Evidence of combined effect of amino acid substitutions within G-H and B-C loops of VP1 conferring serological heterogeneity in foot-and-mouth disease virus serotype A

Cell Culture Adaptive Amino Acid Substitutions in FMDV Structural Proteins: A Key Mechanism for Altered Receptor Tropism

The foot-and-mouth disease virus is a highly contagious and economically devastating virus of cloven-hooved animals, including cattle, buffalo, sheep, and goats, causing reduced animal productivity and posing international trade restrictions. For decades, chemically inactivated vaccines have been serving as the most effective strategy for the management of foot-and-mouth disease. Inactivated vaccines are commercially produced in cell culture systems, which require successful propagation and adaptation of field isolates, demanding a high cost and laborious time. Cell culture adaptation is chiefly indebted to amino acid substitutions in surface-exposed capsid proteins, altering the necessity of RGD-dependent receptors to heparan sulfate macromolecules for virus binding. Several amino acid substations in VP1, VP2, and VP3 capsid proteins of FMDV, both at structural and functional levels, have been characterized previously. This literature review combines frequently reported amino acid substitutions in virus capsid proteins, their critical roles in virus adaptation, and functional characterization of the substitutions. Furthermore, this data can facilitate molecular virologists to develop new vaccine strains against the foot-and-mouth disease virus, revolutionizing vaccinology via reverse genetic engineering and synthetic biology.

Enhancing the Immunogenicity of RBD Protein Variants through Amino Acid E484 Mutation in SARS-CoV-2

In the context of the COVID-19 pandemic, conducting antibody testing and vaccination is critical. In particular, the continued evolution of SARS-CoV-2 raises concerns about the effectiveness of vaccines currently in use and the activity of neutralizing antibodies. Here, we used the Escherichia coli expression system to obtain nine different SARS-CoV-2 RBD protein variants, including six single-point mutants, one double-point mutant, and two three-point mutants. Western blotting results show that nine mutants of the RBD protein had strong antigenic activity in vitro. The immunogenicity of all RBD proteins was detected in mice to screen for protein mutants with high immunogenicity. The results show that the mutants E484K, E484Q, K417T-E484K-N501Y, and K417N-E484K-N501Y, especially the former two, had better immunogenicity than the wild type. This suggests that site E484 has a significant impact on the function of the RBD protein. Our results demonstrate that recombinant RBD protein expressed in E. coli can be an effective tool for the development of antibody detection methods and vaccines.

A severe case of human rhinovirus A45 with central nervous system involvement and viral sepsis

Background

Rhinovirus is a common viral aetiology of upper respiratory infection and is mostly associated with common cold or flu-like illness. Although rhinovirus has been recognized as a pathogen for lower respiratory infections in severe cases credited to advances in molecular detection, central nervous system involvement and multiorgan dysfunction are extremely rare.

Case presentation

A previously healthy 10-year-old girl developed fever, sore throat and conjunctive injection after contact with an upper respiratory infection patient, followed by seizures, haematuria, and severe diarrhoea. She experienced viral sepsis and multiorgan dysfunction after admission. Cerebral computed tomography showed significant diffuse encephaledema. Cerebrospinal fluid analysis showed significantly elevated protein levels. After her consciousness disturbance improved, she still took a long time to recover from haematuria and diarrhoea. We identified a rarely reported rhinovirus A45 in her oropharyngeal and anal swabs by metagenomic next-generation sequencing, and bacterial culture of blood specimens yielded negative results.

Conclusions

This case presents a patient with severe rhinovirus infection, which was very likely responsible for her central nervous system symptoms and viral sepsis.

Effect of cell density on the biological titer and yield of 146S fraction of foot-and-mouth disease virus O in cell suspension

Foot-and-mouth disease (FMD) is a highly infectious disease of cattle and other cloven-hoofed animals, causing huge economic losses annually worldwide. This disease is endemic in Pakistan where the serotypes of the foot-and-mouth disease virus (FMDV) are A, O and ASIA-1. At present, trivalent FMDV vaccines are being used to prevent FMD but the current production process is laborious and is unable to fulfill the needs of the meat and dairy industries. To meet the vaccine needs of Pakistan, the conventional method of using adherent cell lines to produce the vaccine could be replaced by suspension cell cultures which produce higher yields in less time and less volume. Therefore, the aim of this study was to investigate and optimize some of the factors that affect viable cell density and subsequent virus yield. The relationship between the yield of the 146S fraction and the TCID₅₀ of the virus preparations obtained was also evaluated as a mean to control and check the quality of the vaccine product. The results provided optimized conditions for vaccine production using cell suspensions and showed that there was a linear relationship between TCID₅₀ and 146S fraction yield. Either TCID₅₀ or the 146S fraction yield, or both could be used as parameters for quality monitoring during vaccine production. Using TCID₅₀ reduced the number of steps involved in virus production while measuring 146S fraction yield was useful for quality control. However, more studies are required to evaluate the relative effectiveness of vaccines produced by virus cultures using either TCID₅₀ or 146S fraction as quality monitoring tools.

Structures of foot-and-mouth disease virus with bovine neutralizing antibodies reveal the determinant of intra-serotype cross-neutralization

Foot-and-mouth disease virus (FMDV) exhibits broad antigenic diversity with poor intra-serotype cross-neutralizing activity. Studies of the determinant involved in this diversity are essential for the development of broadly protective vaccines. In this work, we isolated a bovine antibody, designated R55, that displays cross-reaction with both FMDV A/AF/72 (hereafter named FMDV-AAF) and FMDV A/WH/09 (hereafter named FMDV-AWH) but only has a neutralizing effect on FMDV-AWH. Near-atomic resolution structures of FMDV-AAF-R55 and FMDV-AWH-R55 show that R55 engages the capsids of both FMDV-AAF and FMDV-AWH near the icosahedral threefold axis and binds to the βB and BC/HI-loops of VP2 and to the B-B knob of VP3. The common interaction residues are highly conserved, which is the major determinant for cross-reaction with both FMDV-AAF and FMDV-AWH. In addition, the cryo-EM structure of the FMDV-AWH-R55 complex also shows that R55 binds to _VP3E70 located at the VP3 BC-loop in an adjacent pentamer, which enhances the acid and thermal stabilities of the viral capsid. This may prevent capsid dissociation and genome release into host cells, eventually leading to neutralization of the viral infection. In contrast, R55 binds only to the FMDV-AAF capsid within one pentamer due to the _VP3E70G variation, which neither enhances capsid stability nor neutralizes FMDV-AAF infection. The _VP3E70G mutation is the major determinant involved in the neutralizing differences between FMDV-AWH and FMDV-AAF. The crucial amino acid _VP3E70 is a key component of the neutralizing epitopes, which may aid in the development of broadly protective vaccines. Importance Foot-and-mouth disease virus (FMDV) causes a highly contagious and economically devastating disease in cloven-hoofed animals, and neutralizing antibodies play critical roles in the defense against viral infections. Here, we isolated a bovine antibody (R55) using the single B cell antibody isolation technique. Enzyme-linked immunosorbent assays (ELISA) and virus neutralization tests (VNT) showed that R55 displays cross-reactions with both FMDV-AWH and FMDV-AAF but only has a neutralizing effect on FMDV-AWH. Cryo-EM structures, fluorescence-based thermal stability assays and acid stability assays showed that R55 engages the capsid of FMDV-AWH near the icosahedral threefold axis and informs an interpentamer epitope, which overstabilizes virions to hinder capsid dissociation to release the genome, eventually leading to neutralization of viral infection. The crucial amino acid _VP3E70 forms a key component of neutralizing epitopes, and the determination of the _VP3E70G mutation involved in the neutralizing differences between FMDV-AWH and FMDV-AAF could aid in the development of broadly protective vaccines.