Immunogenicity and protective efficacy of inactivated coxsackievirus B4 viral particles

Coxsackievirus B4 (CVB4) is associated with a range of acute and chronic diseases such as hand, foot, and mouth disease, myocarditis, meningitis, pancreatitis, and type 1 diabetes, affecting millions of young children annually around the world. However, no vaccine is currently available for preventing CVB4 infection. Here, we report the development of inactivated viral particle vaccines for CVB4. Two types of inactivated CVB4 particles were prepared from CVB4-infected cell cultures as vaccine antigens, including F-particle (also called mature virion) consisting of VP1, VP3, VP2, and VP4 subunit proteins, and E-particle (also called empty capsid) which is made of VP1, VP3, and uncleaved VP0. Both the inactivated CVB4 F-particle and E-particle were able to potently elicit neutralizing antibodies in mice, despite slightly lower neutralizing antibody titres seen with the E-particle vaccine after the third immunization. Importantly, we demonstrated that passive transfer of either anti-F-particle or anti-E-particle sera could completely protect the recipient mice from lethal CVB4 challenge. Our study not only defines the immunogenicity and protective efficacy of inactivated CVB4 F-particle and E-particle but also reveals the central role of neutralizing antibodies in anti-CVB4 protective immunity, thus providing important information that may accelerate the development of inactivated CVB4 vaccines.

Severe pneumonia and pathogenic damage in human airway epithelium caused by Coxsackievirus B4

Coxsackievirus B4 (CVB4) has one of the highest proportions of fatal outcomes of other enterovirus serotypes. However, the pathogenesis of severe respiratory disease caused by CVB4 infection remains unclear. In this study, 3 of 42 (7.2%, GZ-R6, GZ-R7 and GZ-R8) patients with severe pneumonia tested positive for CVB4 infection in southern China. Three full-length genomes of pneumonia-derived CVB4 were sequenced and annotated for the first time, showing their high nucleotide similarity and clustering within genotype V. To analyze the pathogenic damage caused by CVB4 in the lungs, a well-differentiated human airway epithelium (HAE) was established and infected with the pneumonia-derived CVB4 isolate GZ-R6. The outcome was compared with that of a severe hand-foot-mouth disease (HFMD)-derived CVB4 strain GZ-HFM01. Compared with HFMD-derived CVB4, pneumonia-derived CVB4 caused more intense and rapid disruption of HAE polarity, leading to tight-junction barrier disruption, loss of cilia, and airway epithelial cell hypertrophy. More pneumonia-derived CVB4 were released from the basolateral side of the HAE than HFMD-derived CVB4. Of the 18 cytokines tested, only IL-6 and IL-1b secretion significantly increased on bilateral sides of HAE during the early stage of pneumonia-derived CVB4 infection, while multiple cytokine secretions significantly increased in HFMD-derived CVB4-infected HAE. HFMD-derived CVB4 exhibited stronger neurovirulence in the human neuroblastoma cells SH-SY5Y than pneumonia-derived CVB4, which is consistent with the clinical manifestations of patients infected with these two viruses. This study has increased the depth of our knowledge of severe pneumonia infection caused by CVB4 and will benefit its prevention and treatment.

Antiviral activity of some benzo[g]quinazolines against coxsackievirus B4: biological screening and docking study

BACKGROUND

Serotype coxsackievirus B (CVB) infection has been linked to viral myocarditis, dilated cardiomyopathy, meningitis, and pancreatitis in children and young adults. As of yet, no antiviral drug has been authorized for the treatment of coxsackievirus infection. Therefore, there is perpetual demand for new therapeutic agents and the improvement of existing ones. Benzo[g]quinazolines, the subject of several well-known heterocyclic systems, have risen to prominence and played a significant role in the development of antiviral agents, particularly those for anti-coxsackievirus B4 infection.

METHODS

This study investigated the cytotoxicity of the target benzo[g]quinazolines (1-16) in the BGM cells line as well as their anti-coxsackievirus B4 activity. Determination of CVB4 titers using a plaque assay.

RESULTS

Most of the target benzoquinazolines exhibited antiviral activity, however, compounds 1-3 appeared to be the most effective (reduction percentages of 66.7, 70, and 83.3%, respectively). The binding mechanisms and interactions of the three most active 1-3 with the constitutive amino acids in the active site of the multi-target of coxsackievirus B4 (3Clpro and RdRp) targets were also investigated using molecular docking.

CONCLUSION

The anti coxsackievirus B4 activity has resulted, and the top three active benzoquinazolines (1-3) have bonded to and interacted with the constitutive amino acids in the active region of the multi-target coxsackievirus B4 (RdRp and 3Clpro). Further research is required in the lab. to determine the exact benzoquinazolines mechanism of action.

Genomic Epidemiology and Transmission Dynamics of Global Coxsackievirus B4

The aim of this study was to determine the global genetic diversity and transmission dynamics of coxsackievirus B4 (CVB4) and to propose future directions for disease surveillance. Next-generation sequencing was performed to obtain the complete genome sequence of CVB4, and the genetic diversity and transmission dynamics of CVB4 worldwide were analyzed using bioinformatics methods such as phylogenetic analysis, evolutionary dynamics, and phylogeographic analysis. Forty complete genomes of CVB4 were identified from asymptomatic infected individuals and hand, foot, and mouth disease (HFMD) patients. Frequent recombination between CVB4 and EV-B multiple serotypes in the 3D^pol region was found and formed 12 recombinant patterns (A-L). Among these, the CVB4 isolated from asymptomatic infected persons and HFMD patients belonged to lineages H and I, respectively. Transmission dynamics analysis based on the VP1 region revealed that CVB4 epidemics in countries outside China were dominated by the D genotype, whereas the E genotype was dominant in China, and both genotypes evolved at a rate of > 6.50 × 10^-3 substitutions/site/year. CVB4 spreads through the population unseen, with the risk of disease outbreaks persisting as susceptible individuals accumulate. Our findings add to publicly available CVB4 genomic sequence data and deepen our understanding of CVB4 molecular epidemiology.

A Monovalent Mt10-CVB3 Vaccine Prevents CVB4-Accelerated Type 1 Diabetes in NOD Mice

Enteroviruses, which include Coxsackieviruses, are a common cause of virus infections in humans, and multiple serotypes of the group B Coxsackievirus (CVB) can induce similar diseases. No vaccines are currently available to prevent CVB infections because developing serotype-specific vaccines is not practical. Thus, developing a vaccine that induces protective immune responses for multiple serotypes is desired. In that direction, we created a live-attenuated CVB3 vaccine virus, designated mutant (Mt)10, that offers protection against myocarditis and pancreatitis induced by CVB3 and CVB4 in disease-susceptible A/J mice. Here, we report that the Mt10 vaccine protected against CVB4-triggered type 1 diabetes (T1D) in non-obese diabetic (NOD) mice but the expected subsequent development of spontaneous T1D in these genetically predisposed NOD mice was not altered. We noted that Mt10 vaccine induced significant amounts of neutralizing antibodies, predominantly of the IgG2c isotype, and the virus was not detected in vaccine-challenged animals. Furthermore, monitoring blood glucose levels-and to a lesser extent, insulin antibodies-was found to be helpful in predicting vaccine responses. Taken together, our data suggest that the monovalent Mt10 vaccine has the potential to prevent infections caused by multiple CVB serotypes, as we have demonstrated in various pre-clinical models.

Coxsackievirus B4 Transplacental Infection Severely Disturbs Central Tolerogenic Mechanisms in the Fetal Thymus

Thymus plays a fundamental role in central tolerance establishment, especially during fetal life, through the generation of self-tolerant T cells. This process consists in T cells education by presenting them tissue-restricted autoantigens promiscuously expressed by thymic epithelial cells (TECs), thus preventing autoimmunity. Thymus infection by Coxsackievirus B (CV-B) during fetal life is supposed to disturb thymic functions and, hence, to be an inducing or accelerating factor in the genesis of autoimmunity. To further investigate this hypothesis, in our current study, we analyzed thymic expression of autoantigens, at the transcriptional and protein level, following in utero infection by CV-B4. mRNA expression levels of Igf2 and Myo7, major autoantigens of pancreas and heart, respectively, were analyzed in whole thymus and in enriched TECs together along with both transcription factors, Aire and Fezf2, involved in autoantigens expression in the thymus. Results show that in utero infection by CV-B4 induces a significant decrease in Igf2 and Myo7 expression at both mRNA and protein level in whole thymus and in enriched TECs as well. Moreover, a correlation between viral load and autoantigens expression can be observed in the whole thymus, indicating a direct effect of in utero infection by CV-B4 on autoantigens expression. Together, these results indicate that an in utero infection of the thymus by CV-B4 may interfere with self-tolerance establishment in TECs by decreasing autoantigen expression at both mRNA and protein level and thereby increase the risk of autoimmunity onset.

Characterization of Coxsackievirus B4 virus-like particles VLP produced by the recombinant baculovirus-insect cell system expressing the major capsid protein

Coxsackievirus B4 (CV-B4) is suspected to be an environmental factor that has the intrinsic capacity to damage the pancreatic beta cells and therefore causes insulitis and type 1 diabetes (T1D). Although vaccination against CV-B4 could reduce the incidence of this chronic auto-immune disease, there is currently no therapeutic reagent or vaccine in clinical use. By the employment of the Bac-to-Bac® vector system to express the major viral capsid protein, we contributed towards the development of a CV-B4 vaccine by producing CV-B4 virus-like particles (VLPs) from recombinant baculovirus in infected insect cells. In fact Western blot and Immunofluorescence analysis detected the viral protein 1 (VP1) in the cells resulting from the construction of a recombinant bacmid DNA carrying the key immunogenic protein then transfected in the insect cells. Sucrose gradient ultracentrifugation fractions of the infected cell lysates contained the recombinant protein and the electron microscopy demonstrated the presence of VLPs in these sucrose fractions. This study clearly shows for the first time the expression of CVB4 VP1 structure protein alone can form VLPs in the baculovirus-infected insect cell keeping conserved both characteristics and morphology.

Housekeeping Gene Expression in the Fetal and Neonatal Murine Thymus Following Coxsackievirus B4 Infection

The thymus fulfills the role of T-cell production and differentiation. Studying transcription factors and genes involved in T-cell differentiation and maturation during the fetal and neonatal periods is very important. Nevertheless, no studies to date have been interested in evaluating the expressions of housekeeping genes as internal controls to assess the varying expressions of different genes inside this tissue during that period or in the context of viral infection. Thus, we evaluated by real-time quantitative polymerase chain reaction (qPCR) the expression of the most common internal control genes in the thymus of Swiss albino mice during the fetal and neonatal period, and following in utero infection with Coxsackievirus B4. The stability of expression of these reference genes in different samples was investigated using the geNorm application. Results demonstrated that the expression stability varied greatly between genes. Oaz1 was found to have the highest stability in different stages of development, as well as following Coxsackievirus B4 infection. The current study clearly demonstrated that Oaz1, with very stable expression levels that outperformed other tested housekeeping genes, could be used as a reference gene in the thymus and thymic epithelial cells during development and following Coxsackievirus B4 infection.

Human Endogenous Retroviruses and Type 1 Diabetes

PURPOSE OF THE REVIEW

The aim of this review is to discuss recent data pointing at an involvement of human endogenous retroviruses (HERVs) in type 1 diabetes (T1D) onset and progression.

RECENT FINDINGS

The envelope protein of HERV-W family, named HERV-W-Env, was detected in pancreata from T1D patients and was shown to display pro-inflammatory properties and direct toxicity toward pancreatic beta cells. The etiopathogenesis of T1D remains elusive, even if conventional environmental viral infections have been recurrently involved. Nonetheless, a new category of pathogens may provide the missing link between genetic susceptibility and environmental factors long thought to contribute to T1D onset. A number of studies have now shown that HERV sequences, which are normally inactivated or repressed in the human genome, could be activated by environmental viruses. Thus, if similarly activated by viruses associated with T1D, disregarded HERV genes may underlie T1D genetic susceptibility. Moreover, once expressed, HERV elements may display broad pathogenic properties, which identify them as potential new therapeutic targets.

QuantIF: An ImageJ Macro to Automatically Determine the Percentage of Infected Cells after Immunofluorescence

Counting labeled cells, after immunofluorescence or expression of a genetically fluorescent reporter protein, is frequently used to quantify viral infection. However, this can be very tedious without a high content screening apparatus. For this reason, we have developed QuantIF, an ImageJ macro that automatically determines the total number of cells and the number of labeled cells from two images of the same field, using DAPI- and specific-stainings, respectively. QuantIF can automatically analyze hundreds of images, taking approximately one second for each field. It is freely available as supplementary data online at MDPI.com and has been developed using ImageJ, a free image processing program that can run on any computer with a Java virtual machine, which is distributed for Windows, Mac, and Linux. It is routinely used in our labs to quantify viral infections in vitro, but can easily be used for other applications that require quantification of labeled cells.

Evaluation of novel pyrrolopyrimidine derivatives as antiviral against gastroenteric viral infections

Viral gastroenteritis is a major global public-health threat. All age groups are susceptible for this infection, but its most serious consequences affect children. Rotavirus, Coxsackievirus and Adenovirus are the most common viruses that cause gastroenteritis. Herein, we synthesized novel pyrrole, pyrrolo[2,3‑d]pyrimidine and pyrrolo[3,2‑e][1,2,4]triazolo[4,3‑c]pyrimidine derivatives. The non-toxic doses of these compounds were determined using BGM cell lines. We examined all the new compounds for their anti-viral activities against Rotavirus Wa strain and Coxsackievirus B4. Compounds 2a, 2d, 5a, 5c, 5d, 7b, 7j, 7n, 14b, 14c, 14e and 14f exhibited significant antiviral activity. We interpreted the action of these compounds using molecular docking against the homology models of viral polymerase enzymes of these viruses. RMSD value of 5d/Coxsackievirus was higher than the RMSD value for 5d/rotavirus and hence better as a stability parameter, which can be correlated to the biological activity.

Coxsackievirus B4 as a Causative Agent of Diabetes Mellitus Type 1: Is There a Role of Inefficiently Treated Drinking Water and Sewage in Virus Spreading?

This study proposed to detect the enterovirus (EV) infection in children with type 1 diabetes mellitus (T1D) and to assess the role of insufficiently treated water and sewage as sources of viral spreading. Three hundred and eighty-two serum specimens of children with T1D, one hundred serum specimens of children who did not suffer from T1D as control, and forty-eight water and sewage samples were screened for EV RNA using nested RT-PCR. The number of genome copies and infectious units of EVs in raw and treated sewage and water samples were investigated using real-time (RT)-PCR and plaque assay, respectively. T1D markers [Fasting blood glucose (FBG), HbA1c, and C-peptide], in addition to anti-Coxsackie A & B viruses (CVs A & B) IgG, were measured in control, T1D-negative EV (T1D-EV^-), and T1D-positive EV (T1D-EV⁺) children specimens. The prevalence of EV genome was significantly higher in diabetic children (26.2%, 100 out of 382) than the control children (0%, 0 out of 100). FBG and HbA1c in T1D-EV^- and T1D-EV⁺ children specimens were significantly higher than those in the control group, while c-peptide in T1D-EV^- and T1D-EV⁺ children specimens was significantly lower than that in the control (n = 100; p < 0.001). Positivity of anti-CVs A & B IgG was 70.7, 6.7, and 22.9% in T1D-EV⁺, T1D-EV^-, and control children specimens, respectively. The prevalence of EV genome in drinking water and treated sewage samples was 25 and 33.3%, respectively. The prevalence of EV infectious units in drinking water and treated sewage samples was 8.5 and 25%, respectively. Quantification assays were performed to assess the capabilities of both wastewater treatment plants (WWTPs) and water treatment plants (WTPs) to remove EV. The reduction of EV genome in Zenin WWTP ranged from 2 to 4 log₁₀, while the reduction of EV infectious units ranged from 1 to 4 log₁₀. The reduction of EV genome in El-Giza WTP ranged from 1 to 3 log₁₀, while the reduction of EV infectious units ranged from 1 to 2 log₁₀. This capability of reduction did not prevent the appearance of infectious EV in treated sewage and drinking water. Plaque purification was performed for isolation of separate EV isolates from treated and untreated water and sewage samples. Characterization of the EV amplicons by RT-PCR followed by sequencing of these isolates revealed high homology (97%) with human coxsackievirus B4 (CV B4) in 60% of the isolates, while the rest of the isolates belonged to poliovirus type 1 and type 2 vaccine strains. On the other hand, characterization of the EV amplicons by RT-PCR followed by sequencing for T1D-EV⁺ children specimens indicated that all samples contained CV B4 with the same sequence characterized in the environmental samples. CV B4-contaminated drinking water or treated sewage may play a role as a causative agent of T1D in children.

Murine model of acute myocarditis and cerebral cortical neuron edema induced by coxsackievirus B4

Globally, coxsackievirus B4 (CV-B4) has been continuously isolated and evidence suggests an association with the development of pancreatitis and type I diabetes. In addition, CV-B4 is also associated with myocarditis and severe central nervous system (CNS) complications, which remain poorly studied and understood. In the present study, we established an Institute for Cancer Research (ICR) mouse model of CV-B4 infection and examined whether CV-B4 infection resulted in a predisposition to myocarditis and CNS infection. We found high survival in both the treatment and control group, with no significant differences in clinical outcomes observed. However, pathological lesions were evident in both brain and heart tissue of the CV-B4-infected mice. In addition, high viral loads were found in the neural and cardiac tissues as early as 2 days post infection. Expressions of IFN-γ and IL-6 in sera were significantly higher in CV-B4-infected mice compared to uninfected negative controls, suggesting the involvement of these cytokines in the development of histopathological lesions. Our murine model successfully reproduced the acute myocarditis and cerebral cortical neuron edema induced by CV-B4, and may be useful for the evaluation of vaccine candidates and potential antivirals against CV-B4 infection.

Bifidobacteria-derived lipoproteins inhibit infection with coxsackievirus B4 in vitro

The aim of the present study was to investigate the potential of bifidobacteria in protecting cells from coxsackievirus B4 (CV-B4) infection. Bifidobacterial screening identified two of five strains that protected human epithelial type 2 (HEp-2) cell viability when bifidobacteria were incubated with viral particles prior to inoculation. In contrast, no effect was shown by incubating HEp-2 cells with bifidobacteria prior to CV-B4 inoculation. Cell wall lipoprotein aggregates (LpAs) secreted by the selected strains were assayed for their antiviral activity. The two LpAs exhibited antiviral activity when they were incubated with viral particles prior to inoculation of HEp-2 cells. Recombinant LpA-derived protein exhibited identical antiviral activity. To identify the peptide sequences interacting with the virus particles, LpA proteins were aligned with the peptide sequences of the north canyon rim and puff footprint onto coxsackievirus and adenovirus receptor (CAR). The in silico molecular docking study using CV-B3 as template showed low-energy binding, indicating a stable system for the selected peptides and consequently a likely binding interaction with CV-B. Bifidobacterium longum and Bifidobacterium breve peptides homologous to the viral north rim footprint onto CAR sequence formed hydrogen bonds with several viral residues in the north rim of the canyon, which were already predicted as interacting with CAR. In conclusion, proteins from bifidobacterial LpAs can inhibit infection with CV-B4, likely through binding to the capsid amino acids that interact with CAR.

Persistence of Coxsackievirus B4 in pancreatic ductal-like cells results in cellular and viral changes

INTRODUCTION

Although known as cytolytic viruses, group B coxackieviruses (CVB) are able to establish a persistent infection in vitro and in vivo. Viral persistence has been reported as a key mechanism in the pathogenesis of CVB-associated chronic diseases such as type 1 diabetes (T1D). The impact of CVB4 persistence on human pancreas ductal-like cells was investigated.

METHODS

A persistent CVB4 infection was established in ductal-like cells. PDX-1 expression, resistance to CVB4-induced lysis and CAR expression were evaluated. The profile of cellular microRNAs (miRNAs) was investigated through miRNA-sequencing. Viral phenotypic changes were examined, and genomic modifications were assessed by sequencing of the viral genome.

RESULTS

The CVB4 persistence in ductal-like cells was productive, with continuous release of infectious particles. Persistently infected cells displayed a resistance to CVB4-induced lysis upon superinfection and expression of PDX-1 and CAR was decreased. These changes were maintained even after virus clearance. The patterns of cellular miRNA expression in mock-infected and in CVB4-persistently infected ductal-like cells were clearly different. The persistent infection-derived virus (PIDV) was still able to induce cytopathic effect but its plaques were smaller than the parental virus. Several mutations appeared in various PIDV genome regions, but amino acid substitutions did not affect the predicted site of interaction with CAR.

CONCLUSION

Cellular and viral changes occur during persistent infection of human pancreas ductal-like cells with CVB4. The persistence of cellular changes even after virus clearance supports the hypothesis of a long-lasting impact of persistent CVB infection on the cells.

Novel antiviral compounds against gastroenteric viral infections

Viral gastroenteritis is a serious viral infection which affects a large number of individuals around the world, most of them being children. The infection may occur due to different viruses, for example, coxsackievirus, adenovirus, and rotavirus. There is no available cure for such infections, and the treatment mainly depends on hospitalization and administration of nutritional supports. A new antiviral agent against gastroenteritis viral infection will be a breakthrough in healthcare. Pyrrole and pyrrolopyrimidine derivatives are well known for their biological activity as antibacterial, antifungal, and anticancer agents. These compounds also proved to possess antiviral activity. Here, we synthesized novel pyrrole and pyrrolopyrimidine compounds and examined their antiviral activity. We synthesized several new pyrrole, pyrrolo[2,3-d]pyrimidine, and pyrrolo[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives. The characterization of all synthesized compounds was based on microanalysis and spectral data. Moreover, we determined the non-toxic doses of these compounds on BGM, Hep-2, and MA-104 cells. We tested all the synthesized compounds for their antiviral activities against coxsackievirus B4, adenovirus type 7, and rotavirus Wa strain. Several compounds exhibited significant activities as antiviral agents.

Persistent infection of human pancreatic cells with Coxsackievirus B4 is cured by fluoxetine

Group B Coxsackieviruses (CVB) are involved in various acute clinical features and they can play a role in the development of chronic diseases like type 1 diabetes. The persistence of CVB has been described in vitro and in vivo in various models. Fluoxetine was reported to inhibit the replication of CVB1-3, which prompted us to study the in vitro antiviral activity of fluoxetine against CVB4 in models of acute infection. In addition we took advantage of a chronically CVB4-infected Panc-1 cell line to evaluate the antiviral effect of fluoxetine in a model of persistent CVB4 infection. An inhibition of the CVB4 replication was obtained when fluoxetine was added at 5.48μM to Hep-2 cell cultures. No inhibitory effect was observed when CVB4 was mixed with fluoxetine for 2h and filtered to eliminate fluoxetine before inoculation to cells, or when cells were treated up to 96h and washed before viral inoculation. Fluoxetine (5.48μM) reduced viral replication by more than 50% in acutely infected Panc-1 cell cultures. A dramatic decrease of infectious particles levels in supernatants of Panc-1 cells chronically infected with CVB4 was obtained a few days after treatment with fluoxetine and no infectious viral particle was found as soon as day 21 of treatment, and intracellular enteroviral RNA was undetectable by RT-PCR after three weeks of treatment. These data display that fluoxetine can inhibit the replication of CVB4 and can cure Panc-1 cells chronically infected with CVB4.