THE FOURTH STEP: How to freeze these fusion intermediates?

When cells expressing envelope protein are cocultured with cells expressing CD4 and coreceptor, mulitnucleated syncytia mass of protoplasm resulting from fusion of cells form over the course of 6 to 24 hours. To capture transitional intermediates during the process of binding and fusion, the cocultures were fixed in 0.2% formaldehyde after 5 hours. Why 5 hours and not 6+ hours? They wanted the fusion (transitional) intermediates fixed not the multinucleate cells.

This inactivated whole-cell preparation was the fusion-competent (FC) vaccine immunogen.

What's an immunogen substances (antigens) capable of provoking an immune response ?

Model of a fusion-competent immunogen is pictured below:

M

The right picture = virus-cell fusion occuring as the transitional intermediate of gp41
undergoes further changes to form a hairpin structure that draws the two membranes into close proximity.

What's next? You're just a click away to testing this fusion-competent (FC) vaccine with the Transgenic Mouse Model

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