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Thymomas are associated with autoantibody formation. The most common are anti-acetylcholine receptor antibodies, which correspond to myasthenia gravis (MG). Other autoantibodies, such as antistriational antibodies, can occur, but their relation to clinical syndromes is frequently uncertain. The etiology of antistriational antibodies is also poorly understood. In this case, a 61-year-old man with a history of thymoma was admitted with respiratory failure. The patient was positive for anti-acetylcholine receptor antibodies and antistriational antibodies. He developed cardiogenic shock and died within 2 days despite aggressive therapy. Laboratory studies revealed elevated cardiac enzymes and marked IgG elevation against Coxsackie A virus serotypes 9 and 24. Subclinical IgG elevations against additional Coxsackie A and Coxsackie B virus serotypes were also noted. Autopsy revealed lymphohistiocytic infiltrates with multinucleated giant cells in the myocardium and skeletal muscles, including the diaphragm. Giant cell polymyositis and myocarditis is a rare, lethal complication in patients with thymoma and MG. The pathogenesis is uncertain. An autoimmune process, possibly elicited by antistriational antibodies, has been suggested. The coexistence of antistriational antibodies and Coxsackie viral serologies has not been reported. This case may suggest that giant cell polymyositis and myocarditis in patients with thymoma and MG is a postviral autoimmune process.

The 5' UTR of Coxsackievirus B3 (CVB3) contains internal ribosome entry site (IRES), which allows cap-independent translation of the viral RNA and a 5'-terminal cloverleaf structure that regulates viral replication, translation and stability. Here, we demonstrate that host protein PSF (PTB associated splicing factor) interacts with the cloverleaf RNA as well as the IRES element. PSF was found to be an important IRES trans acting factor (ITAF) for efficient translation of CVB3 RNA. Interestingly, cytoplasmic abundance of PSF protein increased during CVB3 infection and this is regulated by phosphorylation status at two different amino acid positions. Further, PSF protein was up-regulated in CVB3 infection. The expression of CVB3-2A protease alone could also induce increased PSF protein levels. Furthermore, we observed the presence of an IRES element in the 5'UTR of PSF mRNA, which is activated during CVB3 infection and might contribute to the elevated levels of PSF. It appears that PSF IRES is also positively regulated by PTB, which is known to regulate CVB3 IRES. Taken together, the results suggest for the first time a novel mechanism of regulations of ITAFs during viral infection, where an ITAF undergoes IRES mediated translation, sustaining its protein levels under condition of translation shut-off., (© The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.)

MicroRNAs (miRNAs) are small non-coding RNAs that can posttranscriptionally regulate gene expression by targeting messenger RNAs. During miRNA biogenesis, the star strand (miRNA*) is generally degraded to a low level in the cells. However, certain miRNA* express abundantly and can be recruited into the silencing complex to regulate gene expression. Most miRNAs function as suppressive regulators on gene expression. Group B coxsackieviruses (CVB) are the major pathogens of human viral myocarditis and dilated cardiomyopathy. CVB genome is a positive-sense, single-stranded RNA. Our previous study shows that miR-342-5p can suppress CVB biogenesis by targeting its 2C-coding sequence. In this study, we found that the miR-10a duplex could significantly up-regulate the biosynthesis of CVB type 3 (CVB3). Further study showed that it was the miR-10a star strand (miR-10a*) that augmented CVB3 biosynthesis. Site-directed mutagenesis showed that the miR-10a* target was located in the nt6818-nt6941 sequence of the viral 3D-coding region. MiR-10a* was detectable in the cardiac tissues of suckling Balb/c mice, suggesting that miR-10a* may impact CVB3 replication during its cardiac infection. Taken together, these data for the first time show that miRNA* can positively modulate gene expression. MiR-10a* might be involved in the CVB3 cardiac pathogenesis.

Translation initiation in Coxsackievirus B3 (CVB3) occurs via ribosome binding to an internal ribosome entry site (IRES) located in the 5'-untranslated region (UTR) of the viral RNA. This unique mechanism of translation initiation requires various trans-acting factors from the host. We show that human La autoantigen (La) binds to the CVB3 5'-UTR and also demonstrate the dose-dependent effect of exogenously added La protein in stimulating CVB3 IRES-mediated translation. The requirement of La for CVB3 IRES mediated translation has been further demonstrated by inhibition of translation as a result of sequestering La and its restoration by exogenous addition of recombinant La protein. The abundance of La protein in various mouse tissue extracts has been probed using anti-La antibody. Pancreatic tissue, a target organ for CVB3 infection, was found to have a large abundance of La protein which was demonstrated to interact with the CVB3 5'-UTR. Furthermore, exogenous addition of pancreas extract to in vitro translation reactions resulted in a dose dependent stimulation of CVB3 IRES-mediated translation. These observations indicate the role of La in CVB3 IRES-mediated translation, and suggest its possible involvement in the efficient translation of the viral RNA in the pancreas.

Many serotypes of echovirus (EV) and Coxsackie B virus (CBV) bind human decay-accelerating factor (DAF) and use it as a receptor for infection. Analogues for DAF have been isolated from mice and rats and characterized; these analogues have amino acid identities to human DAF of approximately 60%. EV serotypes 3, 6', 7, 11-13, and 29 and CBV serotypes 1, 3, and 5 caused hemagglutination of human erythrocytes but not rat or mouse erythrocytes, suggesting failure to bind rodent DAF. To confirm this evidence, radiolabeled viruses were incubated with transfected Chinese hamster ovary (CHO) cells that were abundantly expressing each type of DAF. Only cells that expressed human DAF bound virus. Although binding of EV and CBV was specific for human DAF, complement inhibition by DAF expressed in CHO cells was similar for each analogue.

Coxsackie B viruses interact with two putative cell surface receptor molecules. Experiments with prototype laboratory strains suggest that all 6 coxsackie B serotypes interact with a 46-kDa protein recognized by the monoclonal antibody RmcB, whereas CB1, CB3, and CB5 may also bind to decay accelerating factor. Antireceptor monoclonal antibodies were used to study interactions between low-passage clinical coxsackie B virus isolates and the two receptors. In contrast to observations made with single prototype strains, these data indicate that receptor use by clinical isolates is not strictly related to serotype and that even prototype strains with different passage histories may differ in receptor use. Within a given serotype, variation exists in the capacity of individual virus isolates to bind to specific receptors, and variants with altered receptor specificity may arise during infection in humans and in tissue culture.

We have cloned various lengths of coxsackievirus B3 cDNA encompassing the region encoding the 3C proteinase, which is essential to the viral replication cycle. Such viral cDNAs were fused in frame to the 5'terminal portion of the lacZ' gene carried on the vector pUC118 to express mature 3C proteinase in Escherichia coli. In the E. coli cells containing pCXB108 or pCXB117, constructed for this study, a large amount of 23-kDa protein was synthesized in the presence of IPTG. This protein was purified and was shown to be intact 3C proteinase. These data suggest that 3C proteinase, expressed as a part of a fusion protein, was active in E. coli and released itself from the precursor fusion protein by autocatalytic cleavage.