Chloroquine, an Endocytosis Blocking Agent, Inhibits Zika Virus Infection in Different Cell Models

Delvecchio, Rodrigo; Higa, Luiza M.; Pezzuto, Paula; Valadão, Ana Luiza; Garcez, Patrícia P.; Monteiro, Fábio L.; Loiola, Erick C.; Dias, André A.; Silva, Fábio J. M.; Aliota, Matthew T.; Caine, Elizabeth A.; Osorio, Jorge E.; Bellio, Maria; O’Connor, David H.; Rehen, Stevens; de Aguiar, Renato Santana; Savarino, Andrea; Campanati, Loraine; Tanuri, Amilcar

We characterized the antiviral properties of chloroquine in Vero cells, a model widely used to study viral infections. Vero cells were infected with ZIKV MR766 at an MOI of 2 (i.e., 2 PFU/cell) and were then treated for 5 days with chloroquine in concentrations ranging from 6.25 to 50 µM. Viral infectivity was assessed using the 4G2 antibody, which detects flavivirus envelope E protein. We observed that chloroquine treatment decreased the number of ZIKV-infected cells in a dose-dependent manner. Flow cytometry analysis showed a reduction of 35% and 65% in ZIKV-infected cells when cultures were treated with 25 µM and 50 µM chloroquine, respectively, compared to untreated infected cells ( Figure 1A ). Immunofluorescence staining corroborated these results ( Figure 1B ) and additionally, chloroquine decreased the production of infectious ( Figure 1C ) and total ( Figure 1D ) virus particles, including defective viral particles, by ZIKV-infected cells. To confirm that viral inhibition is independent of chloroquine cytotoxicity, the viability of uninfected cells treated with chloroquine (1.56 to 200 µM) for 5 days was analyzed. Chloroquine did not impact cell viability at concentrations of 50 µM or lower ( Figure 1E ). We further analyzed whether chloroquine treatment could protect Vero cells from ZIKV infection as assessed by cell viability. Chloroquine, ranging from 12.5 to 50 µM, increased cell viability from 55% up to 100% ( Figure 1F ).