Based on the available research findings, it is likely that cells fused into syncytia by SARS-CoV-2 produce a large number of exosomes carrying spike protein. Here is a summary of the key findings:
- SARS-CoV-2 spike-induced syncytia
- The SARS-CoV-2 spike protein (SARS-2-S) is able to induce the formation of syncytia in infected cells.
- Syncytia are multinucleated cells that arise through the fusion of several cells, a process mediated by the spike protein.
- Release of exosomes from syncytia
- It has been shown that syncytia formed by a SARS-CoV-2 infection release exosomes that contain viral components, including the spike protein.
- These exosomes, referred to as “syncytium-derived exosomes” (Syn-Exos), carry specific protein signatures related to the virus.
Detection of spike protein in exosomes
- Spike protein detection
- Studies have demonstrated the presence of SARS-CoV-2 spike protein on the surface of exosomes isolated from infected cells and from vaccinated individuals.
- Transmission electron microscopy has visually confirmed spike protein antigens on exosome surfaces.
- Quantitative increase
- Investigations have shown that the concentration of exosomes carrying the SARS-CoV-2 spike protein increases markedly after an infection or vaccination.
- This suggests that cells producing the spike protein, including syncytia, are likely to release a greater number of spike-containing exosomes.
Implications and mechanisms
- Viral spread and immune response
- Exosomes carrying spike proteins may potentially facilitate the spread of viruses and modulate immune responses.
- These exosomes may play a role in the activation of macrophages and the triggering of inflammatory responses.
- Senescence and pathology
- It has been observed that the syncytia formed by SARS-2 spike exhibit a senescence-like phenotype.
- The senescent outcome of these syncytia, including the release of exosomes, could contribute to disease pathology, particularly in organs such as the heart.
While the study does not explicitly state that syncytia produce a “high number” of spike-containing exosomes compared with non-fused cells, the findings strongly indicate an increased production and release of these exosomes from syncytia. This increased production is likely attributable to the larger size and the altered cellular machinery of syncytia, as well as to the concentrated presence of viral proteins in these fused cells.
It is important to note that ongoing research in this area may provide more definitive quantitative data on the exosome production rates of syncytia compared with non-fused cells infected with SARS-CoV-2.
