Clinical challenges faced in Zimbabwe
- Late diagnosis and initiation of ART.
- Delayed switching to 2nd line ART amongst 1st line failures due to limited access to viral load testing.
- Thus, patients remain on failing regimens, allowing the development of extensively resistant viral strains
- This may foster the transmission of drug resistant virus: vertical and horizontal
Meeting the Resistance Testing needs- Our Solutions
- VL tests that monitor virologic suppression and provide early indication of treatment failure
- Affordable and timely genotypic drug resistance testing
- Identification of key drug resistance mutations that can guide clinical treatment and patient management
- Recommendations for new drug classes; who will require Integrase strand transfer inhibitors (INSTIs) such as Elvitegravir, Raltegravir or Dolutegravir?
Guidelines for ART & HIV-DR Testing recommendations
- Annual VL is the preferred monitoring approach to identify ART failure
- If virologic suppression is not achieved (VL > 1,000 copies/ml) a second test is recommended in 4-6 weeks after adherence counseling.
- ART naive patients should be screened for transmitted Drug resistance upon diagnosis and initiation of therapy (optional)
- Children/ infants exposed to PMTCT should be screened for transmitted Drug resistance (optional)
- HIV-DR testing before switching drug regimens for patients with virological failure on first-line ART (Viral loads >1000 copies/ml) (optional)
- HIV-DR testing before switching drug regimens for patients with virological failure on second-line ART (Viral loads >1000 copies/ml) (recommended)
Viral load testing
The test itself measures the amount of the HIV virus that is present in a person’s blood. Lower amounts of virus means improved health outcomes for a patient as well as less of a chance to transmit HIV to others. When on ART, viral load testing provides a clear picture of whether a patient is responding successfully to HIV treatment.
“Treatment failure is defined as detectable VL>1000 c/ml, i.e. two consecutive VL within 3 month interval with adherence support between measurements after 6 months of using ARV
Cobas Ampliprep Taqman analyzer machine is used for HIV-VL monitoring assays at Newlands Clinic. With a 3-day turnaround time, this machine yields high precision and sensitive results. LOD <20 copies/ml 2
Cepheid has developed a new test for viral load monitoring. The Xpert HIV-1 Viral Load determines viral load from plasma with a turnaround time of 90mins. LOD from plasma is <20 copies/ml, LOQ from plasma 40cps/ml 3,4.
Why does HIV- Drug resistance occur?
HIV replicates its genome with the highest known mutation rate of any living organism. The replication in the absence of any enzymatic proofreading activity is extremely error prone resulting in one mistake on average in every viral genome transcribed. This creates a complex mix of viral quasi-species.
Drugs exert pressure that selects mutations allowing quasi-species (which are resistant to drugs) to develop and expand. If treatment is stopped the wild type virus will re-emerge. Drug resistance occurs by two major pathways. The first pathway is by the transmission of drug resistant virus from a partner or from mother to child and is called primary or transmitted drug resistance (TDR).
Secondary or acquired drug resistance is the other major pathway due to which drug resistance develops. This type of resistance occurs when HIV continues to replicate in the presence of suboptimal levels of ART. Factors such as; rapid clearance, poor absorption, host genetics, drug interactions etc. contribute to insufficient drug levels in the body and thus suboptimal therapy5.
Development of Drug Resistance
It is a genotypic test that detects presence/ absence of mutations in a virus population by identifying codon changes at specific sites known to cause resistance. This helps to guide clinical decisions in the use of ARVs for patient management. Here is the laboratory workflow for HIV genotypic drug resistance testing.
Resistance Data + ART History = Effective ART Administration
Genotypic testing workflow
Citation: Monogram Biosciences- HIV Genotypic Tests7
Example of the HIV-DR Result form
Studies that have determined HIV-drug resistance mutations in different cohorts
An on going study at Newlands Clinic, on 2nd line virologic failures (n=92) has found 89% prevalence of NNRTI resistant mutations. Most common ones being K103N and Y181C. 76% of study participants had at least 1 NRTI mutation; M184V and K65R mutations were most predominant. 49% showed to have developed Thymidine analog mutations (TAMs). PI mutations that confirm second line failure were not as common, and were seen in only 13% of the study group. This helped to deduce treatment failure was due to poor adherence 8.
An adherence intervention trial at a public health clinic was conducted on adolescents failing 2nd line treatment 9. Characterization of drug resistant mutations was carried out on 20 study participants who failed to achieve virologic suppression after 3 months of adherence counseling. PI and NNRTI resistance was seen in 30% and 80% of adolescents respectively. Only 2 of the 20 participants had mutations conferring tenofovir resistance. Although a small sample size this may be indicative of HIV-DR trends among adolescents.
How to get VL testing and HIV-DR testing
- Visit Newlands Clinic
- Get whole blood drawn
- Submit the Request form filled out by the physician
- Make payment
- Collect/receive by email VL results within 3 days
- Collect/ receive by email HIV-DR results within 3 weeks
NB.: The VL should be at least 1000 copies/ml for HIV-DR testing
56 Enterprise Road, Newlands, Harare
Biomedical Research and Training Institute
No. 10 Seagrave road
Mount Pleasant, Harare, Zimbabwe
Phone: +263-4-333091 ; 335641; 333464 ; 336691
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- Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents, National institute of health. https://aidsinfo.nih.gov/contentfiles/lvguidelines/glchunk/glchunk_6.pdf
- COBAS®AmpliPrep/COBAS® TaqMan® HIV-1 Test, v2.0, Roche.
- Cephied, Xpert HIV-1 Viral load Datasheet- CEIVD
- Ceffa, S., Luhanga, R., Andreotti, M., Brambilla, D., Erba, F. et, 2016, Comparison of the Cepheid Gene Xpert and Abott M2000 HIV-real time molecular assays for monitoring HIV-1 viral load and detecting HIV infection. Journal of Virological Methods. 229, p.35-29.
- Rossouw,T,, Lessells, R. and Oliveira, T. 2013, HIV & TB Drug Resistance & Clinical Management Case Book. MRC council. http://www.bioafrica.net/manuscripts/HIVTB_book_chapter1_HIVresistance.pdf
- NAM, AidsMap. Information Booklet. http://www.aidsmap.com/What-is-drug-resistance/page/1327026/
- Monogram Biosciences, HIV Genotypic test http://www.monogrambio.com/hiv-tests/genotypic-assays
- Dr. Chembetete, Newlands Clinic
- Chawana, T.D., Ngara, B., Katzenstein, D., Nathoo, K. and Nhachi, C.F.B. Adolescent Treatment Failure (ATF) study. An adherence intervention and drug resistance among HIV positive adolescents failing 2nd line treatment at a public health clinic- a randomized controlled trial.