Latest studies on rhesus monkeys point to the risk of contracting the AIDS virus via the mouth
A NEW route used by the human
immunodeficiency virus (HIV) to sneak
into the body has been tracked by scientists. A series of studies on rhesus monkeys has suggested that the virus that
causes AIDS can infect individuals
through the mouth, and this includes
even those persons who do not sport
oral sores or bleeding gums. The study
not only underscores the risks of contracting the virus through oral sex, but
also the fact that we are still very naive
about the movements Of HIV from person-to-person at the microscopic level.
Researchers from the Dana-Farber
Cancer Institute in Boston, Massachusetts, and Tulane University in Los
Angeles, California, tried to infect sedated monkeys with the simian immunodeficiency virus (SIV), the virus that causes AIDS in monkeys. They administered
an SIV solution into the mouths of seven
monkeys and found to their surprise
that six of the seven became infected
with the virus even though they did not
have sores, cuts or a gum infection in
their mouths.
These findings "should be a warning
that oral sex is not safe sex," said Ruth M
Ruprecht, an immunologist from the
Dana-Farber Cancer Institute who led
the research team. Public health officials
have expressed great concern over
the study's results. Their fears source
from the fact that many consider the
contraction Of AIDS and oral sex to be
two mutually exclusive options.
Public health officials in the us have
already concluded that unprotected
oral intercourse was unsafe. In recent
years, a number of reports have surfaced about people who had become
infected with HIV even though they had
engaged in only oral sex. The federal
Centers for Disease Control and
Prevention (CDC) in Atlanta, Georgia,
had added unprotected oral sex to the
list of risk behaviours for transmission
of the virus, years ago. But because of
the lack of concrete evidence and the
conclusions reached by few studies
which indicated that saliva contained
compounds that made HIV less infectious, many became smug about the
risks.
Scientists accidentally stumbled
upon this latest finding while conducting an inquiry into a different matter.
Ruprecht and her colleagues had initially set out to probe how AIDS got transmitted from an infected mother to her
newborn child. The team believed that
newborns got infected at birth by swallowing the mother's blood or vaginal
fluids. The scientists supposed that it
was the absence of acid in the infants'
stomachs which probably made them
susceptible to the infection.
To verify their theory, the scientists
dribbled doses of SIV into the mouths of
adult rhesus monkeys who were given a.
drug to neutralise their stomach acids.
The monkeys, unable to inactivate the
AIDS virus, died. But researchers found
that adults who were not given the
drug also got infected. It was inferred
from these tests that an oral dose of
semen from an HIV-infected person can
lead to AIDS in another, if it comes into
contact with tissues in that person's
mouth.
One possible route taken by the
traveling virus could be the tonsils,
which contain large numbers of the
kinds of lymph cells that are vulnerable
to HIV and SIV. The team is trying to
understand the role of a layer of tissue
known as the mucosa (a mucous-secreting membrane that lines the mouth) in
transmitting the virus. The study also
indicated that all other conditions being
the same, oral infection could occur
with virus doses 6,000 times smaller
than those needed to cause the infection
rectally. However, experts pointed out
there is still no evidence that HIV can be
transmitted by casual contact such as
kissing or sharing utensils.
Next, the team tried to find out how
strong a virus solution was needed to
cause infection through the oral route.
They compared the most efficient
method of causing AIDS (direct injection
of viruses into the bloodstream), with
the oral method of infection and found
that it took a viral solution that was 830
times more potent to cause an infection
through the oral passage. The saliva of
an HIV-positive person contains a far
lesser amount of virus with only one
virus per millilitre of saliva, said
Ruprecht. But human semen contains
10 to 50 viruses per millilitre. Hence,
infection is more likely to occur through
semen than through saliva.
These results have come as a
surprise for a lot of people. Helene
Gayle, an HIV-prevention expert at CDC
points out that more educational work
on the risks of oral sex remains to be
done. Gayle plans to distribute educational material to community health
groups and state and local authorities to
get the message across to the public.
However, according to Anthony S
Fauci, chief of the National Institute of
Allergy and Infectious Diseases, parallels could hardly be drawn between the
experiments conducted on the monkeys and the condition found in
humans because the researchers have
used SIV, which is slightly different from
HIV and have also worked with pure
viruses for the tests, while most viruses
in humans are found inside cells. In
fact, there still remain many loose ends
that have to be tied up.
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