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Archive - Apr 14, 2012

New Blood Test Links Strains of Toxoplasma gondii to Severe Illness in Newborns

Scientists have identified which strains of the Toxoplasma gondii parasite, the cause of toxoplasmosis, are most strongly associated with premature births and severe birth defects in the United States. The researchers used a new blood test developed by scientists at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, to pinpoint T. gondii strains that children acquire from their acutely infected mothers while in the womb. Pregnant women can become infected with T. gondii through contact with cat feces that contain infectious forms of the parasite or by eating undercooked meat. Women who become infected while pregnant may miscarry, give birth prematurely, or have babies with eye or brain damage. “If undetected or untreated, congenital toxoplasmosis can have serious consequences for a child’s quality of life,” noted NIAID Director Anthony S. Fauci, M.D. “The findings from this study support the value of screening for toxoplasmosis to identify patients who could benefit from treatment.” Currently available blood tests can determine whether a person has ever been infected with any strain of Toxoplasma parasite. The experimental test developed at NIAID improves upon the older tests because it can detect the presence of strain-specific antibodies that distinguish infecting strains from one another. The test was developed by Michael Grigg, Ph.D., of NIAID’s Laboratory of Parasitic Diseases, and his colleagues. It was applied to blood samples collected between 1981 and 2009 as part of the National Collaborative Chicago-Based Congenital Toxoplasmosis Study. The study of congenitally infected children was initiated by NIAID grantee Rima McLeod, M.D., of the University of Chicago, who is the first author of the new study, published online on April 11, 2012 in Clinical Infectious Diseases.

Direct Transfer of Chloroplast Genes into Cell Nucleus

Chloroplasts, the plant cell’s green solar power generators, were once living beings in their own right. This changed about one billion years ago, when they were swallowed up, but not digested, by larger cells. Since then, they have lost much of their autonomy. As time went on, most of their genetic information found its way into the cell nucleus; today, chloroplasts would no longer be able to live outside their host cell. Scientists on Dr. Ralph Bock’s team at the Max Planck Institute of Molecular Plant Physiology in Germany have discovered that chloroplast genes take a direct route to the cell nucleus, where they can be correctly read in spite of their architectural differences. Their results were published online on April 12, 2012 in Current Biology. Cyanobacteria are among the oldest life forms, and appear to be the forerunners of green chloroplasts in plant cells. They do not possess a true cell nucleus, but their genetic substance is made up of the same four building blocks as that of humans, plants, and animals. Therefore, the genes encoded in the chloroplast DNA can also be read in the cell nucleus; indeed, many genes that were still found in the cell organelles during early evolution are now located exclusively in the genome of the nucleus. How they made their way there has previously been unclear. Two mechanisms appeared likely: either direct transport in the form of DNA fragments from the chloroplasts to the nucleus or transport in the form of mRNA, which is then transcribed back into DNA. The direct transfer of DNA appears to predominate in the chloroplasts, but this pathway raises two problems. The first problem lies in the promoters, the DNA sequences which ensure that genes are recognized as such.