Campylobacter Bacteria in Cattle Manure May Survive Composting
Contrary to popular belief, some disease causing bacteria may actually survive the composting process. Researchers from Agriculture and Agri-Food Canada report in the February 2010 issue of the journal Applied and Environmental Microbiology that campylobacter bacteria in cattle manure can survive composting and persist for long periods in the final product.
Campylobacter bacteria are the most common cause of gastroenteritis in the developed world. They are frequently shed by beef cattle in manure and although the impact on human health is undetermined there appears to be a link in areas such as Alberta, Canada where cases of human campylobacteriosis are extremely common and the cattle density is high.
Composting is described as a process in which organic matter in manure is stabilized through water loss, nutrient transmission, alteration of physical structure, elimination of weed seeds, and the inactivation of coliform bacteria, protozoan cysts and oocysts and viruses. Government agencies in both the United States and Canada recommend composting to reduce pathogen levels in manure.
In the study researchers examined the persistence of naturally occurring campylobacter bacteria in compost derived from manure of beef cattle that were administered antibiotics (AS700) and a control group that were not. Bacterial populations were the same in both groups, however, the temperature of the AS700 compost was more viable and not as high as that of the control group. Water content, total carbon, total nitrogen and electrical conductivity varied significantly between groups. Results showed that no reductions in the quantities of Campylobacter jejuni DNA were observed throughout the 10-month composting period. Further testing suggests that Campylobacter DNA examined from compost was extracted from viable cells.
"The findings of this study indicate that campylobacteria excreted in cattle feces persist for long periods in compost and call into question the common belief that these bacteria do not persist in manure," say the researchers.
(G.D. Inglis, T.A. McAllister, F.J. Larney, E. Topp. 2010. Prolonged survival of Campylobacter species in bovine manure compost. Applied and Environmental Microbiology, 76. 4: 1110-1119.)
Single-Dose HIV DNA Vaccine Induces Long-Lasting Immune Response in Monkeys
For the first time researchers from the U.S. and abroad have shown a single-dose HIV DNA vaccine can induce a long-lasting HIV-specific immune response in nonhuman primates, a discovery that could prove significant in the development of HIV vaccines. They detail their findings in the February 2010 issue of the Journal of Virology.
HIV is persistently spreading at epidemic rates throughout the world emphasizing the need for a vaccine that can substantially reduce viral loads and minimize transmission. History shows vaccines to be the most effective strategy against pandemic infectious diseases such as smallpox, polio, measles and yellow fever, however, the control of HIV not only relies on the production of neutralizing antibodies, but also the development of high frequency, broadly targeted T-cell responses specific to the virus. To date live-attenuated simian immunodeficiency virus (SIV)/HIV vaccines have prompted the most significant immune response against AIDS in a nonhuman primate model, but risk of redeveloping pathogenic forms makes them ineligible for human use.
DNA-based vaccines have become more preferable in controlling infectious diseases due to their safety and ability to induce both humoral and T-cell immune responses. In a previous study the researchers successfully induced long-lasting and potent HIV-specific immune responses in mice following immunization with a single-dose SHIV DNA-based vaccine. In this study rhesus macaques were immunized with a single high dose of the SHIV DNA-based vaccine and monitored for vaccine-induced immune responses. Results showed that all immunized monkeys developed broad HIV-specific T-cell immune responses that persisted for months. Additionally, an unusual reemergence in the blood following an initial decline and in the absence of antibody responses was noted.
"Our comprehensive analysis demonstrated for the first time the capacity of a single high dose of HIV DNA vaccine alone to induce long-lasting and polyfunctional T-cell responses in the nonhuman primate model, bringing new insights for the design of future HIV vaccines," say the researchers.
(G. Arrode-Bruss, D. Sheffer, R. Hedge, S. Dhillon, Z. Liu, F. Villinger, O. Narayan, Y. Chebloune. 2010. Characterization of T-cell responses in macaques immunized with a single dose of HIV DNA vaccine. Journal of Virology, 84. 3: 1243-1253.)
Single-Dose H5N1 Vaccine Safe and Effective in Adults and Elderly
Researchers from Hungary and the UK have developed a single-dose H5N1 influenza vaccine that induces a protective level of immunity against infection in healthy adult and elderly volunteers. The vaccine is the first single-dose regimen to be tested in elderly subjects and it fulfills all European Union and U.S. licensing criteria offering a promising influenza A virus vaccine candidate. They report their findings in the February 2008 issue of the Journal of Virology.
New cases of human H5N1 infection continue to emerge worldwide resulting in severe illness and high fatality rates. In the case of a pandemic, vaccination is likely to be the most effective approach toward minimizing illness and death. Already a variety of candidate vaccines are being tested, however, most require two-dose regimens to be effective.
In the study researchers developed a whole-virion, inactivated, adjuvanted H5N1 vaccine and tested its safety and efficacy in healthy adult and elderly volunteers. Subjects were randomly assigned to receive one or two doses of 3.5 μg of the vaccine or one dose of 6 or 12 μg of the vaccine. Safety and side effects were monitored following vaccination and blood samples were collected to determine immune response. Occasional injection site pain, fever and fatigue were the only reported side effects and while antibody responses were observed in all the subjects, single doses of 6 μg or more fulfilled the European Union and U.S. licensing criteria.
"We found that the present vaccine is safe and immunogenic in healthy adult and elderly subjects and requires low doses and, unlike any other H5N1 vaccines, only one injection to trigger immune responses which comply with licensing criteria," say the researchers.
(Z. Vajo, J. Wood, L. Kosa, I. Szilvasy, G. Paragh, Z. Pauliny, K. Bartha, I. Visontay, A. Kis, I. Jankovics. 2010. A single-dose influenza A (H5N1) vaccine safe and immunogenic in adult and elderly patients: an approach to pandemic vaccine development. Journal of Virology, 84. 3: 1237-1242.)
|Contact: Carrie Slijepcevic|
American Society for Microbiology