Vitamin D status related to immune response to HIV-1

Too much Vitamin D, when you are not deficient, can be harmful, too.

http://www.eurekalert.org/pub_releases/2015-06/ps-vds061515.php

Public Release: 15-Jun-2015
Penn State

Vitamin D plays an important part in the human immune response and deficiency can leave individuals less able to fight infections like HIV-1. Now an international team of researchers has found that high-dose vitamin D supplementation can reverse the deficiency and also improve immune response.

"Vitamin D may be a simple, cost-effective intervention, particularly in resource-poor settings, to reduce HIV-1 risk and disease progression," the researchers report in today's (June 15) online issue of Proceedings of the National Academy of Sciences.

The researchers looked at two ethnic groups in Cape Town, South Africa, to see how seasonal differences in exposure to ultraviolet B radiation, dietary vitamin D, genetics, and pigmentation affected vitamin D levels, and whether high-dose supplementation improved deficiencies and the cell's ability to repel HIV-1.

"Cape Town, South Africa, has a seasonal ultraviolet B regime and one of the world's highest rates of HIV-1 infection, peaking in young adults, making it an appropriate location for a longitudinal study like this one," said Nina Jablonski, Evan Pugh Professor of Anthropology, Penn State, who led the research.

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The researchers note that sunscreen use is not a factor in these populations. However, the darker the skin's pigment, the more ultraviolet B radiation necessary to trigger the precursor chemicals in the body to produce vitamin D.

"The skin of the indigenous people of the Cape, the Khoisan, is considerably lighter than that of either study group and may represent a long-established adaptation to seasonal UVB," according to the researchers. "The darker skin of both study populations -- Xhosia and Cape mixed -- denotes a degree of mismatch between skin pigmentation and environmental UVB resulting from their recent migration into the region."

The researchers found that both groups exhibited vitamin D deficiency during the winter, with women in both groups being more deficient, on average, than the men. Because of vitamin D's impact on the immune system, the researchers provided six weeks of supplemental vitamin D3 to 30 of the Xhosa participants, which brought 77 percent of the participants to optimal vitamin D status.

Jablonski and her team determined that diet, genetics and other variables played very small roles in vitamin D status, although some genetic variations did influence the success of supplementation.

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To test how vitamin D status affected the immune system and HIV-1 in particular, the researchers exposed blood samples from Xhosa and Cape mixed participants taken during the summer and winter when the subjects were vitamin D sufficient or deficient. They found that after nine days, the winter blood samples had greater infection than those taken in summer. After six weeks of vitamin D supplementation, the Xhosa blood sample levels of HIV-1 infection were the same as those during the summer.

"High-dosage oral vitamin D3 supplementation attenuated HIV-1 replication, increased circulating white blood cells and reversed winter-associated anemia," the researchers reported. "Vitamin D3 presents a low-cost supplementation to improve HIV-associated immunity."