SARS-CoV-2 susceptibility and vulnerability of human blastocysts during in vitro preimplantation development.

Laser-assisted hatching makes 90.5% (19/21) of cryopreserved human blastocysts susceptible to authentic SARS-CoV-2 Delta infection, unlike intact zona pellucida embryos.

• Why it matters: Entry-factor expression and pseudovirus data suggested vulnerability, but the effects of authentic infection on lineage specification and developmental competence were unknown.
• What they did: Cryopreserved human embryos were exposed to authentic SARS-CoV-2 (B.1.617.2, Delta) and assessed for infection (viral dsRNA), development at 24 hours (surface area, total cells, NANOG+ and GATA4+ lineages), and digital transcriptomics (mock n = 29; SARS-CoV-2 n = 28; n = 5 minipools).
• The result: Infected blastocysts (n = 48) showed reduced surface area (p = 0.0003), fewer total cells (p = 0.0139), and fewer NANOG+ epiblast cells (p = 0.0054) without changing GATA4+ primitive endoderm (p = 0.5255), with prolonged replication linked to embryonic lysis and death.

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