Research from December Journals of the American Society for Microbiology

December 12, 2000

Electricity increases DNA vaccine effects

Low voltage pulses of electricity appear to increase the strength of an experimental hepatitis C vaccine more than 10-fold . Researchers from Italy and Merck Research Labs report their results in the December issue of the Journal of Virology.

In the study, the researchers tested an experimental DNA-based vaccine against hepatitis C. They injected mice, rats and rabbits with fragments of DNA from the hepatitis virus intended to elicit immunity. Some of the animals then received electrical stimulation treatment in the form of low voltage electrical pulses at the site of immunization. Those animals that received the electrical stimulation showed an immune response that was 10 to 30 times greater than those that had received only the DNA vaccine.

"The method described protentially provides a safe, low-cost treatment that may be scaled up to humans and may hold the key for future development of prophylatic or therapeutic vaccines against hepatitis C and other infectious diseases," say the researchers.

Hepatitis C is a major cause of chronic liver disease, with an estimated 4 million Americans already infected and 36,000 new infections each year. Most infected people show no symptoms and there is currently no vaccine or cure. It is believed to be transmitted by blood and sexual intercourse.

(S. Zucchelli, S. Capone, E. Fattori, A. Folgori, A. Di Marco, D. Casimiro, A.J. Simon, R. Laufer, N. La Monica, R. Cortese and A. Nicosia. 2000. Enhancing B- and T-cell immune response to a hepatitis C virus E2 DNA vaccine by intramuscular electrical gene transfer. Journal of Virology, 74: 11598-11607).

Starving bacteria elude diagnostic tests

The virulent E. coli O157:H7 bacterium can lose its ability to be detected by certain diagnostic tests if it has experienced extended periods without food, say researchers from the National Institute of Health Sciences in Japan. They report their results in the December 2000 issue of the journal Applied and Environmental Microbiology.

All bacteria have certain proteins they display on their surface. These proteins, called antigens, are distinctive, like fingerprints, and can be used to identify the bacteria. Many diagnostic tests used today to detect E. coli O157:H7 contamination in food and environmental samples use this technology. In the study the researchers placed the bacteria in distilled water for 21 months to simulate starvation conditions that might occur during bacterial contamination of recreational or untreated drinking water. They found that after the prolonged period without food, the bacteria could still grow, but could no longer be detected by the O157 O antigen diagnostic tests.

"Many kinds of detection kits and systems utilizing O157 O antigenicity have been developed and widely used to detect a small number of E. coli O157 bacteria in food and environmental samples contaminated with a large number of competitive bacteria," say the researchers. "However, a method which does not depend on immunologic techniques should be used to test for enterohemorrhagic E. coli in foods and other environments, when the organism is suspected to have been under starvation conditions for a long period."

(Y. Hara-Kudo, M. Miyahara and S. Kumagai. 2000. Loss of O157 O antigenicity of verotoxin-producing Escherichia coli O157:H7 surviving under starvation conditions. Applied and Environmental Microbiology, 66: 5540-5543.)

New HIV receptor may offer insight on dementia

An international group headed by researchers from Harvard Medical School has identified an important receptor that HIV-1 may use to target and infect human cells especially those in the nervous system. They have also found a protein that may stop it. They report their results in the December issue of the Journal of Virology.

In addition to the already known CCR5 and CXCR4 receptors it also appears that HIV-1 can bind to and use another receptor, known as APJ, to enter and infect human cells. This receptor is commonly found in the central nervous system and several brain viruses are known to use APJ as a receptor, suggesting that this receptor may be involved in neurological symptoms of AIDS, such as dementia.

The researchers have identified a protein associated with APJ, called apelin, that appears to inhibit the virus' ability to invade cells through APJ. The researchers note that these findings are preliminary and further research needs to be done to understand the complete role that APJ plays in HIV infection. "The identification of specific APJ ligands (apelin) that inhibit HIV-1 infection allows further exploration of the role of the APJ receptor in HIV-1 pathogenesis," say the researchers. "This role is presently unclear, although the expression of APJ in the central nervous system raises the possibility that this protein might contribute to AIDS dementia."

(M. Cayabyab, S. Hinuma, M. Farzan, H. Choe, S. Fukusumi, C. Kitada, N. Nishizawa, M. Hosoya, O. Nishimura, T. Messele, G. Pollakis, J. Goudsmit, M. Fujino and J. Sodroski. 2000. Apelin, the natural ligand of the orphan seven-transmembrane receptor APJ, inhibits human immunodeficiency virus type 1 entry. Journal of Virology, 74: 11972-11976.)

American Society for Microbiology

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