Desmoglein 2 (DSG2) Is A Receptor of Human Adenovirus Type 55 Causing Adult Severe Community-Acquired Pneumonia

Human adenovirus type 55 (HAdV-B55) is a re-emergent acute respiratory disease pathogen that causes adult community-acquired pneumonia (CAP). Previous studies have shown that the receptor of HAdV-B14, which genome is highly similar with HAdV-B55, is human Desmoglein 2 (DSG2). However, whether the receptor of HAdV-B55 is DSG2 is undetermined because there are three amino acid mutations in the fiber gene between HAdV-B14 and HAdV-B55. Here, firstly we found the 3T3 cells, a mouse embryo fibroblast rodent cell line which does not express human DSG2, were able to be infected by HAdV-B55 after transfected with pcDNA3.1-DSG2, while normal 3T3 cells were still unsusceptible to HAdV-B55 infection. Next, A549 cells with hDSG2 knock-down by siRNA were hard to be infected by HAdV-B3/-B14/-B55, while the control siRNA group was still able to be infected by all these types of HAdVs. Finally, immunofluorescence confocal microscopy indicated visually that Cy3-conjugated HAdV-B55 viruses entered A549 cells by binding to DSG2 protein. Therefore, DSG2 is a major receptor of HAdV-B55 causing adult CAP. Our finding is important for better understanding of interactions between adenoviruses and host cells and may shed light on the development of new drugs that can interfere with these processes as well as for the development of potent prophylactic vaccines.

Comparative Genomic Analysis of Re-emergent Human Adenovirus Type 55 Pathogens Associated With Adult Severe Community-Acquired Pneumonia Reveals Conserved Genomes and Capsid Proteins

Human adenovirus type 55 (HAdV-B55) is a recently identified acute respiratory disease (ARD) pathogen in HAdV species B with a recombinant genome between renal HAdV-B11 and respiratory HAdV-B14. Since HAdV-B55 first appeared in China school in 2006, no more ARD cases associated with it had been reported until 2011, when there was an outbreak of adult severe community-acquired pneumonia (CAP) in Beijing, China. Reported here is the bioinformatics analysis of the re-emergent HAdV-B55 responsible for this outbreak. Recombination and protein sequence analysis re-confirmed that this isolate (BJ01) was a recombinant virus with the capsid hexon gene from HAdV-B11. The selection pressures for the three capsid proteins, i.e., hexon, penton base, and fiber genes, were all negative, along with very low non-synonymous (dN) and synonymous (dS) substitutions/site (<0.0007). Phylogenetic analyses of the whole genome and the three major capsid genes of HAdV-B55 revealed the close phylogenetic relationship among all HAdV-B55 strains. Comparative genomic analysis of this re-emergent HAdV-B55 strain (BJ01; 2011) with the first HAdV-B55 strain (QS-DLL; 2006) showed the high genome identity (99.87%), including 10 single-nucleotide non-synonymous substitutions, 11 synonymous substitutions, 3 insertions, and one deletion in non-coding regions. The major non-synonymous substitutions (6 of 10) occurred in the protein pVI in its L3 region, which protein has different functions at various stages of an adenovirus infection, and may be associated with the population distribution of HAdV-B55 infection. No non-synonymous substitutions were found in the three major capsid proteins, which proteins are responsible for type-specific neutralizing antibodies. Comparative genomic analysis of the re-emergent HAdV-B55 strains associated with adult severe CAP revealed conserved genome and capsid proteins, providing the foundation for the development of effective vaccines against this pathogen. This study also facilitates the further investigation of HAdV-B55 epidemiology, molecular evolution, patterns of pathogen emergence and re-emergence, and the predication of genome recombination between adenoviruses.

Fatal pneumonia cases caused by human adenovirus 55 in immunocompetent adults

BACKGROUND

Adenovirus is a frequent cause of mild self-limiting upper respiratory tract infection, gastroenteritis, and conjunctivitis. Severe or fatal infection mostly occurs in newborn, elderly or immunocompromised persons.

METHODS

Fatal adenovirus pneumonia in three immunocompetent adults was identified. The clinical data and virological findings were reported from patients. Additional review of recently recorded fatal patients with adenovirus infection was carried out.

RESULTS

The patients presented with sudden onset respiratory distress that progressed rapidly to respiratory failure and death. Human adenovirus (HAdV)-55 was detected in both nasopharyngeal aspirates and serum samples in all three cases, and moreover detected in lung, liver, and kidney in one case. In another case, remarkably elevated aspartate aminotransferase, alanine transaminase, and lactate dehydrogenase were identified. Three HAdV-55 strains were isolated and genome sequencing revealed a high similarity with other strains from mild infection.

CONCLUSIONS

Fatal infection with HAdv-55 might occur in otherwise healthy adults. Diagnosis of adenovirus infection should be considered in patients with severe pneumonia yielding negative bacterial culture and presenting no response to antibiotic therapy.