A study of the MAYV replication cycle: Correlation between the kinetics of viral multiplication and viral morphogenesis.

Mayaro virus (MAYV) is mainly found in Central and South America and causes a febrile illness followed by debilitating arthritis and arthralgia similar to chikungunya virus (CHIKV). Infection leads to long-term sequelae with a direct impact on the patient's productive capacity, resulting in economic losses. Mayaro fever is a neglected disease due to the limited epidemiological data. In Brazil, it is considered a potential public health risk with the number of cases increasing every year. Most of our knowledge about MAYV biology is inferred from data obtained from other alphaviruses as well as more recent studies on MAYV. Here, we analyzed the kinetics of viral replication through standard growth curves, quantification of intracellular and extracellular particles, and RNA quantification. We compared transmission electron microscopy data during different stages of infection. This approach allowed us to establish a chronological order of events during MAYV replication and its respective timepoints including cell entry through clathrin-mediated endocytosis occurring at 15-30 min, genome replication at 2-3 h, morphogenesis at 4 hpi, and release at 4-6 hpi. We also present evidence of uncharacterized events such as ribosome reorganization as well as clusters of early viral precursors and release through exocytosis in giant forms. Our work sheds new and specific light on the MAYV replication cycle and may contribute to future studies on the field.

Evaluation of kinase inhibitors as potential therapeutics for flavivirus infections.

The recent introduction of Zika virus (ZIKV), the recurrence of dengue virus (DENV), and the lethality of yellow fever virus (YFV) have had a significant impact on Brazilian society and public health. Here, we targeted two cellular kinases implicated in cell proliferation and cancer that are also important for viral replication: mitogen-activated protein kinase kinase (MEK) and Src. We used two MEK inhibitors - trametinib and selumetinib - and two Src inhibitors - saracatinib and bosutinib - to inhibit ZIKV, DENV, and YFV replication in cell culture. The cytotoxicity of the four inhibitors was determined by the observation of abnormal morphology and quantification of adherent cells by crystal violet staining. The antiviral activity of these drugs was assessed based on the reduction of plaque-forming units in cell culture as evidence of the inhibition of the replication of the selected flaviviruses. All four inhibitors showed antiviral activity, but among them, trametinib was the safest and most efficacious against all of the viruses, inhibiting the replication of ZIKV and YFV by 1000-fold, and DENV2/3 by nearly 100-fold. This pan-antiviral effect shows that trametinib could be repurposed for the treatment of flaviviral infections.

Epidemiological Analysis of COVID-19 Cases in Native Amazonian Communities from Peru.

Despite early control measures, SARS-CoV-2 reached all regions of Peru during the first wave of the pandemic, including native communities of the Peruvian Amazon. Here, we aimed to describe the epidemiological situation of COVID-19 in the Amazonas region of Peru using an open database of 11,124 COVID-19 cases reported from 19 March to 29 July 2020, including 3278 cases from native communities. A high-incidence area in northern Amazonas (Condorcanqui) reported a cumulative incidence of 63.84/1000 inhabitants with a much lower death rate (0.95%) than the national average. Our results showed at least eight significant factors for mortality, and the Native Amazonian ethnicity as a protective factor. Molecular confirmatory tests are necessary to better explain the high incidence of antibody response reported in these communities.

pncA gene expression and prediction factors on pyrazinamide resistance in Mycobacterium tuberculosis.

Mutations in the pyrazinamidase (PZAse) coding gene, pncA, have been considered as the main cause of pyrazinamide (PZA) resistance in Mycobacterium tuberculosis. However, recent studies suggest there is no single mechanism of resistance to PZA. The pyrazinoic acid (POA) efflux rate is the basis of the PZA susceptibility Wayne test, and its quantitative measurement has been found to be a highly sensitive and specific predictor of PZA resistance. Based on biological considerations, the POA efflux rate is directly determined by the PZAse activity, the level of pncA expression, and the efficiency of the POA efflux pump system. This study analyzes the individual and the adjusted contribution of PZAse activity, pncA expression and POA efflux rate on PZA resistance. Thirty M. tuberculosis strains with known microbiological PZA susceptibility or resistance were analyzed. For each strain, PZAse was recombinantly produced and its enzymatic activity measured. The level of pncA mRNA was estimated by quantitative RT-PCR, and the POA efflux rate was determined. Mutations in the pncA promoter were detected by DNA sequencing. All factors were evaluated by multiple regression analysis to determine their adjusted effects on the level of PZA resistance. Low level of pncA expression associated to mutations in the pncA promoter region was observed in pncA wild type resistant strains. POA efflux rate was the best predictor after adjusting for the other factors, followed by PZAse activity. These results suggest that tests which rely on pncA mutations or PZAse activity are likely to be less predictive of real PZA resistance than tests which measure the rate of POA efflux. This should be further analyzed in light of the development of alternate assays to determine PZA resistance.

A20-binding inhibitor of nuclear factor-kappaB (NF-kappaB)-2 (ABIN-2) is an activator of inhibitor of NF-kappaB (IkappaB) kinase alpha (IKKalpha)-mediated NF-kappaB transcriptional activity.

NF-κB transcription factors are pivotal players in controlling inflammatory and immune responses, as well as cell proliferation and apoptosis. Aberrant regulation of NF-κB and the signaling pathways that regulate its activity have been involved in various pathologies, particularly cancers, as well as inflammatory and autoimmune diseases. NF-κB activation is tightly regulated by the IκB kinase (IKK) complex, which is composed of two catalytic subunits IKKα and IKKß, and a regulatory subunit IKKγ/NEMO. Although IKKα and IKKß share structural similarities, IKKα has been shown to have distinct biological functions. However, the molecular mechanisms that modulate IKKα activity have not yet been fully elucidated. To understand better the regulation of IKKα activity, we purified IKKα-associated proteins and identified ABIN-2. Here, we demonstrate that IKKα and IKKß both interact with ABIN-2 and impair its constitutive degradation by the proteasome. Nonetheless, ABIN-2 enhances IKKα- but not IKKß-mediated NF-κB activation by specifically inducing IKKα autophosphorylation and kinase activity. Furthermore, we found that ABIN-2 serine 146 is critical for the ABIN-2-dependent IKKα transcriptional up-regulation of specific NF-κB target genes. These results imply that ABIN-2 acts as a positive regulator of NF-κB-dependent transcription by activating IKKα.