Chikungunya virus requires an intact microtubule network for efficient viral genome delivery

Betrayal From the Core: Centriolar and Cytoskeletal Subversion by Infectious Pathogens

Microbes and parasites have evolved several means to evade and usurp the host cellular machinery to mediate pathogenesis. Being the major microtubule-organizing center (MTOC) of the cell, the centrosome is targeted by multiple viral and nonviral pathogens to mediate their assembly and trafficking within the host cell. This review examines the consequence of such targeting to the centrosome and associated cytoskeletal machinery. We have also amassed a substantial body of evidence of viruses utilizing the cilia within airway epithelium to mediate infection and the hijacking of host cytoskeletal machinery for efficient entry, replication, and egress. While infections have been demonstrated to induce structural, functional, and numerical aberrations in centrosomes, and induce ciliary dysfunction, current literature increasingly supports the notion of a pro-viral role for these organelles. Although less explored, the impact of bacterial and parasitic pathogens on these structures has also been addressed very briefly. Mechanistically, the molecular pathways responsible for these effects remain largely uncharacterized in many instances. Future research focusing on the centriolar triad comprising the centrosome, cilia, and centriolar satellites will undoubtedly provide vital insights into the tactics employed by infectious agents to subvert the host centriole and cytoskeleton-based machinery.

In Silico Drug Repurposing Uncovered the Antiviral Potential of the Antiparasitic Drug Oxibendazole Against the Chikungunya Virus

Chikungunya virus (CHIKV) has been reported in over 120 countries and is the causative agent of Chikungunya fever. The debilitating nature of this disease, which can persist months to years after acute infection, drastically impacts the quality of life of patients. Yet, specific antivirals are lacking for the treatment of this disease, which makes the search for new drugs necessary. In this context, the nsP2 protease emerges as an attractive therapeutic target, and drug repurposing strategies have proven to be valuable. Therefore, we combined in silico and in vitro methods to identify known drugs as potential CHIKV nsP2 protease inhibitors with antiviral properties within DrugBank. Herein, we developed a hybrid virtual screening pipeline comprising pharmacophore- and target-based screening, drug-like, and pharmaceutical filtering steps. Six virtual hits were obtained, and two of them, capecitabine (CPB) and oxibendazole (OBZ), were evaluated against CHIKV replication in Vero cells. CPB did not present antiviral activity, whereas OBZ inhibited the replication of two different strains of CHIKV, namely, 181-25 (Asian genotype) and BRA/RJ/18 (clinical isolate from ECSA genotype). OBZ showed potent antiviral activity against the CHIKV BRA/RJ/18 (EC50 = 11.4 μM) with a high selectivity index (>44). Analogs of OBZ (albendazole, fenbendazole, and mebendazole) were also evaluated, but none exhibited anti-CHIKV activity, and further, their stereoelectronic features were analyzed. Additionally, we observed that OBZ acts mainly at post-entry steps. Hence, our results support further in vivo studies to investigate the antiviral potential of OBZ, which offers a new alternative to fight CHIKV infections.

Revealing the structure and organization of intercellular tunneling nanotubes (TNTs) by STORM imaging

Tunneling nanotubes (TNTs) are nanoscale, actin-rich, transient intercellular tubes for cell-to-cell communication, which transport various cargoes between distant cells. The structural complexity and spatial organization of the involved components of TNTs remain unknown. In this work, the STORM super-resolution imaging technique was applied to elucidate the structural organization of microfilaments and microtubules in intercellular TNTs at the nanometer scale. Our results reveal different distributions of microfilaments and intertwined structures of microtubules in TNTs, which promote the knowledge of TNT communications.

Plants extracts from Cameroon pharmacopeia strongly inhibit the Chikungunya virus infection by targeting entry and replication steps

ETHNOPHARMACOLOGICAL RELEVANCE

Cameroon is one of the sub-Saharan African countries affected by Chikungunya virus (CHIKV). With the absence of approved treatment, this disease represents globally a major public health concern. Several plants are traditionally used in Cameroon for the treatment of virus induced fever and arthralgia. But to date there is no study that validate the efficacy of these plants for the treatment of Chikungunya virus infection.

AIM OF THE STUDY

This study aims to explore the inhition effect, mechanism of action of plant extracts against Chikungunya virus.

MATERIAL AND METHODS

An ethnobotanical survey conducted in some regions of Cameroon, led to the identification of nine medicinal plants used in traditional medicine for the healing of fever-related diseases and arthritis. Crude hydro-ethanolic extracts of each plant were prepared by maceration and their effects against CHIKV infection were investigated. CHIKV S27 strain was used to infection in Vero cell line. The antiviral activities were determined by plaque assay and/or RT-PCR targeting E1 envelope gene of CHIKV. Dose-response studies of the active plants were also determined by flow cytometry and Western blot.

RESULTS

Four extracts, Entada africana Guill et Pers. (E4), Entandrophragma cylindricum Sprague (EI), Khaya grandifoliola C. D.C. Sapindales (E2) and Macaranga hurifolia Beille (E6) showed antiviral activity with the half-maximal inhibitory concentration of 8.29; 8.14; 12.81 and 26.89 μg/mL respectively. All extracts were nontoxic up to the concentration of 100 μg/μL. Entandrophragma cylindricum Sprague (EI), Khaya grandifoliola C. D.C. Sapindales (E2), and Entada africana Guill et Pers. (E4) showed strong inhibition on the entry step of viral infection. At the same time, only Entandrophragma cylindricum Sprague (EI) inhibited the viral titer significantly in replication and intercellular assembly steps. Four plant extracts namely Entandrophragma cylindricum Sprague (EI), Macaranga hurifolia Beille (E6), Phragmentera capitata (Sprengel) Balle (E12), and Detarium microcarpum (E13) were effective against egression step.

CONCLUSIONS

Together, the results of this study showed anti-chikungunya activities of Entandrophragma cylindricum Sprague (EI) and Macaranga hurifolia Beille (E6), with therapeutics perspectives and can be promising sources of the development of anti-CHIKV molecule in future.

Manipulation of Host Microtubule Networks by Viral Microtubule-Associated Proteins

Diverse DNA and RNA viruses utilize cytoskeletal networks to efficiently enter, replicate, and exit the host cell, while evading host immune responses. It is well established that the microtubule (MT) network is commonly hijacked by viruses to traffic to sites of replication after entry and to promote egress from the cell. However, mounting evidence suggests that the MT network is also a key regulator of host immune responses to infection. At the same time, viruses have acquired mechanisms to manipulate and/or usurp MT networks to evade these immune responses. Central to most interactions of viruses with the MT network are virally encoded microtubule-associated proteins (MAPs) that bind to MTs directly or indirectly. These MAPs associate with MTs and other viral or cellular MAPs to regulate various aspects of the MT network, including MT dynamics, MT-dependent transport via motor proteins such as kinesins and dyneins, and MT-dependent regulation of innate immune responses. In this review, we examine how viral MAP interactions with the MT network facilitate viral replication and immune evasion.

Intracellular Interactions Between Arboviruses and Wolbachia in Aedes aegypti

Aedes aegypti is inherently susceptible to arboviruses. The geographical expansion of this vector host species has led to the persistence of Dengue, Zika, and Chikungunya human infections. These viruses take advantage of the mosquito’s cell to create an environment conducive for their growth. Arboviral infection triggers transcriptomic and protein dysregulation in Ae. aegypti and in effect, host antiviral mechanisms are compromised. Currently, there are no existing vaccines able to protect human hosts from these infections and thus, vector control strategies such as Wolbachia mass release program is regarded as a viable option. Considerable evidence demonstrates how the presence of Wolbachia interferes with arboviruses by decreasing host cytoskeletal proteins and lipids essential for arboviral infection. Also, Wolbachia strengthens host immunity, cellular regeneration and causes the expression of microRNAs which could potentially be involved in virus inhibition. However, variation in the magnitude of Wolbachia’s pathogen blocking effect that is not due to the endosymbiont’s density has been recently reported. Furthermore, the cellular mechanisms involved in this phenotype differs depending on Wolbachia strain and host species. This prompts the need to explore the cellular interactions between Ae. aegypti-arboviruses-Wolbachia and how different Wolbachia strains overall affect the mosquito’s cell. Understanding what happens at the cellular and molecular level will provide evidence on the sustainability of Wolbachia vector control.

Microfilaments and microtubules alternately coordinate the multi-step endosomal trafficking of Classical Swine Fever Virus

Cytoskeleton, as a ubiquitous structure in the cells, plays an important role in the process of virus entry, replication, and survival. However, the action mechanism of cytoskeleton in the invasion of Pestivirus into host cells remains unclear. In this study, we systematically dissected the key roles of the main cytoskeleton components, microfilaments and microtubules in the endocytosis of porcine Pestivirus, Classical swine fever virus (CSFV). We observed the dynamic changes of actin filaments in CSFV entry. Confocal microscopy showed that CSFV invasion induced the dissolution and aggregation of stress fibers, resulting in the formation of lamellipodia and filopodia. Chemical inhibitors and RNA interference were used to find that the dynamic changes of actin were caused by EGFR-PI3K/MAPK-RhoA/Rac1/Cdc42-cofilin signaling pathway, which regulates the microfilaments to help CSFV entry. Furthermore, co-localization of the microfilaments with clathrin and Rab5 (early endosome), as well as microtubules with Rab7 (late endosome) and Lamp1 (lysosome) revealed that microfilaments were activated and rearranged to help CSFV trafficking to early endosome after endocytosis. Subsequently, recruitment of microtubules by CSFV also assisted membrane fusion of the virions from late endosome to lysosome with the help of a molecular motor, dynein. Unexpectedly, vimentin, which is an intermediate filament, had no effect on CSFV entry. Taken together, our findings comprehensively revealed the molecular mechanisms of cytoskeletal components that regulated CSFV endocytosis and facilitated further understanding of Pestivirus entry, which would be conducive to explore antiviral molecules to control classical swine fever.IMPORTANCEEndocytosis, an essential biological process mediating cellular internalization events, is often exploited by pathogens for their entry into target cells. Previously, we have reported different mechanisms of CSFV endocytosis into the porcine epithelial cells (PK-15) and macrophages (3D4/21); however, the details of microfilaments/microtubules mediated virus migration within the host cells remained to be elucidated. In this study, we found that CSFV infection induced rearrangement of actin filaments regulated by cofilin through EGFR-PI3K/MAPK-RhoA/Rac1/Cdc42 pathway. Furthermore, we found that CSFV particles were trafficked along actin filaments in early and late endosomes, and through microtubules in lysosomes after entry. Here, we provide for the first time a comprehensive description of the cytoskeleton that facilitates entry and intracellular transport of highly pathogenic swine virus. Results from this study will greatly contribute to the understanding of virus-induced early and complex changes in host cells that are important in CSFV pathogenesis.