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

OBJECTIVE

To evaluate the association of type and timing of prophylactic maternal and infant antiretroviral regimen with time to first positive HIV-1 DNA PCR test, in nonbreastfed HIV-infected infants, from populations infected predominantly with HIV-1 non-B subtype virus.

DESIGN

Analysis of combined data on nonbreastfed HIV-infected infants from prospective cohorts in Botswana, Thailand, and the United Kingdom (N = 405).

METHODS

Parametric models appropriate for interval-censored outcomes estimated the time to first positive PCR according to maternal or infant antiretroviral regimen category and timing of maternal antiretroviral initiation, with adjustment for covariates.

RESULTS

Maternal antiretroviral regimens included: no antiretrovirals (n = 138), single-nucleoside analog reverse transcriptase inhibitor (n = 165), single-dose nevirapine with zidovudine (n = 66), and combination prophylaxis with 3 or more antiretrovirals [combination antiretroviral therapy (cART), n = 36]. Type of maternal/infant antiretroviral regimen and timing of maternal antiretroviral initiation were each significantly associated with time to first positive PCR (multivariate P < 0.0001). The probability of a positive test with no antiretrovirals compared with the other regimen/timing groups was significantly lower at 1 day after birth, but did not differ significantly after age 14 days. In a subgroup of 143 infants testing negative at birth, infant cART was significantly associated with longer time to first positive test (multivariate P = 0.04).

CONCLUSION

Time to first positive HIV-1 DNA PCR in HIV-1-infected nonbreastfed infants (non-B HIV subtype) may differ according to maternal/infant antiretroviral regimen and may be longer with infant cART, which may have implications for scheduling infant HIV PCR-diagnostic testing and confirming final infant HIV status.

Delayed HIV detection among infants exposed to postnatal antiretroviral prophylaxis during breastfeeding

OBJECTIVE

The objective of this study is to determine whether detection of HIV infection was delayed in infants exposed to antiretroviral prophylaxis to prevent HIV transmission during breastfeeding.

DESIGN

The Breastfeeding, Antiretrovirals and Nutrition (BAN) study was a randomized trial of 2369 mother-infant pairs conducted from 2004 to 2010. In addition to an intrapartum regimen, all mother-infant pairs were randomly assigned to three antiretroviral intervention arms during 28 weeks of breastfeeding: no further antiretroviral prophylaxis (control arm); infant-daily nevirapine (nevirapine arm); and maternal zidovudine, lamivudine and either nevirapine, nelfinavir or lopinavir-ritonavir (maternal arm). After breastfeeding cessation counselling and stopping the antiretroviral interventions by 28 weeks, 28 infant HIV infections occurred.

METHODS

To determine whether these infections occurred during the breastfeeding and antiretroviral intervention phase but had delayed detection on the antiretroviral arms, we performed ultrasensitive (droplet digital PCR) HIV testing on infants with stored peripheral blood mononuclear cell (PBMC) specimens at 24 weeks (n = 9).

RESULTS

Of the nine infants, all three on the infant nevirapine arm had detectable HIV DNA at 24 weeks, compared with two of four on the maternal antiretroviral arm and one of two on the control arm. For infants with detectable HIV at 24 weeks, the median delay in detection between the ultrasensitive and standard assays was 18.3 weeks for the nevirapine arm, 15.4 weeks for the maternal arm and 9.4 weeks for the control arm.

CONCLUSION

The prolonged inability to detect HIV with standard assays in the context of postnatal antiretroviral prophylaxis suggests that early antiretrovirals may restrict HIV replication sufficiently to lead to missed diagnosis among infected infants. Therefore, repeat virologic testing is warranted beyond the WHO-recommended point of testing at 6 weeks after breastfeeding cessation.

Nonparametric inference and uniqueness for periodically observed progressive disease models

In many studies examining the progression of HIV and other chronic diseases, subjects are periodically monitored to assess their progression through disease states. This gives rise to a specific type of panel data which have been termed "chain-of-events data"; e.g. data that result from periodic observation of a progressive disease process whose states occur in a prescribed order and where state transitions are not observable. Using a discrete time semi-Markov model, we develop an algorithm for nonparametric estimation of the distribution functions of sojourn times in a J state progressive disease model. Issues of uniqueness for chain-of-events data are not well-understood. Thus, a main goal of this paper is to determine the uniqueness of the nonparametric estimators of the distribution functions of sojourn times within states. We develop sufficient conditions for uniqueness of the nonparametric maximum likelihood estimator, including situations where some but not all of its components are unique. We illustrate the methods with three examples.