CD8/CD38 activation yields important clinical information of effective antiretroviral therapy: findings from the first year of the CIPRA-SA cohort.
BACKGROUND
The affordable, reliable, and simplified flow cytometric method on single platform with 2-color (CD45+, CD4+) Panleucogating (PLG-CD4) is used to monitor HIV+ patients on antiretroviral therapy (ART) in South Africa (SA). Viral load (VL) assays are also used to monitor response to ART but are labor-intensive with costs that, in the long run, may remain unsustainable. Cheaper and quicker alternatives to VL such as CD38 tests on CD8+ T cells may therefore play a role in securing the continuation of ART programs in high-volume resource-restricted settings.


METHODS
The single-tube PLG assay (CD45/CD4) was modified to use the full capacity of flow cytometers for 4-color immunofluorescence by including two more parameters: the CD38-activation marker on CD8 T-cells (CD8/CD38). This was introduced at baseline prior to the start of ART and then the changes of CD38+ mean fluorescent intensity (MFI) on CD8+ T-cells were then regularly assessed during follow-up-in comparison with the VL.


RESULTS
A total of 103 patients received ART. By the end of their 4-, 8-, 12-, and 24-week observation periods, 29 (32.2%), 58 (64.4%), 74 (82.2%), and 83 (92.2%) had undetectable VL. This was also reflected by the gradual decrease of CD38 MFI expression on CD8+ T cells, irrespective of whether patients were "high," "moderate," or "low" CD38 responders at baseline. As expected, the CD4+ T cell counts substantially increased during the first 4 weeks from baseline 186 +/- 8.3 (SEM) to 267 +/- 12.3 cells/microl blood. But the recovery was slower over the rest of the 1-year follow-up to reach 334 +/- 18.2 cells/microl at week 48. As these CD4 increments were meager, the longitudinal follow-up of the continuously decreasing CD38 MFI values has become a particularly useful laboratory parameter to ascertain that the patients had indeed been responding well to ART. This monitoring protocol, in uneventful cases, may assist in reducing the frequency of VL testing. Conversely, a rise of CD38 MFI, if significantly higher than that seen at the previous visit even without fully reverting back to high baseline CD38-MFI values, provides an immediate indication for VL testing to judge whether or not the rebound of immune-activation is due to HIV VL-related irregularities. Therefore the CD8/CD38 test can provide the early, albeit not fully HIV-specific, warning signs about nonadherence to ART and/or developing drug resistance.


CONCLUSIONS
This single-tube 4-color PLG-CD4 + CD8/38 activation assay (CD4/CD45/CD8/CD38), can replace the conventional 4-color CD4 protocols by substituting the redundant CD3 reagent with the informative CD38 antibody. This modification carries virtually no extra costs, while adding extra value to CD4 monitoring and enabling real-time, practical management of patients on ART. As a result, the numbers of VL tests required in patients on ART can be reduced-to save costs across our national treatment program which is already equipped with the necessary flow-cytometric screening capacity.
Glencross
Deborah K
DK
Department of Molecular Medicine and Haematology, University of the Witwatersrand, Johannesburg, South Africa. glencross@roussos.co.za
Janossy
George
G
Coetzee
Lindi M
LM
Lawrie
Denise
D
Scott
Lesley E
LE
Sanne
Ian
I
McIntyre
James A
JA
Stevens
Wendy
W
D051997:ADP-ribosyl Cyclase 1 / Q000276:immunology*; D000163:Acquired Immunodeficiency Syndrome / Q000276:immunology*; D023241:Antiretroviral Therapy, Highly Active; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D016827:CD8 Antigens / Q000276:immunology*; D015331:Cohort Studies; D005453:Fluorescence; D006801:Humans; D007391:International Cooperation; D008213:Lymphocyte Activation / Q000276:immunology*; D015203:Reproducibility of Results; D013019:South Africa; D019562:Viral Load
D016827:CD8 Antigens; D051997:ADP-ribosyl Cyclase 1