Prior Exposure to Seasonal Influenza May Explain the Mildness of the 2009 H1N1 Pandemic
Hong Kong researchers suggest a new theory for why swine flu infections turned out to be so mild. Prior exposure to seasonal influenza A, either infection or vaccination, may induce a cross-reactive immune response against the pandemic virus. They report their findings in the July 2010 issue of the Journal of Virology.
Although the outbreak of human H1N1 in 2009 spread to pandemic proportions, the illness was considered mild in most patients compared to seasonal influenza. Currently available seasonal flu vaccines do not offer cross-reactivity to pandemic H1N1 in any age group, suggesting that individuals previously infected or exposed to seasonal influenza A viruses may have memory cell-induced cross-protection to pandemic H1N1.
Prior research showed humans having cross-reactive memory cells to a wide range of H5N1 peptides despite any previous exposure to avian influenza A (H5N1). In this study researchers determined that memory cells established by seasonal influenza viruses can break down pandemic H1N1-infected target cells and ultimately induce cross-protective antibodies.
"Our data suggest that individuals who were infected with seasonal human influenza A viruses previously or who received seasonal human influenza vaccines may derive benefit, at least in part, from the preexisting cross-reactive memory cytotoxic T lymphocytes to reduce the severity of pdmH1N1 infection even without protective antibodies," say the researchers.
(W. Tu, H. Mao, J. Zheng, Y. Liu, S.S. Chiu, G. Qin, P.L. Chan, K.T. Lam, J. Guan, L. Zhang, Y. Guan, K.Y. Yuen, J.S. Malik Peiris, Y.L. Lau. 2010. Cytotoxic T lymphocytes established by seasonal human influenza cross-react against 2009 pandemic H1N1 influenza virus. Journal of Virology, 84. 13: 6527-6535.)
New Test May Simply and Rapidly Detect Lyme Disease
Researchers from the National Institutes of Health have developed a more sensitive test for Lyme disease that may offer earlier detection and lower cost. The details are reported in the June 2010 issue of the journal Clinical and Vaccine Immunology.
Lyme disease is a bacterial infection transmitted to animals and humans by deer ticks. A skin lesion at the site of the bite is one of the first signs of infection followed by potential neurological, cardiac, and rheumatological complications upon entering the bloodstream. The Centers for Disease Control and Prevention currently recommends a two-step blood test for diagnosing the disease, however, several limitations include low sensitivity during the early stages of infection, significant time and expense, and an inability to distinguish between active and prior infection.
In prior studies the luciferase immunoprecipitation system (LIPS) test showed promise at detecting a variety of infectious agents including viral and fungal pathogens. Here, LIPS was evaluated for its ability to detect antibody responses to Borrelia burgdorferi proteins in blood samples taken from a patient group (some healthy and some with Lyme disease) as well as a control group. Results showed that diagnostic levels of 98% to 100% were achieved using LIPS in conjunction with the synthetic protein VOVO.
"These results suggest that screening by the LIPS test with VOVO and other B. burgdorferi antigens offers an efficient quantitative approach for evaluation of the antibody responses in patients with Lyme disease," say the researchers.
(P.D. Burbelo, A.T. Issa, K.H. Ching, J.I. Cohen, M.J. Iadarola, A. Marques. 2010. Rapid, simple, quantitative, and highly sensitive antibody detection for Lyme disease. Clinical and Vaccine Immunology, 17. 6: 904-909.)
Oral Bacteria May Offer Probiotic Potential Against Upper Respiratory Infections
Bacteria in the mouth may offer probiotic potential against upper respiratory tract infections say researchers from the Universit degli Studi di Milano, Milan, Italy, and Tampere University of Technology, Tampere, Finland. They detail their findings in the June 2010 issue of the journal Applied and Environmental Microbiology.
Although internal communication between human hosts and their microbes is only minimally understood, probiotics are live microorganisms thought to promote health within their host. So far, the benefits of probiotics have been predominantly explored in the intestinal tract, however, other initial studies suggest probiotics may contribute to wellness in the stomach, vaginal tract, skin and mouth.
Upper respiratory tract infections are the leading cause of visits to the pediatrician, especially in children between the ages of 5 and 12. Streptococcus pyogenes is one of the main causes associated with such infections and antibiotics are the only treatment currently available with prescription rates running as high as 90%.
"A probiotic strategy effective in the prophylaxis of pharyngitis, therefore, could provide a significant social benefit," say the researchers.
Bacteria newly isolated from the mouths of healthy volunteers were analyzed and two potential probiotic bacterial strains, Streptococcus salivarius RS1 and ST3, were identified. Following comparison with a recently developed oral probiotic prototype, S. salivarius strain K12, all three bound to human pharyngeal cells and antagonized S. pyogenes adhesion and growth. Additionally, all were sensitive to antibiotics routinely used for treating upper respiratory tract infections.
"We suggest that the selected commensal streptococci represent potential pharyngeal probiotic candidates," say the researchers. "They could display a good degree of adaptation to the host and possess potential immunomodulatory and anti-inflammatory properties."
(S. Guglielmetti, V. Taverniti, M. Minuzzo, S. Arioli, M. Stuknyte, M. Karp, D. Mora. 2010. Oral bacteria as potential probiotics for the pharyngeal mucosa. Applied and Environmental Microbiology, 76. 12: 3948-3958.)
|Contact: Carrie Slijepcevic|
American Society for Microbiology