Science Buddies: "Ask an Expert"

Hi,

I have been given mock results from a PCR test on blood samples taken from kidney recipient patients and their donors. The PCR reaction can detect single copies of viral DNA. I have been asked to determine whether 5 patients have been infected with EITHER human herpesvirus 6 (HHV6) or human cytomegalovirus (HCMV) following kidney transplants. I have results for patients, pre-transplantation and 1 week and 3 weeks post-transplantation.

The results are as follows:
Donor for patient A = HCMV+
Donor for patient B = HCMV+ & HHV6+
Donor for patient C = Neg for both viruses
Donor for patient D = HHV6+
Donor for patient E = HCMV+ & HHV6+

Patient A = HCMV+ before and 1 & 3 weeks post-transplant
Patient B = Neg for both viruses before, then HHV6+ at week 1 & HCMV+ at week 3 following transplantation but negative for HHV6.
Patient C = HHV6+ before and 1 & 3 weeks post-transplant.
Patient D = HCMV+ before and HCMV+ & HHV6+ 1 & 3 weeks post-transplant
Patient E = HHV6+ before and HCMV+ & HHV6+ 1 & 3 weeks post-transplant

My answers: I am guessing that Patient A was re-infected by donor A. Patient B was neg for both viruses, developed HHV6 week 1 but this test was neg week 3 & instead positive for HCMV – these viruses do not disappear, you either have it or don’t so assuming there is no contamination error then what virus did he develop post-transplant?? Patient C was HHV6+ prior to transplant but donor is neg for both, so what virus did he develop following transplant? I can see that Patient D was infected with HHV6 from donor post-transplant. Patient E was infected with HCMV from donor post-transplant.

I am struggling to determine what virus Patient A, B and C was infected with following transplant. Can anyone help? I know almost 100% of us are infected with both viruses but do not cause disease in healthy people, that both latent and active viruses show positive when in blood and that both viruses can re-activate under certain conditions such as via infected organ transplants and immunosuppression.

Hi Sharondes,

Welcome to Science Buddies! Normally we answer questions for science projects and not for homework assignments. However, here is some information that should help with this assignment.

1 Donor for patient A = HCMV+
Donor for patient B = HCMV+ & HHV6+
Donor for patient C = Neg for both viruses
Donor for patient D = HHV6+
Donor for patient E = HCMV+ & HHV6+

Patient A = HCMV+ before and 1 & 3 weeks post-transplant

This patient was infected with HCMV+ before the transplant, so the viral infection did not originate from the donor.

Patient B = Neg for both viruses before, then HHV6+ at week 1 & HCMV+ at week 3

This patient was negative for both viruses before, and developed the viral infections after the transplant. Since the donor was positive for both viruses, both infections can be attributed to the donor.

Patient C = HHV6+ before and 1 & 3 weeks post-transplant. This patient had a pre-existing infection with HHV6+ and received a transplant from a negative donor, so could not have obtained the infection from the donor.

Patient D = HCMV+ before and HCMV+ & HHV6+ 1 & 3 weeks post-transplant This patient developed an HHV6+ infection after a transplant from an HHv6+ donor, so the infection came from the donor. The patient has a preexisting HCMV+ infection so this did not come from the donor.

Patient E = HHV6+ before and HCMV+ & HHV6+ 1 & 3 weeks post-transplant This patient developed a new HCMV+ infection from the HCMV+ donor. The HHV6 infection existed before the transplant.

I hope this helps!

Donna Hardy