S.A. scientists making progress against chlamydia In Bexar, infection rate is 60% higher than it is nationwide.

In laboratories on two San Antonio campuses, scientists are making progress against chlamydia, the most common — and perhaps least understood — sexually transmitted disease in the world.

In a series of studies published in recent years, an experimental vaccine developed here has shown promise in fighting off infection and protecting against infertility, the most serious complication of chlamydia in the United States.

Other work is aimed at creating a do-it-yourself test, similar to a home pregnancy test, for the infection, as well as a simpler and less costly way of identifying which cases of infertility are chlamydia-related — an advance that potentially could eliminate the need for more costly and invasive tests in many cases.

While chlamydia is common, and most common in teenagers and young adults, it is easily treated with antibiotics. The problem is that perhaps 70 percent of women and a smaller percentage of men who have it don't notice any symptoms. As the infection remains undetected, it can travel through the reproductive tract and cause pelvic inflammatory disease, infertility and ectopic pregnancies, which can be fatal.

More than 1.2 million chlamydia infections were reported nationwide in 2009, the most recent numbers available. And because most cases are asymptomatic and go undiagnosed, the true number is thought to be much higher. With 10,639 reported cases, Bexar County had the highest infection rate among major Texas counties, and 60 percent higher than the U.S. rate.

“It's a huge cause of infertility,” said Dr. Guangming Zhong, professor of microbiology at the University of Texas Health Science Center, who has been studying the chlamydia bacterium for some 25 years.

Zhong said one study found that close to 70 percent of San Antonio women diagnosed with tubal factor infertility, a condition in which the fallopian tubes are blocked, and the cause of up to a quarter of all infertility cases, had evidence of chlamydia infection.

A decade ago, Zhong discovered the substance at the heart of the vaccine effort, CPAF, or chlamydial protease-like activity factor. A nasal spray vaccine developed with scientists at the University of Texas at San Antonio generated a strong — although not completely protective — immune response in mice. More importantly, it also protected against infertility. Pharmaceutical giant Merck & Co. has licensed the work, and the National Institutes of Health is providing additional support.

Ashlesh Murthy, a research assistant professor of biology at UTSA and lead author of several of the vaccine studies, has been tinkering with the vaccine formula and testing it, along with other potential vaccine candidates, in the lab in collaboration with Zhong and Bernard Arulanandam, associate dean of research in UTSA's College of Science.

“Hopefully we can shorten the (length of infection), and also reduce the pathologies that are associated with it. And infertility is one of those,” Murthy said.

In Bexar County, nearly a third of those infected with chlamydia are 19 and younger; 86 percent are 29 and younger. Females outnumber males by almost 3-to-1, but mainly because chlamydia tests are a routine part of prenatal and family planning visits. That often leaves undiagnosed males as a reservoir to reinfect their partners or infect others.

The World Health Organization estimates that 140 million people worldwide are infected, and that the most serious complication is trachoma, an eye infection and a leading cause of blindness. In some developing countries, 90 percent of the population is infected.

In the mid-1980s Zhong became fascinated by chlamydia, which resembles a virus in how it enters and hides inside host cells. That's one reason a vaccine has been so difficult to develop.

“It's between a virus and a bacteria,” Zhong said. “They get inside the cell. They don't want to destroy the cell, but they want to exploit the cell, utilize it. And when they've finished their cycle and are ready to get out, they don't care anymore. They kill the cell and get out.”

Murthy said the group is still trying to improve the vaccine before trying to test it in people, perhaps adding new components or looking to see if a smaller part of the CPAF protein will be as effective. And they continue to try to better understand why chlamydia behaves as it does.

“Because if we understand that, we may be able to more effectively intervene and protect against it,” Murthy said.