Publications

B cells are key components of cellular and humoral immunity and, like all lymphocytes, are thought to originate and renew from hematopoietic stem cells (HSCs). However, our recent single-HSC transfer studies demonstrate that adult bone marrow HSCs do not regenerate B-1a, a subset of tissue B cells required for protection against pneumonia, influenza, and other infections. Since B-1a are regenerated by transfers of fetal liver, the question arises as to whether B-1a derive from fetal, but not adult, HSCs. Here we show that, similar to adult HSCs, fetal HSCs selectively fail to regenerate B-1a. We also show that, in humanized mice, human fetal liver regenerates tissue B cells that are phenotypically similar to murine B-1a, raising the question of whether human HSC transplantation, the mainstay of such models, is sufficient to regenerate human B-1a. Thus, our studies overtly challenge the current paradigm that HSCs give rise to all components of the immune system.

γδ T cells expressing Vδ2 may be instrumental in the control of malaria, because they inhibit the replication of blood-stage parasites in vitro and expand during acute malaria infection. However, Vδ2 T-cell frequencies and function are lower among children with heavy prior malaria exposure. It remains unclear whether malaria itself is driving this loss. Here we measure Vδ2 T-cell frequency, cytokine production, and degranulation longitudinally in Ugandan children enrolled in a malaria chemoprevention trial from 6 to 36 months of age. We observed a progressive attenuation of the Vδ2 response only among children incurring high rates of malaria. Unresponsive Vδ2 T cells were marked by expression of CD16, which was elevated in the setting of high malaria transmission. Moreover, chemoprevention during early childhood prevented the development of dysfunctional Vδ2 T cells. These observations provide insight into the role of Vδ2 T cells in the immune response to chronic malaria.

BACKGROUND

Antiretroviral therapy (ART) adherence interruptions have been associated with viral rebound; however, the true risk is unknown because HIV RNA has never been measured during ongoing interruptions.

METHODS

The Uganda AIDS Rural Treatment Outcomes Study is an observational longitudinal cohort of adults initiating ART. We monitored adherence with the device that wirelessly transmits records of device openings, and routinely assessed HIV RNA quarterly. When lapses of 48+ hours between device openings were detected, we made unannounced visits to participants to investigate the cause and assess HIV RNA. Generalized estimating equation logistic regressions were used to assess factors associated with viral rebound.

RESULTS

We followed 479 participants (median: 25 months per participant). Most were women (72%), median age was 36 years, median pre-ART CD4 count was 198 cells per microliter, median pre-ART HIV RNA level was 5.0 log10 copies per milliliter, and median duration of prior viral suppression was 13 months. A total of 587 adherence interruptions followed confirmed prior viral suppression, of which 13 (2%) had detectable viral rebound. Viral rebound was associated with duration of adherence interruption (odds ratio: 1.25 for each day beyond 48 hours; P = 0.007) and 30-day adherence before the interruption (odds ratio: 0.73; P = 0.02).

DISCUSSION

This article is the first demonstration of HIV RNA rebound during adherence interruptions objectively measured in real time. Odds of viral rebound increased by 25% with each day beyond 48 hours. Real-time adherence monitoring was feasible in a sub-Saharan African setting. Further research should assess the potential for real-time adherence interventions to sustain adherence to affordable first-line regimens.