Immunomodulating effects of probiotics for microbiota modulation, gut health and disease resistance in pigs
Probiotics are live microorganisms that can confer a health benefit on the host, and amongst various mechanisms probiotics are believed to exert their effects by production of antimicrobial substances, competition with pathogens for adhesion sites and nutrients, enhancement of mucosal barrier integrity and immune modulation. Through these activities probiotics can support three core benefits for the host: supporting a healthy gut microbiota, a healthy digestive tract and a healthy immune system. More recently, the concept of combining probiotics and prebiotics, i.e. synbiotics, for the beneficial effect on gut health of pigs has attracted major interest, and examples of probiotic and prebiotic benefits for pigs are pathogen inhibition and immunomodulation. It remains to be defined in pigs, what exactly is a healthy gut.
Because of the high level of variability in growth and feed conversion between individual pigs in commercial production systems, measuring the impact of probiotics on gut health defined by improvements in overall productivity requires large experiments. For this reason, many studies have concentrated on measuring the effects of the feed additives on proxies of gut health including many immunological measures, in more controlled experiments. With the major focus of studying the balance between gut microbiology, immunology and physiology, and the potential for prevention of intestinal disorders in pigs, we therefore performed a literature review of the immunomodulatory effects of probiotics, either alone or in combination with prebiotics, based on in vivo, in vitro and ex vivo porcine experiments. A consistent number of studies showed the potential capacity in terms of immunomodulatory activities of these feed additives in pigs, but contrasting results can also be obtained from the literature. Reasons for this are not clear but could be related to differences with respect to the probiotic strain used, experimental settings, diets, initial microbiota colonization, administration route, time and frequency of administration of the probiotic strain and sampling for analysis.
The use of proxy measurements of enteric health based on observable immunological parameters presents significant problems at the moment, and cannot be considered robust, reliable predictors of the probiotic activity in vivo, in relation to pig gut health. In conclusion, more detailed understanding of how to select and interpret these proxy measurements will be necessary in order to allow a more rational prediction of the effect of specific probiotic interventions in the future.
America’s past of human experiments revealed
U.S. officials also acknowledged there had been dozens of similar experiments in the United States – studies that often involved making healthy people sick. Attitude similar to Nazi experiments Some of these studies, mostly from the 1940s to the ’60s, apparently were never covered by news media. In federally funded studies in the 1940s, noted researcher Dr. W.
Paul Havens Jr. exposed men to hepatitis in a series of experiments, including one using patients from mental institutions in Middletown and Norwich, Conn. Havens, a World Health Organization expert on viral diseases, was one of the first scientists to differentiate types of hepatitis and their causes. A search of various news archives found no mention of the mental patients study, which made eight healthy men ill but broke no new ground in understanding the disease. Researchers in the mid-1940s studied the transmission of a deadly stomach bug by having young men swallow unfiltered stool suspension.
For a study in 1957, when the Asian flu pandemic was spreading, federal researchers sprayed the virus in the noses of 23 inmates at Patuxent prison in Jessup, Md., to compare their reactions to those of 32 virus-exposed inmates who had been given a new vaccine. Studies using prisoners were uncommon in the first few decades of the 20th century, and usually performed by researchers considered eccentric even by the standards of the day. Last year, the U.S. Department of Health and Human Services’ inspector general reported that between 40 and 65 percent of clinical studies of federally regulated medical products were done in other countries in 2008, and that proportion probably has grown. Syphilis study These issues were still being debated when, last October, the Guatemala study came to light.
In the 1946-48 study, American scientists infected prisoners and patients in a mental hospital in Guatemala with syphilis, apparently to test whether penicillin could prevent some sexually transmitted disease. To focus on federally funded international studies, the commission has formed an international panel of about a dozen experts in ethics, science and clinical research. Some experts say that given such a tight deadline, it would be a surprise if the commission produced substantive new information about past studies.
Chinese Scientists Identify SARS-Like Illness in Pigs
A viral disease that killed more than 24,000 pigs last year in southern China originated in bats, Chinese scientists concluded in a study published Thursday in Nature. The paper sheds light on cross-species transmission of a highly infectious coronavirus – the same virus family that causes severe acute respiratory syndrome, or SARS – as well as the future prevention of disease in both animals and humans. After gene-sequencing a virus found in the dead pigs in Guangdong province and a virus isolated from horseshoe bats in a cave near the farm where the epidemic originated, the scientists found that the two were 98 percent similar. The virus, identified as the swine acute diarrhea syndrome coronavirus, shares certain characteristics with the SARS-CoV, the coronavirus that causes SARS, a lung disease that originated in Guangdong and caused more than 300 deaths in China in 2002. According to the scientists’ research, SADS-CoV is transmitted to pigs through the bats’ feces and has a 90 percent kill rate when it infects piglets that are less than five days old.
Wang Linfa, a professor at Duke-NUS Medical School in Singapore and a contributor to the research, said at a news conference Wednesday that people cannot be infected with the virus by eating pork. The researchers’ experiments found that SADS-CoV can infect human cells in a laboratory – meaning exposure to the virus could still be risky. Such oversight has long been in place in southern China – and the researchers say this was crucial to their quick ID of the virus. Scientists at South China Agricultural University who also participated in the research have helped to establish a surveillance system at pig farms across Guangdong. When the pigs got sick last year, the university acted immediately: After testing, the scientists determined that the pathogen was a previously unknown virus.
South China Agricultural University has been working on a vaccine that could eliminate the disease in pigs. The Chinese researchers collaborated with PREDICT to obtain bat virus samples until they found a match and identified SADS-CoV. International cooperation and databases of precollected samples have greatly reduced the amount of time required to identify potentially deadly viruses, said Wang.