VOA标准英语2012--HIV Superinfections Appear Common

 

HIV Superinfections Appear Common

They’re called HIV “superinfections” and a study indicates they’re much more common than first thought. Researchers say this raises concerns about possible resistance to treatment and may require new approaches to AIDS vaccine¹ research.

Dr. Andrew Redd said there are HIV infections and then there are superinfections.

“A superinfection occurs when an individual is initially² infected with a strain or strains of HIV. And then at some point later on – after that person has developed an initial immune response to their first infecting strain – at that later time point they come into contact through risky³ behavior with a second viral strain and then are superinfected with that second strain,” he said.

Redd is the lead author of the study and a scientist at the National Institute of Allergy⁴ and Infectious Diseases. He said prior to the research done in Uganda it was thought that superinfections were rare, occurring in intravenous drug users or men who have sex with men. Not so.

“What we found in our study was that when we looked at a general population of heterosexual individuals in Uganda we found that it actually isn’t as rare as what we thought. And that it is occurring at a significant rate even in the general population,” he said.

So how does a person become superinfected? Well, it has to do in part with where you are and what HIV subtypes are prevalent.

“There’s geographic⁵ separation between what we call the HIV subtypes, or clades. One of the interesting things about where we work in Uganda is it is at sort of the crossroads of two of those clades. The clades are labeled and named by letter – A,B,C.D. And in Uganda, we have subtype A and subtype D,” said Redd.

Continued risky behavior after initial infection could lead to infection by another subtype of HIV. Current testing methods will confirm whether a person is HIV positive. But they cannot determine what HIV subtypes caused the infection. For that, the researchers need what’s called “viral sequencing” -- an in-depth, complicated look at the viral DNA⁶

Left untreated, superinfection could lead to an accelerated progression of HIV/AIDS. Redd says, though, that standard antiretroviral treatment should be effective against superinfections.

“We have no evidence so far and we don’t think that HIV superinfection affects the response to treatment. From what we can tell, individuals who get superinfected respond to treatment just fine and it lowers their viral load and they get healthier. One of the things that we’re worried about, though, if the possibility that an individual could get superinfected with a viral strain that is already resistant⁷ to the antiretroviral drugs and that would be a major problem. But to date that doesn’t seem to be a huge risk so far,” said Redd.

Superinfections could also affect how HIV vaccine research is conducted. For example, there are individuals who are at risk of HIV superinfection but do not become superinfected. They are somehow protected.

He said, “One question would be what natural immune response to their initial infection is protecting them from the superinfection. And if we can figure that out that may give us a very interesting avenue to pursue for HIV vaccine research.”

Redd added that current HIV vaccine strategies that try to “recreate the natural immune response may be insufficient⁸ to protect an individual from infection.”

1 vaccine   

n.牛痘苗，疫苗；adj.牛痘的，疫苗的

参考例句：

• The polio vaccine has saved millions of lives.脊髓灰质炎疫苗挽救了数以百万计的生命。
• She takes a vaccine against influenza every fall.她每年秋季接种流感疫苗。

2 initially   

adv.最初，开始

参考例句：

• The ban was initially opposed by the US.这一禁令首先遭到美国的反对。
• Feathers initially developed from insect scales.羽毛最初由昆虫的翅瓣演化而来。

3 risky   

adj.有风险的，冒险的

参考例句：

• It may be risky but we will chance it anyhow.这可能有危险，但我们无论如何要冒一冒险。
• He is well aware how risky this investment is.他心里对这项投资的风险十分清楚。

4 allergy   

n.(因食物、药物等而引起的)过敏症

参考例句：

• He developed an allergy to pollen.他对花粉过敏。
• The patient had an allergy to penicillin.该患者对青霉素过敏。

5 geographic   

adj.地理学的，地理的

参考例句：

• The city's success owes much to its geographic position. 这座城市的成功很大程度上归功于它的地理位置。 来自《简明英汉词典》
• Environmental problems pay no heed to these geographic lines. 环境问题并不理会这些地理界限。 来自英汉非文学 - 环境法 - 环境法

6 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

7 resistant   

adj.(to)抵抗的，有抵抗力的

参考例句：

• Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。
• They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。

8 insufficient   

adj.(for，of)不足的，不够的

参考例句：

• There was insufficient evidence to convict him.没有足够证据给他定罪。
• In their day scientific knowledge was insufficient to settle the matter.在他们的时代，科学知识还不能足以解决这些问题。