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Journal of Clinical Microbiology, September 2002, p. 3252-3255, Vol. 40, No. 9
0095-1137/02/$04.00+0 DOI: 10.1128/JCM.40.9.3252-3255.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Laboratoire de Bactériologie-Virologie, GIMAP, Faculty of Medicine of Saint-Etienne,1 Laboratoire de Biologie de la Reproduction, Centre Hospitalier Universitaire de Saint-Etienne, Saint-Etienne,2 Laboratoire de Virologie ,3 Laboratoire de Biologie de la Reproduction, Hôpital Edouard Herriot de Lyon, Lyon, France4
Received 9 January 2002/ Returned for modification 5 May 2002/ Accepted 14 June 2002
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We report herein on the detection of HCV RNA in seminal plasma and, for the first time, in the motile spermatozoon fractions of semen from men chronically infected with HCV and attempting medically assisted reproduction.
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Sequential samples of semen were obtained from nine men: seven men each gave two samples (mean delay between collection of the two samples, 12.4 ± 8 months), one man gave three sequential samples within 8 months, and one man gave seven successive samples within 11 months.
Samples. Plasma samples were separated from blood by centrifugation and frozen at -80°C until use. After 3 days of sexual abstinence, semen samples were obtained by masturbation into a sterile container and were processed within 2 h of ejaculation. One milliliter of the semen sample was centrifuged at 800 x g for 10 min, and the seminal plasma was separated from the cell pellet and stored at -80°C until further use (fraction 1). Another milliliter was submitted to centrifugation through a three-layer discontinuous Percoll (Pharmacia, Uppsala, Sweden) gradient (3 ml of 50, 70, and 90% Percoll, respectively); the motile spermatozoa were recovered from the 90% fraction, observed by microscopic examination for number and to check for the absence of white blood cell contamination, and kept frozen at -80°C as aliquots of 500,000 cells until use (fraction 2). For one patient, 0.5 ml of sterile synthetic medium (BM1; Ellios Biotek Laboratories, Paris, France) used for in vitro cell culture was layered on the top of the 90% fraction obtained after Percoll selection; after incubation for 45 min at 37°C in a 5% CO2 incubator, the upper 0.5 ml was carefully removed and the spermatozoa were counted. This "swim-up" fraction was kept frozen at -80°C as aliquots of 500,000 cells until use (fraction 3) (5).
Detection of HCV RNA in blood plasma. The qualitative detection of HCV RNA in blood plasma was performed by the Cobas AMPLICOR HCV assay (version 2.0; Roche Diagnostics, Meylan, France), according to the instructions of the manufacturer. The quantification of HCV RNA was achieved by the Cobas AMPLICOR HCV Monitor assay (version 2.0; Roche Diagnostics).
Detection of HCV RNA in seminal plasma (fraction 1). The RNA extraction step was performed by a protocol modified from that of the QIAmp viral RNA kit (Qiagen, Courtaboeuf, France), as follows: 250 µl of thawed fraction 1 was diluted (vol/vol) in sterile water and centrifuged at 20,000 x g for 1 h; the supernatant was removed, and the resulting pellet was resuspended in 600 µl of AVL lysis buffer (Qiagen) containing 6.4 µl of the internal control from the Roche Cobas AMPLICOR assay. After an incubation step of 10 min at room temperature, 600 µl of absolute ethanol was added and the whole mixture was centrifuged through a QIAmp column at 6,000 x g for 1 min. After two successive washing steps with AW1 buffer for 1 min at 6,000 x g and AW2 buffer for 3 min at 12,000 x g, the RNA extracts were removed from the column by addition of 200 µl of AVE elution buffer and were centrifuged at 6,000 x g for 1 min. RT and qualitative PCR were done by the Cobas AMPLICOR HCV assay (version 2.0) according to the instructions of the manufacturer. The quantification of HCV RNA in seminal plasma was carried out as follows: the RNA extraction step was similar to that for the qualitative protocol, except that the volume of elution buffer was 400 µl instead of 1,000 µl. RT and quantitative PCR were done by the Cobas AMPLICOR Monitor HCV assay (version 2.0) as recommended by the manufacturer. The final result was expressed as the number of copies per milliliter with reference to the volume of 250 µl used in the extraction step. The sensitivities of the qualitative and quantitative assays were determined by using serial 2-fold dilutions (from 160 to 10 copies/ml) or 10-fold dilutions (from 10,000 to 10 copies/ml), respectively, in HCV-negative seminal plasma of blood plasma from an HCV-infected patient, which had been quantified previously by the Cobas AMPLICOR 4CV Monitor assay; then, each dilution was extracted and tested in six independent experiments.
Detection of HCV RNA in spermatozoon fractions. Twenty-five fractions 2 (motile spermatozoa) from 14 patients and four fractions 3 (swim-up spermatozoa) from 1 patient were tested for the presence of HCV RNA. The RNA extraction was performed by combining a lysis step with proteinase K (50 mg/ml) by use of the RNAeasy Mini kit (Qiagen). With reference to the standard Qiagen protocol, an additional step of elution of the column was performed with the first eluate. The internal control of the Cobas AMPLICOR HCV kit was diluted 1:16 in 50 µl of the column eluate. RT and qualitative PCR were done according to the instructions of the manufacturer. In addition, a test with an extraction control was performed by RT-PCR amplification of an intron-containing region of the protamin 2 gene, as described previously (14). Use of a threshold of 500,000 cells in the PCR experiments was justified by the reproductive amplification of the control gene at this cell concentration but not at a lower one.
HCV genotyping. The genotypes of the HCV strains in blood and seminal samples were determined by sequencing the 5' noncoding region by the TruGene HCV assay (Visible Genetics, Espinay sur Orge, France).
Statistical analysis. Quantitative and qualitative values were compared by Student's t test and the chi-square test, respectively. The threshold for a significant value was 0.05.
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PCR inhibitors were detected in only 1 of 32 (3.3%) seminal plasma specimens, but they were not detected after the seminal sample was diluted 1:2 in RNase-free water. The sensitivity of the qualitative assay, determined in six independent experiments as the lowest dilution found to be positive in all the experiments, was 40 copies/ml (1.6 log copies/ml). By using the same algorithm, the sensitivity of the quantitative assay was 100 copies/ml (2 log copies/ml).
Seminal plasma samples from 4 of 32 patients (12.5%) were found to be positive for HCV RNA by the qualitative test. The four patients had been infected through intravenous drug abuse. The seminal viral loads of these four patients are listed in Table 1. The difference in viral loads between blood and semen ranged from 2.83 to more than 5.34 log copies/ml. The mean blood viral load was significantly higher in patients positive for HCV RNA in semen than in those negative for HCV RNA in semen (6.52 ± 0.55 versus 5.88 ± 0.46 log copies/ml [P = 0.02]) (Table 2). For the four patients positive for HCV RNA in semen, the same HCV genotype was found in both blood and seminal plasma (Table 1).
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TABLE 1. Characteristics of the four men whose seminal plasma was positive for HCV RNA
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TABLE 2. Characteristics of patients whose blood was chronically infected with HCV according to presence or absence of HCV RNA in seminal fluid
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Detection of HCV RNA in spermatozoon fractions. The corresponding motile spermatozoa (fraction 2) collected from the four patients whose seminal plasma was HCV RNA positive were tested for HCV RNA. In addition, 15 fractions 2 belonging to 10 patients whose seminal plasma was negative for HCV RNA were tested. All fractions 2 tested remained negative for HCV RNA with the exception of two of five samples collected from patient 3, in which HCV RNA was persistently detected in seminal plasma from July 2000 to May 2001. Fraction 2 of patient 3 was positive for HCV RNA only for a short time corresponding to the first 2 weeks of April 2001; moreover, the four samples of fraction 3 (swim-up spermatozoa) from patient 3 tested negative during the course of the study.
The efficiency of the extraction step with the spermatozoon fractions was evaluated by the detection of protamin 2 gene RNA, and all specimens tested were found to be positive. In addition, cell samples were found to be positive for the internal control, demonstrating the absence of PCR inhibitors in these fractions.
Assays after assisted reproduction. Eleven attempts at medically assisted reproduction were performed for couples for whom the male partner tested negative for the presence of HCV RNA in seminal plasma. Five women became pregnant, with the occurrence of two singleton births and with one set of triplets and two sets of twins being born. The blood of the nine babies tested negative for HCV RNA at birth, and the babies remained uninfected at least 6 months later.
For patient 3, given that HCV RNA was detected in all seminal plasma samples tested and in two motile spermatozoon fractions, the in vitro fertilization program with fresh semen was discontinued. When the motile spermatozoon fractions became negative, they were frozen in specific highly secure straws for future ART. For the three other patients whose seminal plasma was positive for HCV RNA, the ART were delayed.
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The threshold of the assay reached 40 copies/ml, with a very low rate of false-negative results due to the presence of PCR inhibitors, as demonstrated by the use of a standardized commercial technique that included an internal control. This high rate of sensitivity compared to that of the protocol used in the standard AMPLICOR assay with blood samples can be explained by the addition of a step consisting of high-speed centrifugation of the sample. It was close to the one reported for seminal specimens by Leruez-Ville et al. (10), who used the same PCR kit used in the present study but a silica-based extraction technique.
In addition to previous studies on the same topic, this report provides several new findings: (i) the amount of viral RNA in seminal plasma was larger than 500 copies/ml in three of the four positive patients and was up to 3,000 copies/ml in one patient; (ii) in all four of these patients, the genotypes of the strains in the blood and semen of the same patient were found to be identical; and (iii) a positive correlation between the viral loads in seminal plasma and blood was noted. None of these data describe the compartmentalization of HCV RNA between seminal plasma and blood. They suggest that the semen of patients who are chronically infected with HCV for a long time and who exhibit high viral loads are more likely to be positive for HCV RNA; similar findings have been shown for HIV-infected patients (4, 18).
Another finding original to this study was the detection of HCV RNA not only in seminal plasma but also in spermatozoon fractions used in ART. Relevant controls were used to validate the extraction and amplification steps performed on these cells: for all samples tested the RNA of the protamin 2 gene was amplified and the internal control of the PCR assay was positive. In one patient whose blood and seminal plasma were both chronically infected with HCV, two successive samples of the motile spermatozoon fraction were found to be positive for HCV RNA, whereas the same test performed with spermatozoa corresponding to the swim-up fractions was negative. This observation, which to our knowledge has never been described previously, needs discussion; although the possibility that spermatozoa support HCV replication cannot be definitively excluded, the more valuable explanation relies on the passive adsorption to the cell membrane of HCV RNA or virions present in seminal plasma, as suggested by the intermittent detection of HCV RNA in spermatozoa and by the absence of RNA in the corresponding swim-up fraction. In fact, the adsorption of viral particles to cell membranes could reduce the mobility of the spermatozoa, as described previously for cytomegalovirus (11).
Even though the detection of HCV RNA in fractions of semen does not necessarily imply the presence of replicative virions and the infectivity of spermatozoa via medically assisted reproduction, our results plead for the reinforcement of precaution measures for men whose blood is chronically infected with HCV and who are candidates for ART. It is suggested that seminal plasma be systematically evaluated for the absence of viral RNA in order to ensure that ART are performed with samples free of HCV RNA. In those subjects found to be positive, it is proposed that motile spermatozoa be investigated for the presence of HCV RNA and that only spermatozoon fractions that test negative be used for ART. French authorities have recently recommended a similar algorithm (2). Since HCV loads can vary dramatically within a few days both in seminal plasma and in spermatozoa, the safest approach to ART for patients exhibiting HCV RNA in seminal plasma would consist of the use of cryopreserved cells that tested negative at the time of sampling. Although the uneventful deliveries of infants to the cohort evaluated in the present study are encouraging, the validation of this guideline would need to be assessed with a larger population of chronically infected individuals.
We thank David Miller for valuable advice concerning the analysis of spermatozoon gene expression.
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