This is a close view of the intestinal mucosa in the case of a patient who’d been infested with the human whip worm, Trichuris trichiura The parasitic disease is known as trichuriasis.
This nematode, or roundworm, is also called the human whipworm. The clinical features are most frequently asymptomatic. Heavy infections, especially in small children, can cause gastrointestinal problems (abdominal pain, diarrhea, rectal prolapse) and possibly growth retardation.
T. trichiura is the third most common round worm of humans. It’s found worldwide with infections found more frequently among children in areas with tropical weather and poor sanitation practices. It is estimated that 800 million people are infected throughout the World, which includes the southern United States.
Antimicrobial peptides (AMPs) are molecules produced in the skin to fend off infection-causing microbes. Vitamin D has been credited with a role in their production and in the body’s overall immune response, but scientists at the University of California, San Diego School of Medicine say a hormone previously associated only with maintaining calcium homeostasis and bone health is also critical, boosting AMP expression when dietary vitamin D levels are inadequate.
The finding, published in the May 23, 2012 online issue of Science Translational Medicine, more fully explains how the immune system functions in different situations and presents a new avenue for treating infections, perhaps as an alternative to current antibiotic therapies.
The immunological benefits of vitamin D are controversial. In cultured cell studies, the fat-soluble vitamin provides strong immunological benefits, but in repeated studies with humans and animal models, results have been inconsistent: People with low levels of dietary vitamin D do not suffer more infections. For reasons unknown, their immune response generally remains strong, undermining the touted immunological strength of vitamin D.
Working with a mouse model and cultured human cells, Gallo and colleagues discovered why: When levels of dietary vitamin D are low (it’s naturally present in very few foods), production of parathyroid hormone (PTH), which normally helps modulate calcium levels in blood, is ramped up. More PTH or a related peptide called PHTrP spurs increased expression of AMPs, such as cathelicidin, which kill a broad spectrum of harmful bacteria, fungi and viruses.
“No one suspected a role for PTH or the PTH-related peptide in immunity,” said Richard L. Gallo, MD, PhD, professor of medicine and chief of UCSD’s Division of Dermatology and the Dermatology section of the Veterans Affairs San Diego Healthcare System. “This may help resolve some of the controversy surrounding vitamin D. It fills in the blanks.”
Bacteria direct their movement in response to certain chemicals by controlling the rotation of whip-like appendages called flagella. The sensitivity of the response can be adjusted at the signal’s target, the flagellar motor (pictured above).