Correlation of plasma HIV-1 p24 antigen levels with viral load in samples of HIV positive patients on ART in Uganda

Abstract

Globally, a total of 38.0 million people living with HIV, of which 1.7 million people became newly infected with HIV in 2019. Additionally, an average of 690,000 people died from AIDS-related illnesses in 2019, and 26 million people were reported to access antiretroviral therapy as of the end of June 2020. In Uganda, the prevalence of HIV according to the Ministry of Health (MOH) estimates is 5.6% in adults (15-49 years) of which 6.9% are females and 5.3% are males. Current HIV Viral load testing technologies based on RT-PCR remain a financial and logistical burden to HIV treatment and management programs, HIV p24, because it correlates with viral load, has been tried as a surrogate test, but it met challenges like p24 antigen stability and bioavailability. Recently reagents and buffering technologies have been improved to increase the bioavailability of p24 antigens. Our research group has revisit the possibility of using plasma p24 antigen levels as a surrogate test for HIV viral load. We successfully modified a 4th generation bioelisa HIV-1+2 Ag/Ab qualitative ELISA assay (Werfen) into a p24 quantitative one and used it to quantify the p24 antigen in 160 HIV positive Ugandan samples. We found no correlation between p24 concentration (ng/ml) and viral load (copies/ml) for 90 samples (r = 0.03877, p = 0.7168) We transformed the data by taking the log base 10 of each value (both the p24 concentrations and the viral load copies), and there was still a weak non-significant correlation. (r = 0.0379, p = 0.7224) Our findings however conflict with some emerging trends that report positive correlation between p24 and viral load, meaning the journey to stabilizing our technology is still long. The limitation was that we experienced procurement difficulties where the supply chain was interrupted by delays and this definitely affected the timing of the lab assays. We recommend developing and standardizing a technology based on our own pipeline, standardizing the standards to get optimum dilution factors needed for production of a good sigmoid standard curve and then re-running the experiment especially in Ugandan population with A and D subtypes.