Recent Activity and Insights from Investigating the Gut Microbiome

Recent highlights from research on the gut microbiome include:

• The MNV norovirus induces Crohn's disease symptoms in those mice that carry the ATG16L1 gene variant, suggesting a plausible way in which a virus infection could lead to this disease in susceptible hosts, according to Thaddeus Stappenback and collaborators at Washington University School of Medicine in St. Louis, Mo., whose report appears in the June 25 Cell (141:1135-1145).

• A shift in balance among gut bacteria toward higher levels of proteobacteria could be a signal for the development of colon cancer, according to Temitope Keku and her collaborators at the School of Medicine of the University of North Carolina at Chapel Hill, whose report appears in the May-June 2010 Gut Microbes (1:138-147).

• Gastrointestinal virus genome patterns, which were obtained by analyzing human fecal samples, vary from one individual to another, including within pairs of identical twins, according to Jeffrey Gordon and his collaborators at Washington University School of Medicine in St. Louis, Mo., whose report appears in the 15 July 2010 Nature (466:334-338).

FDA, USDA Move Toward Reducing Antibiotic Resistance in Agricultural Settings

Officials of the Food and Drug Administration (FDA) in June issued draft guidance to reduce the development of resistance to medically important antimicrobial drugs used in food-producing animals. "The overall weight of evidence available supports the conclusion that using medically important antimicrobial drugs for production or growth enhancing purposes (i.e., non-therapeutic or subtherapeutic uses) in food-producing animals is not in the interest of protecting and promoting the public health," agency officials state. Thus, they recommend "phasing in" restrictions that would limit the use of antimicrobial drugs to situations "considered necessary for assuring animal health." U.S. Department of Agriculture (USDA) officials are saying much the same thing. "The use of antibiotics in animal agriculture does lead to some cases of antibacterial resistance among humans and in the animals themselves, and it is important that these medically important antibiotics be used judiciously," says John Clifford, who is deputy administrator for veterinary services at the USDA Animal and Plant Health Inspection Service. He spoke during a July hearing, "Antibiotic Use in Animal Agriculture," convened by the House of Representatives Subcommittee on Health of the Committee on Energy and Commerce.

Tough Pathogens, Host Immune Responses, Varied Outcomes

Sometimes virulent pathogens overcome the host immune system, but other times immunity prevails, particularly when stimulated with carefully tailored vaccines. Here are several recent examples of noteworthy host failures and potential successes in the face of some of particularly formidable pathogens:

• By inhibiting host cell apoptosis, virulent strains of Mycobacterium tuberculosis enhance pathogen spread and delay the recruitment of specialized killer cells to the site of infection, with direct consequences in controlling the bacterial burden in the lung and perhaps explaining how this pathogen can elude host immune responses, according to Samuel Behar of Brigham and Women's Hospital and Harvard Medical School in Boston, Mass., and his collaborators, whose report appears in the July Nature Immunology (11:751-758).

• A particular human antibody, designated VRC01, can block more than 90% of strains of HIV-1; it almost exactly mimics the binding of that virus to a CD4+  cell and thus is helping to renew hopes for developing an effective vaccine against HIV, according to Gary Nabel at the Vaccine Research Center of the National Institute of Allergy and Infectious Diseases in Bethesda, Md., and his collaborators; their report appeared online on 8 July in Nature.

• Swapping essential genes in a pathogen with those of their counterparts from naturally cold-adapted bacteria renders that pathogen temperature sensitive and makes it unable to grow systemically at 37°C but still able to trigger protective, cell-mediated immune responses-in this case, protecting mice against Francisella tularensis subsp. novicida, according to Francis Nano at the University of Victoria in Victoria, British Columbia, Canada, and his collaborators; their report was published online on 12 July in Proceedings of the National Academy of Sciences.

 

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