Helminths, human immunodeficiency virus and tuberculosis.

Helminth infections affect over a quarter of the world's population, especially in the developing countries. These long-lasting parasitic infections cause widespread immune activation and dysregulation, a dominant Th2 cytokine immune profile and an immune hyporesponsiveness state. Considering these profound immune changes and the similar geographic distributions of helminthic infections, HIV and tuberculosis (TB), we suggest that helminthic infections play a major role in the pathogenesis of AIDS and TB. They apparently make the host more susceptible to infection by HIV and Mycobacterium tuberculosis, and impair his/her ability to generate protective immunity against both infections. The implication of these ideas is that without eradication of helminth infections and/or modulation of the immune changes that they cause, HIV and TB vaccines may fail to confer protection against their respective infections in helminth-endemic areas.

Immune activation correlates better than HIV plasma viral load with CD4 T-cell decline during HIV infection.

This study addressed the role of T-cell immune activation in determining HIV-1 plasma viral load and CD4+ T-cell blood levels during HIV-1 infection. A decrease of blood CD4 levels and CD4/CD8 ratios and an increase of CD8 levels in both treated (n = 35) and untreated (n = 19) HIV-positive individuals were more strongly correlated to immune activation (log percentage of HLA-DR+CD3+ cells; R = -0.78, R = -0.77, and R = 0.58, respectively; p <.0001) than to CD4 T-cell proliferation (log percentage of Ki-67+CD4+ cells; R = -0.57 [p <.0001], R = -0.48 [p <.001], and R = 0.37 [p <.01], respectively) or to viral load (R = -0.36 [p <.01], R = -0.23 [p =.09], R = 0.13 [p =.35], respectively). Because almost half of the Ki-67+CD4+ cells were also positive for CTLA-4 (a marker for activated nonproliferating cells), the correlation of CD4 levels to Ki-67 expression is only partially related to cell proliferation and more likely represents mainly immune activation of the cells without proliferation. Taken together, these results suggest that immune activation is the major determinant of CD4 decline and should therefore be considered central for the monitoring of HIV infection and its outcome after antiviral treatment.

Increased CCR5 and CXCR4 expression in Ethiopians living in Israel: environmental and constitutive factors.

HIV coreceptors play a major role in determining susceptibility and HIV cell tropism. The present work studied whether the high expression of these coreceptors found on lymphocytes and monocytes of Ethiopian immigrants to Israel (ETH) is the result of environmental and/or constitutive genetic factors. The study of 26 ETH shortly after their arrival to Israel (new ETH), 22 ETH in Israel over 7 years (old ETH), and 20 Caucasian Israelis (non-ETH) enabled us to address this issue. The new ETH had elevated levels of activated HLA-DR+CD4+ and CD38+CD8+ cells in comparison with both old ETH and non-ETH groups (P < 0.01), most probably related to chronic helminthic infections. Surface CCR5 expression, i.e., the percentage of CCR5+ cells and the number of CCR5 molecules/cell, was higher (2- to 3- and 8- to 31-fold, respectively) in activated than in nonactivated CD4+ cells, in all groups. However, CCR5 expression, in both activated and nonactivated CD4+ cells, was higher in both ETH groups than in the non-ETH group. CXCR4 expression was higher in nonactivated CD4+ cells in all groups and was also higher in both ETH groups, in both activated and nonactivated CD4+ cells, than in the non-ETH group. These findings suggest that constitutive factors, in addition to immune activation caused by environmental factors, account for the elevated expression of CCR5 and CXCR4 on CD4+ cells of ETH. This increased HIV coreceptor expression may make ETH more susceptible to HIV infection and may account in part for the rapid spread of AIDS in Ethiopia and the rest of Africa as well.

Induction of antigen-specific Th1-biased immune responses by plasmid DNA in schistosoma-infected mice with a preexistent dominant Th2 immune profile.

A requisite for vaccines to confer protection against intracellular infections such as Human Immunodeficiency Virus or Mycobacterium tuberculosis is their capacity to induce Th1 immune responses. However, they may fail to do so in Africa and South East Asia, where most individuals have a dominant preexistent Th2 immune profile, due to persistent helminthic parasitic infections, which may undermine any Th1 response. It is well established that DNA vaccines induce strong Th1 biased immune responses against an encoded antigen, depending on the route and mode of immunization. Here, we demonstrate that intradermal immunization with plasmid DNA encoding beta-gal (pCMV-LacZ) of Schistosoma-infected mice, with preexistent dominant Th2 immune background, induce a strong Th1 anti-beta-gal response, as opposed to immunized with beta-gal only. Importantly, the established protective Th2 immune response to schistosomes was not disrupted. These findings strongly support the possibility of using plasmid DNA as a Th1 inducing adjuvant when immunizing populations with a strong preexistent Th2 immune profile.

Chronic immune activation associated with intestinal helminth infections results in impaired signal transduction and anergy.

Helminthic parasites cause widespread, persistent infections in humans. The immigration of Ethiopians to Israel (a group denoted here by "Eth."), many of them infested with helminths and in a chronic immune-activation state, enabled us to investigate the effects of such immune activation on immune responses. We studied the immune profile and immune functions of 190 Eth. and Israeli non-Eth. (Isr.) highly, partially, or non-immune-activated individuals. Immune cells from highly immune-activated individuals were defective in several signaling responses, all of which were restored gradually following anti-helminthic treatment. These cells showed poor transmembrane signaling, as seen by the phosphorylation of various tyrosine kinases and of the MAPK kinases, ERK1/2 and p38; deficient degradation of phosphorylated IkappaBalpha; increased expression of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), which appears to block proliferative responses in these cells; decreased beta-chemokine secretion by CD8(+) cells after stimulation; and reduced proliferation to recall antigen stimulation. Highly immune-activated individuals also showed decreased delayed-type skin hypersensitivity responses to recall antigen before deworming. These findings support the notion that chronic helminthic infections cause persistent immune activation that results in hyporesponsiveness and anergy. Such impaired immune functions may diminish the capacity of these individuals to cope with infections and to generate cellular protective immunity after vaccination.

Increased CCR5 expression with decreased beta chemokine secretion in Ethiopians: relevance to AIDS in Africa.

OBJECTIVE: This study was undertaken to determine the contribution of HIV co-receptors and beta chemokine secretion to the increased susceptibility for human immunodeficiency virus (HIV) infection of peripheral blood mononuclear cells (PBMC) obtained from HIV-seronegative Ethiopian immigrants in Israel (ETH). STUDY DESIGN: Immune activation markers and HIV co-receptor expression on lymphocytes and monocytes, and beta chemokine secretion by CD8+ cells, were compared between ETH and non-Ethiopian Israeli (IS) HIV-negative individuals. RESULTS: The percentage of lymphocytes and monocytes expressing CCR5 was 1.6 and 3.0 times higher in ETH (n = 83) than in IS (n = 45), respectively (P < .001), whereas RANTES and MIP-1alpha secretion was 0.5 and 0.7 times lower (P < .01 and P < .05). The percentage of CCR5-expressing cells and RANTES secretion were inversely correlated (r = -0.7; P < .002). No differences were found in the proportion of CXCR4-expressing cells. No correlation between CCR5 expression and cell activation profile in the whole ETH population was found. However, in highly activated individuals (HLA-DR/CD3 > 7%), a significant decrease in CCR5 expression was observed. CONCLUSIONS: An increased proportion of CCR5-expressing cells with decreased beta chemokine secretion observed in ETH may account for the increased susceptibility to HIV infection of cells obtained from this group. These findings may partly explain the higher susceptibility for HIV infection in Africa and thus the rapid spread of acquired immunodeficiency syndrome (AIDS) in that continent.

Chemokines and chemokine receptors: role in HIV infection.

Our understanding of the host factors that determine susceptibility and progression of HIV infection has been very limited. In particular, it has been not clear why some people remain uninfected being repeatedly exposed to HIV-1, and others who have been infected by HIV, remain clinically asymptomatic for long periods of time. Recently it has been demonstrated that mutated forms of a number of chemokine receptors that act as coreceptors for HIV-1 entry may account for some of these phenomena. Furthermore, chemokines such as RANTES and others, being the natural ligands for chemokine receptors, have been shown to be effective inhibitors of HIV-1 infection. In this review we discuss some of the genetic, immunological, virological and epidemiological data relevant to the very important role chemokines and chemokine receptors play in HIV pathogenesis with special reference to the increased susceptibility of the African host to HIV infection.

Infection by different HIV-1 subtypes (B and C) results in a similar immune activation profile despite distinct immune backgrounds.

We compared the immune activation profile of 46 HIV-negative and 75 HIV-positive Israelis infected with HIV-1 subtype B, with 85 HIV-negative and 102 HIV-positive Ethiopian immigrants to Israel, who were infected with HIV subtype C. The HIV-negative Ethiopians had exceedingly high blood levels of eosinophils, immunoglobulin E (IgE), and p75s tumor-necrosis factor receptors (p75sTNFR); secretion of interleukin-4 (IL-4) and IL-10 by peripheral blood mononuclear cells (PBMC); proportion of human leukocyte antigen (HLA)-DR+ cells within CD3+, CD4+, and CD8+ T-cell subsets; and proportion of CD45RO+ CD4+ cells; while having significantly lower secretion of interferon-gamma (IFN-gamma) by PBMC and percentage of CD45RA+ CD4+ and CD28+ CD8+ cells. HIV infection in both populations was associated with reduced IL-2, IL-4, IL-10, and IL-12 secretion, number of CD28+ and CD45RA+ CD8+ cells, and increased number of HLA-DR+-CD3+, CD4+, and CD8+ cells, and CD45RO+ CD8+ cells. Thus, infection with HIV-1 subtypes B and C of studied Israelis and Ethiopians, respectively, results in a similar immune activation profile at all stages of the infection when living in the same environment, despite the striking different immune profile observed in the HIV-negative Israeli and Ethiopian populations. Together with our previous observations, this indicates that HIV subtype is not a major determinant in the natural course of HIV infection.

Decreased CD4 and increased CD8 counts with T cell activation is associated with chronic helminth infection.

We have previously reported the presence of marked immune dysregulation with a dominant Th2 profile, in a population of Ethiopian immigrants (ETH) in Israel heavily infected with helminths. In order to characterize better this immune dysregulation we studied by flow cytometry the expression of several activation markers on peripheral T cell populations, and lymphocyte apoptosis, in blood samples obtained from 63 'new' ETH (recently arrived), 18 'old' ETH (> 5 years since immigration) and 34 non-Ethiopian Israelis. The main findings in the 'new' ETH group in comparison with the non-Ethiopian controls were: (i) decreased CD4 and increased CD8 lymphocyte counts; (ii) elevated levels of activated T cells (CD3, CD4 and CD8) expressing HLA-DR; (iii) decreased levels of 'naive' CD4+ cells (CD45RA+), with increased levels of 'memory' CD4+ cells (CD45RO+); (iv) decreased numbers of CD28+ CD8+ lymphocytes; (v) marked increase in lymphocyte apoptosis. These T cell alterations and activation profile remained unchanged in 10 'new' ETH in whom the helminth infections persisted for 6-11 months. In contrast, in 18 'old' ETH, without helminth infections, the T cell activation profile was within the normal range. These findings suggest that chronic helminth infections may have a profound effect on the immune system of the host that disappears after eradication of these infections and adjustment to the new environment. It should therefore be taken into consideration for every immunomodulation therapy and especially in vaccine design and trials, in regions endemic for helminth infections.

The two common mutations causing factor XI deficiency in Jews stem from distinct founders: one of ancient Middle Eastern origin and another of more recent European origin.

Previous studies showed that factor XI (FXI) deficiency commonly observed in Ashkenazi Jews is caused by two similarly frequent mutations, type II (Glu117stop) and type III (Phe283Leu) with allele frequencies of 0.0217 and 0.0254, respectively. In Iraqi Jews, who represent the ancient gene pool of Jews, only the type II mutation was observed with an allele frequency of 0.0167. In this study we sought founder effects for each mutation by examination of four FXI gene polymorphisms enabling haplotype analysis in affected Jewish patients of Ashkenazi, Iraqi, and other origins and in Arab patients. Initial population surveys of 387 Middle Eastern Jews (excluding Iraqi Jews), 560 North African/Sephardic Jews, and 382 Arabs revealed allele frequencies for the type II mutation of 0.0026, 0.0027, and 0.0065, respectively. In contrast, the type III mutation was not detected in any of these populations. All 60 independent chromosomes bearing the type III mutation were solely observed in Ashkenazi Jewish patients and were characterized by a relatively rare haplotype. All 103 independent chromosomes bearing the type II mutation in patients of Ashkenazi, Iraqi, Yemenite, Syrian, and Moroccan Jewish origin and of Arab origin were characterized by another distinct haplotype that was rare among normal Ashkenazi Jewish, Iraqi Jewish, and Arab chromosomes. These findings constitute the first example of a mutation common to Ashkenazi Jews, non-Ashkenazi Jews, and Arabs and are consistent with the origin of type II mutation in a founder before the divergence of the major segments of Jews. Our findings also indicate that the type III mutation arose more recently in an Ashkenazi Jewish individual.

Soluble tumor necrosis factor (sTNF) receptors: a possible prognostic marker for bone marrow transplantation-related complications.

Involvement of tumor necrosis factor (TNF) in bone marrow transplantation (BMT)-associated complications has been documented. Biological response to TNF requires interaction with specific cell membrane receptors. Extracellular domains of these receptors are released into body fluids as soluble molecules, and participate in the bioactivity of TNF. Serum levels of p55 and p75 soluble tumor necrosis factor receptors (sTNFR) were determined in 34 patients with different diseases who underwent BMT. Sequential studies initiated 10 days before BMT and continued up to 110 days post-transplantation showed that p55 and p75 sTNFR levels were elevated significantly in patients who subsequently developed major transplant-related complications (TRC). Moreover, both sTNFR levels were increased 2- to 3-fold over control values during post-BMT febrile periods in those patients who at a later stage suffered major TRC. These results indicate that the serum level of sTNFR may be used as a prognostic marker for major TRC in BMT.

Activation of nonspecific cytotoxic cells with a multiple antigenic peptide: specificity and requirements for receptor crosslinkage.

Nonspecific cytotoxic cells (NCC) of teleost fish recognize a conserved antigenic determinant found on the protozoan Tetrahymena pyriformis and on many different tumor target cells. This determinant is located on a 46-kDa Tetrahymena protein referred to as natural killer target antigen (NKTag). The NKTag cognate sequence recognized by NCC is composed of seven to nine amino acids. In the present study, synthetic peptides of the cognate NKTag determinant were prepared as multiple antigenic peptides (MAP). Immobilized MAP activated NCC lysis of IM-9 target cells in the absence of antigen presenting cells or exogenous added cytokines. NCC binding to immobilized MAP produced two- to fivefold increased lysis of IM-9, U937, and HL-60 target cells compared to scrambled control MAP (composed of the same amino acids only in random sequence). NCC receptor crosslinkage was required for activation. Immobilized monomeric homologous cognate peptide did not activate increased NCC lysis of IM-9 target cells; however, NCC preincubated with soluble homologous monomer inhibited MAP activation of lysis. Ligand activation of NCC was antigen specific. Binding of the immobilized ligand with anti-MAP mab 22A12 prior to addition of NCC blocked activation. Mab 22A12 also inhibited NCC lysis of IM-9 target cells. A possible mechanism of NCC activation was determined. Binding of NCC to immobilized MAP produced significantly increased membrane expression of a putative receptor as defined by mab 5C6 binding. These studies demonstrate that activation of NCC by a target cell antigenic determinant depends on crosslinkage of an NCC "receptor" by polymeric repetitive sequences, a soluble or fixed monomer cannot activate but can inhibit activation, and MAP binding initiates increased expression of a putative NCC receptor protein.

Mapping of the epitope recognized by non-specific cytotoxic cells: determination of the fine specificity using synthetic peptides.

NCC recognize a conserved target cell antigen (NKTag) expressed on protozoan parasites and on transformed tumour cells. In the present study, synthetic peptides corresponding to N-terminal, C-terminal and internal NKTag(deduced) amino acid sequences were tested for binding and inhibition of NCC lysis of sensitive target cells. A 20-mer peptide equivalent to amino acids (aa) nos. 55-74 specifically inhibited NCC lysis of human EBV transformed target cells (IM-9). Inhibitory effects were nonreversible and concentration dependent, and 30 min pre-incubation produced optimum inhibition. The inhibitory 20-mer peptide was truncated into 17, 14, 10, 9 and 6-mer peptides and tested for inhibition of cytotoxicity. All produced almost complete inhibition except the 6-mer which had no activity. The NKTag sequence required for NCC binding (minimally) consisted of seven amino acids [aa nos 68-74 (ARG-ASN-LEU-THR-PHE-ILE-LEU-)]. The specificity of inhibition and the distribution of target cells expressing NKTag was determined. A 14-mer peptide composed of aa nos 61-74 inhibited lysis of HL-60, IM-9, DAUDI, YAC-1, U937 and NC-37 target cells. Flanking peptides (aa nos 35-54 and 75-94) were negative. Biotinylated aa nos 61-74 bound to NCC effector cells. The recognition requirements for aa sequence versus aa content were determined. Randomization of the aa in the cognate 9-mer obliterated the inhibitory effects. The 17-mer (cognate) synthetic peptide inhibited conjugate formation between NCC and IM-9 targets. These data demonstrate that NCC recognize a conserved antigen determinant on susceptible target cells consisting of a minimum of 7-9 amino acids in the N-terminal region of NKTag.

Immune dysregulation in Ethiopian immigrants in Israel: relevance to helminth infections?

The infectious disease background and particularly the helminth infections that are endemic in Africa could have profound effects on the host immune system. Studies that we have performed on an Ethiopian HIV- immigrant population that has recently reached Israel, lend support to this notion. They have indeed revealed a very high prevalence of helminth and several other infections with an extreme immune dysregulation, consisting of: (i) highly elevated plasma IgE, IgG, placental isoferritin, p75 soluble TNF receptor (sTNFR) levels and very high blood eosinophilia; (ii) increased secretion from phytohaemagglutinin (PHA)-simulated peripheral blood mononuclear cells (PBMC) of the cytokines IL-2, IL-4, IL-10 and p75 sTNFR, and decreased secretion of interferon-gamma (IFN-gamma) and IL-6; (iii) increased and decreased surface expression of p75 TNFR and IL-6 receptor on lymphocytes, respectively. The causal relationship between this immune dysregulation and the infectious background is highly suggestive, and could have far-reaching implications in the resistance to other infections.

Human interleukin-2-activated adherent natural killer cells recognize a conserved antigen found on tumor cells and protozoan parasites.

Plastic adherent interleukin-2-activated human natural killer (NK) cells (ALAK) lyse many different histological types of tumor target cells. In order to effect their function as cytotoxic mediators of innate immunity, ALAKs may 'recognize' antigen(s) of protozoan parasites, select virus-infected cells and they may release certain cytokines in response to bacterial antigens. In the present study, we demonstrate that CD3-/CD56dim/CD16dim/monoclonal antibody 5C6bright human ALAKs bind to an antigenic determinant on tumor cells independent of target cell H-2 allotype expression. The conserved antigen was originally obtained from the protozoan Tetrahymena pyriformis, however it is also located on the membranes of many ALAK-sensitive tumor cells. The sequence of this protein, i.e. NK target antigen/NKTag, was previously deduced from cDNA. One ALAK cognate determinant of NKTag was identified by inhibition of cytotoxicity using NKTag-derived synthetic peptides. Biotinylated synthetic peptide [amino acids (aa) 58-74] bound to ALAKs, and synthetic peptides corresponding to this sequence inhibited ALAK lysis of U937 target cells. Inhibition effects of peptide binding were nonreversible. To determine the requirements for recognition by ALAKs of this antigenic determinant, the cognate peptide aa 55-74 was truncated to 17-, 14-, 10-, 7- and 6-mer lengths and tested for inhibition of cytotoxicity. All inhibited except the 6-mer. A possible mechanism of peptide inhibition of cytotoxicity following ALAK binding to an antigenic determinant was a requirement for recognition of one anchor peptide (arginine) and receptor occupancy by a minimum of five to six additional amino acids. In antibody-dependent cell-mediated cytotoxicity experiments, synthetic peptide (aa 68-74) inhibited ALAK killing of anti-H-2d-sensitized P815 targets. This same peptide also inhibited conventional lysis of nonsensitized P815 and IM-9 targets. However, the cognate synthetic peptide (aa 58-74) did not inhibit conjugate formation between ALAKs and U937 target cells. These data demonstrate that ALAK binding to a soluble monomeric peptide inhibited cytotoxicity. Peptide binding appeared to negatively regulate cytotoxicity, and the inhibitory effects following peptide binding were nonreversible. Effector:target cell conjugate formation was not affected by peptide binding, however, recognition was required because inhibition was specific for the amino acid sequence of the synthetic peptide.