Altered CD4+ T cell immunity in nurses occupationally exposed to viral pathogens.

Pathogen exposure, including but not limited to herpesviruses, moulds the shape of the immune system, both at a basal state and in response to immune challenge. However, little is known about the impact of high exposure to other viruses on baseline immune signatures and how the immune system copes with repetitive exposures to maintain a balanced functionality. Here we investigated baseline immune signatures, including detailed T cell phenotyping, antigen-specific CD4+ and CD8+ T cell responses and cytokine profile in paediatric (PED) nurses, who have high occupational exposure to viral pathogens including varicella zoster virus (VZV) and respiratory viruses, and in neonatal intensive care unit (NICU) nurses, as a control group with infrequent occupational exposure. Our results show a lower CD4+ T cell response to two VZV proteins (IE62 and gE) and to tetanus toxoid (TT) in PED nurses who are cytomegalovirus (CMV)-seronegative, compared to CMV-seronegative NICU nurses, and that the decline might be more pronounced the more sustained the exposure. This decline might be due to an attrition of VZV- and TT-specific T cells as a result of the continuous pressure on the CD4+ T cell compartment. Moreover, our data suggest that the distinct T cell phenotypes known to be associated with CMV-seropositivity might be less prominent in PED nurses compared to NICU nurses, implying a plausible attenuating effect of occupational exposure on CMV-associated immunosenescence. Overall, this pilot study reveals an impact of occupational exposure to viral pathogens on CD4+ T cell immunity and supports further investigation in a larger cohort.

The health and economic burden of chickenpox and herpes zoster in Belgium.

Varicella-zoster virus causes chickenpox (CP) and after reactivation herpes zoster (HZ). Vaccines are available against both diseases warranting an assessment of the pre-vaccination burden of disease. We collected data from relevant Belgian databases and performed five surveys of CP and HZ patients. The rates at which a general practitioner is visited at least once for CP and HZ are 346 and 378/100 000 person-years, respectively. The average CP and HZ hospitalization rates are 5·3 and 14·2/100 000 person-years respectively. The direct medical cost for HZ is about twice as large as the direct medical cost for CP. The quality-adjusted life years lost for ambulatory CP patients consulting a physician is more than double that of those not consulting a physician (0·010 vs. 0·004). In conclusion, both diseases cause a substantial burden in Belgium.

Author Correction: Multidisciplinary study of the secondary immune response in grandparents re-exposed to chickenpox.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Multidisciplinary study of the secondary immune response in grandparents re-exposed to chickenpox.

Re-exposure to chickenpox may boost varicella-zoster virus (VZV) immunity in the elderly. This secondary immune response is hypothesized to confer protection against herpes zoster. We longitudinally sampled 36 adults over the course of one year after re-exposure to chickenpox. The resulting 183 samples and those of 14 controls were assessed for VZV-specific T-cell immunity and antibody titres. The percentages of VZV-specific CD4+ IL-2-producing T-cells were increased in re-exposed grandparents compared to control participants up to 9 months after re-exposure. Using a longitudinal mixture modelling approach, we found that 25% and 17% of re-exposed grandparents showed a boosting of VZV-specific CD4+ IL-2-producing T-cells and VZV-specific antibodies, respectively. The antibody boosting occurred exclusively in cytomegalovirus (CMV) IgG-positive participants. CMV IgG-positive participants also had higher VZV IE62-specific CD4+ IFN-γ-producing T-cell percentages and VZV-specific antibody titres. The protective effect of re-exposure to chickenpox is likely limited, as boosting only occurred in 17-25% of the VZV re-exposed grandparents and for less than one year.

Creating a robust framework for the analysis of cryopreserved samples in quantitative immunological experiments.

Longitudinal clinical or experimental immunological studies warrant the use of cryopreserved samples for flow cytometric phenotyping. Most notably CD62L+ and CD25+Foxp3+ counts were shown to be reduced by past studies. Here we are the first to compare the effects of cryopreservation on cell type calculations performed on a longitudinal dataset. We first compared lymphocyte subpopulation counts from fresh samples with those from samples frozen for either 5 or 6 months coming from 9 individuals. This way, we found that the cell counts obtained after basic lymphocyte differentiation in CD3+CD4+, CD3+CD8+, CD3-CD19+ and CD3-CD56+ were relatively robust for cryopreservation. However, when further subtyping CD4+ and CD8+ cells, we only found CCR7 and CD45RA to have a relation between fresh and cryopreserved counts, but we could not conclude the same for CD62L. Also, CD4+CD25+Foxp3+ were shown to be approximately 0.5 times less counted after cryopreservation. Next, we performed basic longitudinal calculations for which we either subtracted the cell counts at time 1 from the cell counts at time 2 or calculated the ratio between the cell counts at time 2 and time 1, for both fresh and cryopreserved samples. This way, we found that the use of absolute cell counts supported a good one-to-one relation between fresh and cryopreserved counts for all markers except CD62L and CD4+CD25+Foxp3+. In conclusion, we found no support for the use of CD62L and CD4+CD25+Foxp3+ as markers for calculations on flow cytometric counts from cryopreserved longitudinal datasets. However, all other basic lymphocyte markers proved to be relatively robust if absolute counts were used.