医学考博英语翻译习题

医学考博英语翻译习题

An AIDS Mystery Solved

(1) About 15 years ago

，

a well- meaning man donated blood to the Red Cross in Sydney

，

Australia

，

not knowing he has been exposed to HIV-1

，

the virus that causes AIDS. Much later

，

public- health officials learned that some of the people who got transfusions? containing his blood

had

become

infected

with

the

same

virus;

presumably

they

were

almost

sure

to

die.

But

as

six

years

stretched

to

10

，

then

to

14

，

the

anxiety

of

health

officials

gave

way

to

astonishment.

Although two of the recipients have died from other causes

，

not one of the seven people known

to have received transfusions of the man

’

s contaminated blood has come down with AIDS. More

telling

still

，

the

donor

，

a

sexually

active

homosexual

，

is

also

healthy.

In

fact

his

immune

system

remains

as

robust

as

if

he

had

never

tangled

with

HIV

at

all.

What

could

explain

such

unexpected good fortune?

(2) A team of Australian scientists has finally solved the mystery. The virus that the donor

contracted and then passed on

，

the team reported last week in the journal Science. contains flaws

in its genetic script that appear to have rendered it innocuous?.

“

Not only have the recipients and

the donor not progressed to disease for 15 years

，

”

marvels molecular biologist Nicholas Deacon

of Australia

’

s Macfarlane Burnet Centre for Medical Re- search

，

“

but the prediction is that they

never will.

”

Deacon speculates that this

“

impotent

”

HIV may even be a natural inoculant? that

protects its carriers against more virulent strains? of the virus

，

much as infection with cowpox

warded off smallpox in 18th-century milkmaids.

(3) If this ______ proves right

，

it will mark a milestone in the battle to contain the late-20th

century

’

s most terrible epidemic. For in addition to explaining why this small group of people

infected with HIV has not become sick

，

the discovery of a viral strain that works like a vaccine

would have far-reaching implications.

“

What these results suggest

，

”

says Dr. Barney Graham of

Tennessee

’

s Vanderbilt University

，

“

is that HIV is vulnerable and that it is possible to stimulate

effective immunity against it.

”

(4)

The

strain

of

HIV

that

popped

up?

in

Sydney

intrigues

scientists

because

it

contains

striking abnormalities in a gene that is believed to stimulate viral duplication. In fact

，

the virus is

missing so much of this particular gene

—

known as nef

，

for negative factor

—

that it is hard

to imagine how the gene could perform any useful function. And sure enough

，

while the Sydney

virus

retains

the

ability

to

infect

T

cells

—

white

blood

cells

that

are

critical

to

the

immune

system

’

s ability to ward off infection

—

it makes so few copies of itself that the most powerful

molecular tools can barely detect its presence. Some of the infected Australians

，

for example

，

were found to carry as few as one or two copies of the virus for every 100000 T cells. People with

AIDS

，

by contrast

，

are burdened with viral loads thousands of times higher.

(5)

At

the

very

least

，

the

nef

gene

offers

an

attractive

target

for

drug

developers.

If

its

activity can be blocked

，

suggests Deacon

，

researchers might be able to hold the progression of

disease

at

bay

，

even

in

people

who

have

developed

full-blown

AIDS.

The

need

for

better

AIDS- fighting

drugs

was

underscored

last

week

by

the

actions

of

a

U.S.

Food

and

Drug

Administration advisory panel

，

which recommended speedy approval of two new AIDS drugs

，

including

the

first

of

a

new

class

of

compounds

called

protease?

inhibitors?.

Although

FDA

commissioner David Kessler was quick to praise the new drugs

，

neither medication can prevent

or cure AIDS once it has taken hold.

(6) What scientists really want is a vaccine that can prevent infection altogether. And that

’

s

what makes the Sydney virus so promising

—

and so controversial. Could HIV itself

，

stripped

of nef and adjacent sections of genetic material

，

provide the basis for such a vaccine

，

as Deacon

and his colleagues cautiously suggest? Ongoing work on SIV

，

the simian? immunodeficiency

virus that causes an AIDS-like illness in monkeys

，

indicates that this might be less far- fetched

than

it

sounds.

Ronald

Desrosiers

at

the

New

England

Regional

Primate

Re-search

Center

has

demonstrated that when the nef gene is removed from SIV

，

the virus no longer has the power to

make monkeys sick. Moreover

，

monkeys inoculated? with the nef free SIV developed marked

resistance to the more virulent strain.

(7)

But

few

scientists

are

enthusiastic

about

testing

the

proposition

by

injecting

HIV

—

however

weakened

—

into

millions

of

people

who

have

never

been

infected.

After

all

，

they

note

，

HIV

is

a

retrovirus?

，

a

class

of

infectious

agents

known

for

their

alarming

ability

to

integrate

their

own

genes

into

the

DNA

of

the

cells

they

infect.

Thus

once

it

takes

effect

，

a

retrovirus infection

—

unlike those of viruses that cause measles

，

smallpox and any number of

others diseases

—

is permanent. While some retroviruses are benign

，

others can strike without

warning. Some remain hidden for

years

，

only to trigger disease late in life

when the immune

system starts to decrease.

(8)

This

makes

vaccine

development

extremely

risky.

A

weakened

strain

of

SIV

that

protected adult monkeys

，

for example

，

looked safe until researchers at the Dana Farber Cancer

Institute

in

Boston

showed

that

newborn

monkeys

with

immature

immune

systems

did

not

respond as healthy adults do. All the young primates

，

in fact

，

developed the very disease the

weakened

virus

was

supposed

to

prevent.

For

this

and

a

host

of

other

reasons

，

most

AIDS

researchers argue that the only prudent strategy is to concoct? a hybrid? vaccine

，

putting the key

features

of

a

disabled

AIDS

virus

into

something

more

benign

than

a

retrovirus.

Among

the

leading candidates

：

the vaccinia virus that successfully wiped out smallpox.

(9)

A

handful

of

researchers

，

however

，

argue

that

the

more

dangerous

retroviral

vaccine should not be written off prematurely. Desrosiers

，

for one

，

believes the situation in parts

of

the

developing

world

(where

the

chance

of

HIV

infection

may

reach

40%

among

sexually

active adults) has become so desperate that a retroviral vaccine may be worth the ______. A live

vaccine made from HIV

，

he maintains

，

can be made safer by removing not just the nef gene but

several others as well. Desrosiers has found that he can cripple HIV by chemically deleting four of

its nine known genes and still get a virus that replicates

，

at least in chimpanzees.

(10) At present

，

concerns about safety are so overwhelming that efforts to develop a

live

retroviral

vaccine

are

unlikely

to

win

much

support.

But

that

could

change

as

studies

of

long-term survivors

—

that small

，

charmed circle of people who have been infected with the

AIDS virus but have remained disease- free

—

provide new insights into the weaknesses of the

viral enemy and the untapped strengths of its human targets.

“

These individuals

，

”

observes Dr.

Warner

Greene

，

director

of

the

Gladstone

Institute

of

Virology

and

Immunology

in

San

Francisco

，

“

are natural experiments

，

and they hold a great secret that we are still trying to

decipher?.

”

Indeed

，

it is entirely possible that the eight Australians who have caused such a stir

will be cited by medical texts as the first people on the planet to be successfully

，

if accidentally

，

vaccinated against the AIDS virus

—

a virus that until now has seemed all but invincible.

艾滋之谜揭晓

(1)

大约在

15

年前，澳大利亚悉尼有一位人士好心向红十字会捐血，不知道自己