Most scientists now agree that a new coronavirus is most likely the cause of SARS, according to Friday's edition of Science magazine.

Chinese researchers, too, have found coronavirus-like particles in the lung cells of SARS victims.

The most recent findings were made by two researchers from the Institute of Microbiology and Epidemiology at the Academy of Military Medical Sciences.

However, Hong Tao, a researcher with the Institute for Viral Disease Control and Prevention at the Chinese Center for Disease Control and Prevention, China's CDC, and his colleagues are working steadfastly on chlamydia-like agents they have discovered and isolated from victims.

In an exclusive interview with China Daily, Hong Tao said that he believed that the chlamydia-like agents and the new coronovirus may have played "synthetic roles" in the deadly respiratory illness that spread worldwide.

On Sunday, Hong submitted a paper about their findings to The Lancet, a leading international medical journal based in Britain. International cooperation is very important in the effort to combat SARS, Hong said.

In their research, Hong and his colleagues isolated chlamydia-like agents in the lungs, livers, spleens, kidneys and lymph nodes of two SARS victims, one from Southwest China's Sichuan Province and the other from Beijing.

Previously, they had made the same finding from samples of five victims from Guangzhou in South China's Guangdong Province and North China's Shanxi Province.

At the same time, Hong's colleagues found coronavirus-like particles in the lungs of three of the seven cases.

The team was able to find special electron-dense matrix structures in the cytoplasm, the substance inside the membrane that surrounds the nucleus of the lung's cells, where both chlamydia-like agents and coronavirus-like particles were found.

Li Dexin, a researcher with Hong's group, found that genetically, a segment of coronavirus RNA was successfully amplified, cloned and analyzed by reverse transcription-polymerase chain reaction (RT-PCR).

Their results were identical to those found by foreign counterparts, who have published their findings in the past few weeks.

"The new coronavirus isolated from the lungs of the victims was more reliable," said Hong, who pointed out that those found by foreign researchers when looking at throat swabs might not be as conclusive.

Culprits Team up

Hong has kept abreast of the ample results from both international and Chinese scientists -- some of them his colleagues from China's CDC -- on the coronavirus and devoted much time to it and the chlamydia-like pathogen.

"It's intriguing to see two completely different infectious agents in the same acute disease or in the same tissue," Hong observed.

"We have definitely seen the chlamydia-like agent and the coronavirus in the lungs of three of the seven corpses.

"The fact raises questions to be answered."

In their paper submitted to the Lancet, Hong and his colleagues suggest that the above fact should help explain the unusual infectiousness of the epidemic and the clinical manifestations of SARS.

The disease appears suddenly with flu-like symptoms, like an infection of the upper respiratory tract.

It might be suggestive of the initial attack by the new coronavirus, Hong told China Daily.

However, the attack is followed by a second and much more profound infection of the lower tract, the lungs, where the chlamydia agent might play a dominant role, and/or the two agents synergistically interact to produce a severe infection of the lungs.

Toxic Substances

"Most probably, the majority of the deaths have been from the final onslaught of the chlamydia by its bacteria-like endotoxins, as its partner, the novel coronavirus, has paved the way," Hong says.

The lung damage seen in SARS patients was most likely done by toxic substances released from certain bacterium or bacteria into the blood, which was first found by Bi Shengli, another researcher with Hong's group.

The chlamydia-like agents seem to be able to dissolve cells and in the process the agents release the toxic substance -- endotoxins -- into the patients' blood.

At present, Hong and his colleagues are engaged in establishing animal models to further investigate the cause of SARS and to select the right medicine to fight it.

More Research

Meanwhile, Zhu Qingyu and Qing E'de from the Institute of Microbiology and Epidemiology declared on Friday they had set up an animal model and identified the coronavirus agents in the lung tissue of infected mice.

Also, they had isolated the coronavirus in a cell culture and obtained a sequence of coronavirus by RT-PCR.

The DNA sequence test showed the virus was more than 60 percent identical to the two known human coronaviruses.

In their serological test of the sera samples from 26 patients recovering from SARS with the isolated causative agent antigen, 23 showed positive reactions, Zhu told China Daily.

The samples came from patients in Guangzhou and Beijing.

Meanwhile, 31 healthy control samples were selected from the above two regions. They all tested negative.

As for the animal model, according to Zhu, they have only completed preliminary work and only found some chronovirus agents in the lung tissue of infected mice.

But their findings undoubtedly add to the evidence that a novel coronavirus is one of the agents associated with the outbreak, Zhu said.

Hong said: "It is doubtlessly apparent that the work of looking into the real nature of SARS needs longstanding international efforts and a systematic, comprehensive and multidisciplinary study."

(China Daily April 15, 2003)