Skeletal Muscle Is an Early Site of Zika Virus Replication and Injury, Which Impairs Myogenesis

Japanese encephalitis virus infection causes reactive oxygen species-mediated skeletal muscle damage

Skeletal muscle wasting is a clinically proven pathology associated with Japanese encephalitis virus (JEV) infection; however, underlying factors that govern skeletal muscle damage are yet to be explored. The current study aims to investigate the pathobiology of skeletal muscle damage using a mouse model of JEV infection. Our study reveals a significant increment in viral copy number in skeletal muscle post-JEV infection, which is associated with enhanced skeletal muscle cell death. Molecular and biochemical analysis confirms NOX2-dependent generation of reactive oxygen species, leading to autophagy flux inhibition and cell apoptosis. Along with this, an alteration in mitochondrial dynamics (change in fusion and fission process) and a decrease in the total number of mitochondria copies were found during JEV disease progression. The study represents the initial evidence of skeletal muscle damage caused by JEV and provides insights into potential avenues for therapeutic advancement.

Chikungunya and Mayaro Viruses Induce Chronic Skeletal Muscle Atrophy Triggered by Pro-Inflammatory and Oxidative Response

Chikungunya (CHIKV) and Mayaro (MAYV) viruses are arthritogenic alphaviruses that promote an incapacitating and long-lasting inflammatory muscle-articular disease. Despite studies pointing out the importance of skeletal muscle (SkM) in viral pathogenesis, the long-term consequences on its physiology and the mechanism of persistence of symptoms are still poorly understood. Combining molecular, morphological, nuclear magnetic resonance imaging, and histological analysis, we conduct a temporal investigation of CHIKV and MAYV replication in a wild-type mice model, focusing on the impact on SkM composition, structure, and repair in the acute and late phases of infection. We found that viral replication and induced inflammation promote a rapid loss of muscle mass and reduction in fiber cross-sectional area by upregulation of muscle-specific E3 ubiquitin ligases MuRF1 and Atrogin-1 expression, both key regulators of SkM fibers atrophy. Despite a reduction in inflammation and clearance of infectious viral particles, SkM atrophy persists until 30 days post-infection. The genomic CHIKV and MAYV RNAs were still detected in SkM in the late phase, along with the upregulation of chemokines and anti-inflammatory cytokine expression. In agreement with the involvement of inflammatory mediators on induced atrophy, the neutralization of TNF and a reduction in oxidative stress using monomethyl fumarate, an agonist of Nrf2, decreases atrogen expression and atrophic fibers while increasing weight gain in treated mice. These data indicate that arthritogenic alphavirus infection could chronically impact body SkM composition and also harm repair machinery, contributing to a better understanding of mechanisms of arthritogenic alphavirus pathogenesis and with a description of potentially new targets of therapeutic intervention.

Immunosuppression-induced Zika virus reactivation causes brain inflammation and behavioral deficits in mice

Zika virus (ZIKV) is a neurotropic flavivirus that can persist in several tissues. The late consequences of ZIKV persistence and whether new rounds of active replication can occur, remain unaddressed. Here, we investigated whether neonatally ZIKV-infected mice are susceptible to viral reactivation in adulthood. We found that when ZIKV-infected mice are treated with immunosuppressant drugs, they present increased susceptibility to chemically induced seizures. Levels of subgenomic flavivirus RNAs (sfRNAs) were increased, relative to the amounts of genomic RNAs, in the brains of mice following immunosuppression and were associated with changes in cytokine expression. We investigated the impact of immunosuppression on the testicles and found that ZIKV genomic RNA levels are increased in mice following immunosuppression, which also caused significant testicular damage. These findings suggest that ZIKV can establish new rounds of active replication long after acute stages of disease, so exposed patients should be monitored to ensure complete viral eradication.

Skin muscle is the initial site of viral replication for arboviral bunyavirus infection

The first step in disease pathogenesis for arboviruses is the establishment of infection following vector transmission. For La Crosse virus (LACV), the leading cause of pediatric arboviral encephalitis in North America, and other orthobunyaviruses, the initial course of infection in the skin is not well understood. Using an intradermal (ID) model of LACV infection in mice, we find that the virus infects and replicates nearly exclusively within skin-associated muscle cells of the panniculus carnosus (PC) and not in epidermal or dermal cells like most other arbovirus families. LACV is widely myotropic, infecting distal muscle cells of the peritoneum and heart, with limited infection of draining lymph nodes. Surprisingly, muscle cells are resistant to virus-induced cell death, with long term low levels of virus release progressing through the Golgi apparatus. Thus, skin muscle may be a key cell type for the initial infection and spread of arboviral orthobunyaviruses.

Morphological and functional cardiac alterations in children with congenital Zika syndrome and severe neurological deficits

INTRODUCTION

Zika virus infection during pregnancy causes fetal microcephaly and brain damage. Congenital Zika syndrome (CZS) is characterized by systemic involvement with diffuse muscle impairment, a high frequency of arthrogryposis, and microphthalmia. Cardiac impairment in CZS has rarely been evaluated. Our study assessed morphology and biventricular cardiac function in children with CZS and advanced neurological dysfunction.

METHODS

This cross-sectional study was conducted on 52 children with CZS (Zika group; ZG) and 25 healthy children (control group; CG) in Paraiba, Brazil. Clinical evaluation, electrocardiogram (EKG), and transthoracic echocardiogram (TTE) were performed on all children. Additionally, troponin I and natriuretic peptide type B (BNP) levels, the degree of cerebral palsy, and neuroimaging findings were assessed in the ZG group.

RESULTS

The median age of the study population was 5 years in both groups, and 40.4% (ZG) and 60% (CG) were female. The most prevalent electrocardiographic alteration was sinus arrhythmia in both the ZG (n = 9, 17.3%) and CG (n = 4, 16%). The morphological parameters adjusted for Z score were as follows: left ventricular (LV) end-diastolic diameter in ZG: -2.36 [-5.10, 2.63] vs. CG: -1.07 [-3.43, 0.61], p<0.001); ascending aorta (ZG: -0.09 [-2.08, 1.60] vs. CG: 0.43 [-1.47, 2.2], p = 0.021); basal diameter of the right ventricle (RV) (ZG: -2.34 [-4.90, 0.97] vs. CG: -0.96 [-2.21, 0.40], p<0.01); and pulmonary artery dimension (ZG: -2.13 [-5.99, 0.98] vs. CG: -0.24 [-2.53, 0.59], p<0.01). The ejection fractions (%) were 65.7 and 65.6 in the ZG and CG, respectively (p = 0.968). The left atrium volume indices (mL/m2) in the ZG and CG were 13.15 [6.80, 18.00] and 18.80 [5.90, 25.30] (p<0.01), respectively, and the right atrium volume indices (mL/m2) were 10.10 [4.90, 15.30] and 15.80 [4.10, 24.80] (p<0.01). The functional findings adjusted for Z score were as follows: lateral systolic excursion of the mitral annular plane (MAPSE) (ZG: 0.36 [-2.79, 4.71] vs. CG: 1.79 [-0.93, 4.5], p = 0.001); tricuspid annular plane systolic excursion (TAPSE) (ZG: -2.43 [-5.47, 5.09] vs. CG: 0.07 [-1.98, 3.64], p<0.001); and the S' of the RV (ZG: 1.20 [3.35, 2.90] vs. CG: -0.20 [-2.15, 1.50], p = 0.0121). No differences in biventricular strain measurements were observed between the groups. Troponin I and BNP levels were normal in in the ZG. Grade V cerebral palsy and subcortical calcification were found in 88.6% and 97.22% of children in the ZG group, respectively.

CONCLUSION

A reduction in cardiac dimensions and functional changes were found in CZS patients, based on the TAPSE, S' of the RV, and MAPSE, suggesting the importance of cardiac evaluation and follow-up in this group of patients.

Impaired muscle stem cell function and abnormal myogenesis in acquired myopathies

Skeletal muscle possesses a high plasticity and a remarkable regenerative capacity that relies mainly on muscle stem cells (MuSCs). Molecular and cellular components of the MuSC niche, such as immune cells, play key roles to coordinate MuSC function and to orchestrate muscle regeneration. An abnormal infiltration of immune cells and/or imbalance of pro- and anti-inflammatory cytokines could lead to MuSC dysfunctions that could have long lasting effects on muscle function. Different genetic variants were shown to cause muscular dystrophies that intrinsically compromise MuSC function and/or disturb their microenvironment leading to impaired muscle regeneration that contributes to disease progression. Alternatively, many acquired myopathies caused by comorbidities (e.g., cardiopulmonary or kidney diseases), chronic inflammation/infection, or side effects of different drugs can also perturb MuSC function and their microenvironment. The goal of this review is to comprehensively summarize the current knowledge on acquired myopathies and their impact on MuSC function. We further describe potential therapeutic strategies to restore MuSC regenerative capacity.

The regenerative potential of Pax3/Pax7 on skeletal muscle injury

Background

Skeletal muscle mishaps are the most well-known incidents in society, especially among athletes and the military population. From the various urgency, this accident needs to be cured more quickly. However, the current treatment still has some shortcomings and is less effective. In this case, Paired box 3 and Paired box 7 (Pax3/Pax7) proteins that induce stem cells could potentially be an alternative treatment for skeletal muscle injuries. This paper aimed to analyse the potential treatment of Pax3/Pax7 proteins inducing the stem cell for skeletal muscle injuries.

The main body of the abstract

We did a narrative review by gathering several scientific journals from several leading platforms like PubMed and Scopus. As common accidents, skeletal muscle disease could be due to workplace and non-workplace causes. The highest risk occurs in the athlete and military environment. The treatment of current skeletal muscle injuries is protection, rest, ice, compression, and elevation (PRICE), non-steroidal anti-inflammatory drugs (NSAIDs), and mechanical stimulation. However, it is considered less effective, especially in NSAIDs, inhibiting myogenic cell proliferation. The current finding indicates that the stem cells have markers known as Pax3/Pax7. The role of both markers in muscle injury, Pax3/Pax7, as transcription factors will induce cell division by H3K4 methylation mechanisms and chromatin modifications that stimulate gene activation.

Conclusion

Regulation by Pax3/Pax7 factors that affect stem cells and stem cell proliferation is one of the alternative treatments. This regulation can accelerate the healing of injury victims, especially injuries to the skeletal muscles. Finally, after being compared, Pax3/Pax7 induces stem cells to have the potential to be one of the skeletal muscle injury treatments.

Keywords

Pax3 and Pax7, Pax3/Pax7, Skeletal muscle, Athlete, Stem cells, Cell proliferation, Injuries.

Zika Virus (ZIKV): A New Perspective on the Nanomechanical and Structural Properties

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) from Flavivirus. In 2015, Brazil and other Latin American countries experienced an outbreak of ZIKV infections associated with severe neurological disorders such as Guillain–Barre syndrome (GBS), encephalopathy, and encephalitis. Here, a complete mechanical and structural analysis of the ZIKV has been performed using Atomic Force Microscopy (AFM). AFM analysis corroborated the virus mean size (~50 nm) and icosahedral geometry and revealed high mechanical resistance of both: the viral surface particle (~200 kPa) and its internal content (~800 kPa). The analysis demonstrated the detailed organization of the nucleocapsid structure (such as RNA strips). An interesting finding was the discovery that ZIKV has no surface self-assembling property. These results can contribute to the development of future treatment candidates and circumscribe the magnitude of viral transmission.

A highly sensitive strand-specific multiplex RT-qPCR assay for quantitation of Zika virus replication

Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) is widely used to quantify viral RNA genomes for diagnostics and research, yet conventional RT-qPCR protocols are unable to accurately distinguish between the different viral RNA species that exist during infection. Here we show that false-priming and self-priming occur during reverse transcription with several published Zika virus (ZIKV) primer sets. We developed a RT-qPCR assay using tagged primers and thermostable reverse transcriptase, which greatly reduced the occurrence of nonspecific cDNA products. Furthermore, we optimized the assay for use in multiplex qPCR which allows for simultaneous quantitative detection of positive-strand and negative-strand ZIKV RNA along with an internal control from both human and mosquito cells. Importantly, this assay is sensitive enough to study early stages of virus infection in vitro. Strikingly, using this assay, we detected ZIKV negative-strand RNA as early as 3 h post-infection in mammalian cell culture, at a time point prior to the onset of positive-strand RNA synthesis. Overall, the strand-specific RT-qPCR assay developed herein is a valuable tool to quantify ZIKV RNA and to study viral replication dynamics during infection. The application of these findings has the potential to increase accuracy of RNA detection methods for a variety of viral pathogens.