Back to the future: Advances in development of broad-spectrum capsid-binding inhibitors of enteroviruses

The hydrophobic pocket within viral capsid protein 1 is a target to combat the rhino- and enteroviruses (RV and EV) using small molecules. The highly conserved amino acids lining this pocket enable the development of antivirals with broad-spectrum of activity against numerous RVs and EVs. Inhibitor binding blocks: the attachment of the virion to the host cell membrane, viral uncoating, and/or production of infectious virus particles. Syntheses and biological studies of the most well-known antipicornaviral capsid binders have been reviewed and we propose next steps in this research.

Surveillance of Enteric Viruses and Thermotolerant Coliforms in Surface Water and Bivalves from a Mangrove Estuary in Southeastern Brazil

This study was conducted to evaluate the microbiological quality of a mangrove estuary in the Vitória Bay region, Espírito Santo, Brazil. We analyzed the presence and concentration of enteric viruses and thermotolerant coliforms in water, mussels (Mytella charruana and Mytella guyanensis), and oysters (Crassostrea rhizophorae), collected over a 13-month period. Human adenovirus, rotavirus A (RVA), and norovirus genogroup II were analyzed by quantitative PCR. The highest viral load was found in RVA-positive samples with a concentration of 3.0 × 10⁴ genome copies (GC) L^-1 in water samples and 1.3 × 10⁵ GC g^-1 in bivalves. RVA was the most prevalent virus in all matrices. Thermotolerant coliforms were quantified as colony-forming units (CFU) by the membrane filtration method. The concentration of these bacteria in water was in accordance with the Brazilian standard for recreational waters (< 250 CFU 100 mL^-1) during most of the monitoring period (12 out of 13 months). However, thermotolerant coliform concentrations of 3.0, 3.1, and 2.6 log CFU 100 g^-1 were detected in M. charruana, M. guyanensis, and C. rhizophorae, respectively. The presence of human-specific viruses in water and bivalves reflects the strong anthropogenic impact on the mangrove and serves as an early warning of waterborne and foodborne disease outbreaks resulting from the consumption of shellfish and the practice of water recreational activities in the region.

Molecular detection and genotypic characterization of enteric adenoviruses in a hospital wastewater

Hospital wastewater (HWW) represents a major source of the diffusion of many antibiotics and some toxic pathogenic microorganisms in the aquatic environment. Sanitation services play a critical role in controlling transmission of numerous waterborne pathogens, especially enteric human adenoviruses (HAdVs) that can cause acute gastroenteritis. This study intended to evaluate the human adenoviruses (HAdVs) detection rates, to determine the genotype of these viruses and to assess the efficiency of HAdVs removal in hospital pilot wastewater treatment plant (PWWTP) in Tunis City, Tunisia. Therefore, hospital wastewater samples (n = 102) were collected during the study year from the two biological wastewater treatment techniques: natural oxidizing ponds and the rotating biological disks or biodisks. Nested polymerase chain reaction (Nested PCR) was used to evaluate the HAdVs detection rates. The genotype of HAdVs positive samples was achieved by the sequencing of the PCR products. HAdVs were detected in 64% (65/102) of positive wastewater samples. A substantial increase in the frequencies of HAdVs was observed at the exit of the two wastewater treatment techniques studied. The typing of HAdVs species F showed the occurrence of only HAdVs type 41. This data acquired for the first time in Tunisia showed high persistence and survival of HAdVs in the two biological wastewater treatment techniques experienced, and mainly highlighted the poor virological quality of the treated wastewater intended for recycling, agriculture reuse, and discharges into the natural receiving environments. Consequently, tertiary wastewater treatment appeared necessary in this case to decrease the load of enteric viruses flowing in the water environment.

Effect of T68A/N126Y mutations on the conformational and ligand binding landscape of Coxsackievirus B3 3C protease

3C protease of Coxsackievirus B3 (CVB3) plays an essential role in the viral replication cycle, and therefore, emerged as an attractive therapeutic target for the treatment of human diseases caused by CVB3 infection. In this study, we report the first account of the molecular impact of the T68A/N126Y double mutant (Mutant(Bound)) using an integrated computational approach. Molecular dynamics simulation and post-dynamics binding free energy, principal component analysis (PCA), hydrogen bond occupancy, SASA, R(g) and RMSF confirm that T68A/N126Y instigated an increased conformational flexibility due to the loss of intra- and inter-molecular hydrogen bond interactions and other prominent binding forces, which led to a decreased protease grip on the ligand (3CPI). The double mutations triggered a distortion orientation of 3CPI in the active site and decreases the binding energy, ΔG(bind) (∼3 kcal mol(-1)), compared to the wild type (Wild(Bound)). The van der Waals and electrostatic energy contributions coming from residues 68 and 126 are lower for Mutant(Bound) when compared with Wild(Bound). In addition, variation in the overall enzyme motion as evident from the PCA, distorted hydrogen bonding network and loss of protein-ligand interactions resulted in a loss of inhibitor efficiency. The comprehensive molecular insight gained from this study should be of great importance in understanding the drug resistance against CVB3 3C protease; also, it will assist in the designing of novel Coxsackievirus B3 inhibitors with high ligand efficacy on resistant strains.

Concentration of enteric viruses in large volumes of water using a cartridge-type mixed cellulose ester membrane

A viral adsorption-elution method using a flat/disk-type electronegative membrane (diameter of 47-90 mm) has been widely utilized to concentrate viruses in relatively small volumes of water (up to 10 L) due to limited filtration area. In the present study, we aimed to develop a virus concentration method that is based on the same principle and yet allows concentration of large volumes of water using a cartridge-type electronegative membrane. We modified two electronegative membrane-based methods for this purpose (i.e., Mg(2+) method and Al(3+) method) and determined recovery efficiencies of poliovirus and murine norovirus inoculated in water samples. The virus recovery efficiency of the Al(3+) method substantially decreased as the volume of water sample increased. In contrast, Mg(2+) method showed stable virus recovery efficiencies (10-54 %) even when 40 to 1,000 L of river and tap water samples were processed. The volume of the concentrate (400 mL) can be further reduced to 1.5 mL by a Centricon plus-70 centrifugal ultrafiltration device with overall recovery efficiencies of 8.8-16 %. Our results demonstrated that the newly developed virus concentration method enables detection of as low as 10(1) copies/L of viruses in water samples.

Structure determination of enterovirus 71

Enterovirus 71 is a picornavirus that causes hand, foot and mouth disease but may induce fatal neurological illness in infants and young children. Enterovirus 71 crystallized in a body-centered orthorhombic space group with two particles in general orientations in the crystallographic asymmetric unit. Determination of the particle orientations required that the locked rotation function excluded the twofold symmetry axes from the set of icosahedral symmetry operators. This avoided the occurrence of misleading high rotation-function values produced by the alignment of icosahedral and crystallographic twofold axes. Once the orientations and positions of the particles had been established, the structure was solved by molecular replacement and phase extension.

Structural basis for antiviral inhibition of the main protease, 3C, from human enterovirus 93

Members of the Enterovirus genus of the Picornaviridae family are abundant, with common human pathogens that belong to the rhinovirus (HRV) and enterovirus (EV) species, including diverse echo-, coxsackie- and polioviruses. They cause a wide spectrum of clinical manifestations ranging from asymptomatic to severe diseases with neurological and/or cardiac manifestations. Pandemic outbreaks of EVs may be accompanied by meningitis and/or paralysis and can be fatal. However, no effective prophylaxis or antiviral treatment against most EVs is available. The EV RNA genome directs the synthesis of a single polyprotein that is autocatalytically processed into mature proteins at Gln↓Gly cleavage sites by the 3C protease (3C(pro)), which has narrow, conserved substrate specificity. These cleavages are essential for virus replication, making 3C(pro) an excellent target for antivirus drug development. In this study, we report the first determination of the crystal structure of 3C(pro) from an enterovirus B, EV-93, a recently identified pathogen, alone and in complex with the anti-HRV molecules compound 1 (AG7404) and rupintrivir (AG7088) at resolutions of 1.9, 1.3, and 1.5 Å, respectively. The EV-93 3C(pro) adopts a chymotrypsin-like fold with a canonically configured oxyanion hole and a substrate binding pocket similar to that of rhino-, coxsackie- and poliovirus 3C proteases. We show that compound 1 and rupintrivir are both active against EV-93 in infected cells and inhibit the proteolytic activity of EV-93 3C(pro) in vitro. These results provide a framework for further structure-guided optimization of the tested compounds to produce antiviral drugs against a broad range of EV species.

[Sequence and antigenicity analysis for VP4s of EV71 strains isolated from Children in Beijing]

In order to learn about the correlation between the sequences of VP4 of EV71 and clinical symptoms of patients and analyze the antigenicity of VP4 of EV71, as well as the cross-reactivity with VP4 of CA16, the sequences of VP4 gene from 10 EV71 strains isolated from infants and children with hand, foot and mouth diseases (HFMD) during 2007 to 2009 were determined through standard molecular cloning protocols, and the results were analyzed by EditSeq and MegAlign of DNAStar. Full-length genes of VP4s of EV71 and CA16 were amplified from virus isolates and expressed in E. coli. Then the expressed VP4s were used as antigens to detect IgG antibody in 189 sera samples from people taking health check up and patients of non-HFMD by Western-Blot. They were also used to detect IgM antibody in 14 of sera samples from infants and children with EV71 infection and 12 of sera samples from those with CA16 infection. The nucleotides identities among these 10 sequences of VP4s isolated in our lab were 94.20% - 100.00% and the deduced amino acids were identical. There was no consistent divergence between the sequences of serious cases and those from general HFMD cases. Phylogenetic analysis based on VP4s indicated that these 10 VP4s of EV71 belonged to C4. The nucleotide identities between EV71 VP4 (s67) and CA16 VP4 (s401) was 69.60% and the deduced amino acids identities was 78.60%. In the detection of IgG, the sera-positive rate for EV71 VP4 was 38.10% and the sera-positive rate of CA16 VP4 was 58.20%. The difference in the sera-positive rate between them was significant (chi2 = 15.30, P < 0.01), suggesting that the expressed VP4s of EV71 and CA16 were of good antigenicity and not cross-reactive. There was no positive reaction detected for IgM against VP4s for EV71 or CA16. The data from this study reveal important information for the further study of EV71.

Quantitative real-time PCR of enteric viruses in influent and effluent samples from wastewater treatment plants in Italy

The prevalence of enteric viruses in wastewater, the efficacy of wastewater treatments in eliminating such viruses, and potential health risks from their release into the environment or by recycling of treated wastewaters, are very important issues in environmental microbiology. In this study we performed a quantitative TaqMan real-time PCR (polymerase chain reaction) analysis of enteric viruses on samples of influents and effluents from 5 wastewater treatment plants in and around Rome. Three epidemiologically important, waterborne enteric viruses were analyzed: adenoviruses, enteroviruses and noroviruses (GI and GII) and compared to classical bacterial indicators of fecal contamination. The concentration of adenoviruses was the highest, in both raw and treated waters. Mean values in influents were ranked as follows: adenovirus > norovirus GI > norovirus GII > enterovirus. In effluents, the ranking was: adenovirus > norovirus GI > enterovirus > norovirus GII. Removal efficiencies ranged from 35% (enterovirus) to 78% (norovirus GI), while removal efficiency for bacterial indicators was up to 99%. Since molecular quantification does not necessarily indicate an actual threat to human health, we proceeded to evaluate the infectivity of enterovirus particles in treated effluents through integrated cell culture and real-time PCR. Infectivity assays detected live virions in treated water, pointing to potential public health risks through the release of these viruses into the environment. A better understanding of viral presence and resistance to sewage purification processes have the potential of contributing to the effective management of risks linked to the recycling of treated wastewater, and its discharge into the environment.

[Preparation and identification of the monoclonal antibodies against VP1 capsid protein of Enterovius 71]

OBJECTIVE

To prepare monoclonal antibodies (McAbs) against VP1 capsid protein of Enterovirus 71.

METHODS

Two peptides, SP55 and SP70, containing amino acid 163-177 and 208-222 of VP1, were synthesized respectively. Immunized BALB/c mice with the synthetic peptides to establish the hybridoma cell strains secreting specific McAb to VP1. After the specific McAbs were prepared, identified and analyzed the titer by indirect ELISA assay. The positive clones were selected and their neutralization titer were determined by neutralization test.

RESULTS

Two high titered anti-VP1 antibodies secreted by the hybridoma cells showed good neutralization reaction with enterovirus 71 on RD cells, and the neutralization titer were 1:8 and 1:16 respectively.

CONCLUSION

Two high titered anti-VP1 antibodies, with good neutralization activity, secreted by the hybridoma cells, which lays the foundation for further study.

[Expression of recombinant VP1 protein of enterovirus 71 and development of serological assay for detection of EV71 infection]

OBJECTIVE

To obtain a recombinant purified Enterovirus 71 VPI protein and establishment of an early, rapid and accurate serological ELISA (enzyme-linked immunosorbent assay) for detection of EV71 infection.

METHODS

VP1 gene was amplified by PCR and clonel into pET-21b (+) vector, the positive recombinant plasmid were transformed into E. coli BI21(DE3), and was induced with IPTG, the recombinant protein by SDS-PAGE and Western Blot assays. Finally, the recombinant purified VP1 protein was used as a coated antigen for detection of serum anti-IgM and IgG against EV71 by ELISA.

RESULTS

The purified VP1 was obtained, and it can be recognized by sera of patients with EV71 infection associated with hand-foot-mouth disease. The A values of anti-EV71 IgM and IgG were significantly elevated as compared to healthy objects and HFMD patients without EV71 infection (P < 0.05). The sensitivity and specificity of IgM to EV71 were 73% and 77% compared with the RT-PCR results, respectively;and those of IgG being 82% and 83%, respectively.

CONCLUSIONS

The recombinant protein VP1 was produced and purified, and it was proved to have a good antigenicity and could be used to develop a serological diagnosis kit for EV71 infection in the future.

Nanoengineering artificial lipid envelopes around adenovirus by self-assembly

We have developed a novel, reproducible, and facile methodology for the construction of artificial lipid envelopes for adenoviruses (Ad) by self-assembly of lipid molecules around the viral capsid. No alteration of the viral genome or conjugation surface chemistry at the virus capsid was necessary, therefore difficulties in production and purification associated with generating most surface-modified viruses can be eliminated. Different lipid bilayer compositions produced artificially enveloped Ad with physicochemical and biological characteristics determined by the type of lipid used. Physicochemical characteristics such as vector size, degree of aggregation, stability, and surface charge of the artificially enveloped Ad were correlated to their biological (gene transfer) function. In monolayer cell cultures, binding to the coxsackie and adenovirus receptor (CAR) was blocked using a zwitterionic envelope, whereas enhanced binding to the cell membrane was achieved using a cationic envelope. Envelopment of Ad by both zwitterionic and cationic lipid bilayers led to almost complete ablation of gene expression in cell monolayers, due to blockage of virion endosomal escape. Alternatively, artificial Ad envelopes built from lipid bilayers at the fluid phase in physiological conditions led to enhanced penetration of the vectors inside a three-dimensional tumor spheroid cell culture model and delayed gene expression in the tumor spheroid compared to nonenveloped adenovirus. These results indicate that construction of artificial envelopes for nonenveloped viruses by lipid bilayer wrapping of the viral capsids constitutes a general strategy to rationally engineer viruses at the nanoscale with control over their biological properties.

Attachment of enteric viruses to bottles

Storage of water that was deliberately contaminated with enteric viruses in polyethylene terephthalate (PET) bottles led to a rapid decrease of the apparent viral load, thereby hampering the development of samples for a collaborative evaluation of viral detection methods for bottled water. To determine if this decrease was due to spontaneous inactivation or to adhesion, an elution protocol was developed and combined with a rapid and sensitive real-time reverse transcription-PCR-based method to quantify adsorbed norovirus (NV), hepatitis A virus (HAV), and rotavirus (RV) on bottle walls. The NV retention on PET bottle walls after 20 and 62 days reached an average level of 85% and 95% of the recovered inoculum, respectively. HAV and RV also showed adsorption onto PET bottles, reaching 90% and 80%, respectively, after 20 days of storage. NV and RV attachment was demonstrated to be dependent on the presence of autochthonous flora, whereas HAV adsorption was independent of it. Application of the elution and viral detection protocol to 294 commercially available water bottles obtained from 25 different countries did not give any positive result, thereby providing further evidence that the sources used for this product are free from enteric viruses and support for the theory that bottled water is not a vehicle for viral diseases.

Recombinant Newcastle Disease virus capsids displaying enterovirus 71 VP1 fragment induce a strong immune response in rabbits

The complete VP1 protein of EV71 was truncated into six segments and fused to the C-terminal ends of full-length nucleocapsid protein (NPfl) and truncated NP (NPt; lacks 20% amino acid residues from its C-terminal end) of newcastle disease virus (NDV). Western blot analysis using anti-VP1 rabbit serum showed that the N-terminal region of the VP1 protein contains a major antigenic region. The recombinant proteins carrying the truncated VP1 protein, VP1(1-100), were expressed most efficiently in Escherichia coli as determined by Western blot analysis. Electron microscopic analysis of the purified recombinant protein, NPt-VP(1-100) revealed that it predominantly self-assembled into intact ring-like structures whereas NPfl-VP(1-100) recombinant proteins showed disrupted ring-like formations. Rabbits immunized with the purified NPt-VP(1-100) and NPfl-VP(1-100) exhibited a strong immune response against the complete VP1 protein. The antisera of these recombinant proteins also reacted positively with authentic enterovirus 71 and the closely related Coxsackievirus A16 when analyzed by an immunofluorescence assay suggesting their potential as immunological reagents for the detection of anti-enterovirus 71 antibodies in serum samples.

Modeling the Ligand−Receptor Interaction for a Series of Inhibitors of the Capsid Protein of Enterovirus 71 Using Several Three-Dimensional Quantitative Structure−Activity Relationship Techniques

The structure of enterovirus 71 (EV71) capsid protein VP1 has been constructed by using homology modeling and molecular dynamics simulation techniques. The ligand structures were a series of EV71 VP1 inhibitors synthesized by Shia et al. in 2002 and Chern et al. in 2004. The training set was selected by the VOLSURF4.1/PCA program and the IC50 values varied from 0.06 to 10.83 microm. Then, the training set was analyzed by the following three-dimensional quantitative structure-activity relationship techniques: CoMFA, CoMSIA, CATALYST4.9, and VOLSURF4.1/PCA. The model generated by a two-stage flexible docking procedure and without any structural alignment has far more significant statistics. Highly accurate activities for the test sets were then predicted by the top hypothesis of the CATALYST program and were compared with those predicted by CoMFA, CoMSIA, and VOLSURF. These studies identified some important clues for searching or making more potent inhibitors against the EV71 infection.

Structure of the virus capsid protein VP1 of enterovirus 71 predicted by some homology modeling and molecular docking studies

The homology modeling technique has been used to construct the structure of enterovirus 71 (EV 71) capsid protein VP1. The protein is consisted of 297 amino acid residues and treated as the target. The amino acid sequence identity between the target protein and sequences of template proteins 1EAH, 1PIV, and 1D4M searched from NCBI protein BLAST and WorkBench protein tools were 38, 37, and 36%, respectively. Based on these template structures, the protein model was constructed by using the InsightII/Homology program. The protein model was briefly refined by energy minimization and molecular dynamics (MD) simulation steps. The protein model was validated using some web available servers such as ERRAT, PROCHECK, PROVE, and PROSA2003. However, an inconsistency between the docking scores and the measured activity was observed for a series of EV 71 VP1 inhibitors synthesized by Shia et al. (J Med Chem 2002, 45, 1644) and docked into the binding pocket of the protein model using the DOCK 4.0.2 program. The protein model with an EV 71 VP1 inhibitor docked and engulfed was then refined further by some MD simulation steps in the presence of water molecules. The docking scores obtained for these inhibitors after such a MD refinement were well correlated with the activities. The structure-activity relationships for the ligand-protein model system was also analyzed using the GRID-VOLSURF programs and the corresponding noncrossvalidated and crossvalidated (by leave-one-out) r2 and q2 were 0.99 and 0.61, respectively. The hydrophobic nature of the binding pocket of the protein model was also examined using the GRID21 program. The possibility of improving the potency of the current series of EV 71 VP1 inhibitors was discussed based on all the studies presented.

Chemical synthesis of picornaviral protein primers of RNA replication

Naturally occurring nucleopeptidic replication primers (VPg-pUpU) of poliovirus and coxsackie virus were chemically synthesized. The synthesis was accomplished via block-coupling of two minimally protected fragments of the target structures: a short RNA-nucleopeptide and a longer peptide segment containing diverse side-chain functionalities. The synthetic VPg-pUpU of coxsackie virus was characterized by NMR spectroscopy.

Evidence for neuronal localisation of enteroviral sequences in motor neurone disease/amyotrophic lateral sclerosis by in situ hybridization

Sequences resembling those of human enterovirus type B sequences have been associated with motor neurone disease/amyotrophic lateral sclerosis. In a previous study we detected enteroviral sequences in spinal cord/brain stem from cases of motor neurone disease/amyotrophic lateral sclerosis, but not controls. Adjacent tissue sections to two of those strongly positive for these sequences by reverse-transcriptase polymerase chain reaction were analyzed by in situ hybridization with digoxigenin-labelled virus-specific antisense riboprobes. In one case, a female aged 83 showing 12 month rapid progressive disease, signal was specifically localized to cells identifiable as motor neurones of the anterior horn. In another case, a male aged 63 with a 60-month history of progressive muscle weakness, dysarthia, dyspnoea and increased tendon reflexes, signal was located to neurones in the gracile/cuneate nuclei of the brain stem tissue block that had been analyzed. This case showed loss of neurones in the anterior horn of the spinal cord by histopathologic examination which would account for clinical signs of motor neurone disease/amyotrophic lateral sclerosis. Dysfunction of the gracile/cuneate nuclei might have been masked by the paralytic disease. These structures are adjacent to the hypoglossal nuclei, and suggest either localised dissemination from hypoglossal nuclei or a possible route of dissemination of infection through the brainstem to the hypoglossal nuclei. These findings provide further evidence for the possible involvement of enteroviruses in motor neurone disease/amyotrophic lateral sclerosis.

NMR structures of loop B RNAs from the stem-loop IV domain of the enterovirus internal ribosome entry site: a single C to U substitution drastically changes the shape and flexibility of RNA

The 5'-untranslated region of positive-strand RNA viruses harbors many cis-acting RNA structural elements that are important for various viral processes such as replication, translation, and packaging of new virions. Among these is loop B RNA of the stem-loop IV domain within the internal ribosomal entry site (IRES) of enteroviruses, including Poliovirus type 1 (PV1). Studies on PV1 have shown that specific recognition of loop B by the first KH (hnRNP K homology) domain of cellular poly(rC)-binding protein 2 (PCBP2) is essential for efficient translation of the viral mRNA. Here we report the NMR solution structures of two representative sequence variants of enteroviral loop B RNA. The two RNA variants differ at only one position (C vs U) within a six-nucleotide asymmetric internal loop sequence that is the binding site for the PCBP2 KH1 domain. Surprisingly, the two RNAs are drastically different in the overall shape and local dynamics of the bulge region. The RNA with the 5'-AUCCCU bulge sequence adopts an overall L shape. Its bulge nucleotides, especially the last four, are highly flexible and not very well defined by NMR. The RNA with the 5'-AUUCCU bulge sequence adopts an overall U shape, and its bulge sequence exhibits only limited flexibility. A detailed analysis of the two RNA structures and their dynamic properties, as well as available sequence data and known KH domain-RNA complex structures, not only provides insights into how loop B RNA might be recognized by the PCBP2 KH1 domain but also suggests a possible correlation between structural flexibility and pre-existing structural features for protein recognition.

Coxsackievirus and adenovirus receptor (CAR) is modified and shed in membrane vesicles

Vesicles shed by U87-MG cells contain coxsackievirus and adenovirus receptor (CAR) protein that has been posttranslationally modified. Relative to full-length CAR, migration of the vesicle-associated soluble CAR antigen (CARd6) on SDS-polyacrylamide gels indicated a loss of approximately 6 kDa. HeLa and END-HHV6 cells also shed a similar vesicle-associated CAR protein. Vesicles shed by U87-MG cells following stimulation with calcium and A23187 contained CARd6 similar to that present in vesicles shed constitutively. RD cells transfected to express full-length CAR produced CARd6, but cells that expressed CAR with a truncated cytoplasmic domain produced no equivalent to CARd6. In U87-MG cells, calpain activity was required for release of CARd6 with shed vesicles, and accumulation of CARd6 in cells that rounded up and released from the plastic substrate in response to A23187 treatment was blocked by N-ethylmaleimide. These experiments show that CAR, posttranslationally modified in the cytoplasmic domain, can be released with vesicles shed by cells. Posttranslational modification of the CAR cytoplasmic domain occurs during cell rounding and release from the culture substrate. This modified, vesicle-associated CAR was the principal form of soluble CAR released by the cells.

Virucidal efficacy of glutaraldehyde against enteroviruses is related to the location of lysine residues in exposed structures of the VP1 capsid protein

Glutaraldehyde (GTA) is a potent virucidal disinfectant whose exact mode of action against enteroviruses is not understood. Earlier reports showed that GTA reacts preferentially with the VP1 capsid protein of echovirus 25 and poliovirus 1 and that GTA has affinity for exposed lysine residues on proteins. To investigate further the inactivation of enteroviruses by GTA, seven strains were selected on the basis of differences in their overall number and the positions of lysine residues in the amino acid sequences of the VP1 polypeptide. Inactivation kinetics experiments were performed with 0.10% GTA. The viruses grouped into three clusters and exhibited significantly different levels of sensitivity to GTA. The results were analyzed in the light of current knowledge of the three-dimensional structure of enteroviruses and the viral life cycle. The differences observed in sensitivity to GTA were related to the number of lysine residues and their locations in the VP1 protein. The overall findings suggest that the BC and DE loops, which cluster at the fivefold axis of symmetry and are the most exposed on the outer surface of the virions, are primary reactive sites for GTA.

The coxsackievirus 2B protein suppresses apoptotic host cell responses by manipulating intracellular Ca2+ homeostasis

Enteroviruses, small cytolytic RNA viruses, confer an antiapoptotic state to infected cells in order to suppress infection-limiting apoptotic host cell responses. This antiapoptotic state also lends protection against cell death induced by metabolic inhibitors like actinomycin D and cycloheximide. The identity of the viral antiapoptotic protein and the underlying mechanism are unknown. Here, we provide evidence that the coxsackievirus 2B protein modulates apoptosis by manipulating intracellular Ca(2+) homeostasis. Using fluorescent Ca(2+) indicators and organelle-targeted aequorins, we demonstrate that ectopic expression of 2B in HeLa cells decreases the Ca(2+) content of both the endoplasmic reticulum and the Golgi, resulting in down-regulation of Ca(2+) signaling between these stores and the mitochondria, and increases the influx of extracellular Ca(2+). In our studies of the physiological importance of the 2B-induced alterations in Ca(2+) signaling, we found that the expression of 2B suppressed caspase activation and apoptotic cell death induced by various stimuli, including actinomycin D and cycloheximide. Mutants of 2B that were defective in reducing the Ca(2+) content of the stores failed to suppress apoptosis. These data implicate a functional role of the perturbation of intracellular Ca(2+) compartmentalization in the enteroviral strategy to suppress intrinsic apoptotic host cell responses. The putative down-regulation of an endoplasmic reticulum-dependent apoptotic pathway is discussed.

RNA extraction for quantitative enterovirus RT-PCR: comparison of three methods

Quantification of virus-like RNA sequences in biological fluids, like serum and cerebrospinal fluid, requires an RNA extraction method that is both reproducible and fast. Three RNA extraction methods were tested on enteroviruses: (1) the acid guanidine thiocyanate-phenol/chloroform (AGPC) method; (2) a method based on differential precipitation of the RNA and (3) a 'bind-wash-elute' system based on silica-gel membrane binding. The latter two methods yielded a comparable detection limit as measured by RT-PCR ELISA. The detection limit for the AGPC method was 10 times higher. The relative standard deviation for the bind-wash-elute method (3%) was superior to that of the other methods tested (both 20%) and provides a reliable and fast method to extract (viral) RNA from biological fluids for quantification by RT-PCR.

Bovine lactoferrin inhibits adenovirus infection by interacting with viral structural polypeptides

We recently demonstrated that lactoferrin, an antimicrobial glycoprotein, can inhibit adenovirus infection by competing for common glycosaminoglycan receptors. This study further characterizes the antiadenovirus activity of the protein, thus demonstrating that lactoferrin neutralizes infection by binding to adenovirus particles and that its targets are viral III and IIIa structural polypeptides.

Multimerization reactions of coxsackievirus proteins 2B, 2C and 2BC: a mammalian two-hybrid analysis

Recently, homomultimerization and heteromultimerization reactions of the poliovirus P2 region proteins were investigated using a yeast two-hybrid approach (Cuconati et al., Journal of Virology 72, 1297-1307, 1998). In this study, we investigated multimerization reactions of the 2B, 2C and 2BC proteins of the closely related coxsackie B3 virus (CBV3) using a mammalian two-hybrid system. This system allows the characterization of protein:protein interactions within a cellular environment that more closely mimics the native protein environment. Homomultimerization reactions were observed with the 2BC protein and, albeit weakly, with the 2B protein, but not with the 2C protein. To identify the determinants involved in the 2BC and 2B homomultimerization reactions, several mutants containing deletions or point mutations in the 2B region were tested. Disruption of the hydrophobic character of either the cationic amphipathic alpha-helix or the second hydrophobic domain of the 2B protein disturbed both the 2BC:2BC and the 2B:2B homomultimerization reactions. Disruption of either the cationic or the amphipathic character of the alpha-helix or deletion of the N-terminal 30 amino acids of the 2B protein, however, had no effect on the 2BC and 2B homomultimerization reactions. Heteromultimerization reactions were observed between proteins 2BC and 2B, and also between proteins 2BC and 2C, but not between the 2B and 2C proteins. The 2BC:2B and 2BC:2C heteromultimerization reactions were also mediated by hydrophobic determinants located in the amphipathic alpha-helix and the second hydrophobic domain. The nature of the interactions and their implications for the virus life-cycle are discussed.

Enterovirus sequences resembling coxsackievirus A2 detected in stool and spleen from a girl with fatal myocarditis

A 10-year-old girl who died suddenly was found at post mortem to have myocarditis. Virus could not be cultured from post-mortem stool, spleen or heart but enterovirus RNA was detected in stool and spleen by PCR, and the stool caused flaccid paralysis in newborn suckling mice. A 654 base pair (bp) sequence from the capsid-coding region of the viral genome was amplified from an affected mouse and sequenced. Using this sequence, strain-specific nested primers were designed and used to amplify viral sequences directly from stool and spleen. These sequences were identical to each other and to that obtained from the infected mouse, and most closely resembled Coxsackievirus A2, an uncommon serotype rarely associated with myocarditis. Testing spleen tissue may be useful in etiological investigation of suspected viral myocarditis. PCR proved more sensitive than suckling mouse inoculation in detecting this Coxsackievirus, but a combination of both methods was required for genotypic characterization.

Foot-and-mouth disease virus can utilize the C-terminal extension of coxsackievirus A9 VP1 for cell infection

Foot-and-mouth disease virus (FMDV) is known to employ the conserved Arg-Gly-Asp (RGD) tripeptide located on the variable betaG-betaH loop of the VP1 capsid protein for binding to cells. Coxsackievirus A9 (CAV9) also carries an RGD sequence, but on a short C-terminal extension of its VP1 and in a different amino acid context. This apparent relationship raised the question of whether insertion of the heterologous CAV9 sequence into FMDV would influence infection by the genetically modified FMDV. Four VP1 mutants were generated by PCR mutagenesis of a full-length FMDV cDNA plasmid. After transfection of BHK-21 cells, viral protein synthesis and virus particle formation could be detected. Two of the four mutants, mV9b and mV9d, could be propagated in BHK-21 cells, but not in CV-1 cells. Both of these mutants contained 17 amino acids of the C terminus of CAV9 VP1. Infection of BHK cells could be specifically inhibited by rabbit immune serum raised against a synthetic peptide representing the amino acid sequence of the C-terminal extension of CAV9 VP1. This demonstrated the direct involvement of the inserted sequence in cell infection. In fact, genetically modified FMDV O(1)K was capable of employing the VP1 C-terminal RGD region of CAV9 for infection of BHK cells. In addition, these results show that, even in cell culture-adapted viruses, the RGD-containing betaG-betaH loop plays an important role in virus infectivity.

Interaction of coxsackievirus A21 with its cellular receptor, ICAM-1

Coxsackievirus A21 (CAV21), like human rhinoviruses (HRVs), is a causative agent of the common cold. It uses the same cellular receptor, intercellular adhesion molecule 1 (ICAM-1), as does the major group of HRVs; unlike HRVs, however, it is stable at acid pH. The cryoelectron microscopy (cryoEM) image reconstruction of CAV21 is consistent with the highly homologous crystal structure of poliovirus 1; like other enteroviruses and HRVs, CAV21 has a canyon-like depression around each of the 12 fivefold vertices. A cryoEM reconstruction of CAV21 complexed with ICAM-1 shows all five domains of the extracellular component of ICAM-1. The known atomic structure of the ICAM-1 amino-terminal domains D1 and D2 has been fitted into the cryoEM density of the complex. The site of ICAM-1 binding within the canyon of CAV21 overlaps the site of receptor recognition utilized by rhinoviruses and polioviruses. Interactions within this common region may be essential for triggering viral destabilization after attachment to susceptible cells.

The N-terminal region of the VP1 protein of swine vesicular disease virus contains a neutralization site that arises upon cell attachment and is involved in viral entry

The N-terminal region of VP1 of swine vesicular disease virus (SVDV) is highly antigenic in swine, despite its internal location in the capsid. Here we show that antibodies to this region can block infection and that allowing the virus to attach to cells increases this blockage significantly. The results indicate that upon binding to the cell, SVDV capsid undergoes a conformational change that is temperature independent and that exposes the N terminus of VP1. This process makes this region accessible to antibodies which block virus entry.

Swine vesicular disease: an overview

Swine vesicular disease (SVD) is a notifiable viral disease of pigs included on the Office International des Epizooties List A. The first outbreak of the disease was recognized in Italy in 1966. Subsequently, the disease has been reported in many European and Asian countries. The causative agent of the disease is SVD virus which is currently classified as a porcine variant of human coxsackievirus B5 and a member of the genus enterovirus in the family picornaviridae. From a clinical point of view, SVD is relatively unimportant, rarely causing deaths and usually only a minor setback to finishing schedules. However, the clinical signs which it produces are indistinguishable from those caused by foot-and-mouth disease, and its presence prevents international trade in pigs and pig products. This article reviews recent findings on all aspects of the virus and the disease which it causes.

Cross-talk between orientation-dependent recognition determinants of a complex control RNA element, the enterovirus oriR

The coxsackie B3 virus oriR is an element of viral RNA thought to promote the assembly of a ribonucleoprotein complex involved in the initiation of genome replication. The mutual orientation of its two helical domains X and Y is determined by a kissing interaction between the loops of these domains. Here, a genetic approach was worked out to identify spatial orientation-dependent recognition signals in these helices. Spatial orientation changes (due to linear and rotational shifts) were introduced by appropriate insertions/deletions of a single base pair into one or both of the domains, and phenotypic consequences caused by these mutations were studied. The insertion of a base pair into domain Y caused a defect in viral reproduction that could be suppressed by a base-pair insertion into domain X. Similarly, a defect in viral replication caused by a base-pair deletion from domain X could be suppressed by a base-pair deletion from domain Y. Thus, certain areas of the two domains should cross-talk to one another in the sense that a change of space position of one of them required an adequate reply (change of space position) from the other. Phenotypic effects of the local rotation of one or more base pairs (and of some other mutations) in either domain X or domain Y suggested that the two most distal base pairs of these domains served as orientation-dependent recognizable signals. The results were also consistent with the notion that the recognition of the distal base pair of domain Y involved a mechanism similar to the intercalation of an amino acid residue.

Enteroviral capsid protein VP1 is present in myocardial tissues from some patients with myocarditis or dilated cardiomyopathy

BACKGROUND

There are still discrepancies in the association of enterovirus and myocardial disease, partially due to lack of data on the detection of virus antigens in tissues. It is desirable to localize enteroviral antigens so as to establish a link between the two and to study mechanisms of virus persistence.

METHODS AND RESULTS

Nineteen fixed explanted or postmortem myocardial samples were obtained from patients with myocarditis or dilated cardiomyopathy (DCM). Control samples were collected from 11 subjects who had died accidentally or of noncardiovascular disease. Viral antigen was detected by an improved immunohistochemical technique using an enterovirus group-specific antibody to viral capsid protein VP1. Nine of 11 myocarditis cases (81.8%) and 6 of 8 DCM cases (75%) were positive. Signals were localized in the cytoplasm of myocytes. Intense immunostaining was observed in acute myocarditis, whereas VP1 was detected in scattered myocytes in chronic myocarditis or DCM. Enteroviral RNA was detected in 6 of 11 myocarditis samples (54.5%) and 3 of 8 DCM samples (37.5%) by the reverse transcription-nested polymerase chain reaction, correlating with antigen detection (kappa=0.6+/-0.21). Neither viral antigen nor RNA was detected in any controls.

CONCLUSIONS

Our findings demonstrate a direct link between enterovirus infection and some myocarditis or DCM cases. The pattern of VP1 detection may correlate with disease stage and severity. The data suggest that viral protein synthesis may be involved in persistent enterovirus infection in the pathogenesis of DCM.

Molecular characterisation of Australian bovine enteroviruses

In this study we report the full length (7.4 kb) sequence of two Australian bovine enterovirus (BEV) isolates, K2577 and SL305 and the partial sequence of a third isolate, 66/27, which are the prototypes of the three major serological groups of BEV in Australia. Australian BEV isolates have not previously been related to the international classification of BEV into the major serotypes BEV-1 and BEV-2. The sequences of the three representative Australian isolates were compared to the full length sequence of a Northern Ireland isolate (VG527) classified as BEV-1, as well as two partial sequences of isolates from the United States and the United Kingdom classified as BEV-2. All three Australian isolates were classified as BEV-1 on the basis of closer nucleotide and amino acid similarity to the 5'-UTR and capsid proteins of VG527 than to the BEV-2 isolates (79-81% versus 76-77% nucleotide identity in the 5-UTR, and 86-98% versus 65-77% amino acid identity in the capsid proteins). These results indicate that most if not all Australian BEV are BEV-1. The remainder of the genome, which encodes non-structural proteins involved in viral replication, showed high sequence homology as has been observed among such genes in other enteroviruses. A system for full-length amplification of BEV isolates was also developed and the K2577 isolate was cloned to obtain a full-length, infectious DNA copy of the BEV genome. When RNA transcripts of BEV amplification products were transfected into MDBK cells infectious particles were produced. These virus particles were identical to the original virus isolates. This system can be used as a basis for the development of BEV-vectored vaccines as well in further molecular studies of bovine enteroviruses.

A genotypic characterization of enteroviral antigenic variants isolated in eastern Canada

Antigenic variation within serotypes of enteroviruses can have a significant impact on the effectiveness of routine diagnosis by neutralization assays. The focus of this particular study was to initiate a genetic characterization of echovirus type 9 (E9) antigenic variants and nontypeable strains isolated in Canada from 1991 to 1993. All variant strains were initially identified by the serological parameter of neutralization 'breakthrough' during conventional serotyping using the Lim-Benyesh-Melnick antiserum pools and by assessing neutralization endpoints using micro-neutralization methodology. Both E9 variant and non-variant isolates were further characterized by sequencing amplicons generated from the VP2 capsid protein-coding region of these particular strains. Variants from the provinces of Ontario and New Brunswick were shown to include a number of genotypically distinct strains and all the variant strains were significantly different from non-variant E9 isolates when nucleotide sequences were compared. A similar genetic analysis of two completely non-typeable isolates from Quebec showed that these viruses seemed to belong to a genetic cluster of enteroviruses that included coxsackievirus A16 and enterovirus 71 serotypes. The use of genetic typing by sequence analysis provides a molecular tool for determining the genotypic diversity of variant and non-typeable isolates and their possible relatedness to other enteroviral strains.

[The physicochemical characterization of the strains isolated during the outbreak of epidemic neuropathy in Cuba. II]

The presence of 2 agents such as a Cox A9 strain and another mild cytopathogenic effect-producing strain, both isolated from patients presenting with epidemic neuropathy is reported in this paper. A mild cutopathogenic effect which was propagated in successive dilutions was developed in the dilution 10(-4) by means of the neutralization test of a Coxsackie A9 virus with its homologous hyperimmune serum. A gradient in saccharose was performed in a mild cytopathogenic effect-producing strain and a typical cytopathogenic effect of an Enterovirus developed from one of the fractions passed in tissular cultures in the presence phosphonoacetic acid (PAA). The possible pathogenic role of these viruses are discussed.

[The physicochemical characterization of the agents isolated during the outbreak of epidemic neuropathy in Cuba. I]

This paper reports on the physical and chemical characteristics of agents isolated from serum samples of patients presenting with epidemic neuropathy. The behaviour of isolated enteroviruses was as described for such viruses. Mild cytopathogenic effects-producing agents behaved in a variable form regarding sensitivity to chloroform; on the other hand they were neither sensitive to phosphonoacetic acid (PAA) nor to guanidine hydrochloride (GHC1) and grew in cells previously treated with bromodeoxyuridine (BDUR). These results suggest the presence of agents resembling enteroviruses and enveloped viruses. Further studies for the characterization of such agents need to be performed.

Differentiation and characterization of enteroviruses by computer-assisted viral protein fingerprinting

We have developed and standardized a computerized method for the typing and characterization of enteroviruses with radiolabeled viral protein fingerprints. Enteroviral proteins were radiolabeled with [35S]methionine during growth in cell culture and were then separated by polyacrylamide gel electrophoresis. The dried gel was scanned, and from the resulting computer image (which resembled an autoradiogram) protein patterns were computer extracted and stored in a database. The enterovirus database contained community and prototype strains belonging to 20 different enteroviral serotypes. Each serotype has a discrete protein pattern, and the most important pattern differences for determining each type are in the region of the viral capsid proteins VP1, VP2, and VP3. When the database was challenged with 148 clinical enterovirus strains, 144 (97%) were correctly identified by using the correlation coefficient as a quantitative measure of relatedness between two patterns. This method can identify a type in a single test and represents a practical alternative to virus neutralization because it is less expensive, is much faster (3 rather than 10 days), and does not rely on any virus-specific reagents. The results also show that most of the strains currently isolated from the community have protein patterns different from those of their older prototype strains. Viral protein fingerprinting is an evolving, dynamic system for the typing and characterization of enteroviruses. The method is appropriate for use in clinical virology and reference laboratories for the typing of enteroviruses, for the study of the epidemiology of enteroviruses, and for surveillance of enteroviruses.

Cell-surface interactions of echovirus 22

Echovirus 22 (EV22) is a picornavirus forming a distinct molecular cluster together with echovirus 23. EV22 has an Arg-Gly-Asp (RGD) peptide motif in its capsid protein VP1; similar motifs are known to mediate many cell-cell and microbe-host interactions. To identify peptide sequences that specifically bind to EV22 and potentially play a role in receptor recognition, we have used here peptide libraries displayed in filamentous phage. We isolated an EV22-binding motif CLRSG(R/F)GC. The synthetic CLRSGRGC peptide was able to inhibit EV22 infection. The infection was also inhibited by an RGD-containing peptide representing the C terminus of the EV22 capsid protein VP1 and CWDDGWLC (an RGD-binding peptide; Pasqualini, R., Koivunen, E., and Ruoslahti, E. (1995) J. Cell Biol. 130, 1189-1196). As the EV22-recognizing sequence LRSG is found in the integrin beta1 chain and the entire LRSGRG hexapeptide occurs in the matrix metalloproteinase 9 (MMP-9), we carried out blocking experiments with anti-integrin and anti-MMP-9 antibodies. EV22 infection could be blocked in cell cultures with anti-alphav, -beta1, and, to a lesser extent, with anti-MMP-9 antibodies. These results imply that EV22 recognizes preferentially alphavbeta1-integrin as a cellular receptor and MMP-9 may also play a role in the cell-surface interactions of the virus.

Amplification and cloning of complete enterovirus genomes by long distance PCR

A method for amplification and cloning of complete enterovirus cDNA genomes is described. Viral RNA was reverse transcribed using an optimized protocol and a reverse transcriptase with reduced RNase H activity. Amplicons corresponding to complete genomes of 14 prototype strains of group B coxsackieviruses and echoviruses were amplified using oligonucleotide primers derived from the Coxsackievirus B3 genomic sequence of the 5' and 3' ends and a mixture of thermostable DNA polymerases. Coxsackievirus B2 amplicon was then cloned and the terminal sequences of the insert were determined. Lipofection of individual clones resulted in productive. Coxsackievirus B2 infection. The method described makes it possible to obtain large amounts of complete enterovirus cDNAs and simplifies the construction of infectious full-length cDNA clones. Successful amplification of all enterovirus prototype strains tested emphasizes the general use of the method described, which provides a rapid and efficient alternative to traditional cloning strategies.

Enterovirus genomes in wastewater: concentration on glass wool and glass powder and detection by RT-PCR

Standard methods for detecting enteroviruses in environmental samples require cell culture, which is time consuming and expensive. The reverse transcription-polymerase chain reaction (RT-PCR) is a rapid, sensitive method for detecting enteroviruses in water. However, environmental samples often contain substances that inhibit PCR amplification of target RNA. Hence the virus must be concentrated by procedures that do not interfere with amplification. This study shows that virus concentration by adsorption onto glass powder or glass wool supports is suitable for detecting viral genomes in treated wastewater by RT semi-nested PCR. No enterovirus genome was detected directly in 25 samples of treated wastewater by RT semi-nested PCR. However, samples concentrated by adsorption onto glass wool or glass powder showed that 48% (glass powder) and 56% (glass wool) contained virus. Secondary concentration by organic flocculation was unsuitable for detecting virus concentrated on glass wool (20% positive samples), but it helped to increase the detection of the genome after concentration on glass powder (72% positive samples).

Insulin-dependent diabetes mellitus: the hypothesis of molecular mimicry between islet cell antigens and microorganisms

Insulin-dependent diabetes mellitus (IDDM) in humans and the non-obese diabetic mouse is a polygenic disease, resulting from an autoimmune destruction of the insulin-secreting pancreatic beta cells. At least in NOD mice, the process is mediated through a T helper 1-cell-mediated cytotoxicity pathway. Although there is much circumstantial evidence to suggest that IDDM is environmentally induced, recent studies support the possibility that the inductive event involves cross-reactive immune responses to antigenic epitopes acting as molecular mimics between microbial proteins and autoantigens expressed by pancreatic insulin-secreting beta cells. The following article reviews the evidence for this concept.

Implications for viral uncoating from the structure of bovine enterovirus

We have determined the crystal structure of a bovine enterovirus, revealing that the topologies of the major capsid proteins and the overall architecture of the virion are similar to those of related picornaviruses. The external loops joining beta-strands are truncated and the canyon region is partially filled by an extension of the VP3 G-H loop giving the viral capsid a relatively smooth appearance. These changes may have implications for cell attachment. In spite of these differences the virus maintains a hydrophobic pocket within VP1, occupied by a specific 'pocket factor' which appears to be myristic acid. These observations support the proposal that a kinetic equilibrium exists between occupied and unoccupied pocket states, with occupation inhibiting uncoating.

Preliminary crystallographic analysis of coxsackievirus A9

Coxsackievirus A9 has been crystallized as small rhombic dodecahedra of maximum dimension 0.3 mm. These crystals have been shown, using synchrotron radiation, to diffract X-rays to beyond 3 A, and to have a stability in the beam comparable to that of other related virus crystals. The unit cell is tetragonal with dimensions a = b = 495 A, c = 695 A and alpha = beta = gamma = 90 degrees, with a space group of P4n22. A substantial body of diffraction data has been collected and this crystal form appears to be suitable for structure determination. Phasing of these data will be attempted using molecular replacement.

Characterization of neutralizing antibodies to bovine enterovirus elicited by synthetic peptides

Six synthetic peptides corresponding to regions of bovine enterovirus (BEV), strain VG-5-27, elicited antibodies in mice which reacted with the virus in various assays. These antibodies have been characterised on the basis of their ability to (1) neutralize the virus, (2) bind to the intact virus particle in an immunoprecipitation test, (3) react with the denatured viral proteins, and (4) give immunofluorescent staining of virus infected cells. We have also determined the proportion of antipeptide antibody which binds to the virus in each case. All of the sera immunoprecipitated the virus and neutralized its activity to varying extents. Two of the sera specific for VP 1 sequences failed to react with denatured VP 1 whereas all the other antisera reacted with their respective parental proteins. All of the sera reacted with VG-5-27 infected cells in an immunofluorescence test. The proportion of antibodies to each peptide recognizing intact virus was variable and did not appear to correlate with neutralizing activity. In addition, the ability of each of the sera to react with and neutralize three other strains of the virus was analysed. With one of these strains significant cross-neutralization was observed.

Cytotoxic and viral neutralizing antibodies crossreact with streptococcal M protein, enteroviruses, and human cardiac myosin

The development of autoimmunity in certain instances is related to infectious agents. In this report, cytotoxic monoclonal antibodies (mAbs) that recognize epitopes on both enteroviruses and the bacterium Streptococcus pyogenes are described. Murine anti-streptococcal mAbs that were crossreactive with streptococcal M protein, human cardiac myosin, and other alpha-helical coiled-coil molecules were found to neutralize coxsackieviruses B3 and B4 or poliovirus type 1. The viral-neutralizing anti-streptococcal mAbs were also cytotoxic for heart and fibroblast cell lines and reacted with viral capsid proteins on a Western immunoblot. Alignment of amino acid sequences shared between streptococcal M protein, coxsackie-virus B3 capsid protein VP1, and myosin revealed 40% identity in a 14- to 15-amino acid overlap. Synthetic peptides containing these sequences blocked mAb reactivity with streptococcal M protein. The data show that antibodies against alpha-helical structures of bacterial and viral antigens can lead to cytotoxic reactions and may be one mechanism to explain the origin of autoimmune heart disease.