The success of doctors in Berlin apparently curing a person (the "Berlin patient") of HIV has stimulated scientists in high-income countries to attempt to do the same. It should be noted that the apparent success of the Berlin researchers might have rested on one or more of the following factors:
The protocol used by the Berlin doctors is toxic and caused complications that persisted for several years. Subsequent attempts to replicate their protocol have initially led to several deaths. However, with much caution, researchers are still attempting to effect a cure by making some modifications to the Berlin protocol.
Researchers in Pennsylvania and California have evaluated 10 HIV-positive participants before and after they received intensive chemotherapy for cancer (lymphoma) followed by a transplant of stem cells. Each participant had some stem cells removed prior to chemotherapy and then had them transplanted after their course of chemo was over. These cells were not modified to resist HIV. Participants were taking ART and generally tolerated it during chemo. However, three of them had to interrupt ART because of severe chemo-related side effects.
Technicians developed an in-house viral load test that could detect as little as one copy of HIV RNA in the blood. Using this tool they found that after transplantation, participants had a viral load of about 2 copies/ml.
In one patient, researchers could not detect HIV replication with their ultra-sensitive assay. However, when they analysed his blood with other assays, they found that he had HIV-infected cells (as did all the other participants). Despite being monitored for up to 10 years, the proportion of infected cells in all of the participants did not decline after their transplant.
Chemotherapy is designed to wipe out rapidly dividing tumour cells. The cells of the immune system that contain latent HIV include a group of cells called "resting CD4+ T cells" by researchers. These cells are not active and chemotherapy might not kill them.
Another possibility is that the stem cells used for transplantation contained some cells that were infected with HIV. Therefore, the transplant could have helped to re-establish HIV.
Based on these results, stem cells harvested from ART users whose viral load is less than 50 copies/ml and then transplanted after chemo are not going to reduce the burden of HIV-infected cells or cure HIV.
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