We report data from a 30-month-old child who met the standard diagnostic criteria for HIV-1 infection, received combination ART between 30 hours and 18 months of age, and subsequently had controlled HIV-1 viremia for 12 months while not receiving ART. The absence of rebound viremia, the undetectable replication-competent virus, the almost-complete disappearance of cell-associated HIV-1 DNA, and the absence of HIV-1–specific immune responses while the child was not receiving ART suggest that replication-competent HIV-1 reservoirs may not have been established or were markedly abated, if not extinguished.16

Rare cases of transient HIV infection in infants have been reported, on the basis of intermittent detection of HIV-1 p24 antigen or DNA in peripheral blood.17-20 One cohort study showed that 6.4% of 188 infants had one or more positive tests for HIV that were followed by negative tests.20 However, forensic and phylogenetic studies could not rule out laboratory contamination or sample mislabeling in reported cases of spontaneous HIV-1 clearance.21 In the present case report, the five positive tests indicating HIV-1 infection were performed in CLIA-certified laboratories with the use of separate blood specimens and standard clinical-assay protocols. Under this scenario, repeated sample mix-up or contamination was unlikely. Unfortunately, clinical specimens are not routinely saved, which precluded further assessment of specimens from those time points.

The current standard definition of HIV-1 infection in an infant requires the detection of HIV-1 nucleic acids in at least two separate clinical samples.4 An infant in whom HIV-1 DNA is detected in blood obtained within the first 48 hours after birth is considered to have acquired the infection in utero.22 The detection of HIV-1 proviral DNA in this infant's peripheral blood at 30 hours of age, along with a plasma viral load of 19,812 copies per milliliter detected at 31 hours of age, is consistent with in utero infection. In two separate studies, the median viral loads at birth in infants who had been infected in utero were 10,800 copies per milliliter23 and 26,940 copies per milliliter,24 as compared with undetectable levels in infants who were infected peripartum.

We believe that infection with replicating virus was likely, given the sequential detection of RNA in three serial blood samples obtained during the first few weeks of life while the infant was receiving combination ART with reverse-transcriptase inhibitors. The biphasic decline in viremia after the initiation of ART, with the rapid clearance (steep decline) of short-lived virus-producing cells (e.g., activated CD4+ T cells), followed by a slower decline, is consistent with the inhibition of active infection rather than with the clearance of passively transferred HIV-1–infected maternal cells without infection of the infant's cells. With these findings, the infant met the standard diagnostic criteria for HIV-1 infection (most likely acquired in utero) as well as the criteria for initiation of ART and for participation in clinical trials sponsored by the National Institutes of Health.22-25

We evaluated whether maternal–fetal blood transfusion could account for the detection of HIV-1 nucleic acid in the infant. An initial plasma viral load of approximately 20,000 copies per milliliter in a 2.5-kg neonate is equivalent to a total body count of 5 million HIV-1 RNA copies or approximately 2.5 million virions. Such a result would have required the transfer of approximately 2 liters of maternal blood into this infant (whose total blood volume is only 250 ml). Likewise, the possibility that persistent detection of HIV-1 RNA during the first 3 weeks of life represented the passive transfer of virions from maternal blood is not consistent with the early-infection events associated with postexposure prophylaxis in maternal–fetal transmission or neonatal HIV-1 infection, considering that the half-life of virions is 1 to 2 hours at most. Thus, the repeated detection of HIV-1 RNA in plasma through the infant's first 19 days of life, while the infant was receiving ART, shows that there were virus-producing cells in the infant.

It is also conceivable that maternal microchimerism could have resulted in the detection of HIV-1 nucleic acid in the infant. Microchimerism has been detected in infants born to HIV-positive women but has not been associated with an increased risk of HIV-1 transmission.26 Although we were not able to directly assess maternal cells in the infant's circulation, transfused maternal cells at the levels reported previously (0.3 to 0.6% of neonatal cells26) are not likely to have resulted in the levels of plasma HIV-1 RNA that were detected shortly after birth in this infant.

A curious finding in this infant is the persistence of traces of HIV-1 nucleic acid. The traces of viral nucleic acid may represent the persistence of replication-defective genomes or false positive signals at the threshold of detection of the assays, as was recently reported for the Berlin Patient.27 Attempts to amplify HIV-1 from infant samples obtained for viral sequencing at 24 and 26 months of age were unsuccessful, as were efforts to locate the screening samples obtained when the infant was a newborn to perform viral sequencing. The latter situation also precluded linkage analysis to maternal viral variants, which represents a limitation of this case report.

ART that is initiated between 1 and 3 months of age has been shown to modify HIV-1 persistence in that infants who receive early treatment are often HIV-1 seronegative and do not have circulating viremia while they are receiving ART, but viral rebound has been observed when ART is discontinued.28-30 Approximately 5 to 10% of adults who receive early ART have sustained control of HIV-1 replication after the discontinuation of therapy, although evidence for ongoing HIV-1 infection remains.31,32 The current case differs from those described in children29 and adults32 who receive early treatment in that circulating proviral HIV-1 DNA and plasma HIV-1 RNA were only intermittently detected at levels just above the limits of detection of the assays, replication-competent virus could not be recovered, and the child remains HIV-1 seronegative even though ART was discontinued. This situation closely mimics the virologic and immunologic biomarkers of the Berlin Patient at 5 years of follow-up.27

Viral and host factors could have contributed to the reported outcome in this child. The maternal HIV-1 RNA levels were relatively low at delivery, although fully replication-competent virus, with replication kinetics that were similar to a laboratory strain, was readily cultured from maternal cells 26 months post partum, from a blood sample showing a plasma viral load of nearly 7000 copies per milliliter (Fig. S2 in the Supplementary Appendix). Although neither the mother nor the infant had HLA class I alleles that have been associated with control of HIV-1 infection,33 it is possible that strong maternal immune responses or other unknown host factors were responsible for the relatively low viral load seen in the mother, although maternal samples were not available for additional testing. The child remains in care, and at the age of 36 months, at least 18 months after the cessation of ART, the child has no detectable level of HIV-1 RNA.

This case suggests that very early ART may interfere with either the quantities or qualities of persistent reservoirs of replication-competent virus. Antiretroviral prophylaxis is routinely recommended for infants who have been exposed to HIV-1, with multidrug regimens recommended in high-risk cases. Furthermore, the initiation of ART in infected infants markedly reduces HIV-related mortality among infants25 and is recommended by the World Health Organization. This global standard may facilitate planned proof-of-concept studies of very early ART to modify persistent HIV-1 infection in infants, with an aim toward sparing them a lifetime of therapy.