Koala researchers may have discovered a major cause of male infertility in humans
The Queensland immunologist who helped bring us the chlamydia vaccine for koalas has had another breakthrough, this time providing the first evidence of chlamydia in the testes of men with infertility.
Around 30 to 40% of men who are infertile don’t know why. This world-first discovery suggests that men might be infertile because bacteria have been living inside their testes for years, affecting their sperm quality.
Ken Beagley, a professor of immunology at Queensland University of Technology, and his colleagues, found chlamydia in 46% of the 95 samples of testicular tissue they tested.
These biopsies had previously been taken from men with idiopathic infertility and preserved in paraffin.
In addition to these older samples, the researchers also tested 18 fresh testicular biopsies taken as part of a routine workup from men attending Monash IVF and the Queensland Fertility Group. In these fresh biopsies, the rate of chlamydia infection was 17%.
The “unexpectedly high” prevalence of chlamydia was probably because the study only included men with infertility, the researchers said.
The rate of chlamydia in the general population is estimated to be much lower – around 380 infections per 100,000 people.
“They have fairly convincingly demonstrated that chlamydia was up in the testes and that it was associated with a protein called TC0500, which is a replication marker,” Professor Basil Donovan, the head of the Sexual Health Program at the The Kirby Institute, told TMR. “It was chlamydia that was still alive and replicating, at least when they took the biopsy or preserved it in paraffin. Now, that’s actually a world first. No one’s shown that before.”
One problem with the study was that it didn’t look for chlamydia in the testicular tissue of fertile men. It’s difficult, and probably unethical, to request this tissue from volunteers because the procedure was quite painful, the researchers said.
It might be possible to get men undergoing vasectomy to volunteer some testicular tissue in the future, Professor Donovan suggested.
“If they don’t find chlamydia in normal men but they do find it in sub-fertile men then you’re starting to go, ‘Hang on, we might have a fairly major cause of sub-fertility here’,” Professor Donovan said.
Professor Beagley’s team had a hunch that chlamydia would be found in the testes of humans because they’d observed the same phenomenon in koalas and mice.
Wild male koalas often had chronic chlamydial infections in the testes, Professor Beagley said.
And male lab mice infected with chlamydia have decreased sperm motility , increased sperm DNA damage, and decreased ability for the sperm to bind to ova, he said.
“We haven’t demonstrated a causal effect in humans yet,” he said. “But we know from the animal studies that the cause is highly likely to be the chlamydia.”
Around 72% of the 18 men who provided fresh biopsies had chlamydia antibodies in their serum, meaning there had been a previous exposure to chlamydia. But, of the three men who took a urine test for chlamydia, all tested negative.
It could be that once chlamydia reached the testes, the urinary tract infection had started to clear up, Professor Beagley said. Thus, a standard diagnostic urine test used in an STI clinic would not pick up the ongoing infection in the testes.
It might be possible to test for chlamydia in the sperm, however. “We’ve actually been doing that on a lot of koalas,” said Professor Beagley. “And there are a number of small studies where people have looked at seminal plasma collected from an ejaculate. So that certainly would be something that could be possible.”
The question then, of course, was whether testing for chlamydia in the testes of infertile men actually helped anyone, Professor Donovan said.
“Years and years down the track you might be looking at during trials to see whether antibiotics helps restore these men’s fertility,” he said.
“Some people have actually tried antibiotics and I’ve never seen any overly impressive studies showing that antibiotics that might be active against chlamydia actually did do anything for men’s infertility.”
There was one study from a Spanish group which showed that extended treatment of antibiotics increased the sperm quality in some men, Professor Beagley said. “But it was only a fairly small study,” he said.
