20 February 2021 | New Scientist | 7TWO variants of the SARS-CoV-
coronavirus that causes covid-
have combined their genomes
to form a heavily mutated hybrid
version of the virus.
The “recombination” event
was discovered in a virus sample
in California, provoking warnings
that we may be poised to enter
a new phase of the pandemic.
The hybrid virus is the result
of recombination of the highly
transmissible B.1.1.7 variant
discovered in the UK and the
B.1.429 variant first seen in
California. This second variant may
be responsible for a recent wave
of cases in Los Angeles because
it carries a mutation making it
resistant to some antibodies.
The recombinant was
discovered by Bette Korber at the
Los Alamos National Laboratory
in New Mexico, who told a meetingorganised by the New York
Academy of Sciences on
2 February that she had seen
“pretty clear” evidence of it in
her database of US viral genomes.
If confirmed, the recombinant
would be the first to be detected
in this pandemic. In December
and January, two research groups
independently reported that
they hadn’t seen any evidence
of recombination, even though
it has long been expected as it
is common in coronaviruses.
Unlike regular mutation, where
changes accumulate one at a time,
which is how variants such as
B.1.1.7 arise, recombination can
bring together multiple mutations
in one go. Most of the time, thesedon’t confer any advantage to the
virus, but occasionally they do.
Recombination can be of
major evolutionary importance,
according to François Balloux
at University College London.
It is considered by many to be
how SARS-CoV-2 originated.
Recombination could lead
to the emergence of new and
even more dangerous variants,
although it isn’t yet clear how
much of a threat this first
recombination event might pose.
Korber has only seen a single
recombinant genome among
thousands of sequences and it
isn’t clear whether the virus is
being transmitted from person
to person or is just a one-off.A merger of coronavirus variants in the US has sparked warnings that we
may be entering a new phase of the pandemic, reports Graham LawtonTwo variants combine
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Recombination commonly
occurs in coronaviruses because
the enzyme that replicates their
genome is prone to slipping off
the RNA strand it is copying and
then rejoining where it left off.
If a host cell contains two different
coronavirus genomes, the enzyme
can repeatedly jump from one
to the other, combining different
elements of each genome to
create a hybrid virus.The recent emergence of
multiple variants of the new
coronavirus may have created the
raw material for recombination
because people can be infected
with two different variants at once.
“We may be getting to the
point when this is happening
at appreciable rates,” says Sergei
Pond at Temple University in
Pennsylvania, who keeps an
eye out for recombinants by
comparing thousands of genome
sequences uploaded to databases.
He says there is still no evidence
of widespread recombination, but
that “coronaviruses all recombine,
so it’s a question of when, not if ”.
The implications of the finding
aren’t yet clear because very little
is known about the recombinant’s
biology. However, it does carry
a mutation from B.1.1.7, called
Δ69/70, which makes the UK
variant more transmissible,
and another from B.1.429,
called L452R, which can confer
resistance to antibodies.
“This kind of event could
allow the virus to have coupled
a more infectious virus with a
more resistant virus,” Korber
said at the New York meeting.
Lucy van Dorp, also at
University College London, says
that she hadn’t yet heard about
the recombinant, but “would
not be overly surprised if some
cases start to be detected”. ❚People are tested for
covid-19 in Los Angeles,
where cases have surged“This could have allowed
the virus to couple a more
infectious virus with a
more resistant virus”Daily coronavirus news round-up
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