New Orleans—Using highly sensitive techniques, investigators have discovered that herpes simplex virus type 1 (HSV-1) is present in a high percentage of asymptomatic individuals, said Herbert E. Kaufman, MD, Boyd professor of ophthalmology and pharmacology and experimental therapeutics, Louisiana State University Eye Center, New Orleans.
The study is apparently the largest cross-sectional assessment yet of the presence of HSV-1 DNA in the eyes and mouths of healthy individuals, in terms of population size and samples collected, and is a step toward better understanding of the shedding of HSV-1 by asymptomatic patients, particularly in tears, Dr. Kaufman said.
He explained that as more is learned about virus excretion, researchers might be able to devise better ways of controlling shedding to limit transmission and reduce the incidence of virus-induced blindness. Reduction or prevention of virus excretion could also be useful in evaluation of new antiviral drugs. Dr. Kaufman and his colleagues published their findings in the January issue of Investigative Ophthalmology & Visual Science.1
"We found that this virus is so common that 98% of them secreted herpes either in their tears or in their saliva sometime during the month that we studied them," said Dr. Kaufman. Overall, 49 of 50 subjects shed HSV-1 DNA at least once during the study.
He added that some of these asymptomatic subjects secreted large amounts of HSV-1 DNA and did so frequently, while others produced small amounts less frequently. The significance of these differences is not yet understood.
A diagnostic technique called real-time polymerase chain reaction (PCR) analysis, the gold standard for detection of HSV-1 in clinical samples, was used to test the tear and saliva samples. PCR is faster than conventional methods of detecting HSV DNA and less subject to cross-contamination, Dr. Kaufman said. In addition, the PCR assay is more sensitive and requires much less of the virus than techniques relying on cultured cells.
Serum samples were tested for HSV IgG antibodies by enzyme-linked immunosorbent assay (ELISA) and for HSV-1 by neutralization assay.
Results of the analysis showed that 37 (74%) subjects tested positive for HSV-1 or HSV-2 IgG by ELISA. A similar number were positive for HSV-1 by the neutralization assay. Ten of the 13 subjects who tested negative by ELISA were also negative by the neutralization assay, while three were negative by ELISA and positive by neutralization assay.
The research team also examined 5,529 specimens (2,806 eye swabs and 2,723 mouth swabs) and found that 1,961 (35.5%) contained HSV-1 DNA. An approximately equivalent proportion of eye and mouth swabs were positive, 33.5% (941/2,806) and 37.5% (1,020/2,723), respectively.
Only one individual did not shed HSV-1 DNA in tears or saliva at any time during the study. Three shed HSV-1 DNA in their tears but not their saliva, and two had positive saliva swabs only. Forty-four subjects (88%) had both positive tears and saliva. Forty-six of the subjects (92%) excreted virus DNA in tears at some point, and 45 (90%) excreted virus DNA in saliva during the 30-day period. The percentage of samples with high HSV-1 genome copy numbers was greater in saliva than in tears.
Volunteers in the study included 19 men and 31 women. Thirty-nine of the subjects (78%) were African American, 10 were white, and one individual was identified as "other" in the racial breakdown.