Editor's Note: Science Scan is a roundup of recently published biotechnology-relevant research.
Pathologists in China have isolated and sequenced an animal coronavirus from two Himalayan palm civet cats (Paguma larvata) on sale at a market in Hong Kong. They compared the sequences of five existing genomes of the coronavirus that cause SARS (severe acute respiratory syndrome) in humans.
While the animal and human viruses are closely related, genetic analysis shows clear differences, according to a report in Science dated Sept. 5, 2003. It carries the title "Isolation and Characterization of Viruses Related to the SARS Coronavirus From Animals in Southern China." The report's co-authors are at Queen Mary Hospital in Hong Kong. (See BioWorld Today, July 31, 2003.)
SARS is a recently emerged human disease associated with pneumonia. It was first recognized in November 2002 in Guangdong Province, China. Subsequent to its introduction to Hong Kong in mid-February, the virus spread to more than 30 countries, where it caused disease in over 7,900 patients across five continents.
Human coronavirus appears to be an animal virus that crossed to humans relatively recently. Thus, identifying animals carrying the virus, the Science co-authors point out, is of major scientific interest and public health importance. Since the early cases of SARS in Guangdong reportedly occurred in restaurant workers handling wild mammals as exotic food, the researchers focused initially on wild animals recently captured and marketed for culinary purposes.
Further monitoring of the live animals that pass through markets in southern China may help researchers identify both the elusive virus reservoir and the species-to-species virus transmission events that led to the SARS outbreak. In addition to the civet cats, a raccoon dog (Nyctereutes procyonoides), a ferret badger (Arctonyx collaris) and some humans (Homo sapiens) working at the same market showed evidence of infection with a coronavirus similar to the human SARS virus.
The co-authors conclude their Science article by noting, "Our findings suggest that the markets provide a venue for the animal coronavirus-like viruses to amplify and transmit to new hosts, including humans. It is not clear, however, whether any one or more of these animals are the natural reservoir in the wild. It is conceivable," they add, "that civets, raccoon dogs and ferret badgers were all infected from another, as yet unknown, animal source, which is in fact the true reservoir in nature. However, because of the culinary practices of southern China, these market animals may be intermediate hosts that increase the opportunity for transmission of infection to humans.
"Further extensive surveillance on animals," they conclude, "will help to better understand the animal reservoir in nature and the interspecies transmission events that led to the origin of the SARS outbreak."
A joint team of experts, representing the Chinese government, the World Health Organization and the U.N. Food & Agriculture Organization, have agreed on recommendations for monitoring the live-animal trade and searching for a SARS reservoir. Their advice - including a call for expanded animal testing and international cooperation - went to Chinese authorities Sept. 5.
Six Months After HAART Starts Seen As Optimum Time For HIV/AIDS Prognosis
HAART (highly active antiretroviral therapy) became widespread in more-developed countries from 1996 onward, and has improved the outlook for HIV infection. However, not enough is known about how to predict the prognosis of people with HIV-1 infection starting HAART.
The initial measurement of specific immune response cells (CD4 cells) and viral load at the time patients undertake HAART is related to HIV/AIDS progression.
In general, the lower the CD4 cell count and higher the viral load, the worse the prognosis. As virus concentrations decline quickly in many individuals, with substantial CD4 increased counts within months of starting HAART, the accuracy of predictions of disease progression might be improved by accounting for initial response to therapy. This response might allow the early identification of patients who are at a high risk of progression and who might benefit from modification or intensification of treatment.
An international study in the Aug. 29, 2003, issue of The Lancet carries the self-explaining title: "Prognostic importance of initial response in HIV-1-infected patients starting potent antiretroviral therapy: Analysis of retrospective studies."
Researchers from the University of Bern in Switzerland analyzed 13 follow-up studies from Europe and North America. They included more than 9,000 patients receiving HAART (with a minimum of three drugs) for the first time. Overall, 152 patients died and 874 developed AIDS.
How Can Dietary Lipids Some Day Overcome Tuberculosis In Animal Models, If Not People?
Tuberculosis results in 2 millions deaths each year worldwide. Moreover, about 8 million new cases are reported annually. As such, TB is the leading cause of death from a bacterial disease.
Now, authors of an article in the September issue of Nature Cell Biology suggest that dietary lipids may help overcome such infections in animal models. Their article bears the title "Selected lipids activate phagosome actin assembly in maturation resulting in killing of pathogenic mycobacteria." Its co-authors are at EMBL in Heidelberg, Germany. Their new study might not only explain how the bacterium could subvert normal phagosomal maturation, but also propose new avenues for treating TB.
The causative agents of TB - Mycobacterium tuberculosis - infect white blood cells, where they are held in a specialized membraneous sac called phagosome. Normally, these would mature into a compartment containing degradative enzymes that would break down phagosomal contents. But Mycobacterium blocks that maturation - exactly how is not known.
The authors show that phagosomes containing the bacterium are unable to support the nucleation of actin. This component of the cell's skeletal network seems to be important for that maturation. Most remarkably, the study shows that certain natural lipids can reverse these processes and lower the survival rate of the pathogen in infected cells. Whether dietary lipids might one day become a feasible way to treat TB remains to be determined. However, the authors recommend testing the effectiveness of these lipids to overcome tuberculosis in animal models.