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UTI Antibody Levels Examined on the Path to UTI Vaccine

SAN FRANCISCO — Prior infection with a urinary tract infection (UTI) did not impact an adult’s pre-existing antibodies to vaccine targets used by a laboratory in the development of a vaccine against UTI, a researcher said here.

There was no significant difference in antibody levels in women with an uncomplicated UTI, with or without significant bacteriuria, reported Christine Sarkissian Milner, of the University of Michigan in Ann Arbor, at a poster presentation at ASM Microbe.

In fact, the only significant difference in antibody levels was when comparing samples from healthy men with no history of UTI. They had significantly higher pre-existing antibody levels than the women, but not high enough to be protective.

Researchers were developing a vaccine to target four specific proteins that would confer protection against UTI. The authors noted that higher levels of antigen-specific antibodies correlated with protection when challenged with uropathogenic Escherichia coli in pre-clinical models.

To test this hypothesis in humans, Milner told MedPage Today that her group used urine and sera samples from a series of women with UTI from a study in 2012. In total, there were samples from 64 women with uncomplicated cystitis at the University of Michigan Health Service Clinic. Patients were a median age of 21 (range 18-50), and of these women, 40 had a recurrent UTI and 20 had a non-recurrent UTI. Researchers also examined samples from 20 healthy men, ages 18-40.

“I used males as healthy controls because they are unlikely to develop a UTI, and found that males ironically had higher antibody responses than females,” Milner said.

Otherwise, there was no difference between groups. Researchers noted that all patient sera tested contained antigen-specific IgG to all four vaccine antigens.

“What I was surprised by was there wasn’t any statistical significance in any patient population I looked at — whether or not they had significant or non-significant bacteriuria,” Milner said, noting that she used the clinical definition of bacteriuria (10 5 colony forming units/mL) in urine to distinguish that cutoff.

“The only statistical significance I was able to extrapolate was when I compared females to healthy controls being males. It’s not really what I expected, but it’s what I got,” she added.

Researchers concluded that while adults who are not vaccinated against a UTI have “non-protective levels” of pre-existing antibodies to the vaccine antigens being targeted by the lab in the development of their UTI vaccine.

“These are the baseline responses in any patient population, and we need a vaccine to boost these protective levels. So now we have a better understanding of what these responses look like,” Milner said. “We know they exist, no matter what the patient population is.”

Milner disclosed no relevant relationships with industry.