Science - USA (2020-02-07)

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structural proteins. Researchers hoped
this mock infection with canarypox would
rev up both the cell-killing and antibody-
producing arms of the immune system. The
boost contained a recombinant version of
the surface protein mixed with an immune
system booster, or adjuvant.
In the Thai study, a similar vaccine com-
bination reduced infections by 31%. The
field widely agreed that this wasn’t good
enough to bring the vaccine to market, but
researchers were divided over whether it
made sense to try to build on this vaccine
strategy or abandon it.
Gray says the new trial, which used a
slightly improved vaccine that was tailor-
made for the HIV subtype circulating in
South Africa, was worth the gamble given
the severity of the epidemic there—it is home
to 7.7 million of the world’s 37.9 million HIV-
infected people. “The epidemic is out of con-
trol here and we have to take steps to have a
biomedical intervention,” Gray says. NIAID
Director Anthony Fauci says he has no re-
grets about backing the study, as no other
vaccine had shown even modest promise in
an efficacy study. “I don’t think it was a bad
choice. It was the only choice.”
To this day, no one knows which immune
responses can prevent an HIV infection, but
many researchers have focused on creating
a vaccine that can trigger antibodies capa-
ble of “neutralizing” the virus: blocking its
ability to infect cells in lab studies. The vac-
cines in the Thai trial triggered production
of antibodies that bound to HIV but did not
neutralize it, Fauci notes, raising the possi-
bility this was good enough to offer some
protection. “We were struggling for years
and years, and so we grabbed onto the
slightest positive effect,” he says. “Given the
seriousness of the epidemic, if this was all
we had and vaccines that stimulated neu-
tralizing antibodies were years down the
pipeline, do you do something or nothing?”
Fauci notes that the Thai study enrolled
people at relatively low risk of HIV—their
rate of new infections was about 0.3% per
year. In the South Africa study, the rate
of new infections per year was about 4%
in women and 1% in men. That contrast
might explain why the vaccine appeared to
work in Thailand but not in South Africa.
“It could be the protection was completely
overwhelmed,” Fauci says.
Mitchell Warren, who heads AVAC, a non-
profit HIV prevention advocacy group, says
this latest failure won’t slow the vaccine
field. “There are other products in efficacy
trials and there’s a slightly larger pipeline
in phase I trials than we’ve had in a long
time,” says Warren, who was on the moni-
toring board that recommended stopping
the South African study. j

T

he oceans’ great continent-wrapping

currents, each one moving as much

water as all the world’s rivers com-

bined, can rightly be considered the

planet’s circulatory system. And this

circulation, it appears, has started to

thump faster: For nearly 25 years the cur-

rents have been rapidly speeding up, partly

because of global warming.

That’s the conclusion of a new paper out

this week in Science Advances. Based on

observations combined with models, the au-

thors claim that from 1990 to 2013, the en-

ergy of the currents increased by some 15%

per decade. “This is a really huge increase,”

says Susan Wijffels, an oceanographer at

the Woods Hole Oceanographic Institution.

“It’s going to stimulate a lot of other work.”

If the acceleration is real, it could affect jet

streams, weather patterns, and the amount

of heat stored in the ocean’s depths.

Oceanographers have suspected that cli-

mate warming is affecting ocean circula-

tion, but so far, observations haven’t shown

a trend, says Hu Shijian, an oceanographer

at the Chinese Academy of Sciences’s Insti-

tute of Oceanology and lead author of the

study. The Kuroshio Current, running up

Eastern Asia, has seemed stable, whereas the

Agulhas, flowing along Africa’s eastern coast,

has broadened, fracturing into meandering

eddies. The Atlantic Ocean’s Gulf Stream may

be weakening as Arctic melt slows its driver,

the sinking of salty water in the North At-

lantic, whereas currents in the Pacific Ocean

have seen a strong uptick. Hu decided only

a global view could reveal any overall trend.

No sustained, direct measurements of cur-

rents around the world are available, how-

ever. Instead, Hu’s team turned to so-called

reanalyses, which combine observations of

the ocean and atmosphere with computer

models to fill in the gaps and produce a

global picture. The approach is tricky to use

for time spans of decades: Changes in ob-

servations, for example when new satellites

come online, can cause unknown biases.

So Hu’s team combined five different re-

analyses of ocean circulation, hoping their

differing methods could reveal a true trend.

From each one they extracted the ocean’s

kinetic energy month by month, at a coarse

scale that would ignore the turbulence of

eddies and storms. And each showed a dis-

tinct rise starting around 1990.

Was it real? A look at data from the Argo

array, a fleet of nearly 4000 robotic floats de-

ployed around the world, provided the best

test. The floats have been bobbing up and

down in the ocean’s uppermost 2000 meters

for the past 15 years , measuring tempera-

ture and salinity. They don’t track velocity

through the water column. But their data do

indicate where winds have piled up water,

helping create differences in pressure that

drive large-scale flows. By combining those

A warming climate appears to be altering global currents, reconstructed here from satellite and ship readings.

Climate change spurs global

speedup of ocean currents

Rising winds boost flows in tropics and Southern Ocean

OCEANS

By Paul Voosen

Published by AAAS