Subject
The laboratory studies molecular mechanisms of dengue and Zika virus replication in order to generate information and tools for antiviral strategies and for the rational development of vaccine candidates. These viruses are important human pathogens, that belong to the Flaviviridae family, which includes yellow fever, West Nile and other viruses that cause encephalitis. Dengue virus represents the most important arthropod-borne human viral pathogen around the world. Dengue outbreaks and epidemics are a tremendous public health problem in Latin America.
Flaviviruses are enveloped viruses that have a positive, single strand RNA genome. This molecule plays multiple functions during infection. It contains the information for viral protein synthesis (as mRNA), it carries signals in RNA structures that govern translation, RNA replication and encapsidation. In the laboratory, we take the viral RNA as one of the central themes of our studies. We study how dengue and Zika virus genome work, and we have identified signals in secondary and tertiary RNA structures that govern the viral replication processes. We have found that the viral RNA genome is a dynamic molecule that acquires different conformations during infection. In nature, these viruses switch between mosquitos and humans. Therefore, the requirements and limitations that these viruses encounter in each host are different, encountering different selective pressures. We are thus interested in understanding how viral RNA structures regulate viral replication and adaptation in mosquito and human cells. In order to study these processes, we analyze the function, dynamic and adaptation of the viral ARN during infection in human cells and adult mosquitoes.
Regarding the viral genome functions and its interaction with capsid protein, we study the uncoating and encapsidation mechanisms during infection. The laboratory also studies the interaction of viral and cellular components using proteomics. These studies allow identification not only cellular factors involved in viral replication but also viral mechanisms to evade host antiviral responses.
We believe that the information generated by these studies is important to understand how the viral components work but it is also vital to rationally design attenuated viruses for vaccine development and provide new ideas for antiviral strategies.
During the COVID-19 emergency, the laboratory joined the Coronavirus Unit (coordinated by the MinCyT, the CONICET and the Agencia I+D+i), leading the development of the first national serologic kit for the measurement of anti-SARS-CoV-2 antibodies (COVIDAR IgG and IgM). The laboratory is also involved in various research projects and cooperation with different hospitals and health authorities to characterize the humoral immune response to infection and vaccination.

Approach
Our approach is to combine classical and molecular virology with cellular biology studies added to biochemistry and biophysics to understand mechanisms that lead to dengue and Zika virus infection in mosquito and humans.

Advances
Our laboratory provided the first model for dengue virus RNA synthesis. We identified the promoter element that binds and activates the viral polymerase for initiation of RNA replication. The RNA promoter was found at the 5’ end of the viral RNA, ten thousand nucleotides away from the initiation site. Experiments in cell culture with infectious viruses and in vitro biochemical studies showed that cyclization of the viral genome is necessary for replication. This mechanism was extrapolated to more than 50 viruses, including important human pathogens such as yellow fever and Zika viruses.
Regarding the process of mosquito and human alternation, we described a new mechanism of viral RNA adaptation to each host. This mechanism involves the selection of different viral population in human cells and mosquitoes.
Studies on virus-host interaction revealed that dengue virus replication subverts the host splicing cellular machinery mediated by the viral protein NS5. In addition, we discovered the first link between dengue virus capsid protein and host lipid droplets. We found that the viral capsid progressively accumulates around lipid droplets during infection in human and mosquito cells. Understanding molecular aspects of host-virus interaction is important for defining the mechanisms of viral replication, but also to uncover mechanisms of viral pathogenesis.