HIV-1 Management | High-Sensitivity HIV-1 Viral Load Quantitative Nucleic Acid Testing (NAT) Assay
Acquired Immunodeficiency Syndrome (AIDS) is caused by infection with the Human Immunodeficiency Virus (HIV). HIV targets the immune system's CD4+ T lymphocytes, progressively compromising immune function and leaving the body susceptible to various conditions, including tuberculosis, opportunistic infections, and certain malignancies, which can lead to severe clinical outcomes or death. HIV is transmitted through the body fluids of infected individuals, such as blood, breast milk, semen, and vaginal secretions; it can also be transmitted from mother to child during pregnancy or childbirth.
I. The Critical HIV/AIDS Landscape in China
HIV remains a profound global public health challenge with no definitive cure. The virus continues to circulate worldwide, having claimed approximately 40.43 million lives to date. As of the end of 2022, the global population of people living with HIV (PLWH) was estimated between 39 million and 45.7 million.
In Mainland China, there are a reported 1.22 million PLWH. Notably, nearly 39% of newly diagnosed patients present at an advanced clinical stage (defined by a CD4+ count < 200 cells/µL). Furthermore, HIV drug resistance among treatment-naïve populations is increasing annually (reaching 10% in central regions), posing significant challenges to the national healthcare system and long-term clinical management.
II. High-Sensitivity Nucleic Acid Testing (NAT): Interrupting Transmission via Early Detection
Between 2009 and 2017, the primary sources of new HIV/AIDS reports in medical institutions were preoperative screenings and pre-transfusion testing, followed by screenings at STI clinics, obstetric departments, and prenatal checkups. Most of these cases were identified through passive screening within the healthcare system. In 2017, sexual transmission accounted for 95.1% of new reports, serving as the primary driver of the epidemic in China.
Research indicates that once diagnosed, the role of HIV-infected individuals as sources of infection can be significantly diminished; while 94% of individuals engage in high-risk behaviors prior to diagnosis, these behaviors decrease markedly within 12 weeks of receiving a diagnosis. During the window period, the viral titer in a single drop of blood is, on average, 100 to 1,000 times higher than during the latent phase, rendering the individual 100 to 1,000 times more infectious.
HIV RNA is detectable in plasma as early as one week post-infection. Approximately two weeks post-infection, both HIV RNA and the p24 antigen can be detected, followed by HIV antibody seroconversion at 2–3 weeks. As the earliest detectable biomarker during acute infection, HIV RNA testing significantly shortens the diagnostic window for HIV screening.
Key Insight: During the window period, the viral titer in a single drop of blood is 100 to 1,000 times higher than during the latent phase, making the individual 100 to 1,000 times more infectious.
III. Longitudinal Clinical Management via High-Sensitivity Nucleic Acid Testing (NAT)
HIV-1 Nucleic Acid Testing (NAT) is utilized for both definitive infection diagnosis and viral load (VL) monitoring. In diagnostic applications, it serves as a supplementary test for identifying infections during the acute phase, window period, and advanced stages, as well as for diagnosing HIV in infants under 18 months of age, thereby reducing potential transmission from new cases. In terms of viral load monitoring, it is essential for predicting disease progression, evaluating therapeutic efficacy, and informing ART (antiretroviral therapy) regimen adjustments.
1. Disease Progression Monitoring
Quantitative HIV-1 DNA testing tracks the progression of the disease. For PLWH with HIV-1 DNA levels exceeding 10^3 copies/10^6 PBMCs (peripheral blood mononuclear cells), the risk of progressing to AIDS within five years is high (>25%), regardless of their HIV-1 RNA load or CD4+ levels. Patients on ART should aim to suppress HIV-1 DNA levels below 10^3 copies/10^6 PBMCs to reduce the incidence of AIDS. For those with levels below 300 copies/10^6 PBMCs, the rate of virological failure is significantly lower. Consistent treatment compliance and regular monitoring are recommended to prevent viral rebound and achieve long-term non-progression.
2. Evaluating Therapeutic Efficacy
Quantitative HIV-1 DNA testing provides a novel technical metric for assessing ART outcomes. Lower levels of HIV-1 DNA are predictive of superior clinical outcomes and may allow for simplified therapeutic strategies. Under effective ART, HIV-1 DNA levels should remain stable or show a sustained decline. Conversely, a significant and sustained increase in HIV-1 DNA (e.g., an increase of >1 log_10 for those starting at <100 copies/10^6 PBMCs, or a doubling of levels for those starting at >300 copies) signals a potential viral rebound or the emergence of drug-resistance mutations, necessitating close clinical surveillance.
IV. Pre-NAT II Fully Automated Nucleic Acid Testing System
The Pre-NAT II is a fully automated workstation designed for high-throughput nucleic acid extraction and PCR reaction setup. It is optimized for clinical preoperative screening, specifically for the high-sensitivity detection of HBV, HCV, and HIV. By automating the entire workflow—from extraction to liquid handling—the system minimizes sample loss and cross-contamination while significantly increasing throughput.
Assay Performance Specifications
- Ultra-Sensitivity: Limit of Detection (LoD) as low as 19.3 copies/mL.
- Broad Dynamic Range: Linear quantification range from 29 to 1.16 × 10⁷ copies/mL.
- Dual-Target Detection: Targets the highly conserved pol and gag regions for robust amplification and detection.
