Quantitative changes in T helper or T suppressor/cytotoxic lymphocyte subsets that distinguish acquired immune deficiency syndrome from other immune subset disorders

Immune activation markers in individuals with HIV-1 disease and their correlation with HIV-1 RNA levels in individuals on antiretroviral therapy

Background

Currently CD4+ T lymphocyte counts and HIV-1 RNA levels are being utilized to predict outcome of human immunodeficiency virus (HIV) disease. Recently, the role of immune activation in HIV disease progression and response to treatment is being investigated. This study focused on the expression of CD38 and HLA-DR on lymphocyte subsets in various groups of HIV-infected individuals and to determine their association with HIV-1 disease progression.

Methods

Ninety-eight cases of patients with HIV/AIDS in different disease stages and twenty-four healthy HIV-negative individuals were included in the cross-sectional study. Their immune function and abnormal immune activation markers (CD38 & HLA-DR) were detected using a flowcytometer, and HIV-1 RNA levels in individuals receiving antiretroviral drugs were estimated.

Results

The immune activation marker levels were significantly different between patients with different disease stages (P < 0.001). A significant negative correlation was observed between peripheral blood CD4+ T cell counts and immune activation markers. Also, a significant positive correlation was observed between HIV-1 RNA levels and CD38+CD8+ T lymphocyte.

Conclusion

Immune activation markers (CD38 & HLA-DR) increase with disease progression. CD38+ on CD8+ T lymphocyte correlates well with HIV1 RNA levels in individuals failing on antiretroviral therapy.

Diminished Production of Interleukin 2 and Gamma-Interferon by Cloned «T» Cells from Patients with the Acquired Immunodeficiency Syndrome (AIDS)

A total of 76 T-cell clones established from peripheral blood (PB) of 2 patients with the acquired immune deficiency syndrome (AIDS) and of 141 T-cell clones established from PB of 3 normal donors were compared for their ability to produce interleukin 2 (IL-2) and gamma-interferon (γ-IFN). Twenty-seven clones from AIDS patients and 85 clones from controls expressed the CD4 phenotype, whereas 49 clones from AIDS patients and 56 clones from controls expressed the CD8 phenotype. There were no significant differences in the proportions of IL-2-producing CD4 T-cell clones established from PB of patients with AIDS and controls, but the mean concentration of IL-2 produced by CD4 clones from AIDS patients was significantly lower than that produced by CD4 clones from controls. Both the proportion of γ-IFN-producing CD4 clones and the mean concentration of γ-IFN produced by CD4 clones were significantly lower in AIDS patients than in controls. In contrast, there were no differences between AIDS patients and normal individuals in the proportion of IL-2- or Y-IFN-producing CD8 clones, or in the mean concentration of IL-2 and v-IFN produced by CD8 clones. These data suggest that the reduced ability of PB T-cells from patients with AIDS to produce IL-2 and v-IFN is not simply due to altered proportions or numbers of T-cell sub-populations, but also reflects intrinsic abnormalities of individual CD4 T lymphocytes.

Circulating Plasmablasts from Chronically Human Immunodeficiency Virus-Infected Individuals Predominantly Produce Polyreactive/Autoreactive Antibodies

Understanding the B-cell response during chronic human immunodeficiency virus (HIV) infection is essential for eliciting broad and potent neutralizing antibodies (Abs). In this study, we analyzed the plasmablast repertoire of chronically HIV-infected individuals in combination with antiretroviral therapy (ART). Among the obtained 72 recombinant monoclonal antibodies (mAbs), 27.8% weakly bound to HIV gp140 and were non-neutralizing. Remarkably, 56.9% were polyreactive and 55.6% were autoreactive. The prominent feature of being polyreactive/autoreactive is not limited to anti-gp140 Abs. Furthermore, these polyreactive/autoreactive Abs displayed striking cross-reactivity with DWEYS in the N-methyl-d-aspartate receptor (NMDAR), and this binding induced SH-SY5Y cell apoptosis. We also found higher frequencies of VH4-34 utilization and VH replacement in the plasmablast repertoire of chronically HIV-infected individuals, which may contribute to the generation of poly/autoreactive Abs. Taken together, these data demonstrate that circulating plasmablasts in chronically HIV-infected individuals experienced with ART predominantly produce poly/autoreactive Abs with minimal anti-HIV neutralizing capacity and potential cross-reactivity with autoantigens. This may represent another dysfunction of B cells during chronic HIV infection.

Reference ranges of hematology and lymphocyte subsets in healthy Korean native cattle (Hanwoo) and Holstein dairy cattle

There are no accurate reference ranges for hematology parameters and lymphocyte subsets in Korean native beef cattle (Hanwoo). This study was performed to establish reliable reference ranges of hematology and lymphocyte subsets using a large number of Hanwoo cattle (n = 350) and to compare differences between Hanwoo and Holstein dairy cattle (n = 334). Additionally, age-related changes in lymphocyte subsets were studied. Bovine leukocyte subpopulation analysis was performed using mono or dual color flow cytometry. The leukocyte subpopulations investigated in healthy cattle included: CD2(+) cells, sIgM(+) cells, MHC class II(+) cells, CD3(+) CD4(+) cells, CD3(+) CD8(+) cells, and WC1(+) cells. Although Hanwoo and Holstein cattle are the same species, results showed several differences in hematology and lymphocyte subsets between Hanwoo and Holstein cattle. This study is the first report to establish reference ranges of hematology and lymphocyte subsets in adult Hanwoo cattle.

Semi-automated and standardized cytometric procedures for multi-panel and multi-parametric whole blood immunophenotyping

Immunophenotyping by multi-parametric flow cytometry is the cornerstone technology for enumeration and characterization of immune cell populations in health and disease. Standardized procedures are essential to allow for inter-individual comparisons in the context of population based or clinical studies. Herein we report the approach taken by the Milieu Intérieur Consortium, highlighting the standardized and automated procedures used for immunophenotyping of human whole blood samples. We optimized eight-color antibody panels and procedures for staining and lysis of whole blood samples, and implemented pre-analytic steps with a semi-automated workflow using a robotic system. We report on four panels that were designed to enumerate and phenotype major immune cell populations (PMN, T, B, NK cells, monocytes and DC). This work establishes a foundation for defining reference values in healthy donors. Our approach provides robust protocols for affordable, semi-automated eight-color cytometric immunophenotyping that can be used in population-based studies and clinical trial settings.

Human T-Cell Development and Thymic Egress: An Infectious Disease Perspective

Emigration of mature naïve CD4 SP T cells from the human thymus to the periphery is not fully understood, although elucidation of the mechanisms that govern egress of T cells is crucial to understanding both basic immunology and the immune response in diseases such as HIV infection. Recent work has brought to light the requirement for sphingosine-1-phosphate (S1P) and its receptors in a variety of fields including mature naïve T-cell egress from the thymus of mice. We are examining the expression and function of this novel requisite T-cell egress receptor within the human thymus, characterizing changes observed in the expression and function of this receptor in infectious diseases. To perform this work, we use a variety of humanized murine models reviewed in this article. Future work in the field of T-cell egress, especially as it pertains to S1P receptors, should advance the fields of basic T-cell immunology and immunopathology and open new avenues for exploration into novel therapeutics.

Delay in cART initiation results in persistent immune dysregulation and poor recovery of T-cell phenotype despite a decade of successful HIV suppression

Background

Successful combination antiretroviral therapy (cART) increases levels of CD4+ T-cells, however this increase may not accurately reflect long-term immune recovery since T-cell dysregulation and loss of T-cell homeostasis often persist. We therefore assessed the impact of a decade of effective cART on immune regulation, T-cell homeostasis, and overall T-cell phenotype.

Methods

We conducted a retrospective study of 288 HIV+ cART-naïve patients initiating therapy. We identified 86 individuals who received cART for at least a decade, of which 44 consistently maintained undetectable plasma HIV-RNA levels throughout therapy. At baseline, participants were classified into three groups according to pre-treatment CD4+ T-cell counts: Group I (CD4<200 cells/mm³); Group II (CD4: 200–350 cells/mm³); Group III (CD4>350 cells/mm³). Outcomes of interest were: (1) CD4+ T-cell count restoration (CD4>532 cells/mm³); (2) normalization of CD4:CD8 T-cell ratio (1.2–3.3); (3) maintenance of CD3+ T-cell homeostasis (CD3: 65%–85% of peripheral lymphocytes); (4) normalization of the complete T-cell phenotype (TCP).

Results

Despite a decade of sustained successful cART, complete T-cell phenotype normalization only occurred in 16% of patients, most of whom had initiated therapy at high CD4+ T-cell counts (>350 cells/mm³). The TCP parameter that was the least restored among patients was the CD4:CD8 T-cell ratio.

Conclusions

Failure to normalize the complete T-cell phenotype was most apparent in patients who initiated cART with a CD4+ T-cell count <200 cells/mm³. The impact of this impaired T-cell phenotype on life-long immune function and potential comorbidities remains to be elucidated.

Translational HIV-1 research: from routine diagnostics to new virology insights in Amsterdam, the Netherlands during 1983-2013

An HIV-1 diagnostic laboratory was established in the Academic Medical Center (AMC) of the University of Amsterdam after the discovery of human immunodeficiency virus (HIV) as the cause of the acquired immunodeficiency syndrome (AIDS). The first AIDS patients were diagnosed here in 1981 and since 1983 we have tested the samples of 50992 patients using a variety of assays that greatly improved over the years. We will describe some of the basic results from this diagnostic laboratory and then focus on the spin-off in terms of the development of novel virus assays to detect super-infections and ultra-sensitive assays to measure the intracellular HIV-1 RNA load. We also review several original research findings in the field of HIV-1 virology that stem from initial observations made in the diagnostic unit. This includes the study of genetic defects in the HIV-1 genome and time trends of the replication fitness over 30 years of viral evolution, but also the description of novel HIV-1 variants in difficult-to-diagnose clinical specimen.

Quantification of CD4 responses to combined antiretroviral therapy over 5 years among HIV-infected children in Kinshasa, Democratic Republic of Congo

BACKGROUND

The long-term effects of combined antiretroviral therapy (cART) on CD4 percentage in HIV-infected children are incompletely understood, with evidence from resource-deprived areas particularly scarce even though most children with HIV live in such settings. We sought to describe this relationship.

METHODS

Observational longitudinal data from cART-naive children enrolled between December 2004 and May 2010 into an HIV care and treatment program in Kinshasa, Democratic Republic of Congo were analyzed. To estimate the effect of cART on CD4 percentage while accounting for time-dependent confounders affected by prior exposure to cART, a marginal structural linear mean model was used.

RESULTS

Seven hundred ninety children were active for 2090 person-years and a median of 31 months; 619 (78%) initiated cART. At baseline, 405 children (51%) were in HIV clinical stage 3 or 4; 528 (67%) had advanced or severe immunodeficiency. Compared with no cART, the estimated absolute rise in CD4 percentage was 6.8% [95% confidence interval (CI), 4.7% to 8.9%] after 6 months of cART, 8.6% (95% CI, 7.0% to 10.2%) after 12 months, and 20.5% (95% CI, 16.1% to 24.9%) after 60 months. cART-mediated CD4 percentage gains were slowest but greatest among children with baseline CD4 percentage <15. The cumulative incidence of recovery to "not significant" World Health Organization age-specific immunodeficiency was lower if cART was started when immunodeficiency was severe rather than mild or advanced.

CONCLUSIONS

cART increased CD4 percentages among HIV-infected children in a resource-deprived setting, as previously noted among children in the United States. More gradual and protracted recovery in children with lower baseline CD4 percentages supports earlier initiation of pediatric cART.

T-lymphocyte subsets in apparently healthy nigerian children

Population studies showed that there are differences in T-lymphocytes subpopulation of normal children in different regions, and reference values in an area might be different from another. This study compared the values in our population with CDC and WHO reference values. Blood samples from 279 healthy, HIV-negative children <12 years of age were analysed for complete blood count, CD3+, CD4+, CD8+ counts and percentages. Except for CD8%, mean values for all parameters measured significantly decreased with age. CD4+ counts were higher in females than males, P < .05. Using the WHO criteria, 15.9% of subjects had low total lymphocyte count and 20.6% had low CD4 count. Children <3 years had median CD4% lower than WHO normal values. Our median CD4+ counts correlated with CDC values. Values used by WHO in infants are higher than ours. We suggest that our children be assessed using CDC reference values which correlate with ours.

Human immunodeficiency virus (HIV) infection during pregnancy induces CD4 T-cell differentiation and modulates responses to Bacille Calmette-Guérin (BCG) vaccine in HIV-uninfected infants

Human immunodeficiency virus (HIV)-negative infants born to HIV-positive mothers frequently exhibit a range of immunological abnormalities. We tested the hypothesis that HIV during pregnancy affects the ability of CD4 T cells of HIV-negative infants to respond to vaccine challenge by recruiting HIV-negative infants born to HIV-negative and HIV-positive mothers and measuring their responses to Bacille Calmette-Guérin (BCG) vaccine given at birth. At 2 weeks, maternal HIV status did not influence CD4 T-cell counts or differentiation, but by 10 weeks CD4 counts of infants born to HIV-positive mothers fell to a level characteristic of HIV-positive infants. Among the CD4 T-cell populations, markers of differentiation (CCR7⁻ CD45RA⁻ CD27⁻) and senescence (CD57, PD-1) were more common among infants born to HIV-positive mothers than among infants born to HIV-negative mothers. At 2 weeks of age, we assessed the effector response to heat-killed BCG and tuberculin purified protein derivative (PPD) by overnight interferon (IFN)-γ enzyme-linked immunosorbent spot-forming cell assay (ELISpot), but found no measurable effect of maternal HIV status. At 10 weeks, we assessed CD4 T-cell memory by measuring proliferation in response to the same antigens. We observed a bimodal response that allowed infants to be classified as high or low responders and found that fewer infants born to HIV-positive mothers were able to mount a robust proliferative response, suggesting that their reduced CD4 counts and increased differentiation indicated a deficiency in their ability to develop immunological memory.

Contribution of monocytes to viral replication in macaques during acute infection with simian immunodeficiency virus

Monocytes are known as an alternative target for HIV/SIV infection, but the contribution of monocytes to viral spread in a host is unclear. In this study, CD14 monocytes were monitored in 6 macaques until six weeks postinfection (wpi) with SIVmac239 to evaluate their contribution to viral load. The monocyte count in blood significantly increased with peak viremia at 2 wpi and the expression level of CD14 on monocytes significantly decreased at 1-2 wpi, though the number of CD4(+) T cells was stable in these macaques. The number of CD14 monocytes and the expression level of CD14 on monocytes at 2 wpi were also significantly related to the extent of viremia in plasma. An increased number of monocytes at 2 wpi was associated with a lower postacute viral load, suggesting that monocytes have a role in suppressing the virus. The lower expression level of CD14 in monocytes at 2 wpi was associated with a higher viral load and greater degree of infection of monocytes. This correlation suggests that monocytes with a low level of CD14 may be more susceptible to SIV and may enhance viral replication. The analysis of monocytes in persistently infected macaques revealed that the expression level of CD14 was also significantly low during persistent infection compared with naïve macaques, though the monocyte count was within the normal range. Monocytes may suppress viruses, perhaps by their immune function, during acute infection. However, infection of monocytes may increase the viral load and spread viruses in a host.

High cytotoxic and specific migratory potencies of senescent CD8+ CD57+ cells in HIV-infected and uninfected individuals

CD8+ CD57+ T lymphocytes, present at low levels in the peripheral blood of healthy individuals expand during HIV infection and remain elevated during chronic infection. Their role in the immune response remains unclear. We performed a large-scale gene array analysis (3158 genes) to characterize them and, interestingly, found no distinction in the transcriptional profiles of CD8+ CD57+ T lymphocytes from HIV-infected and uninfected subjects. In both groups, these cells showed specificity for multiple Ags and produced large amounts of IFN-gamma and TNF-alpha. The transcriptional profiles of CD8+ CD57+ and CD8+ CD57- cells, however, differed substantially. We propose that CD8+ CD57+ cells were Ag-driven effector cells with very high cytotoxic effector potential including perforin, granzymes, and granulysin, regardless of HIV status. At both the messenger and protein levels, they expressed more adhesion molecules and fewer chemokine receptors (CCR7 and CXCR4) than CD8+ CD57- cells but expressed preferentially CX3CR1. The lower expression level of genes involved in cell cycle regulation showed limited proliferation capacities of CD8+ CD57+ even in response to TCR and IL-2, IL-7, and IL-15 stimulation. CD8+ CD57+ T cells from both HIV and uninfected subjects maintain effective cytotoxic potentials but are destined to migrate to nonlymphoid tissues without further cycling.

Impact of opportunistic Mycobacterium tuberculosis infection on the phenotype of peripheral blood T cells of AIDS patients

While the detrimental consequences of opportunistic tuberculosis (TB) in the course and outcome of HIV-1 infection are well studied, little information about the impact of the mycobacterial infection on the phenotype of T lymphocytes is available. In this study we analyzed by cytofluorimetry the peripheral blood T cell phenotype of 13 patients with AIDS, 23 HIV-1 negative patients with active pulmonary TB, nine HIV-1/Mycobacterium tuberculosis coinfected individuals, and 21 age- and sex-matched healthy controls. CD4+ T cells were equally depleted in AIDS and coinfection (P<0.001). The findings suggest a rescuing effect of the added mycobacterial infection. CD3 T cell loss was not observed in coinfection, whereas it was severe in AIDS (P<0.001). Similar (albeit less striking) effects were observed with other markers (CD45RA, CD45RO, and CD27) that were diminished in CD4+ T cells of AIDS patients. Apparent detrimental effects of the added mycobacterial infection were the increased expression of the proapoptotic molecule CD95 on CD4+ T cells, and decreased expression of the major costimulatory molecule CD28 on CD8+ T cells. In this work we show that M. tuberculosis infection modifies the T cell phenotype of the HIV-1 infected individual.

Pro- and anti-inflammatory cytokines in human immunodeficiency virus infection and acquired immunodeficiency syndrome

In persons with human immunodeficiency virus (HIV) infection and/or acquired immunodeficiency syndrome (AIDS), the immune system becomes dysfunctional in many ways. There is both immunodeficiency due to the loss of CD4-positive T helper cells and hyperactivity as a result of B-cell activation. Likewise, both decreases and increases are seen in the production and/or activity of cytokines. Cytokine changes in HIV infection have been assessed by a variety of techniques, ranging from determination of cytokine gene expression at the mRNA level to secretion of cytokine proteins in vivo and in vitro. Changes in cytokine levels in HIV-infected persons can affect the function of the immune system, and have the potential to directly impact the course of HIV disease by enhancing or suppressing HIV replication. In particular, the balance between the pro-inflammatory cytokines interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha, which up-regulate HIV expression, and IL-10, which can act both as an anti-inflammatory cytokine and a B-cell stimulatory factor, may play an important role in the progression to AIDS. In light of its ability to suppress the production of pro-inflammatory cytokines and, under some conditions, suppress HIV replication, increased IL-10 may be viewed as beneficial in slowing HIV disease progression. However, an association between increased IL-10 and the development of AIDS-associated B-cell lymphoma highlights the bifunctional nature of IL-10 as both an anti-inflammatory and B-cell-stimulatory cytokine that could have beneficial and detrimental effects on the course of HIV infection and AIDS.

When T-helper cells don't help: immunopathology during concomitant infection

Disease directly caused by immune system action is known as immunopathology. Many factors may lead the immune system to cause rather than cure disease, and autoimmune, allergic, and infection-related immunopathological diseases affect millions of people worldwide. This review presents an analysis of T-helper cell mediated, infection-related immunopathology within the framework of evolutionary ecology. A proximate cause of infection-related immunopathology is an error in the type of T-helper response induced. Distinct subsets of T-helper cells enable different effector mechanisms and therefore work optimally against different types of parasites (e.g., extracellular versus intracellular parasites). Immune responses that cure rather than cause disease require that the T-helper subset be tailored to the parasite. It is thus critical for the immunophenotype to match the "environment" of the parasitic infection. As in other cases of adaptive plasticity, a mismatch between an organism's phenotype and the selective environment can decrease fitness. T-helper response induction may be confounded by coinfection of a single host by multiple parasite species. Because of normally adaptive feedback loops that lend to polarize T-helper responses, it can become impossible for the immune system to mount effective, conflicting responses concurrently. Immunophenotype-environment mismatches may thus be inevitable when simultaneous, conflicting immune responses are required. An ultimate cause of infection-related immunopathology in a multiparasite selection regime is the T-helper response polarization that can propagate response errors and constrain the ability of the immune system to resolve conflicting response requirements. A case study is used to illustrate how coinfection can exacerbate immunopathology and to frame testable predictions about optimal responses to coinfection (e.g., is the observed joint response to coinfection accurately predicted by the average of the component single-infection optimal responses, where the single-infection optima are weighted by the contribution of each to fitness). The case study includes immunological and pathological data from mice infected by Schistosoma mansoni alone and by S. mansoni in combination with Toxoplasma gondii. Such data can inform hypothesis tests of evolutionary ecological principles, and ecological analysis can in turn clarify assumptions about responses to coinfection for a greater understanding of the immune system. The synthesis of evolutionary ecology and immunology could therefore be of mutual benefit to the two disciplines.

Preservation of clonal heterogeneity of the Pneumocystis carinii-specific CD4 T cell repertoire in HIV infected, asymptomatic individuals

The loss of CD4 lymphocytes in HIV disease associates with opportunistic infections. Since diverse CD4 T cell clones respond to an opportunistic pathogen, we asked whether CD4 depletion deletes selected clones in the repertoire (vertical depletion) or it affects all clones by reducing the cell number in each progeny without affecting the overall number of clones (horizontal depletion). Understanding this point may help explain the mode of CD4 depletion and the mode of immunoreconstitution after therapy. Therefore we examined the CD4 T cell repertoire specific for Pneumocystis carinii, a relevant opportunistic pathogen in AIDS, in HIV-infected, asymptomatic individuals. We identified two patients of 36 asymptomatics for lack of proliferation to P. carinii, suggesting selective depletion of specific CD4 cells. To investigate clonal heterogeneity of P. carinii-responsive CD4 lymphocytes, specific CD4 T cell lines were generated and studied by TCR BV gene family usage and CDR3 length analysis (spectratyping). Clonal heterogeneity was similar in antigen-specific CD4 lines generated from P. carinii non-responding HIV seropositives and from controls. Thus, despite undetectable response to the pathogen, residual specific cells probably prevent overt infection and, when expanded in vitro, exhibit a clonal diversity similar to normal controls. These findings suggest a horizontal, rather than vertical, depletion in these asymptomatic patients.

Analysis of the antigen specific T cell repertoires in HIV infection

In addition to HIV infection, several acquired immunodeficiencies lead to depletion of CD4 lymphocytes. These include immunosuppression resulting from high dose cancer chemotherapy or induced to control graft rejection, as well as in autoimmune diseases. The consequence of this depletion is an increased susceptibility to opportunistic infections or the inability to control primary infection in the case of HIV infection. In all instances a full or partial immunoreconstitution is desirable. In order to monitor the cellular immune state of a patient, rational information cannot be simply derived from phenotypic quantification of T lymphocytes. Instead loss or recovery of CD4 cells should be monitored by defining the specificity, the function and the clonality of the relevant cell population. Several methods are now available for this type of investigation. Here we describe an approach for the definition of clonal heterogeneity of antigen specific CD4 lymphocytes, a parameter that may help monitor loss or reconstitution in acquired immunodeficiencies. As examples of antigen specific CD4 T cell responses we focused on Pneumocystis carinii and on cytomegalovirus, as prototypic opportunistic pathogens which are responsible for severe infections in AIDS and in other immunosuppressive conditions which arise for instance following transplantation. Specific CD4 T cell lines were generated from normal controls and from seropositives in order to select antigen specific lymphocytes. The cells were subsequently analyzed for clonal diversity according to TCR BV gene family usage and according to TCR CDR3 size heterogeneity (spectratyping).

Effects of subcutaneous interleukin-2 therapy on phenotype and function of peripheral blood mononuclear cells in human immunodeficiency virus infected patients

In the context of clinical therapy with recombinant human interleukin-2 (IL-2), we monitored immunological alteration in 10 human immunodeficiency virus type-I (HIV-1)-infected individuals, on stable antiretroviral therapy, who had a CD4+ cell count between 200 and 500 cells/mm3. Subcutaneous IL-2 was prescribed thrice weekly (at a dose of 3 x 10(6) IU) for 24 weeks and the patients were followed-up for 32 weeks. IL-2 treatment induced an increase in the CD4+ percentage (P<0.001) and CD4+ cell count (P<0.009). Furthermore. natural killer (NK) cell activity was increased (P<0.001) at week 8 of treatment, whereas lymphokine-activated killer (LAK) cell activity showed a transient, nonsignificant increase at week 8 and was reduced (P<0.001) at 32 weeks. However, the cytotoxic T-lymphocyte (CTL) activity decreased against HIV antigens, and the proliferative response to Candida, IL-2 and phytohaemagglutinin (PHA) declined during the first 8 weeks (P<0.05) and returned to baseline levels after 32 weeks. The HIV RNA level did not change during IL-2 therapy; however, after 8 weeks of follow-up a significant increase (P<0.001) in viral load was observed. In

Impaired thymopoietic potential of immature CD3(-)CD4(+)CD8(-) T cell precursors from SIV-infected rhesus monkeys

Immature thymocyte subpopulations were examined for their capacity to differentiate in a newly developed xenogeneic monkey-mouse fetal thymus organ culture (FTOC) system. We provide evidence for impaired precursor function of CD3(-)CD4(+)CD8(-) thymocytes after in vivo infection with SIVmac251 as indicated by a reduced cell number per FTOC and a lower percentage of thymocytes with more mature phenotypes. Addition of recombinant SIV glycoprotein 120 (rgp120) also resulted in a dose-dependent impairment of T cell maturation in FTOC. The data suggest that in patients infected with HIV, T cell maturation and thus replenishment of peripheral pools may be compromised as a result of intrathymic infection or circulating viral gp120.

Phenotype analysis of peripheral blood mononuclear cells in periparturient dairy cows

Impaired immune function during the periparturient period contributes to the increased susceptibility of the cow to infectious disease around the time of calving. Changes in subpopulations of peripheral blood mononuclear cells during the immediate periparturient period can contribute to the observed immunosuppression in cows, but it is not known exactly when and what changes occur. Using a flow cytometer and monoclonal antibodies directed against antigenic markers on mononuclear cells, the populations of CD3, CD4, CD8, and gamma delta T-cell receptor positive cells were examined in eight periparturient Jersey cows during the 2 wk before and 2 wk after parturition. The percentage of cells that were positive for CD3, CD4, and gamma delta T-cell receptor markers exhibited a significant decline before calving and reached a nadir at calving. These percentages did not return to precalving levels until 2 wk after calving. These data are compatible with the hypothesis that declining T-cell populations may contribute to the immunosuppression reported for dairy cows at calving.

Highly active antiretroviral therapy during early HIV infection reverses T-cell activation and maturation abnormalities. Swiss HIV Cohort Study

OBJECTIVES

To evaluate the impact of early initiation of highly active antiretroviral therapy (HAART) on disease-induced T-cell activation and maturation abnormalities during asymptomatic HIV infection.

DESIGN

A prospective open-label trial of zidovudine, lamivudine and ritonavir in treatment-naive asymptomatic HIV-infected individuals with CD4 cells > or = 400 x 10(6)/l.

METHODS

Peripheral blood CD4+ and CD8+ T cells derived from 15 asymptomatic HIV-infected individuals (median baseline CD4+ cells, 608 x 10(6)/l; CD8+ cells, 894 x 10(6)/l; plasma HIV RNA, 3.93 log10 copies/ml) undergoing therapy with zidovudine (300 mg twice daily), lamivudine (150 mg twice daily), and ritonavir (600 mg twice daily) were assessed for changes in expression of phenotypic markers of T-cell activation (HLA-DR and CD38) and maturation (CD45RA and CD45RO). At weeks 0, 2, 4, 8, 12, 16, 20 and 24, T-cell subsets were quantified by flow cytometry and plasma HIV viral loads determined using reverse transcription PCR.

RESULTS

HAART-induced decrease in plasma HIV RNA levels coincided with a significant reduction in numbers of activated CD4+/HLA-DR+ (maximum change, -36%; P < or = 0.05), CD8+/HLA-DR+ (maximum change, -66%; P < or = 0.005) and CD8+/CD38+ (maximum change, -51%; P < or = 0.01) T cells. A concomitant significant increase in numbers of naive CD4+/CD45RA+ (maximum change, +12%; P < or = 0.005) and memory CD4+/CD45RO+ (maximum change, +6%; P < or = 0.05) T cells was also evident, which contrasted with a significant decrease in memory CD8+/CD45RO+ cells (maximum change, -42%; P < or = 0.005).

CONCLUSION

The observed ability of HAART during early asymptomatic HIV infection to initiate rapid reversal of disease-induced T-cell activation and maturation abnormalities, while preserving pretherapy levels of immune function, supports the concept that therapeutic advantage is to be gained by commencing early aggressive antiretroviral therapy.

Immunologic effects of combined protease inhibitor and reverse transcriptase inhibitor therapy in previously treated chronic HIV-1 infection

OBJECTIVE

To evaluate the efficacy of combination protease and reverse transcriptase inhibitor therapy in correcting HIV-1-induced lymphocyte subset abnormalities in previously treated adults.

DESIGN

A 48-week observational study of lymphocyte subsets in 12 participants in the Multicenter AIDS Cohort Study who were already taking at least one reverse transcriptase inhibitor and added a protease inhibitor to their treatment regimen. Comparison groups were HIV-seronegative homosexual men, HIV-seronegative heterosexual men, and homosexual HIV-1-infected men who were long-term non-progressors.

METHODS

Three-color immunofluorescence and monoclonal antibodies were used to assess HIV-1-induced lymphocyte subset alterations related to immune deficiency and immune activation. Plasma HIV-1 RNA levels were monitored to assess suppression of viral replication.

RESULTS

CD4+ cell counts significantly increased and lymphocyte activation measured as CD38 and HLA-DR expression on CD8+ T cells significantly decreased by 48 weeks. CD4+ cell values remained abnormal even in those who were fully suppressed. Some T-cell activation markers decreased to levels observed in long-term non-progressors. The increase in CD4+ T-cell numbers reached a plateau by week 24, but the increase in resting HLA-DR- CD38-T cells was sustained through week 48. Proportions of CD45RA+ CD62L-selectin+ and CD28+ CD4+ T-cell subsets and Fas expression were not abnormal at baseline compared with seronegative homosexual controls.

CONCLUSIONS

The most significant impact of suppression of viral replication was reversal of T-cell activation. However, normalization of lymphocyte subset perturbations associated with chronic HIV-1 infection was not achieved after 1 year of treatment with current combination antiretroviral regimens. More profound viral suppression, therapy for longer than 1 year, or immunologic augmentation may be needed to fully reverse the abnormalities.

Phenotyping of beluga whale blood lymphocytes using monoclonal antibodies

Widespread efforts are currently made to classify morphologically indistinguishable lymphocyte subpopulations in several species. In order to increase the knowledge in cetacean immunology, cross-reactivity of antibodies against bovine, human, ovine and mouse cell surface proteins was tested on beluga whale (Delphinapterus leucas) peripheral blood lymphocytes using flow cytometry. Anti-MHC class I and II as well as anti-CD2 reacted with virtually all peripheral blood lymphocytes. Anti-TCR gamma delta and anti-CD4 reacted with respectively 31% and 30% of peripheral blood lymphocytes. B lymphocytes were identified by an anti-surface IgM which was present on 6% of blood lymphocytes. Specificity of these antibodies was demonstrated by immunoprecipitation of beluga proteins with similar molecular weight to that of other species. These results could be useful for further immunotoxicological evaluation of highly versus mildly contaminated populations of belugas.

A hypothesis to explain the role of the suppressor and helper T cells in the immunologic selection of highly related human immunodeficiency virus isolates found in infected patients

It is proposed that specific human immunodeficiency virus determinants in seropositive individuals are capable of evoking very strong suppressor T cell responses which inactivate certain helper T cells. This helper T cell suppression may be sufficient to inhibit the cytotoxic T cell recognition of these specific retroviral antigens and significantly reduce neutralizing antibody titers. As a consequence of the poor T helper cell responses to these different antigens, a number of related human immunodeficiency virus isolates are able to escape immune surveillance over the entire course of the infection. The selection and persistence of these distinct but related viral isolates may allow the human immunodeficiency virus infection to progress to other tissues and contribute to the gradual destruction of the remaining helper T cell population. Thus, the development of an effective antiviral therapy and possibly even a cure for the acquired immune deficiency syndrome may depend on the management of the suppressor and helper T cell activity in the infected individual.

Enhancement of HIV-1-induced syncytium formation in T cells by the tyrosyl kinase p56lck

The CD4 glycoprotein is the primary cellular receptor for human immunodeficiency virus type 1 (HIV-1) and has also been reported to be physically associated with p56lck, a tyrosyl protein kinase p56lck is a member of the src family of nonreceptor protein-tyrosine kinases and is expressed predominantly in T lymphocytes. Our objective was to study the effect of p56lck on the biology of HIV-1. For this purpose, we have stably transfected two human p56lck negative T cell lines (C8166-45 and MT-2) with plasmids encoding for this cellular protein. Following coculture with HIV-1-infected cells or infection with cell-free virus, p56lck-expressing cell lines showed a greater propensity for virus-mediated syncytium formation than parental p56lck-negative cells. The enhancement of HIV-1-induced syncytium formation was not associated with the kinase activity of p56lck, as demonstrated by experiments using a kinase-deficient mutant. However, the physical interaction between CD4 and p56lck was shown to be necessary to obtain the enhancement of syncytium formation since a mutated version of p56lck, which is deficient in its capacity to associate with CD4, did not lead to an increase in virus-mediated cell-to-cell fusion events. Finally, we determined that cells transfected with wild-type and kinase-negative mutant p56lck showed a reduced rate of CD4 endocytosis compared to parental p56lck-negative cells. Together, these results suggest that p56lck can be seen as an accessory molecule facilitating HIV-1-mediated syncytium formation in T cells by a mechanism involving the stabilization of the CD4 molecule at the cell surface.

HIV infection--induced posttranslational modification of T cell signaling molecules associated with disease progression

In attempt to elucidate the mechanism of the HIV infection induced T cell unresponsiveness, we studied signal-transducing molecules proximal to the T cell receptor (TCR) in T lymphocytes of HIV-infected individuals. Total amounts of protein tyrosine kinases (PTKs) Lck, Fyn, and ZAP-70 and the zeta chain of the TCR were found significantly decreased in T cells of symptomatic/AIDS patients as well as in T cells of individuals in acute and early asymptomatic stages of HIV infection. Unexpectedly, the detection of Lck, Fyn, and ZAP-70 was reversed after the treatment of cell lysates with dithiothreitol. This suggests that PTKs Lck, Fyn, and ZAP-70 were modified by a mechanism altering the status of sulfhydryl groups. Moreover, this mechanism seems to affect selectively T cells of HIV infected patients since B cell PTKs Syk and Lyn were detected structurally and functionally intact. Interestingly, similar alterations of signaling molecules were not detected in T cells of HIV-infected long-term asymptomatic individuals. Modification of T cell PTKs may thus underlie the HIV-induced impairment of lymphocyte function and may potentially predict disease progression.

Exercise and immunity: a review with emphasis on the horse

Exercise has been recognized as a stress, which can significantly alter the host's immune response and, therefore, its susceptibility to disease. Whereas research in this area has previously focused primarily on human subjects and laboratory animals, it has more recently extended to domestic animals, especially the equine athlete. Despite several studies, defining the relationship among exercise, the immune response, and disease has proven difficult due to a number of factors, including the complexity of the immune system and the variable nature of exercise itself. It now appears that exercise has dual effects on the immune system. Suppressive effects, such as a decline in the ratio of CD4+ to CD8+ cells, diminished lymphocyte function, and a decline in the number and cytolytic activity of natural killer cells have been observed in response to brief high-intensity exercise, prolonged exhaustive exercise, and overtraining. In contrast, moderate training generally has beneficial effects on host defense mechanisms. The mechanisms for regulating the dual effects of exercise are complex, involving a network of neuroendocrine hormones and cytokines.

Relationship of circulating CD4+ T-lymphocytes and p24 antigenemia to the risk of developing AIDS in HIV-infected subjects with oral hairy leukoplakia

To investigate the relationship of circulating CD4+ T-lymphocytes and p24 antigenemia to the development of AIDS in HIV-infected subjects with hairy leukoplakia (HL), we have followed over eight years 173 HIV-positive patients, all asymptomatic at the start of the study, and compared those who developed HL (n=55) to those who did not (n=118). Both groups included injection drug users (IDUs), homosexual men, and hemophiliacs. At the time of their first visit, both HL+ and HL- patients had a normal value of CD4+ cells and a low frequency of p24 antigenemia. During the years of follow-up, patients in the HL+ group showed a greater reduction in CD4+ cells, a significant increase in p24 antigenemia, and a higher rate of progression to AIDS. Our study demonstrates that in HIV-positive patients, HL is associated with more compromised immunological parameters and a higher viral replication and that its appearance has a negative prognostic value in relation to AIDS progression.

Effect of HIV infection on the frequency of cytokine-secreting cells in human peripheral blood

A selective decrease in type 1 cytokine secretion by in vitro stimulated peripheral blood cells is reportedly associated with disease progression in HIV-infected individuals. To examine whether a similar change in cytokine secretion occurs under physiologic conditions in vivo, sensitive and specific ELIspot assays were used to compare the phenotype and frequency of PBMC spontaneously producing interleukin (IL)-2, IL-4, IL-10, and interferon-gamma (IFN-gamma) in 83 HIV-infected subjects and 60 normal controls. Phenotypic analysis of freshly isolated cytokine-secreting cells showed that T cells were the primary source of IL-2, IL-4, and IFN-gamma while CD14+ macrophages/monocytes were the dominant source of IL-10 in vivo. The number of peripheral blood mononuclear cells (PBMC) spontaneously secreting both type 1 and type 2 cytokines was significantly reduced in HIV-infected patients versus controls. The magnitude of this decrease did not correlate with disease severity. Changes in IL-2-secreting cell number correlated with CD4 count, while changes in the frequency of IFN-gamma-secreting cells correlated with disease duration. These findings do not support the contention that a selective reduction in type 1 cytokine production correlates with disease progression.

Characterization of T cell subsets involved in the production of IFN-gamma in asymptomatic HIV-infected patients

Cells capable of interferon (IFN)-gamma synthesis following mitogenic stimulation can be detected and quantified by a recently developed immunofluorescence assay and flow cytometric analysis. The production of IFN-gamma was investigated in a cohort of 20 asymptomatic human immunodeficiency virus (HIV)-seropositive patients with normal numbers of CD4+ lymphocytes, and in 10 healthy subjects. About 60% of asymptomatic stage A1 patients had increased percentages of blood lymphocytes capable of IFN-gamma synthesis, as compared to healthy subjects. The difference reflected the relatively higher numbers of CD8+ cells, in particular the CD8+ T cell subset lacking CD28 antigen expression. The strong correlation between the CD4+/CD8+ ratio and the CD8+CD28+/CD8+CD28- ratio suggests either a role for CD4+ cells in controlling the CD28+ phenotype or a role for CD8+CD28- cells in the decline of CD4+ lymphocytes. The peculiar ability of CD8+CD28- cells to produce high amounts of IFN-gamma, as compared to CD8+CD28+ cells, supports the hypothesis that the CD8+CD28- lymphocytes constitute a population that is functionally distinct from their double-positive counterparts.

Cytokine interactions in human immunodeficiency virus-infected individuals: roles of interleukin (IL)-2, IL-12, and IL-15

Cytokines have been shown to be powerful regulators of the immune response. In this study, we analyze the effect that the newly recognized cytokine interleukin (IL)-15 has on proliferation and cytokine induction using peripheral blood mononuclear cells (PBMCs) and purified CD4+ T cells from patients infected with human immunodeficiency virus (HIV) who are at various stages in their disease. We observed that IL-15 enhances the proliferative response in a dose-dependent manner from PBMCs of HIV-infected individuals when stimulated by polyclonal mitogen, tetanus toxoid, or HIV-specific antigen. The effects of exogenous IL-15 are substantially diminished by adding a neutralizing antibody to the beta chain of the IL-2 receptor. Moreover, the ability of IL-15 to increase proliferation is enhanced by the presence of endogenous IL-2 produced in the cultures. The effect that exogenous IL-15 had on IL-2, IL-4, and interferon (IFN)-gamma induction from PBMC's or CD4+ T cells in response to mitogen or tetanus toxoid was also examined. This was compared to the effect that exogenous IL-2 and IL-12 had under the same conditions. Addition of IL-2 or IL-15 to short-term in vitro cultures of either PBMCs or CD4+ T cells had little effect on IL-2, IL-4, or IFN-gamma production. By contrast, IL-12 caused substantial enhancement of both IL-2 and IFN-gamma production from these cultures. The role that endogenous cytokines have on IFN-gamma induction was also studied. Addition of a neutralizing antibody to the alpha chain of the IL-2 receptor or IL-12 to antigen stimulated cultures caused a striking decrease in IFN-gamma production. Neutralization of endogenous IL-15 also resulted in diminished IFN-gamma production from cultures stimulated with mitogen. IL-4 and IFN-gamma protein production by PBMCs and CD4+ T cells stimulated with mitogen was assessed to see if we could detect a specific bias of cytokine production. Small amounts of IL-4 were detected from CD4+ T cells but not PBMCs from most individuals tested. IFN-gamma and IL-2, however, were also produced from these same cultures. These results further elucidate the mechanism of cytokine regulation in HIV-infected individuals, and they provide evidence that IL-15 may be a useful immune modulator.

The effects of the opiate antagonist naloxone on measures of cellular immunity during rest and brief psychological stress

This study investigated subjective, cardiovascular, and cellular immune system responses in 20 healthy young men during brief mental arithmetic stress compared with a video-watching control task. The role of endogenous opioids in mediating the immunological change to stress was examined by pre-task administration of the opiate antagonist naloxone. Immune changes were followed over a 1 hr post-task period. The results indicate significant physiological arousal and subjective distress as well as increases in NK cell cytotoxicity, numbers of circulating CD8 suppressor/cytotoxic T cells and NK lymphocytes following mental arithmetic but not the control task. Immune measures generally returned to baseline by 1 hr after the stress. Naloxone did not block the increase in NK cell activity or cell numbers following the stressor and had no effect on the other physiological or subjective measures. Thus, the results do not support endogenous opioids as a primary mechanism for immune changes to this type of acute stress. Naloxone did, however, increase NK cell cytotoxicity during the video task without effecting NK cell numbers, suggesting naloxone itself can increase per-cell NK cytotoxicity. Affective ratings for the week preceding testing were inversely related to the increase in NK cell numbers during mental arithmetic. If the increase in NK cell numbers under brief stress is part of an adaptive response to potential injury, then our data suggest that increases in general distress may impede normal immune system adaptation. Acute stress paradigms may be used as potential probes for investigations of individual differences in immune system responsivity.

Three-colour flow cytometric immunophenotyping in HIV-patients; comparison to dual-colour protocols

Flow cytometric measurement of circulating CD4+ lymphocytes is important in the evaluation of disease progression in HIV-infected patients. Development of dyes that can be exited at 488 nm and have emission maximum in the far red area has made three-colour protocols, together with fluorescein isothiocyanate (FITC) and R-phycoerythrin (PE), possible in most clinical flow cytometers. We report here the comparison of a two-tube, three-colour protocol (including CD45/CD4/ CD3 and CD8/CD4/CD3) with our conventional dual-colour protocol. No significant differences were found between percentage of CD3+ lymphocytic cells determined with three different antibody combinations. When the CD8/CD4/CD3 combination was used a systematic overestimation of CD3+ CD4+% cells was found. This turned out to be caused by the formation of 'CD8-escapees'. These are clumps of CD8+ cells that fall outside the lymphocyte gating region, principally because of high side scatter. The problem can be overcome by rigorous vortexing to loosen aggregates. The lymphocyte gating principle used in this protocol (gating on a side scatter/CD45 dot plot) is readily applicable to other antibody combinations. This was demonstrated by measuring CD5+ B lymphocytes, a subset receiving increasing attention in the study of HIV-induced immune deviations. We conclude that our three-colour protocol for CD4+ T-lymphocyte determinations offers significant advantages to the conventional dual-colour method, and we suggest that when possible anti-CD45 be added to dual-colour combinations in order to improve lymphocyte gating.

Unbiased usage of T-cell receptor beta variable region genes in peripheral blood cells of hepatitis C patients: no correlation with superantigen effect

Hepatitis C virus (HCV) infection frequently causes chronic hepatitis and lack of virus clearance in these patients. In addition, many patients infected by HCV also present with hypergammaglobulinemia in the early stage of chronic infection. These observations raise a possible viral superantigen effect induced by HCV, because viral superantigen found in human immunodeficiency virus (HIV) or in replication of defective murine leukemia virus (MuLV) is associated with T-cell dysfunction and polyclonal activation of B cells. The possibility was investigated of whether HCV encodes any superantigen by analyzing the usage of T-cell receptor (TCR) from the peripheral blood lymphocytes (PBL) of patients with chronic hepatitis C. Two groups, one with hypergammaglobulinemia and the other without hypergammaglobulinemia, were studied for the usage of TCR beta chain by reverse transcription-polymerase chain reaction (RT-PCR) analysis. It was found that all genes of V beta variable chain were used in the PBL of these patients. Furthermore, there was no significant difference of the TCR expression pattern between these two groups, nor a complete deletion of a particular T-cell subset in either group. These results do not provide evidence for HCV superantigen, but indicate that the TCR usage in the patients was neither defective nor biased.

Disparity in the percentage of CD4+ T lymphocytes and prognosis of HIV-infected intravenous drug users in Malaysia

The CD4+ T-lymphocyte absolute count (CD4ac), CD4+ T-lymphocyte percentage (CD4%) and total lymphocyte count (Løac) were assessed in HIV-seropositive intravenous drug users (IVDU) with reference to their correlation with the clinical categories A, B, and C as stipulated by the Centre of Disease Control and Prevention, USA (CDC) and with each other. It was found that while the CD4ac and Løac correlated with the clinical categories, CD4% did not. This may suggest that in our local setting, the CD4% may not necessarily be a suitable alternative marker to CD4ac as proposed by CDC. Furthermore, the CD4% of the normal subjects in this study was found to be relatively lower than the reported Caucasian levels. This may indicate that the use of the cut-off level of less than 14% as an AIDS-defining criteria may not be applicable for our HIV-seropositive IVDU. In addition, unlike the CD4ac which correlated directly with CD4% and Løac, the CD4% did not correlate with Løac. Therefore, due to the observed disparity with clinical status of patients and its possibly lower levels in our normal population, CD4% as a marker for staging HIV disease should be used with caution in our setting. Such findings may also have an impact on the use of established markers for the monitoring and classification of HIV-infected individuals in this region.

Ability of HIV to promote a TH1 to TH0 shift and to replicate preferentially in TH2 and TH0 cells

Both interferon gamma (IFN-gamma) produced by T helper 1 (TH1) lymphocytes and interleukin-4 (IL-4) produced by TH2 lymphocytes were reduced in either bulk circulating mononuclear cells or mitogen-induced CD4+ T cell clones from the peripheral blood of individuals infected with human immunodeficiency virus (HIV). There was a preferential reduction in clones producing IL-4 and IL-5 in the advanced phases of infection. However, enhanced proportions of CD4+ T cell clones producing both TH1-type and TH2-type cytokines (TH0 clones) were generated from either skin-infiltrating T cells that had been activated in vivo or peripheral blood T cells stimulated by antigen in vitro when cells were isolated from HIV-infected individuals. All TH2 and most TH0 clones supported viral replication, although viral replication was not detected in any of the TH1 clones infected in vitro with HIV. These results suggest that HIV (i) does not induce a definite TH1 to TH2 switch, but can favor a shift to the TH0 phenotype in response to recall antigens, and (ii) preferentially replicates in CD4+ T cells producing TH2-type cytokines (TH2 and TH0).

Human immunodeficiency virus type 1 (HIV-1) and human hematopoietic progenitor cells

Besides a progressive depletion of CD4+ T-lymphocytes, other peripheral blood cytopenias, (granulocytopenia, anemia and thrombocytopenia) are frequently observed in HIV-1 seropositive individuals, especially in patients with overt AIDS. Various experimental evidences suggest that HIV-1 could play a direct role in the pathogenesis of HIV-1 related peripheral blood cytopenias, affecting the survival/proliferation capacity of hematopoietic progenitors. CD34+ human hematopoietic progenitors, however, are substantially not susceptible to HIV-1 infection either in vitro and in vivo and their defects seem rather related to an alteration of bone marrow and peripheral blood microenvironments due to the presence of soluble HIV-1 specific products.