Genomic analysis of HAdV-B14 isolate from the outbreak of febrile respiratory infection in China

Prevalence of human infection with respiratory adenovirus in China: A systematic review and meta-analysis

BACKGROUND

Human adenovirus (HAdV) is a major pathogen that causes acute respiratory tract infections (ARTI) and is frequently associated with outbreaks. The HAdV prevalence and the predominant types responsible for ARTI outbreaks remains obscure in China.

METHODS

A systematic review was performed to retrieve literature that reported outbreaks or etiological surveillance of HAdV among ARTI patients in China from 2009 to 2020. Patient information was extracted from the literature to explore the epidemiological characteristics and clinical manifestations of the infection of various HAdV types. The study is registered with PROSPERO, CRD42022303015.

RESULTS

A total of 950 articles (91 about outbreaks and 859 about etiological surveillance) meeting the selection criteria were included. Predominant HAdV types from etiological surveillance studies differed from those in outbreak events. Among 859 hospital-based etiological surveillance studies, positive detection rates of HAdV-3 (32.73%) and HAdV-7 (27.48%) were significantly higher than other virus types. While nearly half (45.71%) of outbreaks were caused by HAdV-7 with an overall attack rate of 22.32% among the 70 outbreaks for which the HAdVs were typed by the meta-analysis. Military camp and school were main outbreak settings with significantly different seasonal pattern and attack rate, where HAdV-55 and HAdV-7 were identified as the leading type, respectively. Clinical manifestations mainly depended on the HAdV types and patient's age. HAdV-55 infection tends to develop into pneumonia with poorer prognosis, especially in children <5 years old.

CONCLUSIONS

This study improves the understanding of epidemiological and clinical features of HAdV infections and outbreaks with different virus types, and helps to inform future surveillance and control efforts in different settings.

Outbreaks of Acute Respiratory Disease Associated with Human Adenovirus Infection in Closed Camps, China, December 2011-March 2014

What is already known on this topic?

Human adenovirus (HAdV) was frequently associated with acute respiratory disease (ARD) outbreaks in military camps.

What is added by this report?

HAdV-B7, HAdV-B14, and HAdV-B55 were determined to be responsible for 3, 2, and 4 ARD outbreaks in military camps, China, respectively, with a total attack rate of 28.0% during 2011 to 2014.

What are the implications for public health practice?

The findings suggest that vaccine development and administration in military camps must be prioritized. Quarantining among new recruits before entering into the military and the identification of the major responsible genotypes at the current stage is warranted.

Development and Application of a Fast Method to Acquire the Accurate Whole-Genome Sequences of Human Adenoviruses

The whole-genome sequencing (WGS) of human adenoviruses (HAdVs) plays an important role in identifying, typing, and mutation analysis of HAdVs. Nowadays, three generations of sequencing have been developed. The accuracy of first-generation sequencing is up to 99.99%, whereas this technology relies on PCR and is time consuming; the next-generation sequencing (NGS) is expensive and not cost effective for determining a few special samples; and the third-generation sequencing technology has a higher error rate. In this study, first, we developed an efficient HAdV genomic DNA extraction method. Using the complete genomic DNA instead of the PCR amplicons as the direct sequencing template and a set of walking primers, we developed the HAdV WGS method based on first-generation sequencing. The HAdV whole genomes were effectively sequenced by a set of one-way sequencing primers designed, which reduced the sequencing time and cost. More importantly, high sequence accuracy is guaranteed. Four HAdV strains (GZ01, GZ02, HK35, and HK91) were isolated from children with acute respiratory diseases (ARDs), and the complete genomes were sequenced using this method. The accurate sequences of the whole inverted terminal repeats (ITRs) at both ends of the HAdV genomes were also acquired. The genome sequence of human adenovirus type 14 (HAdV-B14) strain GZ01 acquired by this method is identical to the sequence released in GenBank, which indicates that this novel sequencing method has high accuracy. The comparative genomic analysis identified that strain GZ02 isolated in September 2010 had the identical genomic sequence with the HAdV-B14 strain GZ01 (October 2010). Therefore, strain GZ02 is the first HAdV-B14 isolate emergent in China (September 2010; GenBank acc no. MW692349). The WGS of HAdV-C2 strain HK91 and HAdV-E4 strain HK35 isolated from children with acute respiratory disease in Hong Kong were also determined by this sequencing method. In conclusion, this WGS method is fast, accurate, and universal for common human adenovirus species B, C, and E. The sequencing strategy may also be applied to the WGS of the other DNA viruses.

Adenovirus 14p1 Immunopathogenesis during Lung Infection in the Syrian Hamster

Adenovirus (Ad) infections are usually mild and self-limited, with minimal inflammatory responses. During worldwide outbreaks, Ad14p1, an emerging Ad14 variant, has caused severe pulmonary disease, including acute respiratory distress syndrome (ARDS). This increased pathogenicity of Ad14p1 is not completely understood. In initial studies, we observed that infection of Syrian hamsters with Ad14p1 can cause a patchy bronchopneumonia, with an increased intensity of inflammation, compared to wild type Ad14 infection. The current study compared the dynamics of the immunopathogenesis of Ad14 and Ad14p1 infection of hamster lungs through the first two weeks after infection. Little difference was seen in infection-induced inflammation at day 1. Beginning at day 3, Ad14p1-infected hamsters showed marked inflammation that continued through to day 7. The inflammation began to resolve by day 10 but was still detectable at day 14. In contrast, Ad14-infected hamsters showed little inflammation during the 14-day period of observation. Inflammatory cell type analysis revealed that, at day 1, hamsters infected with either virus had predominantly neutrophil infiltration that began to resolve by day 3. However, at day 5, Ad14p1-infected hamsters had a second wave of neutrophil infiltration that was accompanied by edema which persisted to a variable extent through to day 10. These differences were not explained by an increased Ad14p1 replication rate, compared with Ad14 in vitro, but there was prolonged persistence of Ad14p1 in hamster lungs. There were differences in lung tissue cytokine and chemokine responses to Ad14p1 vs. Ad14 infection that might account for the increased leukocyte infiltrates in Ad14p1-infected hamsters. This animal model characterization provides the basis for future translational studies of the viral genetic mechanisms that control the increased immunopathogenesis of the emergent, Ad14p1 strain.

Rapid Construction of a Replication-Competent Infectious Clone of Human Adenovirus Type 14 by Gibson Assembly

In 1955, Human adenovirus type 14 (HAdV-B14p) was firstly identified in a military trainee diagnosed as acute respiratory disease (ARD) in the Netherlands. Fifty years later, a genomic variant, HAdV-B14p1, re-emerged in the U.S. and caused large and fatal ARD outbreaks. Subsequently, more and more ARD outbreaks occurred in Canada, the UK, Ireland, and China, in both military and civil settings. To generate a tool for the efficient characterization of this new genomic variant, a full-length infectious genomic clone of HAdV-B14 was successfully constructed using one-step Gibson Assembly method in this study. Firstly, the full genome of HAdV-B14p1 strain GZ01, the first HAdV-B14 isolate in China, was assembled into pBR322 plasmid by Gibson Assembly. The pBRAdV14 plasmid, generated by Gibson Assembly, was analyzed and verified by PCR, restriction enzymes digestion and the sequencing. Secondly, viruses were rescued from pBRAdV14-transfected A549 cells. The integrity of the rescued viruses was identified by restriction enzyme analysis. The complete sequence of the infectious clone was further sequenced. No mutation was found in the infectious clone during the construction when compared with the parental virus and pBR322 sequences. The direct immunofluorescence assay indicated the expression of the hexon protein. Finally, typical virions were observed; the one-step growth curves further showed that the DNA replication and viral reproduction efficiency of pBRAd14 derived viruses was similar with that of wild-type HAdV-B14 strain. The successful construction of the replication-competent infectious clone of pBRAdV14 facilitates the development of vaccine and antiviral drugs against HAdV-B14, as well as provides a novel strategy for rapid construction of infectious viral clones for other large-genome DNA viruses.

The relationship between human adenovirus 36 and obesity in Chinese Han population

The study aimed to explore the prevalence of human adenovirus-36 (HAdV-36) infection and the association of HAdV-36 with obesity in Chinese Han population. A qualitative determination using ELISA was performed to determine by duplication of the antibodies to HAdV-36 in the serum samples. Logistic regression analysis was used to analyze the association between HAdV-36 seropositivity and obesity. The overall HAdV-36 seroprevalence was 49.8% amongst 824 participants. The prevalence of HAdV-36 seropositive was 42.9 and 51.4% in the obese and non-obese participants, respectively, which was not statistically significant (P=0.05). There were significant differences in the anthropometric and biochemical parameters observed between the two groups except for height (P=0.067) and total cholesterol (TC) (P<0.29). After the adjustment for age and gender, HAdV-36 seropositivity was a protective factor for obesity (odds ratio (OR) = 0.69, 95% confidence intervals (95% CI) = 0.48-0.97, P=0.03). In the male population, the adjusted OR for AD-36 antibody-positive status was statistically decreased for obese adults (OR = 0.59; 95% CI = 0.39-0.91; P=0.02). However, the similar result was not obtained in the female population (OR = 0.90; 95% CI = 0.48-1.67; P=0.73). We found a high prevalence of HAdV-36 infection in China and significant association between HAdV-36 infection and obesity or weight gain after the adjustment for age and gender. The HAdV-36 infection may be related to the weight loss in Chinese Han population, especially in the male group, which needs to be further confirmed.

Vaccine development for human mastadenovirus

Human mastadenovirus (HAdVs) can cause a broad spectrum of diseases in both children and adults, including acute respiratory infection, gastroenteritis, epidemic keratoconjunctivitis. Populations susceptible to adenovirus infection include children, immunocompromised patients and military recruits. To date, seven species (A-G) including more than 79 genotypes have been characterized, of which HAdV-B3, B4, B7 and the recently reemerged types 14 and 55 often lead to severe pneumonia. The live oral enteric-coated adenovirus type 4 and 7 vaccine, which was approved for use in US military personnel of 17 through 50 years of age, had been shown to be safe and highly effective in numerous clinical trials and by ongoing surveillance of febrile respiratory illness. However, there is currently no vaccine approved for general use in children and adults in any part of the world. This review article will summarize the epidemiological data available for adenovirus and the effectiveness of the adenovirus vaccine in the US military. It will also provide a brief overview of innovative vaccine strategies, animal models for vaccine evaluation, and issues regarding vaccine production.

A tetravalent vaccine comprising hexon-chimeric adenoviruses elicits balanced protective immunity against human adenovirus types 3, 7, 14 and 55

Human adenovirus (Ad) species B contains several of the most important types associated with acute respiratory diseases, Ad3, -7, -14 and -55, which often lead to severe lower respiratory tract diseases and epidemic outbreaks. However, there is currently no Ad vaccine approved for general use. The major capsid protein, hexon, is the primary determinant recognized by neutralizing antibodies (NAbs). In this study, four recombinant Ads that have the same genome sequence as Ad3 with the exception of the hexon genes, rAd3EGFP, rAd3H7, rAd3H14 and rAd3H55, were combined as a tetravalent Ad candidate vaccine against Ad3, -7, -14 and -55. The replication efficiencies of chimeric rAd3H14, rAd3H7 and rAd3H55 were similar to that of rAd3EGFP. Recombinant rAd3EGFP, rAd3H7, rAd3H14 and rAd3H55 induced high titers of NAbs against Ad3, -7, -14 and -55, respectively, which were comparable to those induced by wild-type Ads. The mixture of the four recombinant Ads in equal proportions, rAdMix, or rAdMix inactivated by β-propiolactone, induced balanced NAb responses against Ad3, -7, -14 and -55 in mice without reciprocal immunological interference. In co-culture the four recombinant Ads replicated with a similar efficiency without reciprocal inhibition, and the progeny virions may be chimeric. Purified co-culture, rAdMix-C, also elicited balanced immune responses, suggesting a simple method for multivalent vaccine production. These results indicate the possible advantage of the four Ads as a live combined vaccine. Importantly, pre-immunization with rAdMix conferred protection against Ad3, -7, -14 or -55 challenge in mice in vivo. Thus, this research provides a novel tetravalent Ad vaccine candidate against Ad3, -7, -14 and -55.

Comparative genomic analysis of two emergent human adenovirus type 14 respiratory pathogen isolates in China reveals similar yet divergent genomes

Human adenovirus type 14 (HAdV-B14p) was originally identified as an acute respiratory disease (ARD) pathogen in The Netherlands in 1955. For approximately fifty years, few sporadic infections were observed. In 2005, HAdV-B14p1, a genomic variant, re-emerged and was associated with several large ARD outbreaks across the U.S. and, subsequently, in Canada, the U.K., Ireland, and China. This strain was associated with an unusually higher fatality rate than previously reported for both this prototype and other HAdV types in general. In China, HAdV-B14 was first observed in 2010, when two unrelated HAdV-B14-associated ARD cases were reported in Southern China (GZ01) and Northern China (BJ430), followed by three subsequent outbreaks. While comparative genomic analysis, including indel analysis, shows that the three China isolates, with whole genome data available, are similar to the de Wit prototype, all are divergent from the U.S. strain (303600; 2007). Although the genomes of strains GZ01 and BJ430 are nearly identical, as per their genome type characterization and percent identities, they are subtly divergent in their genome mutation patterns. These genomes indicate possibly two lineages of HAdV-B14 and independent introductions into China from abroad, or subsequent divergence from one; CHN2012 likely represents a separate sub-lineage. Observations of these simultaneously reported emergent strains in China add to the understanding of the circulation, epidemiology, and evolution of these HAdV pathogens, as well as provide a foundation for developing effective vaccines and public health strategies, including nationwide surveillance in anticipation of larger outbreaks with potentially higher fatality rates associated with HAdV-B14p1.

Detection and Genetic Characterization of Adenovirus Type 14 Strain in Students with Influenza-Like Illness, New York, USA, 2014-2015

During the 2014-15 influenza season, 13/168 respiratory samples from students with influenza-like illness (ILI) at a college in New York, USA, were positive for human adenovirus (HAdV); 4/13 samples were positive for HAdV-B14p1. During influenza season, HAdV should be included in the differential diagnostic panel used to determine the etiology of ILI.

Neutralizing epitopes mapping of human adenovirus type 14 hexon

Human adenoviruses 14 (HAdV-14) caused several clusters of acute respiratory disease (ARD) outbreaks in both civilian and military settings. The identification of the neutralizing epitopes of HAdV-14 is important for the surveillance and control of infection. Since the previous studies had indicated that the adenoviruses neutralizing epitopes were likely to be exposed on the surface of the hexon, four epitope peptides, A14R1 (residues 141-157), A14R2 (residues 181-189), A14R4 (residues 252-260) and A14R7 (residues 430-442) were predicted and mapped onto the 3D structures of hexon by homology modeling approach. Then the four peptides were synthesized, and all the four putative epitopes were identified as neutralizing epitopes by enzyme-linked immunosorbent assay (ELISA) and neutralization tests (NT). Finally we incorporated the four epitopes into human adenoviruses 3 (HAdV-3) vectors using the "antigen capsid-incorporation" strategy, and two chimeric adenoviruses, A14R2A3 and A14R4A3, were successfully obtained which displayed A14R2 and A14R4 respectively on the hexon surface of HAdV-3 virions. Further analysis showed that the two chimeric viruses antiserum could neutralize both HAdV-14 and HAdV-3 infection. The neutralization titers of anti-A14R4A3 group were significantly higher than the anti-KLH-A14R4 group (P=0.0442). These findings have important implications for the development of peptide-based broadly protective HAdV-14 and HAdV-3 bivalent vaccine.

Whole-genome Sequencing for Tracing the Transmission Link between Two ARD Outbreaks Caused by a Novel HAdV Serotype 7 Variant, China

From December 2012 to February 2013, two outbreaks of acute respiratory disease caused by HAdV-7 were reported in China. We investigated possible transmission links between these two seemingly unrelated outbreaks by integration of epidemiological and whole-genome sequencing (WGS) data. WGS analyses showed that the HAdV-7 isolates from the two outbreaks were genetically indistinguishable; however, a 12 bp deletion in the virus-associated RNA gene distinguished the outbreak isolates from other HAdV-7 isolates. Outbreak HAdV-7 isolates demonstrated increased viral replication compared to non-outbreak associated HAdV-7 isolate. Epidemiological data supported that the first outbreak was caused by introduction of the novel HAdV-7 virus by an infected recruit upon arrival at the training base. Nosocomial transmission by close contacts was the most likely source leading to onset of the second HAdV-7 outbreak, establishing the apparent transmission link between the outbreaks. Our findings imply that in-hospital contact investigations should be encouraged to reduce or interrupt further spread of infectious agents when treating outbreak cases, and WGS can provide useful information guiding infection-control interventions.