Intestinal Worm Infection Remotely Worsens Outcomes for Sexually Transmitted Viral Infections

Parasitic intestinal worm (helminth) infections can cause sexually transmitted viral infections to be much more severe elsewhere in the body, according to a study published in Cell Host & Microbe. According to the study, helminth-infected mice developed significantly more severe symptoms after infection with a genital herpes virus (herpes simplex virus), results that the researchers believe are also transferrable to humans.

“The results themselves surprised us in their clarity,” said William Horsnell, PhD, in a press release. “Genital herpes disease is often accompanied by scarring of the vagina, known as necrosis. In our study, this serious symptomatology occurred twice as often as normal after helminth infestation.”

The worms themselves never directly infest the female genital tract, remaining in the intestines post-ingestion. According to the researchers, this is indicative of a previously unknown remote effect of helminth infection.

The investigators were able to demonstrate that specific white blood cells specialized in fighting parasitic infection, eosinophil granulocytes, are responsible for the necrotization. These cells contain cell-decomposing enzymes stored in granules, released when the cell comes in contact with a parasite.

“In our case, however, the worm infestation in the intestine causes eosinophilic granulocytes to accumulate in the vagina during a concurrent genital herpes infection,” Horsnell said in the release. “They then secrete their cell-damaging enzymes there, even though no helminths are present. And it's this misdirected immune response that leads to the serious damage in the mucosa of the vagina that we've observed.”

According to the researchers, the accelerated maturation of granulocytes in the vagina is caused by the immune messenger interleukin-33 (IL-33). When inhibited, the mice in the study developed significantly less tissue damage in the genital tract. The study authors are now searching for drugs to inhibit IL-33 that are suitable for use in humans and inexpensive to produce.

REFERENCE

Worm infestation in intestine has a remote effect on viral defenses [news release]. EurekAlert; April 15, 2021. Accessed May 4, 2021. https://www.eurekalert.org/pub_releases/2021-04/uob-wii041521.php