High Prevalence of Infectious Adeno-associated Virus (AAV) in Human Peripheral Blood Mononuclear Cells Indicative of T Lymphocytes as Sites of AAV Persistence.

Seroepidemiology shows that infections with adeno-associated virus (AAV) are widespread, but diverse AAV serotypes isolated from humans or nonhuman primates have so far not been proven to be causes of human disease. In view of the increasing success of AAV-derived vectors in human gene therapy, definition of the in vivo sites of wild-type AAV persistence and the clinical consequences of its reactivation is becoming increasingly urgent. Here, we identify the presumed cell type for AAV persistence in the human host by highly sensitive AAV PCRs developed for the full spectrum of human AAV serotypes. In genomic-DNA samples from leukocytes of 243 healthy blood donors, 34% were found to be AAV positive, predominantly AAV type 2 (AAV2) (77%), AAV5 (19%), and additional serotypes. Roughly 11% of the blood donors had mixed AAV infections. AAV prevalence was dramatically increased in immunosuppressed patients, 76% of whom were AAV positive. Of these, at least 45% displayed mixed infections. Follow-up of single blood donors over 2 years allowed repeated detection of the initial and/or additional AAV serotypes, suggestive of fluctuating, persistent infection. Leukocyte separation revealed that AAV resided in CD3+ T lymphocytes, perceived as the putative in vivo site of AAV persistence. Moreover, infectious AAVs of various serotypes could be rescued and propagated from numerous samples. The high prevalence and broad spectrum of human AAVs in leukocytes closely follow AAV seroepidemiology. Immunosuppression obviously enhances AAV replication in parallel with activation of human cytomegalovirus (HCMV) and human herpesvirus 6 (HHV-6), reminiscent of herpesvirus-induced AAV activation. IMPORTANCE: Adeno-associated virus is viewed as apathogenic and replication defective, requiring coinfection with adenovirus or herpesvirus for productive infection. In vivo persistence of a defective virus requires latency in specialized cell types to escape the host immune response until viral spread becomes possible. Reactivation from latency can be induced by diverse stimuli, including infections, typically induced upon host immunosuppression. We show for the first time that infectious AAV is highly prevalent in human leukocytes, specifically T lymphocytes, and that AAV is strongly amplified upon immunosuppression, along with reactivation of latent human herpesviruses. In the absence of an animal model to study the AAV life cycle, our findings in the human host will advance the understanding of AAV latency, reactivation, and in vivo pathogenesis.

Epigenomic Profiling of Human CD4+ T Cells Supports a Linear Differentiation Model and Highlights Molecular Regulators of Memory Development.

The impact of epigenetics on the differentiation of memory T (Tmem) cells is poorly defined. We generated deep epigenomes comprising genome-wide profiles of DNA methylation, histone modifications, DNA accessibility, and coding and non-coding RNA expression in naive, central-, effector-, and terminally differentiated CD45RA+ CD4+ Tmem cells from blood and CD69+ Tmem cells from bone marrow (BM-Tmem). We observed a progressive and proliferation-associated global loss of DNA methylation in heterochromatic parts of the genome during Tmem cell differentiation. Furthermore, distinct gradually changing signatures in the epigenome and the transcriptome supported a linear model of memory development in circulating T cells, while tissue-resident BM-Tmem branched off with a unique epigenetic profile. Integrative analyses identified candidate master regulators of Tmem cell differentiation, including the transcription factor FOXP1. This study highlights the importance of epigenomic changes for Tmem cell biology and demonstrates the value of epigenetic data for the identification of lineage regulators.

Regular blood donation may help in the management of hypertension: an observational study on 292 blood donors.

BACKGROUND: Hypertension is one of the leading global risks for cardiovascular events worldwide. There is preliminary evidence that regular blood donation may be beneficial. STUDY DESIGN AND METHODS: Unselected blood donors were included in this observational study. Blood pressure (BP) was measured before and after blood donation, with participants donating between one and four occasions in a 1-year study period. RESULTS: In this study, 292 donors were enrolled. At baseline, 146 had elevated BP (> 140/90 mmHg). In hypertensives, after four blood donations, systolic and diastolic blood pressure (SBP and DBP, respectively) decreased from a mean of 155.9 ± 13.0 to 143.7 ± 15.0 mmHg and from 91.4 ± 9.2 to 84.5 ± 9.3 mmHg, respectively (each p < 0.001). There was a clear dose effect with decreasing BP by the increasing number of blood donations. After at least four blood donations, donors with Stage II hypertensive baseline values (≥ 160 mmHg SBP and/or ≥ 100 mmHg DBP) were found to have the most marked reduction in BP, with 17.1 mmHg (95% confidence interval [CI], -23.2 to -11.0; p < 0.0001) and 11.7 mmHg (95% CI, -17.1 to -6.1; p = 0.0006) for SBP and DBP, respectively. The decrease in BP was not significantly associated with changes of blood count or variables of iron metabolism. CONCLUSIONS: Regular blood donation is associated with pronounced decreases of BP in hypertensives. This beneficial effect of blood donation may open a new door regarding community health care and cost reduction in the treatment of hypertension.