Evaluation of Viral Replication by Tonate Virus (TONV) and Zika Virus (ZIKV), Within an ex Vivo Trophoblast and Placental Model

C6/36 cells will be cultured in L15 culture medium (Leibovitz's L-15 medium), supplemented with 5% FBS (Fetal Bovine Serum) and 1% penicillin/streptomycin at 28°C in a humidified atmosphere containing 5% C02. ZIKV and TONV will be expanded and titrated using C6/36 cells. The viral stock will be aliquoted in 100 µL aliquots and stored at -80°C.

Placental tissues will be handled within one hour of delivery. The chorionic villi will be dissected into 5mm sections and the tissues washed abundantly, minimum 3 times with a standard culture medium (RPMI-1640 supplemented with 10% heat-inactivated fetal calf serum (FCS), 1% L-Glutamine and 1% Penicillin/Streptomycin) to remove maternal blood, membranes and blood clots.

Collagen gel sponges will be placed in 6-well plate wells containing 3mL of culture medium (RPMI-1640 supplemented with 15% heat-inactivated fetal bovine serum (FCS), 1% Penicillin/streptomycin, 0 1% Gentamycin, 1% Amphotericin B, 1% L-Glutamine, 1% non-essential amino acid, 1% sodium pyruvate) per well. Chorionic villi will be dissected into 5mm sections and placed on top of collagen gel sponges at the interface between culture medium and air.

The tissues will be lysed by mechanical disruption in a lysis buffer + 4%TCEP (Tris(2-carboxyethyl)phosphine hydrochloride) (Machery-Nagel ref: 740395.107) with the Precellys system. The lysed tissues will be diluted in 100 mg/mL of Macherey-Nagel lysis buffer, aliquoted and stored at -80°C until extraction. Total RNA will be extracted in duplicate using the Nucleospin 96 RNA Core kit (Macherey Nagel ref: 740466.4), following the supplier's instructions.

Standard samples, controls and ZIKV and TONV viral RNA will be extracted and tested in parallel under the same conditions. The extracted RNA will be subjected to reverse transcriptase, using the Superscript One-Step RT-qPCR kit (Invitrogen ref: 11732088) according to the manufacturer's recommendations, with a probe and primer specific for ZIKV and TONV.