Test method for evaluating the permeability of intact prophylactics to viral-size microspheres under simulated physiologic conditions

Concentration and detection of hepatitis A virus and its indicator from artificial seawater using zeolite

Hepatitis A virus (HAV) infection is the leading worldwide cause of acute viral hepatitis, and outbreaks caused by this virus often occur in fecal polluted waters. Rapid concentration and detection of viral contamination in water environments can prevent economic loss and can identify the source of contamination within a short time. However, conventional methods for virus concentration are often laborious, time consuming, and subject to clogging. Furthermore, most methods require a secondary concentration step to reduce the final volume of samples. We developed a method to concentrate HAV from seawater using zeolite in aid of rapid detection. In this method,artificial seawater was inoculated with HAV (7-8 log TCID50) and filtered with zeolite. The viruses were then eluted from zeolite with sodium dodecyl sulfate and detected via real-time PCR (qPCR). Zeolite was able to concentrate HAV from artificial seawater with ∼99% efficiency in less than 5min and was more efficient in seawater than in fresh water. The entire concentration and detection can be done in approximately 2h. Compared to existing methods, this method eliminated the need for a secondary concentration step as well as the necessity to modify the pH or salinity of the seawater during concentration, and was simple and inexpensive.

Condom use and vaginal Y-chromosome detection: the specificity of a potential biomarker

OBJECTIVE

Detection of vaginal Y-chromosome sequences (YCS) may be a useful biomarker to validate sexual behavior reporting in women. We describe the effects of condom use on the detection of vaginal YCS.

METHODS

Fifty-six women were asked to abstain from sexual intercourse for 14 days. On day 15, participants were asked to engage in sexual intercourse with their male partners using condoms. Self-collected vaginal swabs were obtained on days 14, 16, and 17. YCS were detected using the Roche LightCycler with the use of positive controls.

RESULTS

Fourty-four of 56 women completed the study. Five women (11.4%) had detectable YCS. The overall specificity of the YCS assay with condom use was 92% (95% CI: 80%-98%). Although women who reported receptive oral sex and digital penetration within 48 hours of swab collection had a higher detection rate of YCS [RR 2.3 (95% CI: 1.1-4.6) and 3.6 (95%CI: 1.6-8.5), respectively], the mean concentration of YCS was much less than that associated with unprotected vaginal intercourse (P <0.001)

CONCLUSIONS

Condom use during intercourse appears to prevent vaginal YCS detection; this may be a useful biomarker to validate self-reported condom use.

Virus transmission through compromised synthetic barriers: part I--effect of unsteady driving pressures

Although synthetic membranes such as gloves, condoms, and instrument sheaths are used in environments with highly time-varying stresses, their effectiveness as barriers to virus transmission is almost always tested under static conditions. In this paper it is shown how a previously developed mathematical model can be used to transform information from static barrier tests into predictions for more realistic use conditions. Using a rate constant measured for herpes adsorption to latex in saline, and an oscillatory trans-membrane pressure representative of coitus, the amount of virus transmitted through a hole (2 microm diameter) in a condom is computed. Just beyond the exit orifice of the pore, transport is dominated by the rapidly dissipating viscous jet of virus suspension, which results in an accumulation of viruses roughly 20 pore radii from the barrier surface during each cycle. Due to virus adsorption to the barrier surfaces, the simulations reveal a gradual decrease in virus flow with increasing number of cycles, and thus a slow divergence from predictions based upon steady-state conditions. Still, over the 500 cycles simulated, steady-state predictions approximate the net number of viruses transmitted to within 25 percent error.

Virus transmission through compromised synthetic barriers: part II--influence of pore geometry

When stressed during normal use, synthetic barriers such as gloves and condoms can develop tears that are undetectable by the user. It is of considerable public-health importance to estimate the quantity of virus transmitted through the tear, in the event of viral contamination of the fluid medium. A mathematical model that accounts for virus adsorption to the barrier material was used to compute the quantity of virus transmitted through defects of various geometries. Slits were modeled as cylinders of elliptic cross section, and upper and lower bounds for the transmission rate of HIV and Hepatitis B virus (HBV) were calculated for barrier-use scenarios such as coitus and gripping of surgical instruments. For a 1-microm high slit, HIV transmission was found to be negligible for all likely use scenarios. HIV transmission became potentially significant for a 5-microm slit. Due to its high titer, HBV transmitted at potentially important levels even through the 1-microm slit. The dependence of the transmission rate upon pore aspect ratio was determined and found to be very strong for high-adsorption situations and near-circular pores. Numerical predictions of virus transport through a laser-drilled hole in a condom matched experimental measurements well, even when the tapered nature of the geometry is ignored.

Implications of laboratory tests of condom integrity

BACKGROUND

There is sufficient evidence from Food and Drug Administration laboratory experiments and clinical studies to draw conclusions about the relative importance of holes and breakage to condoms. The laboratory test methods determined penetration of viruses or virus-size microspheres through holes in condoms under conditions that simulated or exaggerated those expected in actual use, and determined the frequency with which condoms might pass virus or microspheres and the amounts of passage in each case.

GOALS

To summarize and comment on the significance of test results on latex, polyurethane, and natural membrane condoms as barriers to virus passage.

STUDY DESIGN

Published and unpublished data addressing three distinct concerns were analyzed: (1) passage of virus or microspheres through small holes or pores inherent in the material of "intact" condoms which are undetectable by the standard water leak quality assurance test, (2) passage of virus or microspheres through larger holes in "leaker" condoms detectable by the water leak test but marketed because of the finite acceptable quality level (AQL) of the test, and (3) passage of virus through condoms that break during use.

RESULTS

Extrapolating to the passage of semen expected during actual use allowed an analysis of the relative importance of breakage and water-leak-detectable or water-leak-undetectable holes.

CONCLUSIONS

The relative importance of breaks and holes is related to the volume of semen that contains an "infectious dose" of a sexually transmitted disease (STD). When 0.1 mL to 1.0 mL exposures to semen are necessary for disease transmission, the risk during latex condom use primarily results not from holes, but from breakage of condoms. For smaller volumes of semen exposure (0.00001 mL and less), the presence of holes can be as important as breaks. The same qualitative argument pertains to a comparison of "leaker" condoms to the large majority of "intact" condoms.

An in vitro evaluation of condoms as barriers to a small virus

BACKGROUND

Because of the possible presence of small holes, the effectiveness of condoms as barriers to virus transmission is controversial.

GOALS

To determine the proportion of condoms that allow virus penetration and the amounts of virus that penetrate.

STUDY DESIGN

A sensitive, static test was used to evaluate different condom types as barriers to a small virus, including brand with or without lubrication and ones of different materials. The test included some physiologic-based parameters and some parameters that exaggerated expected actual use conditions.

RESULTS

Under test conditions, 2.6% (12 of 470) of the latex condoms allowed some virus penetration; the median level of penetration was 7 x 10(-4) ml. Lubricated condoms performed similarly to nonlubricated ones. Polyurethane condoms yielded results higher than but not statistically different from those for latex condoms.

CONCLUSIONS

Few condoms allowed any virus penetration. The median amount of penetration for latex condoms when extrapolated to expected actual use conditions was 1 x 10(-5) ml (volume of semen). Thus, even for the few condoms that do allow virus penetration, the typical level of exposure to semen would be several orders of magnitude lower than for no condom at all.

Elution of viruses by ionic and nonionic surfactants

The ionic and nonionic surfactants sodium dodecyl sulfate and Triton X-100, respectively, eluted two viruses, phi X174 and PRD1, which were adsorbed to the ionic and nonionic binding membranes cationic polysulfone and nitrocellulose, respectively. Results indicated that complete elution was readily achieved only when combinations of surfactants and binding membranes were matched (i.e., ionic-ionic or nonionic-nonionic).

Minimized virus binding for tests of barrier materials

Viruses are used to test the barrier properties of materials. Binding of virus particles during passage through holes in the material may yield misleading test results. The choices of challenge virus and suspending medium may be important for minimizing confounding effects that might arise from such binding. In this study, different surrogate viruses, as well as different support media, were evaluated to determine optimal test parameters. Two membranes with high-binding properties (nitrocellulose and cationic polysulfone) were used as filters to compare binding activities of different surrogate challenge viruses (MS2, phi X174, T7, PRD1, and phi 6) in different media. The media consisted of buffered saline with surfactants, serum, or culture broth as additives. In addition, elution rates of viruses that bound to the membranes were determined. The results suggest that viruses can bind by hydrophobic and electrostatic interactions, with phi X174 displaying the lowest level of binding by either process. The nonionic detergents Triton X-100 and Tween 80 (0.1%) equally minimized hydrophobic interactions. Neither anionic nor cationic surfactants were as effective at nontoxic levels. Serum was effective at reducing both hydrophobic and electrostatic binding, with 2% being sufficient for eliminating binding under our test conditions. Thus, phi X174 remains the best choice as a surrogate virus to test barrier materials, and Triton X-100 (0.1%) remains a good choice for reducing hydrophobic binding. In addition, binding of viruses by barrier materials is unlikely to prevent passage of blood-borne pathogens.

Viral leakage risk differences in latex condoms

Through use of a new bacteriophage assay capable of detecting a single viral plaque-forming unit (PFU), viral leakage through multiple replicates of several types of latex condoms has been evaluated. Stocks were used that had been preserved from a previous large study in which viral leakage had been assessed preliminarily in several brands. In the present research, much larger numbers of replicates--on the order of magnitude of 100 condoms per brand--were used. Leakage was demonstrated in single production lots of each of seven brands of condoms. With one notable exception, percent leakage ranged from 0.9 to 22.8%; 100% of the specimens of one profoundly flawed brand leaked. All test condoms were subjected to conditions intended to model these prevailing during coitus. Because the condoms used in this study were aged, current stocks of two widely sold brands were tested for comparison. Of these, 11.8% of one brand leaked, 25.7% of the other. The relevance of the results, which gave a high, albeit physiologically appropriate, challenge to the test brands, is discussed--so too is the significance to condom users of results deriving from a leakage assay of exquisitely high sensitivity.

A simple method to test condoms for penetration by viruses

A method by which virus penetration through condoms can be tested with simple, inexpensive equipment is described. The method uses chi X174 bacteriophage as the challenge virus and physiologically relevant pressure. Penetration by 0.1 microliters (or less) of challenge suspension can be readily detected. As examples, latex and natural-membrane condoms were examined.