Ho ho ho! Gather ’round, my little elves, for a tale not of the North Pole, but of a brave little soul who faced a challenge much graver than a blizzard on Christmas Eve. In a world where the measles virus (MeV) can be naughtier than the Grinch, it sometimes leaves behind a rare but serious condition called subacute sclerosing panencephalitis (SSPE), a bit like coal in a stocking, but far worse.

Now, there’s no magical sleigh to whisk away SSPE, and no approved potions or elixirs to treat it. But in our story, a 5-year-old child, much like those who eagerly await my arrival each year, was given a glimmer of hope with a treatment called remdesivir, a nucleoside analog that’s a bit like the candy canes of medicine—sweet in theory, but not a cure-all.

With the first two courses of this experimental treatment, our young hero’s quality of life twinkled like the star atop the Christmas tree. Alas, the third course was like getting socks instead of toys—no further joy was brought, and the child, like the last leaf of autumn, eventually succumbed to the condition.

After the winter’s snow had melted, a post-mortem examination of the child’s brain was like looking at the aftermath of a snowstorm—neurons lost, demyelination evident, and MeV RNA-positive cells as abundant as snowflakes. Next-generation sequencing, a bit like my list-checking, revealed a complete MeV genome with mutations as unique as snowflakes, including a hypermutated M gene, a hallmark of SSPE.

But not all was silent night; the mutations in the polymerase (L) gene did not confer resistance to our candy cane, remdesivir. And a curious mutation, N465I, in the F gene, made the virus hyperfusogenic, spreading through the brain like reindeer through the night sky, no longer sticking to lymphocytes but infecting neural cultures with ease.

In the spirit of Christmas, this case lights a candle of hope for remdesivir as a potential SSPE treatment and reminds us of the importance of understanding these viral Scrooges. So, as we hang our stockings and trim our trees, let’s not forget the ongoing battle against such invisible foes, and the need for science to lead the sleigh.

IMPORTANCE

Just as I, Santa, deliver joy, MeV delivers quite the opposite, causing acute, systemic disease and being a rather unwelcome guest in humans. It can sneak into the brain without an invitation, causing SSPE, a condition as rare as a white Christmas in the tropics, but as devastating as a blizzard. These SSPE-causing viruses are like mischievous elves, with a hypermutated genome and a hyperfusogenic F protein that helps them spread faster than rumors of my whereabouts on Christmas Eve.

While no treatment is as certain as my annual journey, remdesivir has shown a glimmer of promise, like the first light of dawn on Christmas morning. It worked against MeV in vitro, and in our tale, it brought temporary relief without letting the virus outsmart it. This encourages more exploration of remdesivir for SSPE, much like the search for the perfect Christmas gift. And understanding the viral proteins? Well, that’s as important as knowing the right way to wrap a present. It helps us understand how these viruses spread their not-so-jolly cheer.