Franciele Martins Santos

Mayaro virus (MAYV) is an emerging arbovirus member of the Togaviridae family and Alphavirus genus. MAYV infection causes an acute febrile illness accompanied by persistent polyarthralgia and myalgia. Understanding the mechanisms involved in arthritis caused by alphaviruses is necessary to develop specific therapies. In this work, we investigated the role of the CCL2/CCR2 axis in the pathogenesis of MAYV-induced disease. For this, wild-type (WT) C57BL/6J and CCR2 ^−/− mice were infected with MAYV subcutaneously and evaluated for disease development. MAYV infection induced an acute inflammatory disease in WT mice. The immune response profile was characterized by an increase in the production of inflammatory mediators, such as IL-6, TNF, and CCL2. Higher levels of CCL2 at the local and systemic levels were followed by the significant recruitment of CCR2 ⁺ macrophages and a cellular response orchestrated by these cells. CCR2 ^−/− mice showed an increase in CXCL-1 levels, followed by a replacement of the macrophage inflammatory infiltrate by neutrophils. Additionally, the absence of the CCR2 receptor protected mice from bone loss induced by MAYV. Accordingly, the silencing of CCL2 chemokine expression in vivo and the pharmacological blockade of CCR2 promoted a partial improvement in disease. Cell culture data support the mechanism underlying the bone pathology of MAYV, in which MAYV infection promotes a pro-osteoclastogenic microenvironment mediated by CCL2, IL-6, and TNF, which induces the migration and differentiation of osteoclast precursor cells. Overall, these data contribute to the understanding of the pathophysiology of MAYV infection and the identification future of specific therapeutic targets in MAYV-induced disease. IMPORTANCE: This work demonstrates the role of the CCL2/CCR2 axis in MAYV-induced disease. The infection of wild-type (WT) C57BL/6J and CCR2 ^−/− mice was associated with high levels of CCL2, an important chemoattractant involved in the recruitment of macrophages, the main precursor of osteoclasts. In the absence of the CCR2 receptor, there is a mitigation of macrophage migration to the target organs of infection and protection of these mice against bone loss induced by MAYV infection. Much evidence has shown that host immune response factors contribute significantly to the tissue damage associated with alphavirus infections. Thus, this work highlights molecular and cellular targets involved in the pathogenesis of arthritis triggered by MAYV and identifies novel therapeutic possibilities directed to the host inflammatory response unleashed by MAYV.

Uncertainty over the therapeutic benefit of parenteral remdesivir in coronavirus disease 2019 (COVID-19) has resulted in varying treatment guidelines. In a multicenter open-label, controlled, adaptive, pharmacometric platform trial, low-risk adult patients with early symptomatic COVID-19 were randomized to 1 of 8 treatment arms including intravenous remdesivir (200 mg followed by 100 mg daily for 5 days) or no study drug. The primary outcome was the rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) clearance (estimated under a linear model fit to the daily log₁₀ viral densities, days 0–7) in standardized duplicate oropharyngeal swab eluates, in a modified intention-to-treat population. This ongoing adaptive trial is registered at ClinicalTrials.gov (NCT05041907). The 2 study arms enrolled 131 patients (remdesivir n = 67, no study drug n = 64) and estimated viral clearance rates from a median of 18 swab samples per patient (a total of 2356 quantitative polymerase chain reactions). Under the linear model, compared with the contemporaneous control arm (no study drug), remdesivir accelerated mean estimated viral clearance by 42% (95% credible interval, 18%–73%). Parenteral remdesivir accelerates viral clearance in early symptomatic COVID-19. Pharmacometric assessment of therapeutics using the method described can determine in vivo clinical antiviral efficacy rapidly and efficiently.

The Covid-19 pandemic has created an unprecedented need for epidemiological monitoring using diverse strategies. We conducted a project combining prevalence, seroprevalence, and genomic surveillance approaches to describe the initial pandemic stages in Betim City, Brazil. We collected 3239 subjects in a population-based age-, sex- and neighbourhood-stratified, household, prospective; cross-sectional study divided into three surveys 21 days apart sampling the same geographical area. In the first survey, overall prevalence (participants positive in serological or molecular tests) reached 0.46% (90% CI 0.12% – 0.80%), followed by 2.69% (90% CI 1.88% – 3.49%) in the second survey and 6.67% (90% CI 5.42% - 7.92%) in the third. The underreporting reached 11, 19.6, and 20.4 times in each survey, respectively. We observed increased odds to test positive in females compared to males (OR 1.88 95% CI 1.25 – 2.82), while the single best predictor for positivity was ageusia/ anosmia (OR 8.12, 95% CI 4.72 – 13.98). Thirty-five SARS-CoV-2 genomes were sequenced, of which 18 were classified as lineage B.1.1.28, while 17 were B.1.1.33. Multiple independent viral introductions were observed. Integration of multiple epidemiological strategies was able to describe Covid-19 dispersion in the city adequately. Presented results have helped local government authorities to guide pandemic management.

The Mayaro virus (MAYV) is an endemic arbovirus in South American countries, where it is responsible for sporadic outbreaks of Mayaro fever. Clinical manifestations include fever, headache, ocular pain, rash, myalgia, and debilitating and persistent polyarthralgia. Understanding the mechanisms associated with MAYV-induced arthritis is of great importance due to the potential for its emergence, urbanization and dispersion to other regions. 15-day old Balb/c mice were infected by two distinct pathways, below the forelimb and in the rear footpad. Animals were observed for a period of 21 days. During this time, they were monitored every 24 hours for disease signs, such as weight loss and muscle weakness. Histological damage in the muscles and joints was evaluated 3, 7, 10, 15 and 20 days post-infection. The cytokine profile in serum and muscles during MAYV infection was evaluated by flow cytometry at different post-infection times. For pain analysis, the animals were submitted to the von Frey test and titre in different organs was evaluated throughout the study to obtain viral kinetics. Infection by two distinct pathways, below the forelimb and in the rear footpad, resulted in a homogeneous viral spread and the development of acute disease in animals. Clinical signs were observed such as ruffled fur, hunched posture, eye irritation and slight gait alteration. In the physical test, both groups presented loss of resistance, which was associated with histopathological damage, including myositis, arthritis, tenosynovitis and periostitis. The immune response was characterized by a strong inflammatory response mediated by the cytokines TNF-α, IL-6 and INF-γ and chemokine MCP-1, followed by the action of IL-10 and IL-4 cytokines. The results showed that Balb/c mice represent a promising model to study mechanisms involved in MAYV pathogenesis and for future antiviral testing. The Mayaro virus, although restricted to some regions of Latin America, has great potential for emergence, which makes it of great medical-scientific interest. Therefore, pathogenesis study of the MAYV in an animal model has fundamental importance for the determination of viral and host factors that contribute to disease development. In addition, it will allow develop and evaluate the effectiveness of possible antiviral agents. In this study, the authors were able to standardize a disease model for the MAYV in BALB / c mice. From the obtained data it is possible to observe the induction of acute arthritis and myositis, accompanied by the reduction of physical strength of the animals. As described for other alphaviruses in both animal models and patient, the proinflammatory mediators TNF-α, IL-6, INF-γ and MCP-1 were elevated in the serum of MAYV-infected animals and therefore appeared to be mediators which also play an important role in the pathogenesis of MAYV.

Background: Yellow fever outbreaks have re-emerged in Brazil during 2016-18, with mortality rates up to 30%. Although urban transmission has not been reported since 1942, the risk of re-urbanization of yellow fever is significant, as Aedes aegypti is present in most tropical and sub-tropical cities in the World and used to be the main vector in the past. The introgression of Wolbachia bacteria into Ae. aegypti mosquito populations is being trialed in several countries (www.worldmosquito.org)as a biocontrol method against dengue, Zika and chikungunya. Here, we studied the ability of Wolbachia to reduce the transmission potential of Ae. aegypti mosquitoes for yellow fever virus (YFV). Methods: Two recently isolated YFV (primate and human) were used to challenge field-derived wild-type and Wolbachia-infected (wMel +) Ae. aegypti mosquitoes. The YFV infection status was followed for 7, 14 and 21 days post-oral feeding (dpf). The YFV transmission potential of mosquitoes was evaluated via nano-injection of saliva into uninfected mosquitoes or by inoculation in mice. Results: We found that Wolbachia was able to significantly reduce the prevalence of mosquitoes with YFV infected heads and thoraces for both viral isolates. Furthermore, analyses of mosquito saliva, through indirect injection into naïve mosquitoes or via interferon-deficient mouse model, indicated Wolbachia was associated with profound reduction in the YFV transmission potential of mosquitoes (14dpf). Conclusions: Our results suggest that Wolbachia introgression could be used as a complementary strategy for prevention of urban yellow fever transmission, along with the human vaccination program.