Human adenovirus type 4 (HAdV-4) associated acute respiratory tract infection in children & genetic characteristics of HAdV-4 in China: a prospective multicenter study

Abstract

Background: Human adenovirus (HAdV) is an important pathogen causing acute respiratory infection (ARI) in children. Many countries, including China, have experienced sporadic or outbreaks related to HAdV-4, and death cases were reported. However, there is little research on HAdV-4 and the epidemic situation of HAdV-4 in China is little known. This study was designed to comprehend the prevalence and genetic characteristics of HAdV-4 in ARI children in China.

Methods: Respiratory tract samples from ARI children hospitalized in six hospitals of Northern and Southern China from 2017 to 2020 were collected for HAdV detection and typing. Clinical information was collected from HAdV-4 positive patients for clinical characteristics and epidemiological analysis. The main capsid proteins and the whole genome sequences were amplified and sequenced for bioinformatics analysis.

Results: There were 2847 ARI children enrolled, and 156 (5.48%) HAdV positive samples were detected. Eleven HAdV-4 positive samples were identified, accounting for 0.39% of the total samples and 7.05% of the HAdV positive samples. The main manifestations were fever and cough. Two children had conjunctivitis. Two children were diagnosed with severe pneumonia and developed respiratory failure. One of them developed hemophagocytic syndrome and checked in pediatric intensive care unit (PICU). This child had ventricular septal defect. All the children recovered. The isolated strains of HAdV-4 obtained in this study and the reference strains from China located in the same phylogenetic branch (HAdV-4a), while the prototype strain and vaccine strains formed another branch (HAdV-4p). Upon comparison with the prototype strain, there were a few amino acid mutations existing in three major capsid proteins. According to recombination analysis, no new recombination was found.

Conclusions: The detection rate of HAdV-4 in children hospitalized with ARI was 0.39% in the total samples and 7.05% of all HAdV positive samples. HAdV-4 isolates obtained in this study and other reference strains from China belonged to the HAdV-4a subtype. Our data provided reference for the monitoring, prevention and control of HAdV-4, as well as the research and development of vaccines and drugs.

Keywords: Acute respiratory infection; Children; Clinical characteristics; Genetic characteristics; Human adenovirus type 4.

Fig. 1

Phylogenetic analysis of the whole genome of HAdV-4. The phylogenetic tree was constructed by the neighbor-joining method and the Kimura two-parameter model using 1,000 replicates. The whole-genome sequences of HAdV-4 previously gained in China are indicated by cyan dots. Pink dots indicate the prototype strain and vaccine strains. Strains gained in this study are indicated by red dots

Fig. 2

Phylogenetic analysis of three major capsid protein genes. The phylogenetic trees of (A) Hexon, (B) Penton base, and (C) Fiber genes were constructed by the neighbor-joining method and the Kimura two-parameter model using 1,000 replicates. The three major capsid protein gene sequences of HAdV-4 previously gained in China are indicated by cyan dots. Pink dots indicate the prototype strain and vaccine strains. Sequences of isolates gained in this study are indicated by red dots

Fig. 3

Amino acid variation analysis of three major capsid proteins. (A) Amino acid in the Loop1 and Loop2 of Hexon. (B) Amino acid in the RGD Loop and HVR1 of Penton base. (C) Amino acid in the key regions binding to CAR and Knob of Fiber. In the HAdV-4 prototype strain RI-67, the position of Loop1 was at 135–297 amino acid, and that of Loop2 was at 401–451 amino acid of Hexon. The position of RGD Loop was at 295–353 amino acid, and that of HVR1 was at 146–165 amino acid of Penton base. The regions binding to CAR were 253, 255, 256, and 274 amino acid location, and that of Knob was 318–425 amino acid location of Fiber

Fig. 4

Nucleotide variation analysis of the ITR region. The 11 ITR gene sequences gained in this study, the prototype strain, vaccine strains, ITR gene sequences gained in China in the past, HAdV-4 strain that was first found NF-I binding sites adapting to host (Genbank accession number: KX384956, V0014/France/1978), and other HAdV types except HAdV-4 are all shown in the Figure. In the V0014 strain, the NF-I was 20–33 nucleotide location of the part of the ITR sequence shown in the figure