Foreign gene transfer to cardiomyocyte using a replication-defective recombinant coxsackievirus B3 without cytotoxicity

Specific elimination of coxsackievirus B3 infected cells with a protein engineered toxin-antitoxin system

Backgrounds

Coxsackievirus B3 (CVB3) is a member of the family Picornaviridae, and along with polio-viruses, belongs to the Enterovirus genus. The CVB3 genome is composed single-stranded RNA encoding polyproteins, which are cleaved to individual functional proteins by 2A and 3C proteases proteins which have been targeted for drug development. Here, we showed that protease activity required to activate a toxic protein may be used to prevent viral infection.

Methods

We modified the MazE-MazF antitoxin-toxin system of Escherichia coli to fuse a C-terminal fragment of MazE to the N-terminal end of toxin MazF with a linker having a specific protease cleavage site for CVB3. This fusion protein formed a stable dimer and was capable of inactivating the mRNA interferase activity of MazF which cleaves the ACA sequence in mRNA substrates.

Results

The incubation of 2A proteases with the fusion proteins induced cleavage between the MazE and MazF fragments from the fusion proteins; the subsequent release of MazF significantly inhibited virus replication. Additionally, we note that, CVB3 infected HeLa cells quickly died through a MazF toxin mediated effect before virus protein expression.

Conclusion

These findings suggest that the MazEF fusion protein has a strong potential to be developed as an anti-virus therapy following CVB3 infection.

Arrayed CRISPR screen with image-based assay reliably uncovers host genes required for coxsackievirus infection

Pooled CRISPR screens based on lentiviral systems have been widely applied to identify the effect of gene knockout on cellular phenotype. Although many screens were successful, they also have the limitation that genes conferring mild phenotypes or those essential for growth can be overlooked, as every genetic perturbation is incorporated in the same population. Arrayed screens, on the other hand, incorporate a single genetic perturbation in each well and could overcome these limitations. However, arrayed screens based on siRNA-mediated knockdown were recently criticized for low reproducibility caused by incomplete inhibition of gene expression. To overcome these limitations, we developed a novel arrayed CRISPR screen based on a plasmid library expressing a single guide RNA (sgRNA) and disrupted 1514 genes, encoding kinases, proteins related to endocytosis, and Golgi-localized proteins, individually using 4542 sgRNAs (three sgRNAs per gene). This screen revealed host factors required for infection by coxsackievirus B3 (CVB3) from Picornaviridae, which includes human pathogens causing diverse diseases. Many host factors that had been overlooked in a conventional pooled screen were identified for CVB3 infection, including entry-related factors, translational initiation factors, and several replication factors with different functions, demonstrating the advantage of the arrayed screen. This screen was quite reliable and reproducible, as most genes identified in the primary screen were confirmed in secondary screens. Moreover, ACBD3, whose phenotype was not affected by siRNA-mediated knockdown, was reliably identified. We propose that arrayed CRISPR screens based on sgRNA plasmid libraries are powerful tools for arrayed genetic screening and applicable to larger-scale screens.

Soluble coxsackievirus B3 3C protease inhibitor prevents cardiomyopathy in an experimental chronic myocarditis murine model

BACKGROUND

Coxsackievirus B3 (CVB3) is a common cause of myocarditis and dilated cardiomyopathy. CVB3 3C protease (3CP) cleaves the viral polyprotein during replication. We tested whether a water soluble 3CP inhibitor (3CPI) had antiviral effects in a chronic myocarditis model.

METHODS

Chronic myocarditis was established using DBA/2 strain mice. Starting on post-infection (p.i) day 3, CVB3-infected mice (n=41) were treated with 3CPI by daily intraperitoneal (i.p.) injection at a concentration of 50 μM (1.7 mg/kg/day) per day for 3 consecutive days. Additional mice (n=49) were injected with PBS as a control.

RESULTS

The 5-week survival rate was significantly higher with 3CPI treatment (82.3% versus 47.9%; P<0.05). Organ virus titers at day 3 and 7 and myocardial damage were significantly lower in 3CPI-treated mice. Echocardiography at day 31 indicated strong protection of heart function by 3CPI (FS, 51.2±1.5 versus 26.1±1.5%; P<0.001). Hemodynamic measurements indicated that 3CPI treatment markedly reduced CVB3-induced LV dysfunction on day 31 (dP/dTmax, 5302±352 versus 4103±408 mmHg/s, P<0.05; dP/dTmin, -3798±212 versus -2814±206 mmHg/s, P<0.01).

CONCLUSIONS

Water soluble 3CPI was delivered through i.p. injection after CVB3 infection. This agent preserved heart function and decreased organ viral titers and myocardial damage. Soluble 3CPI may be beneficial in the treatment of cardiomyopathy associated with enterovirus infection.

ORI2 inhibits coxsackievirus replication and myocardial inflammation in experimental murine myocarditis

We purified ORI2 [3-(3,4-dihydroxyphenyl)acrylic acid 1-(3,4-dihydroxyphenyl)-2-methoxycarbonylethyl ester] from an extract of the plant Isodon excisus. We tested the antiviral effect of ORI2 in a coxsackievirus-induced myocarditis model. Coxsackievirus B3 (CVB3) is a common cause of myocarditis and dilated cardiomyopathy. Activation of extracellular signal-regulated kinase (ERK) and Akt signaling in virus-infected cells is essential for CVB3 replication. Antiviral compounds were screened by HeLa cell survival assay. Several purified natural compounds were added to HeLa cells cultured in 96-well plates for 30 min after 1 multiplicity of infection (m.o.i) CVB3 infection. ORI2 significantly improved HeLa cell survival in a dose-dependent manner. For in vivo studies, BALB/c mice (n=20) were infected with CVB3, then 10 of the mice were treated by daily intraperitoneal injections of ORI2 (100 mM) for 3 consecutive days. ORI2 treatment significantly improved early survival in the treated mice compared to untreated mice (85% vs. 50%, respectively). Organ virus titers and myocardial damage were significantly lower in the ORI2-treated mice than in untreated mice. These results demonstrate that ORI2, delivered by intraperitoneal injection after CVB3 infection, has a significant antiviral effect by markedly inhibiting virus replication, resulting in a decrease in organ virus titer and myocardial damage. ORI2 may be developed as a potential therapeutic agent for the treatment of CVB3 infections.