Adenovirus type 7 peptide diversity during outbreak, Korea, 1995-2000

A seroepidemiological survey of adenovirus type 7 circulation among healthy adults in China and in Sierra Leone, West Africa

Adenovirus type 7 (HAdV7) is one of the most pathogenic human adenoviruses (HAdVs) and can cause severe illness and even death, particularly in people with weakened immune systems. Many countries worldwide have experienced epidemics of this highly contagious pathogen, including China and Sierra Leone; however, studies describing the seroprevalence of anti-HAdV7 neutralizing antibodies (nAbs) are still lacking. Herein, we established an efficient neutralization assay based on a recombinant luciferase-expressing HAdV7 virus (HAd7-Luc) to monitor historical HAdV7 infections and predict outbreak distributions. Among the 2,350 serum samples collected from eight sites in China and Sierra Leone in this cross-sectional serological survey, the overall proportion of anti-HAdV7-seropositive individuals was nearly 60%, with higher seroprevalence rates in Sierra Leone than in China. Regionally, HAdV7 nAb titers were higher in China than in Sierra Leone and showed a geographic variation across different regions. Regardless of the location, the seropositive rate of HAdV7 nAb was lower than that of HAdV5 nAb, as was the nAb titer. The prevalence rates of antibodies against HAdV7 and HAdV5 were both related to age but not to sex. In addition, serologic cross-reactions were rarely observed among people infected with HAdV7 and HAdV5. These results indicate a humoral immune response acquired through endemic HAdV7 infection and enrich the understanding of not only the epidemiological prevention and control of HAdV7 but also the clinical application of HAdV7-based vaccines or gene therapy tools.

Adenovirus: Epidemiology, Global Spread of Novel Types, and Approach to Treatment

Adenoviruses (AdVs) are DNA viruses that typically cause mild infections involving the upper or lower respiratory tract, gastrointestinal tract, or conjunctiva. Rare manifestations of AdV infections include hemorrhagic cystitis, hepatitis, hemorrhagic colitis, pancreatitis, nephritis, or meningoencephalitis. AdV infections are more common in young children, due to lack of humoral immunity. Epidemics of AdV infection may occur in healthy children or adults in closed or crowded settings (particularly military recruits). The vast majority of cases are self-limited. However, the clinical spectrum is broad and fatalities may occur. Dissemination is more likely in patients with impaired immunity (e.g., organ transplant recipients, human immunodeficiency virus infection). Fatality rates for untreated severe AdV pneumonia or disseminated disease may exceed 50%. More than 100 genotypes and 52 serotypes of AdV have been identified and classified into seven species designated HAdV-A through -G. Different types display different tissue tropisms that correlate with clinical manifestations of infection. The predominant types circulating at a given time differ among countries or regions, and change over time. Transmission of novel strains between countries or across continents and replacement of dominant viruses by new strains may occur. Treatment of AdV infections is controversial, as prospective, randomized therapeutic trials have not been done. Cidofovir has been the drug of choice for severe AdV infections, but not all patients require treatment. Live oral vaccines are highly efficacious in reducing the risk of respiratory AdV infection and are in routine use in the military in the United States but currently are not available to civilians.

Genetic variability of human adenovirus type 7 circulating in mainland China

Human adenovirus (HAdV-7) is a highly contagious pathogen that causes severe respiratory illnesses. However, the epidemic patterns and genetic variability of HAdV-7 circulating in mainland China have not been well elucidated. In this study, we used Chinese HAdV sentinel surveillance data obtained from 2012-2015 to investigate the clinical features of 122 HAdV-7-positive cases and performed amplification and sequence determination of three capsid genes (penton base, hexon, and fiber) from 69 isolated viruses covering from seven provinces of China. Additionally, we compared with data from representative sequences of 21 strains covering seven more provinces in China and 32 international HAdV-7 strains obtained from GenBank database to determine the phylogenetic, sequence variations, and molecular evolution of HAdV-7. The results indicated that HAdV-7 infection occurred throughout the year, and a high proportion of severe cases (27 cases, 22.1%) exhibited infantile pneumonia. Moreover, phylogenetic analysis showed that all HAdV-7 strains could be divided into two major evolutionary branches, including subtype 1 and subtype 2, and subtype 3 was also formed according to analysis of the penton base gene. Subtypes 1 and 2 co-circulated in China before 2008, and HAdV-7 strains currently circulating in China belonged to subtype 2, which was also the predominant strain circulating worldwide in recent years. Further sequence variation analysis indicated that three genes of HAdV-7 were relatively stable across time and geographic space, particularly for viruses within subtypes, which shared almost the same variation sites. Owing to continuous outbreaks caused by HAdV-7, resulting in increased illness severity and fatality rates in China, the establishment of a national HAdV surveillance system is urgently needed for the development of effective preventive and infection-control interventions for adenovirus respiratory infections in China.

A Murine Monoclonal Antibody With Potent Neutralization Ability Against Human Adenovirus 7

B1-type human adenoviruses (HAdVs) HAdV-3, HAdV-7, and HAdV-55 have caused epidemics in North America, Asia, and Europe. However, to date, no adenovirus vaccines or antiviral drugs have been approved for general use. In the present work, a scFv-phage immune library was constructed and mouse monoclonal antibody (MMAb) 10G12 was obtained through selection. 10G12 is specific for HAdV-7 and binds the hexon loop1 and loop2 (LP12), resulting in strong neutralization activity against HAdV-7. Additionally, it is stable in serum and buffer at various pH values. The findings provide insight into adenovirus and antibody responses and may facilitate the design and development of adenovirus vaccines and antiviral drugs.

Identification of adenovirus neutralizing antigens using capsid chimeric viruses

Human adenoviruses (HAdV) 3 and 7 can cause acute respiratory disease epidemics and outbreaks. Identification of neutralizing epitopes is vital for surveillance and vaccine development. In this study, we generated the recombinant capsid-chimeric human adenoviruses rAd3E-Fk7, containing the Ad3E backbone and the HAdV-7 fiber knob, and rAd3E-H7Fk7, which contain an Ad3E backbone but HAdV-7 hexon and fiber knob. In vitro neutralization tests with these chimeric adenoviruses using both mouse and human antisera indicated that hexon and fiber knob are the major targets recognized by neutralizing antibodies against HAdV-3 or HAdV-7, and other capsid proteins including the penton base and fiber shaft may not contribute to neutralizing antibody responses. In conclusion, both hexon and fiber knob structures in HAdV-3 and HAdV-7 may be the proteins which induce neutralizing antibody responses and thus may be important for adenovirus vaccine and drug development.

A recombinant trivalent vaccine candidate against human adenovirus types 3, 7, and 55

Human adenoviruses types 3 (HAdV-3), 7 (HAdV-7) and 55 (HAdV-55) are major pathogens of acute respiratory infections (ARI) in children and adults. More than one type of HAdV can infect patients simultaneously, and the infections are sometimes fatal. However, there is currently no vaccine approved for general use in children and adults. Thus, development of a multivalent HAdV vaccine to combat HAdV infection becomes imperative. In this study, we constructed a new recombinant trivalent human adenovirus vaccine (rAdMHE3-h55), which expresses the hexon protein of HAdV-55 in the E3 region of rAdMHE3, a previously prepared bivalent vaccine candidate against HAdV-3 and HAdV-7. The results of in vitro neutralization assays indicate that rAdMHE3-h55 can induce the production of neutralizing antibodies against HAdV-3, HAdV-7, and HAdV-55 in mice. Furthermore, immunization with the recombinant trivalent vaccine candidate completely protected the mice challenged with HAdV-3, HAdV-7, orHAdV-55, respectively, showing lower lung viral loads and less lung Pathological changes was compared with those in unvaccinated mice. The current findings contribute to the development of a new adenovirus vaccine candidate and also advance this construction method for the generation of recombinant adenovirus vaccines. In conclusion, our recombinant trivalent vaccine rAdMHE3-h55 can provides protection against challenge with HAdV-3, HAdV-7, or HAdV-55 in mice. Future work of optimizing this vaccine candidate may lead to a more effective way of preventing respiratory diseases caused by common human adenoviruses.

Adenovirus: Epidemiology, Global Spread of Novel Serotypes, and Advances in Treatment and Prevention

Adenoviruses (AdVs) are DNA viruses that typically cause mild infections involving the upper or lower respiratory tract, gastrointestinal tract, or conjunctiva. Rare manifestations of AdV infections include hemorrhagic cystitis, hepatitis, hemorrhagic colitis, pancreatitis, nephritis, or meningoencephalitis. AdV infections are more common in young children, due to lack of humoral immunity. Epidemics of AdV infection may occur in healthy children or adults in closed or crowded settings (particularly military recruits). The disease is more severe and dissemination is more likely in patients with impaired immunity (e.g., organ transplant recipients, human immunodeficiency virus infection). Fatality rates for untreated severe AdV pneumonia or disseminated disease may exceed 50%. More than 50 serotypes of AdV have been identified. Different serotypes display different tissue tropisms that correlate with clinical manifestations of infection. The predominant serotypes circulating at a given time differ among countries or regions, and change over time. Transmission of novel strains between countries or across continents and replacement of dominant viruses by new strains may occur. Treatment of AdV infections is controversial, as prospective, randomized therapeutic trials have not been conducted. Cidofovir is the drug of choice for severe AdV infections, but not all patients require treatment. Live oral vaccines are highly efficacious in reducing the risk of respiratory AdV infection and are in routine use in the military in the United States, but currently are not available to civilians.

Antigenic variability among two subtypes of human adenovirus serotype 7

Human adenovirus type 7 (HAdV-7) is one of the major serotypes responsible for acute respiratory infection. It is important to investigate the antigenic variabilities of different HAdV-7 genomic subtypes for vaccine development. Phylogenetic analysis of global HAdV-7 strains and major antigen proteins showed that HAdV-7 could be classified into two subtypes. There were three highly variable regions (HVR1, HVR4, and HVR7) in the hexon protein that varied between subtypes. Within each of the subtypes, these regions were conserved. Two subtype HAdV-7 strains isolated in China were used to immunize mice for antigenic characterization. Mice immunized with one subtype strain showed 4-8-fold lower neutralizing antibody titers against another subtype strain. ELISA results showed that the variation in HVR1, 4, and 7 regions contributed to antigenic change, and it may be concluded that the three regions contain subtype-specific epitopes. In summary, strains of HAdV-7 could be divided into two subtypes using genome sequence and antigenic analysis; our results could be important for HAdV-7 vaccine development.

Outbreak of acute respiratory disease caused by human adenovirus type 7 in a military training camp in Shaanxi, China

Outbreaks of ARD associated with HAdV have been reported in military populations in many countries. Here, we report an ARD outbreak caused by HAdV‐7 in a military training camp in Shaanxi Province, China, from February to March of 2012. Epidemic data and samples from the patients were collected, and viral nucleotides from samples and viral isolations were detected and sequenced. IgG and IgA antibodies against HAdV, and the neutralization antibodies against the viral strain isolated in this outbreak, were detected. Epidemiological study showed that all personnel affected were males with an average age of 19.1 years. Two peaks appeared on the epicurve and there was an 8‐day interval between peaks. Laboratory results of viral nucleotide detection carried out with clinical specimens were positive for HAdV (83.33%, 15/18). Further study through serum antibody assay, virus isolation and phylogenetic analysis showed that HAdV‐7 was the etiological agent responsible for the outbreak. IgA antibody began to appear on the 4th day after the onset and showed 100% positivity on the 8th day. The virus strain in the present outbreak was highly similar to the virus isolated in Hanzhong Shaanxi in 2009. We conclude that HAdV‐7 was the pathogen corresponding to the outbreak, and this is the first report of an ARD outbreak caused by HAdV‐7 in military persons in China. Vaccine development, as well as enhanced epidemiological and virological surveillance of HAdV infections in China should be emphasized.

Serotype-specific neutralizing antibody epitopes of human adenovirus type 3 (HAdV-3) and HAdV-7 reside in multiple hexon hypervariable regions

Human adenovirus types 3 and 7 (HAdV-3 and HAdV-7) occur epidemically and contribute greatly to respiratory diseases, but there is no currently available licensed recombinant HAdV-3/HAdV-7 bivalent vaccine. Identification of serotype-specific neutralizing antibody (NAb) epitopes for HAdV-3 and HAdV-7 will be beneficial for development of recombinant HAdV-3/HAdV-7 bivalent vaccines. In this study, four NAb epitopes within hexon hypervariable regions (HVRs) were predicted for HAdV-3 and HAdV-7, respectively, by using bioinformatics. Eight hexon chimeric adenovirus vectors with the alternation of only one predicted neutralizing epitope were constructed. Further in vitro and in vivo neutralization assays indicated that E2 (residing in HVR2) and E3 (residing in HVR5) are NAb epitopes for HAdV-7, and E3 plays a more important role in generating NAb responses. Cross-neutralization assays indicated that all four predicted epitopes, R1 to R4, are NAb epitopes for HAdV-3, and R1 (residing in HVR1) plays the most important role in generating NAb responses. Humoral immune responses elicited by the recombinant rAdH7R1 (containing the R1 epitope) were significantly and durably suppressed by HAdV-3-specific NAbs. Surprisingly, the rAdΔE3GFP-specific neutralizing epitope responses induced by rAdMHE3 (R3 replaced by E3) and rAdMHE4 (R4 replaced by E4) were weaker than those of rAdMHE1 (R1 replaced by E1) or rAdMHE2 (R2 relaced by E2) in vitro and in vivo. Furthermore, rAdMHE4 replicated more slowly in HEp-2 cells, and the final yield was about 10-fold lower than that of rAdΔE3GFP. The current findings contribute not only to the development of new adenovirus vaccine candidates, but also to the construction of new gene delivery vectors.

Adenovirus serotype 7 associated with a severe lower respiratory tract disease outbreak in infants in Shaanxi Province, China

BACKGROUND

Pneumonia caused by adenovirus infection is usually severe especially with adenovirus serotype 7 commonly associated with lower respiratory tract disease outbreaks. We reported an outbreak of 70 cases of severe pneumonia with one death of infants in Shaanxi Province, China. Sampling showed adenovirus 7 (Ad7) as the primary pathogen with some co-infections.

RESULTS

Two strains of adenovirus and two strains of enterovirus were isolated, the 21 pharynx swabs showed 14 positive amplifications for adenovirus; three co-infections with respiratory syncytial virus, two positive for rhinovirus, one positive for parainfluenza 3, and four negative. Adenovirus typing showed nine of the nine adenovirus positive samples were HAdV-7, three were HAdV-3 and two were too weak to perform sequencing. The entire hexon gene of adenovirus was sequenced and analyzed for the two adenovirus serotype 7 isolates, showing the nucleic acid homology was 99.8% between the two strains and 99.5% compared to the reference strain HAdV-7 (GenBank accession number AY769946). For the 21 acute phase serum samples from the 21 patients, six samples had positives results for ELISA detection of HAdV IgA, and the neutralization titers of the convalescent-phase samples were four times higher than those of the acute-phase samples in nine pairs.

CONCLUSIONS

We concluded adenovirus was the viral pathogen, primarily HAdV-7, with some co-infections responsible for the outbreak. This is the first report of an infant pneumonia outbreak caused by adenovirus serotype 7 in Shaanxi Province, China.

Molecular Classification of Human Adenovirus Type 7 Isolated From Acute Respiratory Disease Outbreak (ARD) in Korea, 2005-2006

Objectives

To assess the genomic characteristics of human adenoviruses (HAdVs) that caused small-scale epidemics in Korea and compare sequence analysis and restriction fragment length polymorphism (RFLP).

Methods

Two hundred sixty-two throat swabs were collected from geographically distinct two cohabitation facilities during outbreaks in August 2005 and February–May 2006. 148 isolates were obtained using the adenocarcinomic human alveolar basal epithelial cells (A549 cells) from 262 specimens. The sequences of 448 bp partial hexon gene of isolates were analized and compared with serotype results using neutralizing test. The hexon (1.2 kb), fiber, and E4 ORF 6/7 34.7 kDa protein (2.1 kb) genes were further analysed in 10 randomly selected specimens. RFLP of the genomic DNA for genotyping was also performed and compared with sequence information.

Results

All the isolates were localized into the same cluster when phylogenetic tree was generated based on hexon gene using Clustal W. While fiber and E4 ORF 6/7 34.7 kDa protein genes were analysed, the tree was divided into two clusters. Interestingly, isolates with same genetic characteristics of hexon gene did not show identical RFLP patterns in accordance with their origin of episode, rather phylogenetic analysis of fiber and E4 ORF 6/7 34.7 kDa protein genes were correlated with RFLP patterns.

Conclusion

These results indicate that serotype classification based on hexon gene might not be enough to discriminate HAdV serotype, and additional genetic characteristics including fiber and/or E4 ORF 6/7 should be recruited to dispose subgroup of HAdV serotype.

Assessment of genetic variability among subspecies b1 human adenoviruses for molecular epidemiology studies

Adenoviruses exhibit considerable intraserotypic genetic variability. Restriction enzyme analysis of the adenoviral genome is currently the most widely used procedure for the characterization of adenovirus isolates and has been extensively used for molecular epidemiological studies of subspecies B1 adenovirus infections. Comparison of restriction site maps between viral genomes is qualitatively consistent with DNA sequence homology providing that a sufficient number of sites are known. This technique is simple, sensitive, and can be adapted for screening numerous isolates and is therefore particularly useful for analysis of closely related genomes. Restriction enzyme analysis is still the only molecular approach that, at a reasonable cost, can give a "genome-wide" characterization of an adenovirus strain. Polymerase chain reaction (PCR) amplification followed by sequencing of the generated amplicon is the approach of choice for the detailed analysis of specific regions of the viral genome. Several laboratories have recently adopted PCR amplification of the hexon and/or fiber genes for the determination of adenovirus serotype identity, replacing identification by seroneutralization and hemmaglutination-inhibition. This approach permits rapid and objective type-specific identification of human adenoviruses and is especially useful for the characterization of serologically intermediate strains frequently identified among field strains of subspecies B1 adenoviruses.

Genetic heterogeneity of the hexon gene of adenovirus type 3 over a 9-year period in Korea

Hexon sequences were analyzed in 29 epidemiologically unrelated adenovirus type 3 (Ad3) isolates from the 7 genome types to understand the molecular basis of the genome-type diversity of Ad3 associated with childhood pneumonia in Korea during the period 1991-1999. Nine nucleotide substitutions were observed among the 29 Ad3 strains. Five of the 9 involved amino acid changes in loops 1 (Gly to Val at codon 205 and Thr to Ile at 211) and loop 2 (His to Asn at 417, Thr to Ala at 429, and Ala to Asp at 439). The predicted hydropathic characteristics of this region have been affected by these amino acid changes. The region surrounding codons from 417 to 439 of Ad3a16 and Ad3a18 manifested greater hydrophobicity than the region of other genome types (Ad3a, Ad3a13, Ad3a14, Ad3a15, and Ad3a17). In particular, three amino acid changes in loop 2 were associated with two new genome types, namely, Ad3a16 and Ad3a18, which were recognized during later epidemics in 1998-1999. Phylogenetic relatedness revealed that these two genome types clustered into distinct lineages in the phylogenetic tree. This result suggests that the genetic heterogeneity of Ad3 hexon could play a potential role in the appearance of new genome types and that it could affect the antigenic characteristics of Ad3.

Intranasal delivery of vaccines against HIV

HIV poses a serious health threat in the world. Mucosal transmission of HIV through the genitourinary tract may be the most important route of transmission. Intranasal immunisations induce vaginal and systemic immune responses. Various protein-, DNA- and RNA-based immunopotentiating adjuvants/delivery systems and live bacterial and viral vectors are available for intranasal immunisations, and these systems may differ in their ability to induce a specific type of immune response (e.g., a cytotoxic T cell versus an antibody response). As the protection against HIV may require both cytotoxic T cell and antibodies, a combination of adjuvants/delivery systems for combinations of mucosal and parenteral immunisations may be required in order to develop a protective anti-HIV vaccine.