Silvia Azaña, an embryologist at inviTRA, talks to us in this video about sperm washing. As Silvia tells us:
Despite being controversial, it is generally believed that sperm cells themselves do not transmit the retrovirus. Therefore, semen washing involves carefully processing the semen sample with the specific goal of separating only the motile sperm. In this way, the possibility of the woman becoming infected with the virus during reproductive treatment is practically null.
In order to carry out the semen washing procedure, the man must provide a semen sample to the andrology laboratory staff. Subsequently, using various techniques, the spermatzoa with the best motility are separated from the remaining components found in the semen, such as seminal plasma, lymphosytes, epithelial cells, immotile spermatzoa, etc.
The most common and widely used method for separating the best sperm from the rest of the semen sample is to apply a double washing process. Therefore, a density gradient is performed followed by a swim-up. In order to perform the density gradient, various layers with different concentrations are placed in a tube. As a result of this process, a density gradient is established to separate the various semen fractions. The seminal sample is then added to the top of the tube, but after centrifugation, the mobile sperm will remain at the bottom of the tube.
To perform the swim-up, the sperm recovered in the previous step are added to another tube containing culture medium. Following this, the tube must be incubated under specific controlled conditions. Subsequently, after the designated incubation period has passed, the spermatzoa with the best motility will have swam to the top of the tube from where they will be recovered by specialists. However, before the recovered sperm can be used in any type of reproductive treatment, it is necessary to confirm the complete absence of viruses in the sample.
For this reason, half of the processed sample is analyzed, usually by PCR, in order to accurately confirm the absence of virus. The other half is carefully frozen while awaiting results. If the test result is negative, indicating that no virus is present, half of the sample that has been kept frozen is considered suitable for use in assisted reproduction treatment. If viruses are detected, the frozen sample is discarded to prevent any risk of transmission. In this last case, it would be necessary to begin the entire semen washing procedure, starting again with a new semen sample.
Nevertheless, these samples are often free of viruses a high percentage of the time. Moreover, it can confidently be stated that the success rate of this procedure is very high, as no cases of HIV transmission have been reported after semen washing so far.
