A NANOTHERAPEUTIC STRATEGY WITH 6-METHYL MERCAPTOPURINE RIBOSIDE SHOWS POTENTIAL ACTIVITY AGAINST ZIKA VIRUS

The Zika virus (ZIKV) is an RNA virus from the Flavivirus genus, and the ZIKV infection is associated with Guillain-Barré syndrome, neuropathy and myelitis in adults and children. The viral transmission persists in the Americas, and antiviral therapy is still lacking. 6-methyl mercaptopurine riboside (6MMPr) was reported as a candidate molecule against ZIKV. However, it has low bioavailability in the central nervous system (CNS) and risk of hepatotoxicity. Thus, this study sought to develop 6MMPr-Poly(lactic acid-co-glycolic acid) (PLGA) nanoparticles (NPs), which were prepared by double emulsification method. The NPs were characterized for hydrodynamic particle size (HPZ), polydispersity index (PdI), zeta potential (ζ), transmission electron microscopy (TEM) and encapsulation efficiency (EE). Their cytotoxicity was evaluated in Vero CCL-81, SH-SY5H and HepG2 cells. The antiviral activity was assessed in ZIKV-infected Vero CCL-81 (7.6 – 60.5 μM). We also investigated the ability of 6MMPr-PLGA-NPs to cross the blood-brain barrier (BBB) by zebrafish injection and bioimaging. PLGA NPs showed 142 nm ± 10.9, PdI of 0.195 ± 0.038 and ζ of -28.2 mV ± 6.1, while 6MMPr-PLGA-NPs had 135.2 nm ± 16.5, 0.157 ± 0.048 and -29.4 mV ± 4.8, respectively. 6MMPr-PLGA-NPs showed EE of 51.2% as determined by HPLC. TEM imaging revealed spherical nanoparticles with negligible aggregation. Free 6MMPr was more toxic than encapsulated 6MMPr in all cell lines. In ZIKV-infected Vero CCL-81 cells, the treatments with free 6MMPr and 6MMPr-PLGA-NPs were capable of reducing ZIKV titres (by viral titration and qPCR), with superior selectivity index for 6MMPr-PLGA-NPs (14.63 vs. 47.28, respectively). Fluorescent NPs (Lumogen F-300 dye, Basf) reached the zebrafish CNS, as visualized by confocal imaging. Seen all together, these findings demonstrate a well-developed rational plan for a novel 6MMPr formulation as a potential therapy against ZIKV.
This work was supported by Programa Inova Fiocruz (VPPIS-001-FIO-18-59), FACEPE (APQ-0443-4.03/18), and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.