this Opinion, the characteristics that make adenoviruses a risk, which include efficient intra- and interspecies transmission, thermostable particles, persistent/latent infections in diverse hosts, and the ability to readily recombine and escape herd immunity, are discussed.

Understanding Post Entry Sorting of Adenovirus Capsids; A Chance to Change Vaccine Vector Properties

Adenovirus vector-based genetic vaccines have emerged as a powerful strategy against the SARS-CoV-2 health crisis. This success is not unexpected because adenoviruses combine many desirable features of a genetic vaccine. They are highly immunogenic and have a low and well characterized pathogenic profile paired with technological approachability. Ongoing efforts to improve adenovirus-vaccine vectors include the use of rare serotypes and non-human adenoviruses. In this review, we focus on the viral capsid and how the choice of genotypes influences the uptake and subsequent subcellular sorting. We describe how understanding capsid properties, such as stability during the entry process, can change the fate of the entering particles and how this translates into differences in immunity outcomes. We discuss in detail how mutating the membrane lytic capsid protein VI affects species C viruses' post-entry sorting and briefly discuss if such approaches could have a wider implication in vaccine and/or vector development.

Detection of zoonotic pathogens in animals performed at the University Hospital Institute Méditerranée Infection (Marseille - France)

At the University Hospital Institute Méditerranée Infection (IHU, Marseille, France), for almost thirty years, veterinarians have been carrying out epidemiological investigations, together with doctors, on animals living near human cases of zoonoses, on the one hand, and on the other hand, transverse and longitudinal epidemiological surveillance studies on animals which are reservoirs, vectors or sentinels of potentially zoonotic infections,. This article presents the methods adopted and the results obtained from these studies. They have been the subject of 76 peer-reviewed publications relating to wild animals (37 publications) and/or domestic animals (48 publications). These studies were often carried out in the field with veterinarians from the French army's health service (39 publications). They were at the origin of the detection of some thirty zoonotic pathogens in the laboratories of the IHU (64 publications) and/or other French laboratories (18 publications). Our approach is an original embodiment of the "One Health" concept.

Potential zoonotic pathogens hosted by endangered bonobos

Few publications, often limited to one specific pathogen, have studied bonobos (Pan paniscus), our closest living relatives, as possible reservoirs of certain human infectious agents. Here, 91 stool samples from semicaptive bonobos and bonobos reintroduced in the wild, in the Democratic Republic of the Congo, were screened for different infectious agents: viruses, bacteria and parasites. We showed the presence of potentially zoonotic viral, bacterial or parasitic agents in stool samples, sometimes coinfecting the same individuals. A high prevalence of Human mastadenoviruses (HAdV-C, HAdV-B, HAdV-E) was observed. Encephalomyocarditis viruses were identified in semicaptive bonobos, although identified genotypes were different from those identified in the previous fatal myocarditis epidemic at the same site in 2009. Non-pallidum Treponema spp. including symbiotic T. succinifaciens, T. berlinense and several potential new species with unknown pathogenicity were identified. We detected DNA of non-tuberculosis Mycobacterium spp., Acinetobacter spp., Salmonella spp. as well as pathogenic Leptospira interrogans. Zoonotic parasites such as Taenia solium and Strongyloides stercoralis were predominantly present in wild bonobos, while Giardia lamblia was found only in bonobos in contact with humans, suggesting a possible exchange. One third of bonobos carried Oesophagostomum spp., particularly zoonotic O. stephanostomum and O. bifurcum-like species, as well as other uncharacterized Nematoda. Trypanosoma theileri has been identified in semicaptive bonobos. Pathogens typically known to be transmitted sexually were not identified. We present here the results of a reasonably-sized screening study detecting DNA/RNA sequence evidence of potentially pathogenic viruses and microorganisms in bonobo based on a noninvasive sampling method (feces) and focused PCR diagnostics.

While We Endure This Pandemic, What New Respiratory Virus Threats Are We Missing?

In this paper, we review recent human respiratory virus epidemics, their zoonotic nature, and our current inability to identify future prepandemic threats. We propose a cost-efficient, One Health surveillance strategy that will be more efficient and more sustainable than previous efforts.