Infection of human monocyte-derived dendritic cells
Background
Andes virus (ANDV), a rodent-borne Hantavirus, is the major etiological agent of Hantavirus cardiopulmonary syndrome (HCPS) in South America, which is mainly characterized by a vascular leakage with high rate of fatal outcomes for infected patients. Currently, neither specific therapy nor vaccines are available against this pathogen. ANDV infects both dendritic and epithelial cells, but in despite that the severity of the disease directly correlates with the viral RNA load, considerable evidence suggests that immune mechanisms rather than direct viral cytopathology are responsible for plasma leakage in HCPS. Here, we assessed the possible effect of soluble factors, induced in viral-activated DCs, on endothelial permeability. Activated immune cells, including DC, secrete gelatinolytic matrix metalloproteases (gMMP-2 and -9) that modulate the vascular permeability for their trafficking.
Methods
A clinical ANDES isolate was used to infect DC derived from primary PBMC. Maturation and pro-inflammatory phenotypes of ANDES-infected DC were assessed by studying the expression of receptors, cytokines and active gMMP-9, as well as some of their functional status. The ANDES-infected DC supernatants were assessed for their capacity to enhance a monolayer endothelial permeability using primary human vascular endothelial cells (HUVEC).
Results
Here, we show that in vitro primary DCs infected by a clinical isolate of ANDV shed virus RNA and proteins, suggesting a competent viral replication in these cells. Moreover, this infection induces an enhanced expression of soluble pro-inflammatory factors, including TNF-α and the active gMMP-9, as well as a decreased expression of anti-inflammatory cytokines, such as IL-10 and TGF-β. These viral activated cells are less sensitive to apoptosis. Moreover, supernatants from ANDV-infected DCs were able to indirectly enhance the permeability of a monolayer of primary HUVEC.
Conclusions
Primary human DCs, that are primarily targeted by hantaviruses can productively be infected by ANDV and subsequently induce direct effects favoring a proinflammatory phenotype of infected DCs. Finally, based on our observations, we hypothesize that soluble factors secreted in ANDV-infected DC supernatants, importantly contribute to the endothelial permeability enhancement that characterize the HCPS.
Background
Hantaviruses are rodent-born enveloped RNA-viruses belonging to Bunyaviridae family. Two major severe pathologies associated to Hantaviruses have been reported: hemorrhagic fever with renal syndrome (HFRS) in the Eurasia and Hantavirus cardiopulmonary syndrome (HCPS) in the Americas. HCPS is more frequently associated (40%) to fatal outcomes than HFRS (<1%). Andes Hantavirus (ANDV) is the major etiological agent of the HCPS in South America, syndrome characterized by the presence of high amounts of pulmonary fluids leading to an edema evolving to a cardiogenic shock that synergistically acts with hypovolemia due to capillary leakage resulting in an abrupt cardiopulmonary collapse. Although disease severity directly correlates with the viral RNA load [3], considerable evidence exists suggesting that immune mechanisms rather than direct viral cytopathology are indeed responsible for the massive vascular dysfunction and plasma leakage of HFRS and HCPS.