Investigation into the presence of and serological response to XMRV in CFS patients

Abstract

The novel human gammaretrovirus xenotropic murine leukemia virus-related virus (XMRV), originally described in prostate cancer, has also been implicated in chronic fatigue syndrome (CFS). When later reports failed to confirm the link to CFS, they were often criticised for not using the conditions described in the original study. Here, we revisit our patient cohort to investigate the XMRV status in those patients by means of the original PCR protocol which linked the virus to CFS. In addition, sera from our CFS patients were assayed for the presence of xenotropic virus envelope protein, as well as a serological response to it. The results further strengthen our contention that there is no evidence for an association of XMRV with CFS, at least in the UK.

Figure 1. PCR amplification for XMRV in CFS patients.

(A) Amplification products from nested PCR using XMRV env primers are shown. The env specific product which is 352 nt long was not amplified from CFS patients 37–48, as shown in lanes 1–12, but was amplified from the plasmid pXMRV, lane 13. The no-template controls are shown in lanes 14–19 and the DNA marker in lane 20. (B) The gag specific product, 736 nt in length, was not amplified from the same CFS patient DNA samples, lanes 1–12. The DNA marker is shown in lane 13, the plasmid pXMRV in lane 14 and the water controls in lanes 15–20.

Figure 2. Antibody ELISA using sera from CFS patients and normal health subjects (NHS).

The absorbance A₄₀₅ values for 130 sera from CFS patients and NHS are shown. For the antibody ELISA whole NZB xenotropic virus was coated to the microtitre plate following incubation with serum samples overnight. Antibodies were detected by incubation with anti-human IgG antibodies labelled with alkaline phosphatase. The solid lines represent the mean. The BSA background of 0.071 is represented by the dotted line.

Figure 3. Antigen-capture ELISA using sera from CFS patients and NHS.

(A) Goat anti-Rauscher MLV gp70 (lane a) and goat anti-NZB xenotropic virus (lane b) antibodies were tested for their reactivity against NZB xenotropic virus in 2-fold serial dilutions starting with 10 µg/ml. The A₄₀₅ values are given. For the antigen capture ELISA, xenotropic virus envelope was captured onto the microtitre plate using 83A25 rat monoclonal antibody . Detection was then carried out using goat anti-Rauscher antibodies or goat anti-NZB xenotropic MLV gp70 antibodies. (B) Results using goat anti-Rauscher MLV gp70 antibodies. The solid lines represent the mean and the dotted line indicates the BSA background of 0.161. (C) Results shown for goat anti-NZB xenotropic virus antibodies. The solid line represents the mean and dotted line indicates the BSA background of 0.095.