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Abstract Mononuclear phagocytes are considered to be main targets for Dengue Virus (DENV) replication. These cells are activated after infection, producing proinflammatory mediators, including tumour-necrosis factor-α, which has also been detected in vivo. Nitric oxide (NO), usually produced by activated mononuclear phagocytes, has antimicrobial and antiviral activities. Methods The expression of DENV antigens and inducible nitric oxide synthase (iNOS) in human blood isolated monocytes were analysed by flow cytometry using cells either from patients with acute Dengue Fever or after DENV-1 in vitro infection. DENV-1 susceptibility to iNOS inhibition and NO production was investigated using NG-methyl L-Arginine (NGMLA) as an iNOS inhibitor, which was added to DENV-1 infected human monocytes, and sodium nitroprussiate (SNP), a NO donor, added to infected C6/36 mosquito cell clone. Viral antigens after treatments were detected by flow cytometry analysis. Results INOS expression in activated monocytes was observed in 10 out of 21 patients with Dengue Fever and was absent in cells from ten healthy individuals. DENV antigens detected in 25 out of 35 patients, were observed early during in vitro infection (3 days), significantly diminished with time, indicating that virus replicated, however monocytes controlled the infection. On the other hand, the iNOS expression was detected at increasing frequency in in vitro infected monocytes from three to six days, exhibiting an inverse relationship to DENV antigen expression. We demonstrated that the detection of the DENV-1 antigen was enhanced during monocyte treatment with NGMLA. In the mosquito cell line C6/36, virus detection was significantly reduced in the presence of SNP, when compared to that of untreated cells. Conclusion This study is the first to reveal the activation of DENV infected monocytes based on induction of iNOS both in vivo and in vitro, as well as the susceptibility of DENV-1 to a NO production.

Introduction: Acute febrile illnesses (AFI) are a frequent chief complaint in outpatients. Because the capacity to investigate the causative pathogen of AFIs is limited in low- and middle-income countries, patient management may be suboptimal. Understanding the distribution of causes of AFI can improve patient outcomes. This study aims to describe the most common etiologies diagnosed over a 16-years period in a national reference center for tropical diseases in a large urban center in Rio de Janeiro, Brazil., Methods: From August 2004-December 2019, 3591 patients > 12 years old, with AFI and/or rash were eligible. Complementary exams for etiological investigation were requested using syndromic classification as a decision guide. Results. Among the 3591 patients included, endemic arboviruses such as chikungunya (21%), dengue (15%) and zika (6%) were the most common laboratory-confirmed diagnosis, together with travel-related malaria (11%). Clinical presumptive diagnosis lacked sensitivity for emerging diseases such as zika (31%). Rickettsia disease and leptospirosis were rarely investigated and an infrequent finding when based purely on clinical features. Respiratory symptoms increased the odds for the diagnostic remaining inconclusive., Conclusions: Numerous patients did not have a conclusive etiologic diagnosis. Since syndromic classification used for standardization of etiological investigation and presumptive clinical diagnosis had moderate accuracy, it is necessary to incorporate new diagnostic technologies to improve diagnostic accuracy and surveillance capacity., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Bressan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

HIV-infected subjects under virological control still exhibit a persistent proinflammatory state. Thus, chronic HIV infection changes the host homeostasis towards an adapted immune response that may affect the outcome of coinfections. However, little is known about the impact of HIV infection on inflammatory amplification and clinical presentation in dengue. Platelets have been shown to participate in immune response in dengue and HIV. We hypothesized that altered platelet responses in HIV-infected subjects may contribute to altered inflammatory milieu and disease progression in dengue. We prospectively followed a cohort of 84 DENV-infected patients of whom 29 were coinfected with HIV under virological control. We report that dengue and HIV coinfection progress with reduced inflammation and milder disease progression with lower risk of vascular instability. Even though the degree of thrombocytopenia and platelet activation were similar between dengue-infected and HIV plus dengue-coinfected patients, plasma levels of the platelet-derived chemokines RANTES/CCL5 and PF4/CXCL4 were lower in coinfection. Consistently, platelets from coinfected patients presented defective secretion of the stored-chemokines PF4 and RANTES, but not newly synthesized IL-1β, when cultured ex vivo. These data indicate that platelets from HIV-infected subjects release lower levels of chemokines during dengue illness, which may contribute to milder clinical presentation during coinfection.

Background: Zika virus (ZIKV) emergence in South America revealed the lack of knowledge regarding clinical manifestations in HIV-infected individuals., Objectives: We described the clinical characteristics, laboratory manifestations, differential diagnosis, and outcome of ZIKV infection in a large, single-center cohort of HIV-infected patients., Methods: HIV-infected patients aged 18 years and older with clinical suspected arboviral disease from an ongoing cohort were followed from February 2015 through December 2015. Acute serum samples were tested for ZIKV, dengue virus (DENV), and chikungunya virus by real-time reverse transcriptase polymerase chain reaction, anti-DENV immunoglobulin (Ig)M/IgG, and syphilis assays; convalescent samples were tested for anti-DENV IgM/IgG; and urine samples were tested for ZIKV by real-time reverse transcriptase polymerase chain reaction. ZIKV disease was defined according to the Pan American Health Organization (PAHO) guidelines., Results: Of 101 patients, ZIKV was confirmed in 43 cases and suspected in 34, and another diagnosis was assumed for 24 patients (dengue, secondary/latent syphilis, respiratory infections, human parvovirus B19, adverse drug reaction, musculoskeletal disorders, and acute gastroenteritis). ZIKV-confirmed and ZIKV-suspected patients reported similar signs and symptoms. Pruritic rash was the most common symptom, followed by myalgia, nonpurulent conjunctivitis, arthralgia, prostration, and headache. In the short-term follow-up [median 67.5 days (interquartile range: 32-104.5)], CD4 cell count (Z = -0.831, P = 0.406) and HIV viral load (Z = -0.447, P = 0.655) did not change significantly after ZIKV infection. There were no hospitalizations, complications, or deaths., Conclusions: Among HIV-infected patients with suspected arboviral disease, 42.6% were ZIKV-infected. CD4 cell counts and HIV viral load were not different after ZIKV infection. Differential diagnosis with other diseases and adverse drug reaction should be evaluated.

Dengue is the most frequent hemorrhagic viral disease and re-emergent infection in the world. Although thrombocytopenia is characteristically observed in mild and severe forms of dengue, the role of platelet activation in dengue pathogenesis has not been fully elucidated. We hypothesize that platelets have major roles in inflammatory amplification and increased vascular permeability during severe forms of dengue. Here we investigate interleukin (IL)-1β synthesis, processing, and secretion in platelets during dengue virus (DV) infection and potential contribution of these events to endothelial permeability during infection. We observed increased expression of IL-1β in platelets and platelet-derived microparticles from patients with dengue or after platelet exposure to DV in vitro. We demonstrated that DV infection leads to assembly of nucleotide-binding domain leucine rich repeat containing protein (NLRP3) inflammasomes, activation of caspase-1, and caspase-1-dependent IL-1β secretion. Our findings also indicate that platelet-derived IL-1β is chiefly released in microparticles through mechanisms dependent on mitochondrial reactive oxygen species-triggered NLRP3 inflammasomes. Inflammasome activation and platelet shedding of IL-1β-rich microparticles correlated with signs of increased vascular permeability. Moreover, microparticles from DV-stimulated platelets induced enhanced permeability in vitro in an IL-1-dependent manner. Our findings provide new evidence that platelets contribute to increased vascular permeability in DV infection by inflammasome-dependent release of IL-1β.

Introduction: The mortality of malaria in the extra-Amazon region is about 80 times higher than in the Amazon region, where malaria is concentrated (99.8% of cases). In areas of dengue transmission, delay in the diagnosis and treatment of malaria in patients with fever who reside in areas of malaria transmission can be due to the confusion between the clinical diagnoses of both diseases by nonspecialist doctors, among other factors. This work presents some of the consequences of delayed diagnosis in three patients with malaria by Plasmodium falciparum, P. malariae and P. vivax, who, after following the usual route for Dengue treatment, sought our institution, where they were correctly diagnosed and adequately treated., Methods: Description of three cases of malaria with delayed diagnosed malaria referred to the Outpatient Clinic for Acute Febrile Diseases, IPEC/FIOCRUZ-RJ, between 2007 and 2008., Results: A Brazilian from Mozambique, primo-infected with P. falciparum was diagnosed with malaria six days after the onset of fever and died of cerebral malaria and shock. Another patient with P.malariae malaria presented a severe and prolonged course, but was cured after specific treatment. A third patient, with delayed diagnosis of P. vivax malaria, acquired it in the Atlantic Forest region in the State of Rio., Conclusions: Health professionals from non-endemic areas for malaria should be trained to optimize the surveillance and early treatment of malaria and prevent morbid and fatal outcomes. An investigation of outbreaks of autochthonous malaria in the State of Rio de Janeiro is suggested.

Unlabelled: Mononuclear phagocytes are considered to be main targets for Dengue Virus (DENV) replication. These cells are activated after infection, producing proinflammatory mediators, including tumour-necrosis factor-alpha, which has also been detected in vivo. Nitric oxide (NO), usually produced by activated mononuclear phagocytes, has antimicrobial and antiviral activities., Methods: The expression of DENV antigens and inducible nitric oxide synthase (iNOS) in human blood isolated monocytes were analysed by flow cytometry using cells either from patients with acute Dengue Fever or after DENV-1 in vitro infection. DENV-1 susceptibility to iNOS inhibition and NO production was investigated using NG-methyl L-Arginine (NGMLA) as an iNOS inhibitor, which was added to DENV-1 infected human monocytes, and sodium nitroprussiate (SNP), a NO donor, added to infected C6/36 mosquito cell clone. Viral antigens after treatments were detected by flow cytometry analysis., Results: INOS expression in activated monocytes was observed in 10 out of 21 patients with Dengue Fever and was absent in cells from ten healthy individuals. DENV antigens detected in 25 out of 35 patients, were observed early during in vitro infection (3 days), significantly diminished with time, indicating that virus replicated, however monocytes controlled the infection. On the other hand, the iNOS expression was detected at increasing frequency in in vitro infected monocytes from three to six days, exhibiting an inverse relationship to DENV antigen expression. We demonstrated that the detection of the DENV-1 antigen was enhanced during monocyte treatment with NGMLA. In the mosquito cell line C6/36, virus detection was significantly reduced in the presence of SNP, when compared to that of untreated cells., Conclusion: This study is the first to reveal the activation of DENV infected monocytes based on induction of iNOS both in vivo and in vitro, as well as the susceptibility of DENV-1 to a NO production.