It all started with scientists musing about how to
efficiently wipe out an entire mosquito population. The technology that
was born is powerful yet terrifying.
Gene drives are the techniques to introduce a gene
into an animal population and let it spread through the population very
rapidly till it is found in 100% of the organisms. How does it work? A
gene drive is introduced into a particular organism, say mosquito. It is
inherited by 50% of its offspring. The offspring has the gene drive on
one chromosome and a normal gene on the other chromosome from its other
parent. The gene drive has an inbuilt CRISPER, which cuts out the normal
gene on the opposite chromosome. The cut is repaired using the drive as
the template. Now both chromosomes have the gene drive. This way the
gene drive rapidly spreads through the population till all have the
modified gene.
In September 2018, Andrea Crisanti, a geneticist at
the Imperial College London, took a caged population of Anopheles Gambia
and introduced a gene drive, which disrupts a fertility gene called
doublesex. This prevents the female mosquito from biting or laying
eggs. Within 8-10 generations, the entire population had crashed. Other
scientists are working on gene drives against candida, rodents etc.
A more ambitious project is a gene drive that gets activated when any
virus infects a mosquito, whether it is dengue, chikungunya, Zika or
yellow fever.
Because of the inherent potential for misuse – which
can have grave and unpredictable outcomes – scientists have
simultaneously started building reverse drives that can undo the
original drive on command. Can human beings predict the ultimate
consequences of tinkering with genetics on a population scale? Ominous
questions face us today. It may be best that we tread cautiously. (Nature
9 July 2019)
The PERCH Study
The Pnemonia Etiology Research for Child Health
(PERCH) study was an ambitious project to identify the causes of severe
pneumonia in six resource poor countries: Bangladesh, Thailand, South
Africa, The Gambia, Zambia, Mali and Kenya. They tested nasopharyngeal,
urine, blood, induced sputum, lung aspirates, gastric aspirates and
pleural fluid using cultures and/or polymerase chain reaction (PCR in
1-5 year olds admitted for severe pneumonia. Viruses accounted for 61.4%
and bacteria for 27.3%. An interesting finding was that M.
tuberculosis can present as acute pneumonia in 5.9%. The study
showed that finding bacteria on a nasopharyngeal swab was not useful in
clinical decision making, but viruses like RSV and parainfluenza found
on nasopharyngeal swab were likely to be the etiological agents.
The study also found that in lower income countries,
secondary bacterial infection after a viral pneumonia was common. In
these settings, overcrowding and possible genetic mechanisms led to
dense nasopharyngeal colonization with S. Pnemoniae and H.
influenzae. Drip aspiration of these bacteria resulted in bacterial
pneumonias after mucosal breach by viral infections.
The PERCH study has found that 14% of acute
pneumonias are vaccine preventable. The next organism to target would be
RSV that accounted for 31.1% of all pneumonias. When we go to war
against childhood pneumonia, knowing who the enemy is, will make all the
difference. (Lancet 27 June 2019)
Social Robots for Hospitalized Children
‘Huggable’ is a robotic teddy bear that was recently
used in Boston Children’s Hospital to comfort and entertain hospitalized
children. A study recently published in the journal Pediatrics
compared a tablet-based virtual Huggable and a traditional teddy bear,
and found that the robotic teddy bear scored better on many points.
Children who used the robotic teddy bear moved around more, interacted
more, and were more emotionally connected with it. The robot can change
expressions, sing and play games. This makes it a valuable addition to
make the intimidating hospital environment more child-friendly.
Human-human interaction is steadily decreasing and
people are looking to technology to fill the yawning gap. (Pediatrics.
2019;144:e20181511)
Modifying the Gut Microbiome for Food Allergies
A recent study from Boston Children’s hospital has
found that some bacteria in the gut are associated with food allergies
and some help to reverse it. Fecal samples were collected every 4-6
months from babies who developed food allergies, and from controls who
did not have food allergies. Using computational methods, researchers
analyzed the difference in the gut microbiota of the two groups.
They then made a mouse model for egg allergy. Two
separate consortia of five or six species of bacteria derived from the
human gut that belonged to species within the Clostridiales or
the Bacteroidetes could suppress food allergies in the mouse
model, fully protecting the mice and keeping them resistant to egg
allergy. Giving other species of bacteria did not provide protection.
A whole new way to treat food allergies appears to be just around the
corner. (Nature Medicine. 2019; DOI: 10.1038/s41591-019-0461-z)