Tips from the Journals of the American Society for Microbiology

03/18/05

Norovirus Prevalent in Those Suffering from Traveler's Diarrhea

Norovirus may be the most common cause of travelers' diarrhea for United States citizens returning from Mexico and Guatamala say researchers from the U.S., Guatemala, Mexico and Sweden. Their findings appear in the March 2005 issue of the Journal of Clinical Microbiology.

It is estimated that 20 to 50 percent of the people traveling to tropical areas of the world will experience traveler's diarrhea (TD). TD, defined as three or more loose stool movements in a 24-hour period, frequently results from exposure to bacterial or viral pathogens. Noroviruses (NoV's) are considered to be one of the leading causes of nonbacterial gastro-related illnesses resulting in over 23 million cases annually.

In the study stool samples were collected from 34 patients with traveler's diarrhea and tested for the presence of norovirus. The virus was detected in 65 percent of the samples tested, with time spent at travel destinations playing an important role in determining infection frequency.

"This study is the first of its kind to indicate that NoVs may be a major cause of illness among United States travelers who experience TD during extended stays in developing countries," say the researchers. The high frequency of NoV infection among TD cases examined in this study suggests that further investigations concerning the role of these viruses in TD are warranted."

(A.R. Chapin, C.M. Carpenter, W.C. Dudley, L.C. Gibson, R. Pratdesaba, O. Torres, D. Sanchez, J. Belkind-Gerson, I. Nyquist, A. Karnell, B. Gustafsson, J.L. Halpern, A.L. Bourgeois, K.J. Schwab. 2005. Prevalence of norovirus among visitors from the United States to Mexico and Guatemala who experience traveler's diarrhea. Journal of Clinical Microbiology, 43. 3: 1112-1117.)

DNA Vaccine Protects Against AIDS, Not HIV

While a new DNA vaccine may not be able to prevent HIV infection, it could protect against progression to full-blown AIDS. Researchers from Kansas report their findings in the March 2005 issue of the Journal of Virology.

Developing a vaccine to protect against HIV in attempt to gain control of the AIDS pandemic is a top priority for researchers throughout the world. Extensive testing has been conducted with live vaccines to determine if immunization would be effective at prevention, but they are not suitable for human use due to the potential that the vaccine viruses could mutate and reacquire the ability to cause disease.

DNA vaccines offer a new possibility for treatment. The have the advantages of safety, low cost of production, and ease of use in field conditions due to their minimal need for refrigeration.

In the study the DNA of a simian/human immunodeficiency virus (SHIV) was made noninfectious by removing the gene that makes reverse transciptase (a protein the virus requires to replicate). Four macaques were injected with the noninfectious vaccine, while two control animals remained unvaccinated. Both groups were challenged with SHIV. All four of the immunized macaques became infected with the challenge virus, but three survived. The two control subjects died.

"The results showed strong evidence that this type of vaccine could prevent AIDS and established that a DNA vaccine, such as this one, could be used alone, without the need for booster doses with viral proteins, for large-scale immunization programs," say the researchers.

(D.K. Singh, Z. Liu, D. Sheffer, G.A. Mackay, M. Smith, S. Dhillon, R. Hegde, F. Jia, I. Adany, O. Narayan. 2005. A noninfectious simian/human immunodeficiency virus DNA vaccine that protects macaques against AIDS. Journal of Virology, 79. 6: 3419-3428.)

Newly Identified Protein May Inhibit Hepatitis Virus

A newly identified family of proteins may inhibit replication of the Hepatitis B (HBV) and C (HCV) viruses say researchers from California. Their findings appear in the March 2005 issue of the Journal of Virology.

Hepatitis B (HBV) and C (HCV) are viruses that infect the liver, and in some cases can cause liver failure requiring a transplant for survival. The protein interferon, produced by animal cells when they are invaded by viruses, is released into the bloodstream or intercellular fluid to induce healthy cells to manufacture an enzyme that counters the infection. One class of interferons (alpha) is used to treat chronic infection with HBV and HCV. There is a vaccine available to prevent the spread of HBV but not HCV.

In the study, a new class of interferons, interferon lambda, was tested for its ability to inhibit HBV and HCV replication. Results showed 90% inhibition of HBV after twenty-four hours and 90-99% inhibition in HCV five days posttreatment.

"We have demonstrated here that replication of HBV and HCV is sensitive to the antiviral activities of interferon lambda," say the researchers. "These results suggest the possibility that interferon lambda may be therapeutically useful in the treatment of chronic HBV or HCV infection."

(M.D. Robek, B.S. Boyd, F.V. Chisari. 2005. Lambda interferon inhibits hepatitis B and C virus replication. Journal of Virology, 79. 6: 3851-3854.)

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