Time to first positive HIV-1 DNA PCR may differ with antiretroviral regimen in infants infected with non-B subtype HIV-1

A new highly sensitive single-tube nested real-time PCR assay: Clinical utility in perinatal HIV-1 diagnosis

Real time PCR is one of the major tools for molecular diagnosis, however not always reaches the required sensitivity, especially in detecting early infectious disease. To overcome this problem, nested PCR is commonly performed, since it is highly sensitive, but it is time-consuming, prone to cross-contamination and difficult to standardize. Therefore, we developed a sensitive and specific single-tube nested real-time PCR (STN-real-time PCR) assay and evaluated its clinical utility on early infant HIV-1 diagnosis (EID). The STN-real-time PCR enables the simultaneous amplification of four HIV-1 specific amplicons by the use of an internal and external pair of primers targeting ltr/gag region, and another one corresponding to human albumin as an internal control. Thermocycling had different annealing temperatures to favor the sequential use of each pair of primers, and included an initial touchdown step to broaden specificity and increase sensitivity. Finally, HIV-1 was detected by melting curve analysis. A total of 234 samples collected retrospectively and prospectively from HIV-1 exposed infants aged <18 months were used to evaluate the performance of the assay and compare it with a routine diagnostic nested-multiplex PCR. The developed assay had a limit of detection of 3 copies of HIV-1 DNA per reaction and had a sensitivity of 31 % more than routine diagnostic nested-multiplex PCR when testing samples near delivery. In conclusion, we developed a new assay by turning a conventional nested-PCR into a faster, more sensitive and feasible STN-real-time PCR assay for EID and potentially useful for detection of pathogens with variable genomes and present in low copy numbers.

Flexible paper-based Ni-MOF composite/AuNPs/CNTs film electrode for HIV DNA detection

It is very important to develop a rapid, simple, low cost point-of-care (POC) method for the early diagnosis of pathogens. In this work, a flexible paper-based electrode based on nickel metal-organic framework (Ni-MOF) composite/Au nanoparticles/carbon nanotubes/polyvinyl alcohol (Ni-Au composite/CNT/PVA) was constructed to detect target human immunodeficiency virus (HIV) DNA by DNA hybridization using methylene blue (MB) as a redox indicator. The CNT/PVA and Ni-Au composite were deposited on the cellulose membrane by vacuum filtration and drop-coating method in turn to obtain Ni-Au composite/CNT/PVA (CCP) film electrode. Compared to the CNT/PVA film electrode, CCP film electrode makes a higher loading of the probe DNA for its large specific surface area and conjugated π-electron system that can provide hydrogen bond sources to achieve interactions between MOF and single-stranded DNA, which improves the sensitivity for detecting target DNA. The variation of peak current for MB molecules adsorbed onto DNA before and after hybridization with HIV DNA was monitored. Electrochemical results proved that the CCP film maintained stable electrochemical property even after bending 200 times or stretching under different strains from 0% to 20%. The flexible paper electrode showed excellent sensing performance with a linear range of 10 nM-1 μM and a low detection limit of 0.13 nM. The target HIV DNA was successfully detected even in complex serum samples using the flexible CCP film electrode. Therefore, the simple and inexpensive flexible paper-based MOF composite film electrode can also be utilized for other pathogens POC diagnosis.

Negative Diagnostic PCR Tests in School-Aged, HIV-Infected Children on Antiretroviral Therapy Since Early Life in Johannesburg, South Africa

BACKGROUND

Younger age at antiretroviral therapy (ART) initiation has been associated with smaller HIV reservoirs. We investigated whether younger age of ART initiation is associated with testing negative and weaker signal on a standard HIV diagnostic test in treated children.

METHODS

At exit from a longitudinal study at 2 sites in Johannesburg, South Africa, 316 school-aged, HIV-infected children on continuous ART started at a median age of 6.3 months, were tested with standard total nucleic acid PCR used for infant diagnosis. All negative results were repeated. Simultaneous viral load (VL) and CD4 T-cell counts/percentages, along with data collected over the prior 4 years, were used in multivariable regression to predict negative PCR results and higher cycle threshold (Ct) values (weaker signal).

RESULTS

Seven children (2.2%, 95% confidence interval: 0.6 to 3.8) in the full cohort had negative PCR results; all 7 were in a subset of 102 (6.9%, 95% confidence interval: 2.0 to 11.8) who had initiated ART at age 0-4 months and had VL <50 copies/mL at the time of PCR testing. Only one repeat tested as negative. Younger age at ART initiation, VL <50 copies/mL at time of test, sustained VL <400 copies/mL, lower CD4 T-cell counts, and ever treated with efavirenz were significant predictors of weaker signal on the diagnostic test.

CONCLUSIONS

In a small proportion of children who start ART in the first months of life and remain on continuous therapy, standard diagnostic HIV PCR tests may result as negative. Repeat testing may resolve uncertainty of diagnosis.

Evolving complexities of infant HIV diagnosis within Prevention of Mother-to-Child Transmission programs

Early diagnosis of HIV infection among infants and children is critical as prompt initiation of antiretroviral therapy prevents morbidity and death. Yet despite advances in the accuracy and availability of infant HIV diagnostic testing, there are increasing challenges with making an early definitive diagnosis. These challenges relate primarily to advances in prevention of mother-to-child transmission (PMTCT) of HIV. Although PMTCT programs have proven to be highly effective in reducing infant HIV infection, infants who are HIV-infected may achieve virological suppression and loss of detectability of HIV nucleic acid prior to diagnosis because of antiretroviral drug exposure. Hence, false-negative and indeterminate HIV polymerase chain reaction (PCR) results can occur, especially among high-risk infants given multi-drug prophylactic regimens. However, the infant HIV diagnostic landscape is also complicated by the inevitable decline in the positive predictive value of early infant diagnosis (EID) assays. As PMTCT programs successfully reduce the mother-to-child transmission rate, the proportion of false-positive EID results will increase. Consequently, false-negative and false-positive HIV PCR results are increasingly likely despite highly accurate diagnostic assays. The problem is compounded by the seemingly intractable prevalence of maternal HIV within some settings, resulting in a considerable absolute burden of HIV-infected infants despite a low mother-to-child transmission rate.

HIV diagnostic challenges in breast-fed infants of mothers on antiretroviral therapy

BACKGROUND

Prompt initiation of antiretroviral therapy (ART) for HIV-infected infants is strongly recommended but diagnostic confirmation is important as committing children to life-long ART carries serious health and social implications.

METHODS

Two HIV-exposed infants in Johannesburg, South Africa were identified presenting with unusual trajectories of diagnostic nucleic acid amplification tests (NAAT) and viral load results.

RESULTS

Case 1 had repeat indeterminate NAAT results during the first 3 weeks of life; repeat testing thereafter was negative with undetectable viral load including after daily nevirapine prophylaxis ended. ART was not initiated at this time. Case 2 had a single positive NAAT result at 1 month of age that prompted initiation of ART. Subsequent results were negative and ART was discontinued. Repeat negative NAAT with viral load below the limit of quantification or undetectable continued to be obtained. Shortly after and around weaning, positive NAAT results with high viral load (7.1 and 6.03 log10 copies/ml for Cases 1 and 2, respectively) were observed in both children. Both mothers were treated with tenofovir, emtricitabine and efavirenz during breastfeeding. Testing with ultrasensitive assays on early samples conclusively revealed HIV-1 proviral DNA in Case 1. Testing with ultrasensitive assays after the early period but prior to weaning did not detect HIV in either infant.

CONCLUSION

We hypothesize that breast milk from the mothers of these two rare cases had HIV-specific or nonspecific factors that led to the undetectable results in already infected infants until breastfeeding ended. Our results raise the importance of repeat testing of HIV-exposed breast-fed infants after complete cessation of all breastfeeding.

A Clinical Score to Support Antiretroviral Management of HIV-exposed Infants on the Day of Birth

BACKGROUND

The benefits of combination antiretroviral (ARV) prophylaxis for infants whose HIV exposure is recognized near birth have been established, and the benefits of early ARV therapy are well known. Decisions about ARVs can be supported by the probability that the child has acquired HIV.

METHODS

Using 2005-2010 data from Enhanced Perinatal Surveillance of the Centers for Disease Control and Prevention, we developed a tool for use at birth to help predict HIV acquisition of HIV-exposed infants to support ARV management. A logistic regression model, fit using a fully Bayesian approach, was used to determine maternal variables predictive of infant HIV acquisition. We created a score index from these variables, established the sensitivity and specificity of each possible score, and determined the distribution of scores among infants, with and without HIV, in our study population.

RESULTS

Multivariable analysis of data from 8740 HIV-exposed infants (176 infected and 8564 uninfected) yielded 4 maternal variables in the perinatal HIV acquisition prediction model: sexually transmitted infection, substance use, last HIV viral load before delivery and ARV use. Using the regression coefficient estimates, we rescaled each possible score to make the maximum score equal to 100. For each score, sensitivity and specificity were determined; the area under the receiver operating characteristic curve was 0.79. Median index scores for infants with HIV and without HIV were 43 (first quartile 27 and third quartile 60), and 12 (first quartile, 0 and thirs quartile, 29), respectively.

CONCLUSIONS

Decisions to begin infants on 3 ARVs-whether considered therapeutic or prophylactic-can be supported by data available on the day of birth.