'Cruise Ship Virus' Vaccine Shows Promise
By John Gever, Senior Editor, MedPage Today
Published: September 14, 2012


SAN FRANCISCO -- An investigational vaccine targeting the virus that spoils cruise ship vacations and sends college kids to the hospital was safe and prompted large and rapid immune responses in a phase I clinical study, a researcher reported here.

Within a week of receiving the first of two doses of the product, participants showed 10- to 100-fold mean increases in antibodies against two norovirus subtypes, said John Treanor, MD, of the University of Rochester in Rochester, N.Y. The increases lasted for the full 56 days of subsequent blood sample collection,

No severe or serious adverse events considered to be related to the vaccine were seen, he told attendees here at the Interscience Conference on Antimicrobial Agents and Chemotherapy. The most common adverse effects were mild to moderate injection-site pain and mild headache, Treanor said.

He said the antibody responses were very good -- enough so that it might be possible that a single dose would be sufficient, although he emphasized that it was also possible that the second dose would make the response more durable.

The company developing the vaccine, Ligocyte Pharmaceuticals of Bozeman, Mont., is now conducting additional trials with the product. A Ligocyte official said that the first viral challenge tests in vaccinated individuals had just been conducted this week.

Noroviruses are a group of foodborne pathogens that cause acute vomiting and diarrhea as well as some flu-like symptoms such as fever and myalgia. Sometimes called the "cruise ship virus" because of several heavily publicized outbreaks among passengers on these vessels, it is also a growing problem for schoolchildren, college dorm residents, prisoners, military personnel, and others in institutional settings.

In a separate presentation at ICAAC, Hoonmo Koo, MD, of Baylor College of Medicine in Houston, noted that norovirus also appears to be responsible for many cases of so-called traveler's diarrhea, as well as episodes of vomiting and diarrhea in toddlers.

With the increasing use of effective vaccines against rotavirus, Koo said, it was likely that norovirus will "soon eclipse rotavirus" as the leading cause of viral gastrointestinal illness in young children.

Late last year, clinical trial results with a first-generation norovirus vaccine were published in the New England Journal of Medicine showing that the intranasally delivered product offered significant protection against challenge with Norwalk virus, the first member of the norovirus family to be identified.

However, Treanor explained, that product -- based on virus-like particles derived from Norwalk virus -- would not be expected to be effective against other subtypes.

Five main serotype groups of norovirus are known, with Norwalk virus belonging to Group I. There are a greater number of Group II viruses known, with one serotype called GII.4 now the most common among clinical isolates.

The vaccine tested in the current study includes virus-like particles carrying antigens from GII.4 and Norwalk virus, and was designed to be given intramuscularly.



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