Tips from the journals of the American Society for Microbiology

A new vaccine strategy inducing antibodies capable of blocking interaction among disease-causing proteins may offer a safe and effective approach against respiratory syncytial virus (RSV). The researchers from the University of Georgia, Athens and the Centers for Disease Control and Prevention, Atlanta, Georgia report their findings in the January 2010 issue of the Journal of Virology.

RSV is a significant human virus that can cause life-threatening respiratory illness in infants, young children, and the elderly. Several prior attempts at RSV vaccine candidates have failed due to lack of protection and greater risk of serious disease. Previous studies have provided strong evidence that G protein peptides can induce protective immunity against RSV, however, CX3C-CX3CR1 G protein interaction may contribute to disease pathogenesis making it an important target for RSV prevention.

In the study researchers studied mice vaccinated with G protein peptides or polypeptides containing the CX3C for antibody production and disease prevention. Results showed that vaccinated mice generated antibodies capable of inhibiting G protein CX3C-CX3CR1 interaction, reducing viral level in the lungs, and minimizing weight loss and pulmonary inflammation.

“The results suggest that RSV vaccines that induce antibodies that block G protein CX3C-CX3CR1 interaction may offer a new, safe, and efficacious RSV vaccine strategy,” say the researchers.

(W. Zhang, Y. Choi, L.M. Haynes, J.L. Harcourt, L.J. Anderson, L.P. Jones, R.A. Tripp. 2010. Vaccination to induce antibodies blocking the CX3C-CX3CR1 interaction of respiratory syncytial virus G protein reduces pulmonary inflammation and virus replication in mice. Journal of Virology, 84. 2: 1148-1157.)

Tree Shrew Offers Small-Animal Model of Hepatitis C Virus Infection

Researchers from Japan suggest that the tree shrew may be a practical small-animal model for studying the progression of human hepatitis C virus (HCV) infection. This discovery would replace the need for rare and expensive studies using chimpanzees, currently the only validated animal model for HCV. They report their findings in the January 2010 issue of the Journal of Virology.

HCV is a highly potent viral infection that can ultimately lead to chronic hepatitis, liver steatosis, cirrhosis, and hepatocellular carcinoma. The current course of treatment against HCV includes interferon therapy (stimulating the processes within cells that slow the reproduction and growth of the virus) in conjunction with the antiviral drug ribavirin, however, the combination treatment is difficult for patients to endure and is often ineffective.

The tupaia (Tupaia belangeri), also known as a tree shrew, is a small non-primate mammal commonly found in certain regions of Southeast Asia. Previous studies have shown tupaias to be susceptible to a wide range of human-pathogenic viruses, including hepatitis B. In this study researchers inoculated tupaias with HCV and analyzed the progress of infection over a three-year period. Results showed mild hepatitis and intermittent viremia during the acute phase of infection, chronic hepatitis that worsened over time, and the detection of liver steatosis, cirrhotic nodules and the production of new tumors.

“These data suggest that the tupaia is a practical animal model for experimental studies of HCV infection,” say the researchers. “Comparative studies of HCV infection in different species will help us to understand the basic mechanisms of persistent infection.”

(Y. Amako, K. Tsukiyama-Kohara, A. Katsume, Y. Hirata, S. Sekiguchi, Y. Tobita, Y. Hayashi, T. Hishima, N. Funata, H. Yonekawa, M. Kohara. 2010. Pathogenesis of hepatitis C virus infection in Tupaia belangeri. Journal of Virology, 84. 1: 303-311.)

Phage Therapy May Reduce Salmonella Infection in Pigs

An anti-salmonella phage cocktail administered to healthy pigs may limit transmission of the bacteria from infected pigs during transport to processing facilities and ultimately minimize the cases of human salmonella food-borne illness. The researchers from Purdue University and USDA ARS, Livestock Behavior Research Unit, West Lafayette, Indiana, report their findings in the January 2010 issue of the journal Applied and Environmental Microbiology.

According to the Centers for Disease Control and Prevention there are approximately 40,000 confirmed human cases of salmonellosis in the United States each year, of which an estimated 400 result in death. Salmonella is transmitted among animals through contact with infected feces. Contamination numbers are often at their highest when healthy and infected animals are housed together in trailers and holding pens on their way to processing facilities, ultimately deterring many on-farm anti-salmonella intervention strategies. Infection and increased shedding of bacteria just prior to entering processing facilities presents a significant problem in terms of food safety.

Phage therapy involves the use of viruses that invade and kill harmful bacterial cells. In a preliminary study researchers inoculated 3 to 4 week-old pigs with salmonella bacteria and then immediately administered the anti-salmonella phage cocktail. Results showed that salmonella colonization was reduced by 99.0 to 99.9% in the tonsils and parts of the small and large intestines. Additionally, they tested the efficacy of phage therapy in a production-like setting by inoculating four market-weight pigs with salmonella bacteria and placing them in a holding pen for 48 hours enabling contamination to occur. Two groups of healthy pigs, one receiving the anti-salmonella phage cocktail and the other a control, were then comingled with the infected pigs in the contaminated pen. Results showed significantly reduced salmonella concentrations in parts of both the small and large intestines.

“The data presented here demonstrate that administering a phage cocktail to pigs prior to exposure to a salmonella-contaminated environment can effectively reduce salmonella colonization in naïve pigs,” say the researchers. “We further show that the phage cocktail could be effectively microencapsulated, making feed or water delivery possible.”

(S.K. Wall, J. Zhang, M.H. Rostagno, P.D. Ebner. 2010. Phage therapy to reduce preprocessing Salmonella infections in market-weight swine. Applied and Environmental Microbiology, 76. 1: 48-53.)

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