Off-Label Use of Urine Assay Detects Zika in Semen

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NEW ORLEANS -- A private fertility lab identified Zika virus in semen samples, using an assay normally used for urine, a researcher said here.

Zika was identified in semen with a high level of sensitivity and specificity after being processed in the urine transport kit, reported Hisham Greiss, MD, of Fertility & Cryogenics Lab in Downers Grove, Ill., and colleagues.

At a poster presentation at the ASM Microbe meeting, Greiss described this as an "off label" use of the assay since it is not approved for such use. He added that he is offering it clinically for anyone who wants to test semen for Zika, but taking it to the FDA is a matter for the manufacturer of the test.

"I just validated it at our end," Greiss told MedPage Today. "Whether it will be acceptable to the FDA or not, I don't know."

To see whether the urine assay -- Hologic's Aptima ZIKV, for which the FDA has given emergency authorization -- could be used with semen samples, the authors spiked 107 neat semen samples with 3 viral copies/mL of recombinant Zika virus a total of 238 times on six days. The researchers also spiked 100 additional semen samples with 5 viral copies/mL to the Aptima urine specimen transport tubes, which contained 2 mL of urine transport medium, and tested immediately. This experiment was repeated a total of three times. Five viral copies/mL was finally chosen as the limit of detection after testing 3, 5, 10, 15 and 20 copies/mL.

Researchers then tested cross-reactivity using samples from individuals who seroconverted for West Nile virus, Chagas, and dengue, as well as recombinant dengue, chikungunya, HPV and herpes simplex virus 1. The authors also tested herpes simplex virus 2, chlamydia and gonorrhea for cross-reactivity.

They also ran five negative control semen samples in each experiment, none of which showed reactivity with the ZIKV assay.

For the first experiment on the 238 neat samples, there were 231 true positives and seven false negatives. The authors pointed out that neat semen is often viscous and had "gelatinous filaments" that could interfere with the test. But when these samples were rocked for 5 minutes and tested, four then became positive.

However, in the second experiment, where the semen was processed in the testing kit, all 300 samples came back positive, resulting in a 100% sensitivity and specificity.

Greiss said that he has already received semen samples from Florida, as well as fertility clinics in "Beverly Hills and Fifth Avenue" to test for Zika prior to assisted reproductive technology procedures -- even though his research has yet to be published.

He said he spoke with Hologic about going forward with the research, but the company says they need "enough demand" for the test because it's expensive. Still, Greiss is prepared to go forward if the manufacturer is willing.

"Getting it to FDA standards for me is not a big problem," he said.

Zika Vaccine Shows Promise in Mice

In another presentation, a single-dose Zika vaccine based on the NS1 protein showed 100% protection in mice, reported Farshad Guirakhoo, PhD, of GeoVax Inc. in Atlanta.

The authors noted that the vaccine was tested at the CDC in Fort Collins, Colo. Two groups of mice had the virus injected into their brain. One group received the NS1 vaccine, while the control group received a sham vaccine. Overall, 100% of the mice in the intervention group were protected, while 80-90% of the sham-immunized mice in the control group died within 7 to 10 days.

Researchers cited the unique qualities of an NS1-based vaccine, which could potentially limit the vector-based transmission of the virus. They said that NS1 proteins can interfere with the immune system of the mosquito, which could enhance vaccine effectiveness in endemic areas.