Parasites Catching Viruses?
(Ivanhoe Newswire) – When we have a parasite, the organism feeds off us. Well, according to new research, parasites can have their own parasites feeding off of them, too!
Researchers from Harvard Medical School, Brigham and Women's Hospital and SUNY Upstate Medical University have found that the pathogenicity of the sexually transmitted protozoan parasite Trichomonas vaginalis—the cause of trichomoniasis—is fueled by a viral invader. Trichomoniasis infections are more common than all bacterial STDs combined. Annually, trichomoniasis affects nearly 250 million people, typically as vaginitis in women and urethritis in men.
"Trichomoniasis is associated with devastating consequences for women due to inflammation and related risks of reproductive disease," Raina Fichorova, leader of the research team as well as associate professor of obstetrics, gynecology and reproductive biology at Brigham and Women's Hospital, was quoted as saying. "Our future goal is to determine how the viral symbiont and its inflammatory 'halo' affect the risk of preterm delivery and low birth weight."
"This is only one of two incidences that we know of for which the pathogenicity of a protozoan virus has been characterized," Max Nibert, Harvard Medical School professor of microbiology and immunology and co-author of the paper, was quoted as saying. "When found together, the result is an increase in virulence of the protozoan parasite to the human host, leading to exacerbated disease."
Trichomonas vaginalis attaches itself to the surface of human cells and feeds on them. The virus, called Trichomonasvirus, infects the protozoan and increases its pathogenic power by fueling virus-specific inflammatory responses. Moreover, carrying the protozoan parasite predisposes women to acquire sexually transmitted viruses, particularly HIV and human papillomavirus, or HPV, both of which can lead to serious diseases such as AIDS and cervical cancer. According to Nibert, the virus-parasite symbiosis is the norm rather than the exception with this particular protozoan. Upwards of 80 percent of Trichomonas vaginalis isolates carry the virus. "Unlike flu viruses, for example, this virus can't spread by jumping out of the cell into another one," Nibert was quoted as saying. "It just spreads between cells when they divide or mate."
Currently, trichomoniasis is treated with the antibiotic metronidazole. But this treatment is only effective on the protozoan. "When the medication is used, the dying or stressed protozoa release unharmed virions, which then signal to the human cells," Fichorova was quoted as saying. As a result, the symptoms are aggravated, and this in turn might increase the danger it poses to pregnant women and their children.
"Ahead is more research to better understand the viral cycle and structural features that might be vulnerable to drugs, which will lead to opening new doors for better treatment of trichomoniasis and related diseases," Fichorova was quoted as saying. "Our complementary expertise, interdisciplinary team efforts and strong collaboration is the key to our future success." Nibert added that basic research on Trichomonas vaginalis is not nearly as supported as he thinks it should be. "It is unfortunate that a human pathogen of such worldwide significance has been neglected to such a degree," he said.
Source: Public Library of Science, November 2012