DANGEROUS microbes that invade blood supplies could be eradicated using a
鈥渘eutron bomb鈥� strategy that kills viruses and bacteria but leaves red blood
cells intact. The creators of the technique believe it will give blood
transfusion services a vital defence against new pathogens that emerge to
threaten blood supplies.
Results from the first human trial of the treatment, which targets the DNA of
viruses and bacteria, were announced last week at the meeting of the American
Society of Hematology in San Francisco.
Each year, more than 40 million units of blood are used to treat patients
around the world. In developed countries, at least, the blood supply is
extremely safe thanks to regular screening and elimination of donors infected
with dangerous viruses such as HIV and hepatitis B.
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But health experts worry about emerging viruses, for which no tests exist.
Bacterial contamination of blood is also a growing problem. 鈥淚t is now causing
more death and sickness than viral contamination,鈥� says James AuBuchon of the
Dartmouth-Hitchcock Medical Center in New Hampshire, who conducted the trial for
the Massachusetts-based company Vitex.
Rather than try to detect blood-borne pathogens, John Chapman and his
colleagues at Vitex decided to destroy a very broad spectrum of microbes but
leave blood cells untouched, in much the same way a neutron bomb kills people
but leaves buildings standing. They took advantage of a peculiarity of red blood
cells: they contain no nucleus, so don鈥檛 depend on DNA or RNA. Viruses and
bacteria, however, universally rely on these nucleic acids to replicate and
function.
Chemists at Vitex created a family of small molecules they call Inactine,
which easily penetrate the membranes of cells and the protein coats of viruses.
Once inside, the positively charged Inactine molecules cuddle up to the
negatively charged DNA or RNA and unleash a chemical assault that leaves the
molecule scarred and unable to function. Treatment with Inactine can reduce
viral and bacterial contamination 10,000-fold or more鈥攅nough to cleanse
most blood samples.
Yet, as AuBuchon told blood specialists last week, this lethal assault does
not seem to harm red blood cells. His study involved taking two units of blood
from 12 healthy volunteers and treating one with Inactine and using the other as
a control. After the cells had been treated, the residual Inactine was removed
and the cells were stored for 28 days. Metabolic tests showed the cells were
essentially identical to untreated cells.
More importantly, the new data shows the treated cells caused no problems
when they were re-infused into the volunteers.
鈥淲e believe this is not just an incremental, but a fundamental change in the
way we can protect the blood supply,鈥� says Chapman.