Human Memory B Cells Producing Potent Cross-Neutralizing Antibodies against Human Parechovirus: Implications for Prevalence, Treatment, and Diagnosis

The Research Progress on Immortalization of Human B Cells

Human B cell immortalization that maintains the constant growth characteristics and antibody expression of B cells in vitro is very critical for the development of antibody drugs and products for the diagnosis and bio-therapeutics of human diseases. Human B cell immortalization methods include Epstein-Barr virus (EBV) transformation, Simian virus 40 (SV40) virus infection, in vitro genetic modification, and activating CD40, etc. Immortalized human B cells produce monoclonal antibodies (mAbs) very efficiently, and the antibodies produced in this way can overcome the immune rejection caused by heterologous antibodies. It is an effective way to prepare mAbs and an important method for developing therapeutic monoclonal antibodies. Currently, the US FDA has approved more than 100 mAbs against a wide range of illnesses such as cancer, autoimmune diseases, infectious diseases, and neurological disorders. This paper reviews the research progress of human B cell immortalization, its methods, and future directions as it is a powerful tool for the development of monoclonal antibody preparation technology.

Neutralizing Ljungan virus antibodies in children with newly diagnosed type 1 diabetes

Ljungan virus (LV), a Parechovirus of the Picornavirus family, first isolated from a bank vole at the Ljungan river in Sweden, has been implicated in the risk for autoimmune type 1 diabetes. An assay for neutralizing Ljungan virus antibodies (NLVA) was developed using the original 87-012 LV isolate. The goal was to determine NLVA titres in incident 0-18 years old newly diagnosed type 1 diabetes patients (n=67) and school children controls (n=292) from Jämtland county in Sweden. NLVA were found in 41 of 67 (61 %) patients compared to 127 of 292 (44 %) controls (P=0.009). In the type 1 diabetes patients, NLVA titres were associated with autoantibodies to glutamic acid decarboxylase (GADA) (P=0.023), but not to autoantibodies against insulin (IAA) or islet antigen-2 (IA-2A). The NLVA assay should prove useful for further investigations to determine levels of LV antibodies in patients and future studies to determine a possible role of LV in autoimmune type 1 diabetes.

Parechovirus A prevalence in adults in The Netherlands

Human parechoviruses (HPeV) of the species Parechovirus A are highly prevalent disease-causing pathogens in children worldwide. HPeVs are capable of causing severe disease in adults as well, but the prevalence in adults may be much lower. The aim of our present study was to determine the prevalence of HPeV in clinical samples from adults sent in for diagnostic procedures in a tertiary hospital in the Netherlands. From a total of 10,645 samples obtained from 6175 patients, 20 samples from 11 patients (0.18%) tested positive for HPeV by RT-PCR. Two patients were positive for HPeV-1, two for HPeV-3, and one for HPeV-6. Six HPeVs could not be typed. Eight of the 11 HPeV-positive patients were immunocompromised. Due to comorbidity, we were unable to attribute the patients’ clinical symptoms to the HPeV infection. The HPeV prevalence in adults found in this study is low compared to HPeV prevalence in children. This may be largely explained by the high seropositivity rates in adults, although there could be other mechanisms involved.

Parechovirus A Pathogenesis and the Enigma of Genotype A-3

Parechovirus A is a species in the Parechovirus genus within the Picornaviridae family that can cause severe disease in children. Relatively little is known on Parechovirus A epidemiology and pathogenesis. This review aims to explore the Parechovirus A literature and highlight the differences between Parechovirus A genotypes from a pathogenesis standpoint. In particular, the curious case of Parechovirus-A3 and the genotype-specific disease association will be discussed. Finally, a brief outlook on Parechovirus A research is provided.

Seroepidemiology of Parechovirus A3 Neutralizing Antibodies, Australia, the Netherlands, and United States

Recent parechovirus A3 (PeV-A3) outbreaks in Australia suggest lower population immunity compared with regions that have endemic PeV-A3 circulation. A serosurvey among populations in the Netherlands, the United States, and Australia before and after the 2013 Australia outbreak showed high PeV-A3 neutralizing antibody prevalence across all regions and time periods, indicating widespread circulation.

Establishment of Systems to Enable Isolation of Porcine Monoclonal Antibodies Broadly Neutralizing the Porcine Reproductive and Respiratory Syndrome Virus

The rapid evolution of porcine reproductive and respiratory syndrome viruses (PRRSV) poses a major challenge to effective disease control since available vaccines show variable efficacy against divergent strains. Knowledge of the antigenic targets of virus-neutralizing antibodies that confer protection against heterologous PRRSV strains would be a catalyst for the development of next-generation vaccines. Key to discovering these epitopes is the isolation of neutralizing monoclonal antibodies (mAbs) from immune pigs. To address this need, we sought to establish systems to enable the isolation of PRRSV neutralizing porcine mAbs. We experimentally produced a cohort of immune pigs by sequential challenge infection with four heterologous PRRSV strains spanning PRRSV-1 subtypes and PRRSV species. Whilst priming with PRRSV-1 subtype 1 did not confer full protection against a subsequent infection with a PRRSV-1 subtype 3 strain, animals were protected against a subsequent PRRSV-2 infection. The infection protocol resulted in high serum neutralizing antibody titers against PRRSV-1 Olot/91 and significant neutralization of heterologous PRRSV-1/-2 strains. Enriched memory B cells isolated at the termination of the study were genetically programmed by transduction with a retroviral vector expressing the Bcl-6 transcription factor and the anti-apoptotic Bcl-xL protein, a technology we demonstrated efficiently converts porcine memory B cells into proliferating antibody-secreting cells. Pools of transduced memory B cells were cultured and supernatants containing PRRSV-specific antibodies identified by flow cytometric staining of infected MARC-145 cells and in vitro neutralization of PRRSV-1. Collectively, these data suggest that this experimental system may be further exploited to produce a panel of PRRSV-specific mAbs, which will contribute both to our understanding of the antibody response to PRRSV and allow epitopes to be resolved that may ultimately guide the design of immunogens to induce cross-protective immunity.

Genetic diversity of human parechoviruses in stool samples, Germany

Human parechoviruses (HPeV) are ubiquitous and mainly occur in early infancy. They are known to cause various clinical manifestations including acute gastroenteritis. To gain insight into the diversity of circulating HPeV genotypes, stool samples from patients (n = 539) with clinical signs of infectious gastroenteritis which showed negative results for other common viral and bacterial enteric pathogens were obtained during three years, 2008 to 2010. Real-time RT-PCR showed HPeV RNA in 34 (6.3%) of the samples. The HPeV detection rate was highest (8.8%) in samples derived from infants and young children under the age of two years. Genotyping was based on VP3/VP1 junction nucleic acid sequences and revealed predominant HPeV-1B (n = 16) and HPeV-3 (n = 12) strains. Those prevailed minor HPeV-6 (n = 3) as well as HPeV-2, -4 and -5 (n = 1, each) strains. To ascertain the assigned HPeV-2 genotype of uncommon strain LPZ04-2008, analysis of complete coding sequences was performed. In complete VP1 analysis strain LPZ04-2008 showed 81.2% nucleic acid identity with HPeV-2 reference strain Williamson. In phylogenetic analysis VP1 of strain LPZ04-2008 clustered with a recent HPeV-2 strain from the UK. Regarding clinical manifestations, severe disease occurred HPeV-1B, -3 and - 6 infections. In conclusion, this paper a high genetic diversity of HPeV in stool samples, including rare strains. The investigation adds data on the whole coding sequences of the rare HPeV-2 strain. Genotyping results confirm previously reported association of more severe illness with HPeV-3 and HPeV-1B strains.

Human Parechovirus 1, 3 and 4 Neutralizing Antibodies in Dutch Mothers and Infants and Their Role in Protection Against Disease

BACKGROUND

Human parechoviruses (HPeVs) are common pathogens in young children, and in the Netherlands, HPeV1, HPeV3 and HPeV4 are the most frequently detected genotypes. HPeV3 in particular has been associated with severe disease in young infants below 3 months of age while the other genotypes more often infect older children and elicit mild symptoms. We investigated if maternal neutralizing antibodies (nAbs) against HPeV1, HPeV3 and HPeV4 protect young Dutch infants from severe disease related to HPeV infection.

METHODS

We conducted a prospective case-control study of Dutch mother-infant pairs. Thirty-eight HPeV-infected infants and their mothers were included as cases, and 65 HPeV-negative children and their mothers as controls.

RESULTS

In control infants, we observed nAb seropositivity rates of 41.4%, 33.3% and 27.6%, with median nAb titers of 1:16, 1:12 and 1:8, against HPeV1, HPeV3 and HPeV4, respectively. In control mothers, nAb seropositivity rates were 84.6%, 55.4% and 60.0% with median nAb titers of 1:128, 1:32 and 1:45 against HPeV1, HPeV3 and HPeV4, respectively. The HPeV3 nAb seroprevalence was significantly lower in HPeV3-infected infants and their mothers (0.0% with P < 0.05 and 10.0% with P < 0.001, respectively). In contrast, no differences in nAb seroprevalence against HPeV1 or HPeV4 could be detected between case and control infants or mothers.

CONCLUSIONS

Our results suggest that young Dutch infants are protected against severe disease related to HPeV1 and HPeV4 by maternal nAbs, but less so against HPeV3 explaining the distinct age distributions and disease severity profiles of children infected with these HPeV genotypes.

Progress in human picornavirus research: New findings from the AIROPico consortium

Several research groups in Europe are active on different aspects of human picornavirus research. The AIROPico (Academia-Industry R&D Opportunities for Picornaviruses) consortium combined the disciplines of pathogenesis, diagnostics and therapy development in order to fill the gaps in our understanding of how picornaviruses cause human disease and how to combat them. AIROPico was the first EU consortium dedicated to human picornavirus research and development, and has largely accelerated and improved R&D on picornavirus biology, diagnostics and therapy. In this article, we present the progress on pathogenesis, diagnostics and treatment strategy developments for human picornaviruses resulting from the structured, translational research approach of the AIROPico consortium. We here summarize new insights in protection against infection by maternal or cross-protective antibodies, the visualisation of interactions between virus and neutralizing antibodies by cryoEM structural imaging, and the outcomes from a picornavirus-infected human 3D organoid. Progress in molecular detection and a fast typing assay for rhinovirus species are presented, as well as the identification of new compounds potentially interesting as therapeutic compounds.

Intrinsically-disordered N-termini in human parechovirus 1 capsid proteins bind encapsidated RNA

Human parechoviruses (HPeV) are picornaviruses with a highly-ordered RNA genome contained within icosahedrally-symmetric capsids. Ordered RNA structures have recently been shown to interact with capsid proteins VP1 and VP3 and facilitate virus assembly in HPeV1. Using an assay that combines reversible cross-linking, RNA affinity purification and peptide mass fingerprinting (RCAP), we mapped the RNA-interacting regions of the capsid proteins from the whole HPeV1 virion in solution. The intrinsically-disordered N-termini of capsid proteins VP1 and VP3, and unexpectedly, VP0, were identified to interact with RNA. Comparing these results to those obtained using recombinantly-expressed VP0 and VP1 confirmed the virion binding regions, and revealed unique RNA binding regions in the isolated VP0 not previously observed in the crystal structure of HPeV1. We used RNA fluorescence anisotropy to confirm the RNA-binding competency of each of the capsid proteins’ N-termini. These findings suggests that dynamic interactions between the viral RNA and the capsid proteins modulate virus assembly, and suggest a novel role for VP0.

Recent advances in veterinary applications of structural vaccinology

The deployment of effective veterinary vaccines has had a major impact on improving food security and consequently human health. Effective vaccines were essential for the global eradication of Rinderpest and the control and eradication of foot-and-mouth disease in some regions of the world. Effective vaccines also underpin the development of modern intensive food production systems such as poultry and aquaculture. However, for some high consequence diseases there are still significant challenges to develop effective vaccines. There is a strong track record in veterinary medicine of early adoption of new technologies to produce vaccines. Here we provide examples of new technologies to interrogate B cell responses and using structural biology to improve antigens.

Human Parechovirus: an Increasingly Recognized Cause of Sepsis-Like Illness in Young Infants

Human parechovirus (HPeV) is increasingly being recognized as a potentially severe viral infection in neonates and young infants. HPeV belongs to the family Picornaviridae and is currently divided into 19 genotypes. HPeV-1 is the most prevalent genotype and most commonly causes gastrointestinal and respiratory disease. HPeV-3 is clinically the most important genotype due to its association with severe disease in younger infants, which may partly be explained by its distinct virological properties. In young infants, the typical clinical presentation includes fever, severe irritability, and rash, often leading to descriptions of "hot, red, angry babies." Infants with severe central nervous system (CNS) infections are at an increased risk of long-term sequelae. Considering the importance of HPeV as a cause of severe viral infections in young infants, we recommend that molecular diagnostic techniques for early detection be included in the standard practice for the investigation of sepsis-like illnesses and CNS infections in this age group.

Human picornaviruses associated with neurological diseases and their neutralization by antibodies

Picornaviruses are the most commonly encountered infectious agents in mankind. They typically cause mild infections of the gastrointestinal or respiratory tract, but sometimes also invade the central nervous system. There, they can cause severe diseases with long-term sequelae and even be lethal. The most infamous picornavirus is poliovirus, for which significant epidemics of poliomyelitis were reported from the end of the nineteenth century. A successful vaccination campaign has brought poliovirus close to eradication, but neurological diseases caused by other picornaviruses have increasingly been reported since the late 1990s. In this review we focus on enterovirus 71, coxsackievirus A16, enterovirus 68 and human parechovirus 3, which have recently drawn attention because of their links to severe neurological diseases. We discuss the clinical relevance of these viruses and the primary role of humoral immunity in controlling them, and summarize current knowledge on the neutralization of such viruses by antibodies.

The Complete Genome Sequence of a Human Parechovirus from a Child with Diarrhea in China Revealed Intertypic Recombination

A human parechovirus (HPeV), CH-ZXY1, was detected in feces from a child with diarrhea. Phylogenetic trees over three different genomic regions revealed discordant topological structures. Recombination analysis indicates that CH-ZXY1 is a recombinant resulting from recombination between HPeV5 and HPeV1, which was confirmed by PCR covering the recombination breakpoint.

Molecular epidemiology of enterovirus and parechovirus infections according to patient age over a 4-year period in Spain

The epidemiology and clinical association of enterovirus (EV) and parechovirus (HPeV) infections, as well as the type-distribution-according-to-age, were determined during a 4-year study period in Spain. During 2010-2013, a total of 21,832 clinical samples were screened for EV and the detection frequency was 6.5% (1,430). Of the total EV-negative samples, only 1,873 samples from 2011 to 2013 were available for HPeV testing. HPeV was detected in 42 (2%) of them. Positive samples were genotyped using PCR and sequencing. EV infections occurred in all age groups of patients: neonates (17%), children 28 days to 2 years (29%), children 2-14 years (40%), and adults (14%). Thirty-four different EV types were identified. HPeV infections were detected exclusively in infants <8 m (70% neonates, P < 0.05). All but one HPeV were HPeV-3. Differences in type frequency detection were found according to age and clinical manifestation. Coxsackievirus (CV)-B4 (61%), CV-B5 (83%), and HPeV-3 (64%) were more frequent in neonates than in older patients (P < 0.05). Echovirus (E)-3 (60%), E-18 (47%), E-25 (62%), CV-A6 (61%), CV-A16 (72%), and EV-71 (75%) were mainly detected in children 28 days to 2 years (P < 0.05), whereas, E-6 (79%), E-20 (88%), and E-30 (85%) were predominant in children >2 years and adults (P < 0.05). Clinically, meningitis was associated with EV (P < 0.01) whereas, encephalitis was more frequent in HPeV-infected patients. CV-B types were associated with myocarditis (90%; P < 0.05) and EV species A with hand-foot-mouth-disease/atypical exanthema (88%; P < 0.05). J. Med. Virol. 89:435-442, 2017. © 2016 Wiley Periodicals, Inc.

Stable long-term cultures of self-renewing B cells and their applications

Monoclonal antibodies are essential therapeutics and diagnostics in a large number of diseases. Moreover, they are essential tools in all sectors of life sciences. Although the great majority of monoclonal antibodies currently in use are of mouse origin, the use of human B cells to generate monoclonal antibodies is increasing as new techniques to tap the human B cell repertoire are rapidly emerging. Cloned lines of immortalized human B cells are ideal sources of monoclonal antibodies. In this review, we summarize our studies to the regulation of the replicative life span, differentiation, and maturation of B cells that led to the development of a platform that uses immortalization of human B cells by in vitro genetic modification for antibody development. We describe a number of human antibodies that were isolated using this platform and the application of the technique in other species. We also discuss the use of immortalized B cells as antigen-presenting cells for the discovery of tumor neoantigens.

Detection of Human Parechoviruses in Clinical and Municipal Wastewater Samples in Miyagi, Japan, in 2012-2014

In order to study the epidemiology of human parechovirus (HPeV) infections and to evaluate the feasibility of environmental surveillance, we analyzed 281 stool samples, 265 nasopharyngeal swab samples, and 79 municipal wastewater samples for HPeV. The samples were collected in Miyagi Prefecture, Japan, between April 2012 and March 2014. HPeV was detected by reverse-transcription-PCR targeting the partial 5'-untranslated region and was genotyped by sequencing the capsid VP1 region. Seven stool samples (2.5%) and 1 nasopharyngeal swab sample (0.4%), all of which were from children under 2 years old, and 14 wastewater samples (18%) were positive for HPeV. Clear seasonality was observed: all positive samples were collected between July and December during the study period. All strains detected in the stool and wastewater samples had genotype HPeV1, and the strain from the nasopharyngeal swab sample had genotype HPeV6. A phylogenetic analysis revealed that all HPeV1 strains from the stool samples cluster together with those from the wastewater samples, indicating that the HPeV1 strains circulating in human populations can also be detected in municipal wastewater.

Structural Basis of Human Parechovirus Neutralization by Human Monoclonal Antibodies

Since it was first recognized in 2004 that human parechoviruses (HPeV) are a significant cause of central nervous system and neonatal sepsis, their clinical importance, primarily in children, has started to emerge. Intravenous immunoglobulin treatment is the only treatment available in such life-threatening cases and has given moderate success. Direct inhibition of parechovirus infection using monoclonal antibodies is a potential treatment. We have developed two neutralizing monoclonal antibodies against HPeV1 and HPeV2, namely, AM18 and AM28, which also cross-neutralize other viruses. Here, we present the mapping of their epitopes using peptide scanning, surface plasmon resonance, fluorescence-based thermal shift assays, electron cryomicroscopy, and image reconstruction. We determined by peptide scanning and surface plasmon resonance that AM18 recognizes a linear epitope motif including the arginine-glycine-aspartic acid on the C terminus of capsid protein VP1. This epitope is normally used by the virus to attach to host cell surface integrins during entry and is found in 3 other viruses that AM18 neutralizes. Therefore, AM18 is likely to cause virus neutralization by aggregation and by blocking integrin binding to the capsid. Further, we show by electron cryomicroscopy, three-dimensional reconstruction, and pseudoatomic model fitting that ordered RNA interacts with HPeV1 VP1 and VP3. AM28 recognizes quaternary epitopes on the capsid composed of VP0 and VP3 loops from neighboring pentamers, thereby increasing the RNA accessibility temperature for the virus-AM28 complex compared to the virus alone. Thus, inhibition of RNA uncoating probably contributes to neutralization by AM28.

IMPORTANCE

Human parechoviruses can cause mild infections to severe diseases in young children, such as neonatal sepsis, encephalitis, and cardiomyopathy. Intravenous immunoglobulin treatment is the only treatment available in such life-threatening cases. In order to develop more targeted treatment, we have searched for human monoclonal antibodies that would neutralize human parechoviruses 1 and 2, associated with mild infections such as gastroenteritis and severe infections of the central nervous system, and thus allow safe treatment. In the current study, we show how two such promising antibodies interact with the virus, modeling the atomic interactions between the virus and the antibody to propose how neutralization occurs. Both antibodies can cause aggregation; in addition, one antibody interferes with the virus recognizing its target cell, while the other, recognizing only the whole virus, inhibits the genome uncoating and replication in the cell.