Age-related ranges of memory, activation, and cytotoxic markers on CD4 and CD8 cells in children

Relationship between CCR5(WT/Δ32) heterozygosity and HIV-1 reservoir size in adolescents and young adults with perinatally acquired HIV-1 infection

BACKGROUND

Several host factors contribute to human immunodeficiency virus (HIV) disease progression in the absence of combination antiretroviral therapy (cART). Among them, the CC-chemokine receptor 5 (CCR5) is known to be the main co-receptor used by HIV-1 to enter target cells during the early stages of an HIV-1 infection.

OBJECTIVE

We evaluated the association of CCR5^(WT/Δ32) heterozygosity with HIV-1 reservoir size, lymphocyte differentiation, activation and immunosenescence in adolescents and young adults with perinatally acquired HIV infection receiving cART.

METHODS

CCR5 genotype was analysed in 242 patients with vertically transmitted HIV-1 infection from Paediatric Spanish AIDS Research Network Cohort (coRISpe). Proviral HIV-1 DNA was quantified by digital-droplet PCR, and T-cell phenotype was evaluated by flow cytometry in a subset of 24 patients (ten with CCR5^(Δ32/WT) genotype and 14 with CCR5^(WT/WT) genotype).

RESULTS

Twenty-three patients were heterozygous for the Δ32 genotype but none was homozygous for the mutated CCR5 allele. We observed no difference in the HIV-1 reservoir size (455 and 578 copies of HIV-1 DNA per million CD4⁺ T cells in individuals with CCR5^(WT/WT) and CCR5^(Δ32/WT) genotypes, respectively; p 0.75) or in the immune activation markers between both genotype groups. However, we found that total HIV-1 DNA in CD4⁺ T cells correlated with the percentage of memory CD4⁺ T cells: a direct correlation in CCR5^(WT/Δ32) patients but an inverse correlation in those with the CCR5^(WT/WT) genotype.

CONCLUSIONS

This finding suggests a differential distribution of the viral reservoir compartment in CCR5^(WT/Δ32) patients with perinatal HIV infection, which is a characteristic that may affect the design of strategies for reservoir elimination.

Establishment and Replenishment of the Viral Reservoir in Perinatally HIV-1-infected Children Initiating Very Early Antiretroviral Therapy

BACKGROUND

Combination antiretroviral therapy (cART) generally suppresses the replication of the human immunodeficiency virus type 1 (HIV-1) but does not cure the infection, because proviruses persist in stable latent reservoirs. It has been proposed that low-level proviral reservoirs might predict longer virologic control after discontinuation of treatment. Our objective was to evaluate the impact of very early initiation of cART and temporary treatment interruption on the size of the latent HIV-1 reservoir in vertically infected children.

METHODS

This retrospective study included 23 perinatally HIV-1-infected children who initiated very early treatment within 12 weeks after birth (n = 14), or early treatment between week 12 and 1 year (n = 9). We measured the proviral reservoir (CD4(+) T-cell-associated HIV-1 DNA) in blood samples collected beyond the first year of sustained virologic suppression.

RESULTS

There is a strong positive correlation between the time to initiation of cART and the size of the proviral reservoir. Children who initiated cART within the first 12 weeks of life showed a proviral reservoir 6-fold smaller than children initiating cART beyond this time (P < .01). Rapid virologic control after initiation of cART also limits the size of the viral reservoir. However, patients who underwent transient treatment interruptions showed a dramatic increase in the size of the viral reservoir after discontinuation.

CONCLUSIONS

Initiation of cART during the first 12 weeks of life in perinatally HIV-1-infected children limits the size of the viral reservoir. Treatment interruptions should be undertaken with caution, as they might lead to fast and irreversible replenishment of the viral reservoir.

Cytokine profiles in peripheral blood of children and adults with Crohn disease

BACKGROUND

Increasing evidence suggests that cytokine dysregulation in T-helper 1 and T-helper 2 (TH1/TH2) subsets contributes to the pathogenesis of Crohn disease (CD). The present pilot study examines the hypothesis that cytokine profiles differ between pediatric and adult patients with CD.

METHODS

Production of TH1 cytokines interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) and of TH2 cytokines interleukin-4 (IL-4) and IL-6 was analyzed in peripheral blood of patients with CD and healthy controls (n=20) using flow cytometry after in vitro stimulation.

RESULTS

In both pediatric and adult subjects, frequencies of TNF-α CD4+ T cells were higher in patients with CD than in controls (P=0.009 and P=0.047, respectively). Percentages of cells expressing IL-4 were slightly increased (P=0.036), whereas those for IFN-γ were decreased (P=0.009) in pediatric patients with CD compared with controls. As expected, the overall production of TH1 cytokines was higher in adults compared with pediatric subjects. When memory CD4+CD45RO+ T cells were considered, lower IFN-γ expression was observed in pediatric subjects with CD compared with controls (P=0.009), matching the trend seen in the general CD4+ T cell population. The percentage of CD4+CD45RO+ T cells was increased in adult patients with CD compared with pediatric patients with CD (P=0.016).

CONCLUSIONS

The present study describes a peripheral blood TH1/TH2 cytokine imbalance in CD and suggests different immunological mechanisms in children and adults for disease pathogenesis.

Neuronal DNA content variation (DCV) with regional and individual differences in the human brain

It is widely assumed that the human brain contains genetically identical cells through which postgenomic mechanisms contribute to its enormous diversity and complexity. The relatively recent identification of neural cells throughout the neuraxis showing somatically generated mosaic aneuploidy indicates that the vertebrate brain can be genomically heterogeneous (Rehen et al. [2001] Proc. Natl. Acad. Sci. U. S. A. 98:13361-13366; Rehen et al. [2005] J. Neurosci. 25:2176-2180; Yurov et al. [2007] PLoS ONE:e558; Westra et al. [2008] J. Comp. Neurol. 507:1944-1951). The extent of human neural aneuploidy is currently unknown because of technically limited sample sizes, but is reported to be small (Iourov et al. [2006] Int. Rev. Cytol. 249:143-191). During efforts to interrogate larger cell populations by using DNA content analyses, a surprising result was obtained: human frontal cortex brain cells were found to display "DNA content variation (DCV)" characterized by an increased range of DNA content both in cell populations and within single cells. On average, DNA content increased by approximately 250 megabases, often representing a substantial fraction of cells within a given sample. DCV within individual human brains showed regional variation, with increased prevalence in the frontal cortex and less variation in the cerebellum. Further, DCV varied between individual brains. These results identify DCV as a new feature of the human brain, encompassing and further extending genomic alterations produced by aneuploidy, which may contribute to neural diversity in normal and pathophysiological states, altered functions of normal and disease-linked genes, and differences among individuals.

Lymphoid organ development in rabbits: major lymphocyte subsets

Although rabbits represent an important animal model, little is known about the lymphoid organ development in this species. In the present study, lymphocyte subsets in peripheral blood, spleen, mesenteric and popliteal lymph nodes in newborn and 2-, 4-, 6- and 8-week old and adult were characterized. Lymphocyte subsets were detected using flow cytometry and monoclonal antibodies against rabbit CD4, CD8, T-cell-specific antigen and cross-reactive antibody against B-cell antigen CD79alpha. In neonates, lower numbers of T cells were detected in both peripheral blood and spleen than in mesenteric lymph nodes. In comparison with other compartments, CD79alpha(+) cells prevailed in the spleen. Post-natal development was characterized by a decreased CD4(+)/CD8(+) ratio due to increasing frequency of CD8(+) lymphocytes in all organs but mesenteric lymph nodes, where it was due to decreased numbers of CD4(+) lymphocytes. Another significant feature was the increase of B cells in peripheral blood and mesenteric lymph nodes.

Comparison of IgG4 assays using whole parasite extract and BmR1 recombinant antigen in determining antibody prevalence in brugian filariasis

Background

Brugia malayi is endemic in several Asian countries with the highest prevalence in Indonesia. Determination of prevalence of lymphatic filariasis by serology has been performed by various investigators using different kinds of antigen (either soluble worm antigen preparations or recombinant antigens). This investigation compared the data obtained from IgG4 assays using two different kinds of antigen in a study on prevalence of antibodies to B. malayi.

Methods

Serum samples from a transmigrant population and life long residents previously tested with IgG4 assay using soluble worm antigen (SWA-ELISA), were retested with an IgG4 assay that employs BmR1 recombinant antigen (BmR1 dipstick [Brugia Rapid™]). The results obtained with the two antigens were compared, using Pearson chi-square and McNemar test.

Results

There were similarities and differences in the results obtained using the two kinds of antigen (SWA and BmR1). Similarities included the observation that assays using both antigens demonstrated an increasing prevalence of IgG4 antibodies in the transmigrant population with increasing exposure to the infection, and by six years living in the area, antibody prevalence was similar to that of life-long residents. With regards to differences, of significance is the demonstration of similar antibody prevalence in adults and children by BmR1 dipstick whereas by SWA-ELISA the antibody prevalence in adults was higher than in children.

Conclusions

Results and conclusions made from investigations of prevalence of anti-filarial IgG4 antibody in a population would be affected by the assay employed in the study.

Acute chylothorax in children: selective retention of memory T cells and natural killer cells

OBJECTIVE

To assess for immunodeficiency in patients with hypogammaglobulinemia in the setting of draining acute chylothorax.

STUDY DESIGN

Humoral and cellular immunity was evaluated in 8 patients with chylothorax. Chylous fluid was also analyzed to document cellular losses. Data regarding clinical course and immunologic characteristics were reviewed retrospectively.

RESULTS

All patients had hypogammaglobulinemia (IgG=179+/-35 mg/dL) as well as lymphopenia (985+/-636 cells/mm(3)). T cells were decreased and natural killer cells increased in peripheral blood. The converse was found in chylous fluid. The ratio of CD3+/CD45RA+ naive: CD3+/CD45RO+ memory T cells was greater in chyle than in peripheral blood. In vitro proliferative responses to antigens and mitogens were similar to control subjects, and previously immunized patients maintained evidence of protective vaccine-specific humoral immunity. To treat hypogammaglobulinemia, patients received intravenous immunoglobulin (IVIG) to maintain IgG within normal range; 6 of 8 patients had serious infections before receiving IVIG compared with 4 of 8 patients during the period of IVIG administration.

CONCLUSION

Draining chylothorax resulted in IgG and lymphocyte depletion with preferential retention of memory T cells and natural killer cells in the circulation. Overall, protective-specific antibody levels and T cell function were maintained. IVIG administration did not lead to discernible protection from infectious complications in this small group of patients.

Polyunsaturated fatty acids and T-cell function: implications for the neonate

Infant survival depends on the ability to respond effectively and appropriately to environmental challenges. Infants are born with a degree of immunological immaturity that renders them susceptible to infection and abnormal dietary responses (allergies). T-lymphocyte function is poorly developed at birth. The reduced ability of infants to respond to mitogens may be the result of the low number of CD45RO+ (memory/antigen-primed) T cells in the infant or the limited ability to produce cytokines [particularly interferon-y, interleukin (IL)-4, and IL-10. There have been many important changes in optimizing breast milk substitutes for infants; however, few have been directed at replacing factors in breast milk that convey immune benefits. Recent research has been directed at the neurological, retinal, and membrane benefits of adding 20:4n-6 (arachidonic acid; AA) and 22:6n-3 (docosahexaenoic acid; DHA) to infant formula. In adults and animals, feeding DHA affects T-cell function. However, the effect of these lipids on the development and function of the infant's immune system is not known. We recently reported the effect of adding DHA + AA to a standard infant formula on several functional indices of immune development. Compared with standard formula, feeding a formula containing DHA + AA increased the proportion of antigen mature (CD45RO+) CD4+ cells, improved IL-10 production, and reduced IL-2 production to levels not different from those of human milk-fed infants. This review will briefly describe T-cell development and the potential immune effect of feeding long-chain polyunsaturated fatty acids to the neonate.

Adults acquire filarial infection more rapidly than children: a study in Indonesian transmigrants

To dissociate the influence of host age from length of exposure on acquisition of filarial infection, we examined the development of microfilaraemia and anti-filarial IgG4 in all ages of a naive population that became suddenly exposed to Brugia malayi as a result of transmigration. Responses in 247 transmigrants, who had settled for periods of several months up to 6 years in their new homesteads, were compared with those of 133 life-long residents. As shown in earlier studies, anti-filarial IgG4 increased with age in the indigenous populations, whose age is equivalent to length of exposure. However, by examining transmigrants, it became clear that development of specific IgG4 was influenced by age, since levels of this antibody were consistently higher in transmigrant adults than in transmigrant children, despite an equal length of exposure to filarial infection. Examining microfilaraemia, it was confirmed that infection establishes more rapidly in adults than in children.

Cellular immune responses in neonates

Reduced numbers of lymphocytes and antigen presenting cells have been described as some of the main factors responsible for antigenic tolerance or low responsiveness in neonates. However, by changing the parameters of immunization, such as dose of antigen and frequency of antigen presenting cells we and others have shown that neonates have the option of developing the same variety of immune responses seen in adults. Several aspects of the development of cellular immunity in human and murine neonates are reviewed in this article, with a special focus on the development of T cell mediated responses, from ontogeny to effector function.

Age-dependent altered proportions in subpopulations of tonsillar lymphocytes

Age-related changes in functional subsets of lymphocytes may influence the potential to build up immune responses. In particular, the capacity of tonsillar lymphocytes to counter infections may be altered during ageing. In order to address this question we investigated the proportional distribution of several subsets of tonsillar T and B cells with regard to ageing. Tonsils were derived from 119 patients between 2 and 65 years of age. Lymphocyte subsets were monitored by three-colour fluorescence of relevant CD markers in flow cytometry. As a general tendency the percentage of CD3+ T cells steadily increased whereas that of CD19+ B cells decreased at the same time. No significant differences were observed between lymphocytes of patients with and without inflammatory history of the tonsils. The percentage of CD8+ T cells declined whereas that of CD4+ T cells increased during the same time span. CD45RA+ T cells increased during the first two decades of life and gradually decreased thereafter. In contrast, CD45RO+ T cells showed an opposite trend. No differences were seen in the population of CD3-/CD56+ natural killer (NK) cells. The mature B cell marker CD40 showed no significant changes during ageing. However, CD38+ B cells, representing B cells of late maturation stages, dramatically declined up to the age of 65. In a similar manner the CD5+ subpopulation of B cells decreased during ageing. Substantial changes in major tonsillar T and B cell populations as shown in this study may have an impact on the ageing process of the immune system.

Differentiation of T lymphocytes in the human adenoid as measured by the expression of CD45 isoforms

Encounter of antigen by T lymphocyte on antigen-presenting cells results in changes in the expression of several cell surface molecules, including the abundant cell surface glycoprotein CD45. We have characterized the expression of the CD45 isoforms CD45RA and CD45RO in CD4+ and CD8+ T lymphocytes in the adenoids and peripheral blood of young children. We found that the relative proportions of CD45RA-,CD45RO+ antigen-experienced T cells was higher in the adenoids than in peripheral blood, and that the proportion of naive or resting CD45RA+,CD45RO- T cells was lower in the adenoids than in peripheral blood. The frequency of bright double-positive CD45RA+,CD45RO+ T cells, which represent cells in transition from the CD45RA+ to CD45RO+ phenotype, was higher in the adenoids than in peripheral blood. The frequency of another double-positive cell population, but with unknown ontogeny, expressing both CD45RA and CD45RO at a low level, was higher in peripheral blood than in adenoidal T cells. It was found that the frequency of adenoidal antigen-experienced CD45RA-,CD45RO+ T lymphocytes increased with increasing age of the child. These results are consistent with the model that the adenoids serve as a site for conversion of CD45RA+ to CD45RO+ T lymphocytes, and that the maturation of the immune system in young children is associated with phenotypic changes in T lymphocytes residing in secondary lymphoid organs.

CD4+ and CD8+ cell cytokine profiles in neonates, older children, and adults: increasing T helper type 1 and T cytotoxic type 1 cell populations with age

The growing body of evidence suggestive of T helper types 1 and 2 (Th1/Th2) including their counterparts T cytotoxic types 1 and 2 (Tc1/Tc2) cell responses during various human disease states necessitates determination of normal T cell subsets' cytokine profiles. We show here, using intracellular cytokine staining and flow cytometry, that in healthy subjects interferon (IFN)-gamma producing CD4+ (Th1) and CD8+ (Tc1) cell populations progressively increase with age with strong correlation to CD45RO surface antigen expression. Meanwhile populations of cells capable of producing IL-4 (Th2 and Tc2) are comparably minimal across all age groups. Collectively, these results may reflect the maturation and expansion of Th1 and Tc1 cell populations from the neonatal period to adulthood, most probably dependent on antigen exposure.

Transfusion-related immunomodulation in Chinese children with thalassaemia

BACKGROUND AND OBJECTIVES

Multiple transfusions can induce immunomodulation. This study was carried out to investigate the immunological status of 50 transfusion-dependent children with beta-thalassaemia, taking into account that lymphocyte characteristics are affected by sex, age and race. We paid particular attention to the influence of transfusion and serum ferritin on the lymphocyte subsets which may be affected by the exposure to foreign antigens.

MATERIALS AND METHODS

By multicolour immunofluorescent analysis using flow cytometry, we determined lymphocyte characteristics with regard to major subsets (T lymphocytes, B lymphocytes and NK cells), activation (membrane IL-2 receptor CD25, HLA-D) and memory/naive T cells (CD45RO/CD45RA). Data from 51 age- and sex-balanced children served as controls.

RESULTS

The normal Chinese children had higher NK levels than the beta-thalassaemia children. The levels of CD25 and HLA-D indicated a broad-based increase in activation status. Memory T cells were also increased when compared with their normal counterparts. We found additional and more marked alterations in the lymphocyte subsets of those who had received over 100 transfusions. While levels of NK cells were inversely correlated with the number of transfusions, CD25+ cells increased with transfusions.

CONCLUSION

Many multitransfused beta-thalassaemia children have altered levels of lymphocyte subsets compared with normals. What remains to be investigated is the long-term consequence of possessing low NK and non-MHC-restricted T cells (CD3+CD56+CD16+) and a high activation status in terms of resistance of infections and development of malignancy.

Increased losses of CD4+CD45RA+ cells in late stages of HIV infection is related to increased risk of death: evidence from a cohort of 347 HIV-infected individuals

OBJECTIVE

To examine changes in the distribution of CD4+CD45RA+ (naive) and CD4+CD45RO+ (memory) lymphocytes in various stages of HIV infection and the effect of these changes on disease progression.

DESIGN AND METHODS

Expression of CD45RA+ and CD45RO+ on CD4+ lymphocytes was analysed by flow cytometry in a prospectively followed cohort of 300 HIV-infected individuals (median follow-up time, 2.90 years; range, 0.02-4.54 years) and in a group of 102 age- and sex-matched uninfected controls. Survival analysis was performed considering AIDS development and death as endpoints.

RESULTS

The median CD4+CD45RA+/CD45RO+ ratio was 1.3 (25-75% quartiles, 0.9-2.4) in controls; it was increased to 1.8 (1.1-2.5) in 40 HIV-infected individuals with CD4+ cell counts > 500 x 10(6)/l (P < 0.05); it was similar at 1.4 (0.8-2.0) in 106 HIV-infected individuals with CD4+ cell counts of 200-500 x 10(6)/l; and it was decreased to 0.9 (0.5-1.4) in 154 HIV-infected individuals with CD4+ cell counts < 200 x 10(6)/l (P < 10[-6]). When fitted in a Cox model adjusting for the total number of CD4+ cells and age a lower concentration of CD4+CD45RA+ cells was associated with an increased risk of dying. The concentration of CD4+CD45RO+ cells was not significantly associated with AIDS or death in age- and CD4+ cell count-adjusted Cox models.

CONCLUSIONS

This study confirms a selective loss of memory CD4+ cells early in HIV infection followed by increased loss of naive CD4+ cells in later stages of the infection. The loss of naive CD4+ cells seems to be important in the pathogenesis of terminal HIV infection.

Immunophenotyping of T lymphocytes by three-color flow cytometry in healthy newborns, children, and adults

Reagents are now available which allow simultaneous assessment of three different fluorescence wave-lengths on most commercially available flow cytometers. Such three-color analyses provide more information than single- or dual-color analyses. The present study was undertaken in order to establish age-related differences in lymphocyte subpopulations by simultaneously measuring three surface antigens in newborns, children, and adults. A whole blood method was used to label cells with antibodies conjugated to FITC, PE, and perCP. We found that the percentage of lymphocytes expressing HLA-DR/CD28/CD8, HLA-DR/ CD38/CD8, CD95/CD45RO/CD8, CD95/CD45RO/CD4, CD95/CD4, and CD95/CD8 showed relative increases with age. The percentage of lymphocytes expressing CD28/CD8, CD38/CD8, and CD38/CD4 showed relative decreases with age, while the subset HLA-DR/CD38/ CD4 did not change. Three-color flow cytometry is a powerful tool to more precisely define lymphocyte subsets than the current two-color methods. We present values using a three-color panel in healthy newborns, children, and adults.

Immunodeficiency in non-tuberculous mycobacterial disease

T-cell immunity was investigated in eight patients with non-tuberculous mycobacterial disease, to see whether impaired immune function might be the explanation for their infection. Cellular immune function was evaluated in vitro by measuring the proliferation of peripheral blood mononuclear cells in response to both non-specific mitogens (phytohaemagglutinin and pokeweed mitogen) and specific recall antigens (streptokinase-streptodornase and purified protein derivative from Mycobacterium tuberculosis), and in vivo, by measuring the skin test response to a panel of recall antigens. Functionally relevant T-lymphocyte sub-populations (CD4, CD8, activated CD3 and gamma/delta T-cells) were enumerated by two-colour flow cytometry. The results were compared with those for a group of patients with pulmonary tuberculosis, with groups of controls matched for age and smoking habit, and with a patient group receiving steroid treatment. The patients with non-tuberculous mycobacterial disease had poor or absent skin test responses; in vitro, their response to recall antigens was depressed, although their response to mitogens was normal. The patients had significantly raised levels of CD8 lymphocytes and activated T-cells, but lacked any circulating gamma/delta T-cells. There were also differences between the various control groups. In conclusion, this study demonstrates a deficiency in the cellular immune system of these patients, which is most readily detectable by skin testing, or by measuring lymphocyte proliferative responses to recall antigens. However, the study also shows changes in cellular immune responses in controls matched for age and smoking and in patients on steroid treatment, and underscores the need for matched controls. Further work needs to be done to ascertain whether the cellular immune deficiency is a cause of, or is caused by, the mycobacterial infections, and also to investigate the pathological significance of the alterations in T-cell sub-populations.