Recombinant Human Rhinovirus 16 VP3 (a.a. 331-562) [His]

Human rhinovirus (HRV) was first discovered in the 1950s. Since Price isolated the first strain using tissue culture methods, more than 120 HRV serotypes have been identified so far. It is the virus with the most serotypes in humans. Together with influenza virus and respiratory syncytial virus, it is considered the main causative virus of respiratory tract infections. Clinical studies have shown that HRV infection generally causes symptoms such as upper respiratory tract infections, otitis media and sinusitis. Although previous studies have shown that HRV infection generally causes relatively benign upper respiratory diseases, recent clinical studies have found that HRV is also the main cause of chronic lung disease and its deterioration. In recent years, the incidence rates of lower respiratory tract infections, community-acquired pneumonia, severe pneumonia and acute respiratory distress syndrome (ARDS) caused by HRV have also increased significantly. The pathogenesis and clinical manifestations of HRV infection are directly related to the pathogenicity of the virus. At present, supportive care is still the main method of treatment and there are no antiviral drugs for HRV.

Figure 1. Human rhinovirus genomic organization, virion structure, and species. (Sources: Stobart CC, et al. 2017)

HRV belongs to the genus Enterovirus of the family Picornaviridae. It is a single-stranded positive-strand RNA virus with a genome of approximately 7200 bp, a single open reading frame and a 5' non-coding region consisting of a short peptide. Its structure is a 20-27 nm diameter, non-enveloped 20-sided virion. The 4 protein subunits VP1, VP2, VP3 and VP4 form a protein capsid with 60 capsomers. The remaining non-structural proteins participate in viral genome replication and assembly. VP1, VP2 and VP3 proteins express the antigenic diversity of the virus, while VP4 fixes the viral RNA core to the capsid internally. Each of these four capsid proteins has 60 protein protrusions, giving the virion an icosahedral structure. There is a canyon in VP1, which is the site for HRV to bind to host cell surface receptors. Depending on the type of receptor, viral replication is taken up by endocytosis or endocytosis. Among the known HRV serotypes, more than 90% use the cell surface receptor intercellular adhesion molecule-1 (ICAM-1) to enter cells, and a few enter cells through low-density lipoprotein receptor (LDLR) attachment. Some antiviral drugs can induce canyon changes, inhibiting viral adhesion and viral uncoating. Due to the lack of a lipid envelope, HRV is inactivated in organic solvents such as ether, chloroform, ethanol and 5% benzene. HRV is heat-sensitive and loses infectivity at 50°C to 56°C. HRV is the virus with the most human serotypes, including HRVlA, HRV1B, HRV2-HRV86 and HRV88-HRVl00. HRV87 is currently identified as a nucleic acid-sensitive strain of enterovirus 68. Some cross-neutralization tests have shown that HRV has no group antigen. Based on different receptor groups, the prototype HRV can be divided into two types, namely serotype A and serotype B. In recent years, some sequencing results have shown new virus strains, HRV-A2, HRV-16, HRV-NY, HRV-QPM, HRV-X and HRV-C, which are considered to be group C of HRV, but due to different sequencing methods and lack of full sequence data, and the fact that these new viruses cannot be successfully cultured, the serotype cannot be determined yet. HRV-16 VP3 is the VP3 protein of the 16th serotype of HRV. It is an important target for HRV research.

Respiratory epithelial cells are the target cells infected by HRV. The complex formed by HRV and ICAM-1 causes changes in the surface structure of the virus to form a stronger connection, and then replicates in respiratory epithelial cells and local lymphoid tissues, causing an inflammatory response. The HRV receptor action site is located in a depression 20 angstroms deep from the surface, called the "canyon" area. HRV can hide the receptor binding site in the "canyon" area or depression, making it impossible for large antibodies to enter. At the same time, the mutation of the external residues of the "canyon" area allows the virus to evade the immune surveillance of host cells. The host's response to HRV infection is the main cause of symptoms. Under the regulation of the cholinergic neural pathway, the permeability of nasal mucosal blood vessels increases and the secretion of mucus increases, leading to symptoms such as runny nose and nasal congestion. Experiments have confirmed that antiviral drugs can lock viral particles, making VP4 and VP1 in a state where they cannot extend, thereby hindering the uncoating process. Because HRV usually does not cause infection in other anatomical parts, respiratory specimens should be collected as soon as possible for laboratory testing after symptoms appear. Although the virus can be isolated from 1 day before to 6 days after the onset of symptoms, the HRV titer is highest within the first 2 days of symptom onset. For upper respiratory tract infections, nasopharyngeal swabs are preferred over oropharyngeal swabs; for lower respiratory tract infections, tracheal, bronchial aspirates, BALF and lung biopsy specimens are usually used for testing. The following HRV detection methods are usually used: 1. Antigen and antibody detection; Since HRV lacks common group antigens, its antigen cannot be detected. Antibodies in serum and nasal secretions can be measured by neutralization, complement fixation, and enzyme-linked immunosorbent assay (ELISA). However, it can only be detected 1 to 2 weeks after infection. IgA mainly appears in nasal secretions, while IgG mainly appears in serum. However, antibody detection cannot be used for the diagnosis of acute infection and is only used for epidemiological studies. 2. Nucleic acid detection; The genome of picornaviruses has a high degree of nucleic acid homology in the 5′ non-structural region. By designing primers or probes based on the 5′ non-structural region, all serotypes of HRV can theoretically be detected. Reverse transcription-polymerase chain reaction (RT-PCR) and nucleic acid sequence-specific amplification detection methods are more commonly used. Metagenomic next-generation sequencing (mNGS) directly performs high-throughput sequencing of nucleic acids in samples. It is unbiased and improves the virus detection rate. 3. Isolation and culture; human fetal lung fibroblast cell lines, certain HeLa cell clones and human embryonic kidney cell lines are the most commonly used HRV culture methods in clinical laboratories. Virus isolation and culture can occasionally detect infections that cannot be detected by RT-PCR primers or probes due to gene mutations. HRV can only grow in cells of human or monkey origin. Different sensitive cells may mutate in their sensitivity to HRV. In order to obtain the best culture results, at least two sensitive cell lines should be cultured simultaneously.

HRV-16
Rhinovirus 16
RV-16