Effects of prolactin and cortisol on natural killer (NK) cell surface expression and function of human natural cytotoxicity receptors (NKp46, NKp44 and NKp30)

The surface density of the triggering receptors (e.g. NKp46 and NKp30) responsible for natural killer (NK) cell-mediated cytotoxicity determines the ability of NK cells to kill susceptible target cells. In this study, we show that prolactin up-regulates and cortisol down-regulates the surface expression of NKp46 and NKp30. The prolactin-mediated activation and the cortisol-mediated inhibition of natural cytotoxicity receptor (NCR) surface expression reflects gene regulation at the transcriptional level. NKp46 and NKp30 are the major receptors involved in the NK-mediated killing of K562, a human chronic myelogenous leukaemia cell line. Accordingly, the prolactin dramatically increased the NK-mediated killing of the K562 cell line, whereas cortisol abolished this activity. Our data suggest a mechanism by which prolactin activates the lytic function of NK cells, and cortisol inhibits the NK-mediated attack.

Inflammatory responses in Ebola virus-infected patients

Ebola virus subtype Zaire (Ebo-Z) induces acute haemorrhagic fever and a 60-80% mortality rate in humans. Inflammatory responses were monitored in victims and survivors of Ebo-Z haemorrhagic fever during two recent outbreaks in Gabon. Survivors were characterized by a transient release in plasma of interleukin-1beta (IL-1beta), IL-6, tumour necrosis factor-alpha (TNFalpha), macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta early in the disease, followed by circulation of IL-1 receptor antagonist (IL-1RA) and soluble receptors for TNFalpha (sTNF-R) and IL-6 (sIL-6R) towards the end of the symptomatic phase and after recovery. Fatal infection was associated with moderate levels of TNFalpha and IL-6, and high levels of IL-10, IL-1RA and sTNF-R, in the days before death, while IL-1beta was not detected and MIP-1alpha and MIP-1beta concentrations were similar to those of endemic controls. Simultaneous massive activation of monocytes/macrophages, the main target of Ebo-Z, was suggested in fatal infection by elevated neopterin levels. Thus, presence of IL-1beta and of elevated concentrations of IL-6 in plasma during the symptomatic phase can be used as markers of non-fatal infection, while release of IL-10 and of high levels of neopterin and IL-1RA in plasma as soon as a few days after the disease onset is indicative of a fatal outcome. In conclusion, recovery from Ebo-Z infection is associated with early and well-regulated inflammatory responses, which may be crucial in controlling viral replication and inducing specific immunity. In contrast, defective inflammatory responses and massive monocyte/macrophage activation were associated with fatal outcome.

Erythrocyte binding antigen (EBA-175) of Plasmodium falciparum: improved genotype determination by nested polymerase chain reaction

We have designed primers to the conserved region of the erythrocyte binding antigen (EBA)-175 gene which amplify specifically the two alleles by polymerase chain reaction (PCR) and by nested PCR. This approach provides a specific, sensitive and rapid method for genotype determination in a large number of Plasmodium falciparum field isolates.

Simian immunodeficiency virus from mandrill (Mandrillus sphinx) SIVmnd experimentally infects human and nonhuman primate cells

This study set out to characterize the features of experimental infection by simian immunodeficiency virus in mandrill (SIVmnd) (Mandrillus sphinx), cynomolgus macaque (Macaca fascicularis), rhesus macaque (Macaca mulatta), chimpanzee (Pan troglodytes), African green monkey (Cercopithecus pygerythrus), baboon (Papio cynocephalus) and human cells. Purified cells were exposed to a primary isolate of SIVmnd grown in the infected mandrill peripheral blood mononuclear cells, and viral p27 gag antigen was quantitated by antigen capture ELISA. Human cells have been found to be infected by SIVmnd. SIVmnd infection in cynomolgus macaque, rhesus macaque, baboon, mandrill and human cells were more effective than in vervet and chimpanzee cells. In addition, the lymphocytic cell lines SupT1, CEMx174 and Molt4 clone 8 were consistently infected by SIVmnd, whereas U937, a monocytic cell line, was not.

Early immune responses accompanying human asymptomatic Ebola infections

In a recent study we identified certain asymptomatic individuals infected by Ebola virus (EBOV) who mounted specific IgG and early and strong inflammatory responses. Here, we further characterized the primary immune response to EBOV during the course of asymptomatic infection in humans. Inflammatory responses occurred in temporal association with anti-inflammatory phase composed by soluble antagonist IL-1RA, circulating TNF receptors, IL-10 and cortisol. At the end of the inflammatory process, mRNA expression of T-cell cytokines (IL-2 and IL-4) and activation markers (CD28, CD40L and CTLA4) was up-regulated, strongly suggesting T-cell activation. This T-cell activation was followed by EBOV-specific IgG responses (mainly IgG3 ang IgG1), and by marked and sustained up-regulation of IFN gamma, FasL and perforin mRNA expression, suggesting activation of cytotoxic cells. The terminal down-regulation of these latter markers coincided with the release of the apoptotic marker 41/7 NMP in blood and with the disappearance of viral RNA from PBMC, suggesting that infected cells are eliminated by cytotoxic mechanisms. Finally, RT-PCR analysis of TCR-V beta repertoire usage showed that TCR-V beta 12 mRNA was never expressed during the infection. Taken together, these findings improve our understanding about immune response during human asymptomatic Ebola infection, and throw new light on protection against Ebola virus.

Comparative analysis of natural killer cell activity, lymphoproliferation and lymphocyte surface antigen expression in nonhuman primates housed at the CIRMF Primate Center, Gabon

Six different species of nonhuman primates housed at the CIRMF Primate Center, cynomolgus monkeys (Macaca fascicularis), rhesus monkeys (Macaca mulatta), mandrills (Mandrillus sphinx), vervets (Cercopithecus aethiops pygerythrus), chimpanzees (Pan troglodyte) and baboons (Papio hamadryas), were evaluated for their natural killer cell activity and for the ability of their peripheral blood mononuclear cells to proliferate in response to known mitogens (concanavalin A, phytohemagglutinin and staphylococcal enterotoxin A) and to react with a panel of mouse monoclonal antibodies directed against human leukocyte surface antigens. Basic information on normal immune functions in these primates is important because of their use as experimental animal models for the study of human diseases such as acquired immunodeficiency syndrome (AIDS), hepatitis, loiasis and malaria.

Apoptosis in fatal Ebola infection. Does the virus toll the bell for immune system?

In fatal Ebola virus hemorrhagic fever massive intravascular apoptosis develops rapidly following infection and progressing relentlessly until death. While data suggest that T lymphocytes are mainly deleted by apoptosis in PBMC of human fatal cases, experimental Ebola infection in animal models have shown some evidence of destruction of lymphocytes in spleen and lymph nodes probably involving both T and B cells. Nevertheless, we are able to conclude from the accumulated evidence that early interactions between Ebola virus and the immune system, probably via macrophages, main targets for viral replication, lead to massive destruction of immune cells in fatal cases.

Detection of simian immunodeficiency virus (SIV)-specific T-cell-mediated cytotoxicity in the peripheral blood from infected cynomolgus monkeys

We have previously demonstrated that peptide immunization restimulates the memory CD4 T-cell response, but fails to induce cytotoxic T lymphocyte (CTL) in cynomolgus macaques. To examine the nature of protective immunity to simian immunodeficiency virus (SIV) in this study, freshly isolated peripheral blood mononuclear cells (PBMC) from four infected juvenile cynomolgus macaques and from three uninfected control macaques were assessed for CTL activity monthly for 9 consecutive months, beginning 1 month after detection of infection. Target cells consisted of major histocompatibility (MHC) haploidentical parental PBMC which were stimulated with mitogen and then pulsed with heat-killed SIVcyn. CTL activity was demonstrated in PBMCs from all four infected animals. The effector cells are T cells which mediate cytotoxicity against SIVcyn-pulsed target cells in an MHC-restricted manner. Furthermore, the cytotoxicity is virus specific and predominantly, if not exclusively, mediated by CD8+ T cells; it is also MHC class I restricted. Incubation of target cells with pepstatin A during antigen pulsing prior to the cytotoxic assay inhibited target cell generation, suggesting that viral antigens are processed via an endocytic pathway.

Impairment of natural killer cell activity in Chlamydia trachomatis infected individuals

Natural killer (NK) cell activity is impaired in Chlamydia trachomatis-infected patients. The mechanisms behind the altered NK functions are not clear, but data concerning NK and antibody-dependent cellular cytotoxicity (ADCC) activity have been reported. To investigate whether this impairment is related to a defect at the target cell binding and/or the postbinding level, we evaluated highly purified NK cells obtained from 125 C. trachomatis-infected patients and compared them with 101 normal controls for their ability to kill K-562 and U-937 cell lines using a 51Cr release assay; release tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma); and kill anti-IgM preincubated P-815 cell line (ADCC activity). We found a decrease in the lytic capability of NK cells from C. trachomatis-infected patients against target cell lines; decreased ability to kill bound target cells; and low levels of released TNF-alpha and INF-gamma after incubation with U-937 cells. Taken together, these findings suggest that the impaired NK cell reaction during chlamydial infection is related to defects both at the target and postbinding levels. However, the precise mechanisms remain to be determined. The inability to restore normal NK activity after long-term culture in the presence of high levels of recombinant IL-2 support the hypothesis of an anergic process during chlamydial infection.

[Comparative analysis of 2 diagnostic methods of human loiasis: IgG4 serology and nested PCR]

By evaluating the diagnostic methods developed in our laboratory, the prevalence of loaiosis was estimated among 201 individuals from the province of Haut Ogooué in Gabon using IgG4 serology and nested-PCR. The study showed that the prevalence of loaiosis was higher than that described using standard microscopy. IgG4-based ELISA (Enzyme Linked Immunosorbant Assay) using crude extract of Loa loa microfilariae showed that 80% (35/44) of microfilaraemic individuals (MF') and 56% (88/157) of amicrofilaraemics (AMF) presented antibodies. By contrast, L. loa specific DNA amplified by nested-PCR was detected in all MF and in 68% (106/157) of AMF. Among the 201 samples tested, 95 (47%) gave positive results in both tests. These results indicate that the presence of IgG4 antibodies directed against crude extract of L. loa microfilariae is not linked to the positivity of nested-PCR assay (chi 2 for paired data = 8.78; P < 0.02). We conclude that the PCR assay is more sensitive than the detection of IgG4 antibodies (directed against crude extract of L. loa microfilariae) in detecting loaiosis, and particularly occult loaiosis (infection without circulating microfilariae).

Sequence conservation of repeat 3 region of the gene coding for the 15 kDa polyprotein within human and simian Loa loa

The human and simian strains of Loa loa microfilariae are morphologically identical even though their periodicities vary. When using primate models (Mandrillus sphinx) of human loaisis for vaccination trials, the absence of any ongoing simian L. loa infection must be demonstrated. Nested primers derived from a human strain of L. loa (targeted on the repeat 3 region of the gene encoding the 15 kDa polyprotein; 15r3) amplified at 366 bp sequence from simian L. loa genomic DNA and blood lysates from mandrills infected with simian L. loa. This nested-PCR assay has been tested on 12 amicrofilaremic (AMF) mandrills (without filarial microfilariae) and was positive in four mandrills. The nested-PCR product derived from simian L. loa genomic DNA and from three of four AMF mandrills has been sequenced. No difference was observed between the four sequences, which, in addition, were 99.18% identical to the 15r3 of human L. loa. Therefore, the 15r3 sequence is conserved within human and simian L. loa. These results suggest that the four PCR-positive mandrills without circulating microfilariae had occult simian L. loa infections. The study demonstrates the ability of a nested-PCR assay to identify animals naturally infected with simian L. loa.

Alloreactivity and association of human natural killer cells with the major histocompatibility complex

All NK cells potentially lytic for autologous cells but not expressing self-major histocompatibility complex (MHC)-reactive receptors could be eliminated by a negative selection mechanism during ontogeny. This idea is based on the existence of a NK cell subset expressing a specific inhibitory receptor for allogeneic MHC alleles. As ancestral haplotypes of the MHC appear to define identical MHC haplotypes in unrelated individuals, unrelated individuals having the same ancestral haplotype should also have the same NK-defined allospecificities that have been shown to map to the human MHC. To test this prediction, multiple cell lines from unrelated individuals having the same ancestral haplotypes were tested for the NK-defined allospecificities. It was found that cells having the same ancestral haplotypes do have the same NK-defined specificities. Furthermore, the NK-defined phenotype of cells that possess two different ancestral haplotypes can be predicted from the NK-defined phenotypes of unrelated cells that are homozygous for the ancestral haplotypes concerned. Although the group 1 and 2 NK-defined allospecificities can be explained to some extent by HLA-C alleles, evidence is presented that additional genes may modify the phenotype conferred by HLA-C.

CD4/GP120mac251 interaction induces phospholipase A2 (PLA2) activation in cynomolgus monkey lymphocytes

Cynomolgus monkey are susceptible to infection with select simian immunodeficiency virus (SIV). We investigated the early interactions between SIV envelope glycoproteins (gp120mac251) and macaque lymphocytes. Our results demonstrate that the soluble viral glycoprotein induce a specific phospholipase A2 (PLA2) activation in lymphocytes through CD4. This PLA2 activation, induced after envelope glycoprotein-CD4 interaction, because of its locally destabilizing membrane effect, may have important implications for preparing the lymphocyte membrane for fusion with the viral particle. However, this effect is not sufficient to accomplish fusion. These data indicate that the specific step of fusion may be downstream from PLA2 activation.

Peptide immunization restimulates the memory CD4 T cell response but fails to induce cytotoxic T lymphocytes in cynomolgus monkeys

A potential strategy to induce peptide specific CTL in vivo was investigated. A synthetic vaccine consisting of an SIV-derived, HLA-A2. 1-binding CTL epitope and a tetanus toxin-derived T helper epitope was evaluated for its capacity to induce peptide-specific CTL in monkeys. Thirteen animals were immunized and boosted twice with 150 microg of CTL plus 250 microg of the T helper peptide (p30). Peripheral blood mononuclear cells (PBMC) were regularly analysed for cytotoxic and proliferative responses before, between, and after the immunizations, and the serum was tested for anti-peptide antibodies. No unequivocal induction of SIV peptide-specific CTL in any of the monkeys was observed. However, a wide pattern of mild and transient side reactions were observed, ranging from local redness at the injection site to generalized exanthema, myalgias, arthralgias, and fever. The side-effects were related to the T helper epitope, as they were similar to the side-effects experienced after tetanus immunization, correlated to the magnitude of the p30-specific in vitro proliferative response, and occurred only if p30 was co-injected. No antibody against the SIV-derived peptides nor against p30 was detectable in the serum after repeated immunizations. The data suggest that the CTL peptide, at the concentration used in this study, failed to induce a cytotoxic immune response in vivo, although the T helper peptide seems to be capable of restimulating the specific memory T cells.

Human occult loiasis: field evaluation of a nested polymerase chain reaction assay for the detection of occult infection

A nested polymerase chain reaction (nested PCR) assay, targeted on the repeat 3 region (15r3) of the gene coding for a Loa loa 15 kD polyprotein, was developed to detect L. loa infection. The assay has a sensitivity of 95% and is 100% specific with regard to sympatric filarial parasites: Mansonella perstans, Onchocerca volvulus and Wuchereria bancrofti. In this field study in a mixed filarial (L. loa and M. perstans) endemic region of Gabon, 157 L. loa amicrofilaraemic blood samples (AMF; diagnosed by leucoconcentration followed by standard microscopic examination) from the residents from four villages were screened by the 15r3-nested PCR assay. The assay detected 106 occult infected subjects among the 157 AMF individuals (68%), including 59 of 87 adults (68%) and 47 of 70 children (67%). In each village the prevalence of occult infection was, respectively, 38%, 52%, 79% and 80% for Moyabi, Djoutou, N'djokaye and Okoumbi. The annual transmission potential (ATP) of loiasis has been estimated to be 250 infective larvae (L 3) per man per year for Moyabi and Djoutou, 1800 for N'djokaye and 433000 L3/man/year for Okoumbi. This implies a correlation between occult infection of loiasis and the intensity of transmission. By contrast, the prevalence of L. loa microfilariae was 21% for Okoumbi, 22%, for N'djokaye and 19% for Djoutou and Moyabi. These results show that the prevalence of loiasis in this region of Gabon is higher than previously described by standard microscopic examination and that the application of this assay will be significant in the development of control strategies for loiasis.

HIV and SIV envelope glycoproteins induce phospholipase A2 activation in human and macaque lymphocytes

We investigated the early interactions between HIV-1, HIV-2, and simian immunodeficiency virus (SIV) envelope glycoproteins gp120(IIIB), gp105(ROD), and gp120(mac251), and human and macaque cells of the lymphocytic series. Our results demonstrate that the soluble viral glycoproteins induce a specific phospholipase A2 (PLA2) activation in lymphocytes through CD4. This PLA2 activation was induced after envelope glycoprotein-CD4 interaction and, because of its local membrane-destabilizing effect, may have important implications for preparing the lymphocyte membrane for fusion with the viral particle. However, this effect is not sufficient to accomplish fusion. These data indicate that the specific step of fusion may be downstream from PLA2 activation.

High levels of antibodies to annexins V and VI in patients with rheumatoid arthritis

OBJECTIVE

Glucocorticoids are powerful antiinflammatory agents widely used for the treatment of rheumatoid arthritis (RA). Synthesis and/or secretion of annexin I (A-I) is induced by these steroids. Annexins V and VI are also found extracellularly but are not induced by glucocorticoids. Annexins may be potent antagonists of phospholipase A2 (PLA2). Since autoantibodies to A-I have been reported in patients with RA, we studied the reactivity of sera from patients with RA to A-V and A-VI.

METHODS

Sera from 26 patients with RA were assessed for anti-A-V and anti-A-VI antibodies and compared with sera from 26 sex/age matched healthy subjects. IgG and IgM antibodies were analyzed in an ELISA: A correlation study with disease activity and corticosteroid treatment schedule was performed.

RESULTS

Sera from patients with RA contained significantly higher levels of IgG [anti-A-V and anti-A-VI] autoantibodies than control sera, both being correlated. This rise in antiannexin antibody titers was correlated with the RA activity score, and negatively correlated with the daily dose of corticosteroids.

CONCLUSION

High levels of IgG (anti-A-V and anti-A-VI) antibodies were found in sera from patients with RA. We suggest that antiannexin autoantibodies may play a role in the clinical course of RA by impairing the anti-PLA2 effect of annexins.

Role of 1,2-sn diacylglycerol in airway smooth muscle stimulated by carbachol

Activation of muscarinic receptors in airway smooth muscle leads to breakdown of membrane polyphosphoinositides. In agreement with others, we show here that muscarinic stimulation elicits inositol-1,4,5-triphosphate formation. In addition, we show that carbachol also elicits total diacylglycerol and 1,2-sn diacylglycerol accumulation in a specific and dose-dependent manner (EC50 values: 2.1 x 10(-8) M for 1,2-sn diacylglycerol). The time-course of inositol-1,4,5-triphosphate accumulation is compatible with that of the clonic phase of muscle contraction. Since this derivative can mobilize intracellular Ca2+ stores, it may play a second-messenger role in the initial phase of contraction. The time-course of diacylglycerol accumulation is compatible with the muscarinic-induced tonic phase of smooth-muscle contraction. Carbachol induces similar dose-dependent reductions in isoproterenol-induced muscle relaxation (EC50 values for relaxation concentration-response curves to isoproterenol: 3 x 10(-6) M and 2.1 x 10(-5) M, with carbachol at 10(-7) M and 10(-4) M, respectively), and increases in adenylate cyclase activity (EC50 values for the concentration-response to isoproterenol: 1.2 x 10(-6) M and 1.5 x 10(-5) M, with carbachol at 10(-7) M and 10(-4) M, respectively). Since it is known that carbachol-induced uncoupling of beta 2-adrenergic receptors is proportional to the breakdown of polyphosphoinositides, and that 1,2-sn diacylglycerol is a potent activator of protein kinase C, 1,2-sn diacylglycerol could be mediating the uncoupling of beta 2-adrenergic receptors, via activation of alpha-protein kinase C and subsequent phosphorylation of receptor, and/or cyclase, and/or G proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoxin A4 inhibits phosphoinositide hydrolysis in human neutrophils

Lipoxins (LX) are trihydroxytetraene metabolites derived from arachidonic acid via an interaction between the 5- and 15-lipoxygenases. Preincubation of [3H] myo-inositol labeled PMN with 10-7M and 10-5M LXA4 for 1 minute at 37 degrees C resulted in a concentration dependent inhibition of the generation of [3H] IP3 and [3H] IP in cells subsequently stimulated by increasing doses of LTB4 or FMLP for 1 minute at 37 degrees C. Preincubation of PMN with LXA4 did not inhibit specific binding of [3H] LTB4 to PMN. These results indicate that LXA4 inhibits chemotactic factor-induced phosphoinositide hydrolysis at a post-receptor level.