Effect of IL-12 and soluble IL-4 receptor on the herpesvirus infection in human SCID chimeras whose Th2 cells predominate

Th2 cytokines, commonly detected in burn patients, have been shown as inhibitors for the generation of Th1 cells that are essential for the host's resistance against herpes simplex virus type 1 (HSV-1) infection. In this study, the possibility of immunological treatment through the regulation of Th1/Th2 responses was examined in two kinds of human severe combined immunodeficiency (SCID) chimera models reflecting human immune functions. SCID mice injected with a mixture of PBMC from a healthy donor and Th2 cells experimentally generated from the same healthy PBMC (Th2 SCID chimeras) were more susceptible to HSV-1 infection when compared with SCID mice injected with healthy donor PBMC (healthy SCID chimeras). When Th2 SCID chimeras were individually treated with human IL-12 (hIL-12) or human soluble IL-4 receptor (hsIL-4R), hIFN-gamma was not produced in their sera after antihuman CD3 mAb stimulation. However, hIFN-gamma production in sera of Th2 SCID chimeras treated with the combination therapy of hIL-12 and hsIL-4R was recovered at levels observed in healthy SCID chimeras. When Th2 SCID chimeras infected with HSV-1 were treated with saline, hIL-12, hsIL-4R or a combination of hIL-12 and hsIL-4R, 13%, 13%, 25% or 100% of them survived, respectively. Also, Th1 responses (hIFN-gamma production) were demonstrated in Th2 SCID chimeras that became resistant against HSV-1 infection after the combination treatment. These results suggest that individuals whose Th2 cells predominated may be immunologically controlled by the combination treatment between a Th1 response inducer and a Th2 response inhibitor.     

Lack of Th17 cell generation in patients with severe burn injuries

Immunodeficient patients with severe burn injuries are extremely susceptible to infection with Candida albicans. In addition to Th1 cells, IL-17-producing CD4(+) T cells (Th17 cells) have recently been described as an important effector cell in host anti-Candida resistance. In this study, therefore, we tried to induce Th17 cells in cultures of severely burned patient PBMC by stimulation with the C. albicans Ag (CAg). In the results, the biomarkers for Th17 cells (IL-17 production and intracellular expression of IL-17 and retinoic acid receptor-related orphan receptor γt) were not displayed by burn patient PBMC stimulated with CAg, whereas these biomarkers of Th17 cells were detected in cultures of healthy donor PBMC stimulated with CAg. Burn patient sera were shown to be inhibitory on CAg-stimulated Th17 cell generation in healthy donor PBMC cultures; however, Th17 cells were induced by CAg in healthy donor PBMC cultures supplemented with burn patient sera that were previously treated with anti-IL-10 mAb. Also, the biomarkers of Th17 cells were not induced by CAg in healthy donor PBMC cultures supplemented with rIL-10. IL-10 was detected in serum specimens derived from severely burned patients. These results indicate that Th17 cells are not generated in burn patient PBMC cultures supplemented with CAg. IL-10, produced in response to burn injuries, is shown to be inhibitory on Th17 cell generation. The high susceptibility of severely burned patients to C. albicans infection might be influenced if burn-associated IL-10 production is intervened.     

Induction of protective immune responses against R5 human immunodeficiency virus type 1 (HIV-1) infection in hu-PBL-SCID mice by intrasplenic immunization with HIV-1-pulsed dendritic cells: possible involvement of a novel factor of human CD4(+) T-cell origin

The potential of a dendritic cell (DC)-based vaccine against human immunodeficiency virus type 1 (HIV-1) infection in humans was explored with SCID mice reconstituted with human peripheral blood mononuclear cells (PBMC). HIV-1-negative normal human PBMC were transplanted directly into the spleens of SCID mice (hu-PBL-SCID-spl mice) together with autologous mature DCs pulsed with either inactivated HIV-1 (strain R5 or X4) or ovalbumin (OVA), followed by a booster injection 5 days later with autologous DCs pulsed with the same respective antigens. Five days later, these mice were challenged intraperitoneally with R5 HIV-1(JR-CSF). Analysis of infection at 7 days postinfection showed that the DC-HIV-1-immunized hu-PBL-SCID-spl mice, irrespective of the HIV-1 isolate used for immunization, were protected against HIV-1 infection. In contrast, none of the DC-OVA-immunized mice were protected. Sera from the DC-HIV-1- but not the DC-OVA-immunized mice inhibited the in vitro infection of activated PBMC and macrophages with R5, but not X4, HIV-1. Upon restimulation with HIV-1 in vitro, the human CD4(+) T cells derived from the DC-HIV-1-immunized mice produced a similar R5 HIV-1 suppressor factor. Neutralizing antibodies against human RANTES, MIP-1alpha, MIP-1beta, alpha interferon (IFN-alpha), IFN-beta, IFN-gamma, interleukin-4 (IL-4), IL-10, IL-13, IL-16, MCP-1, MCP-3, tumor necrosis factor alpha (TNF-alpha), or TNF-beta failed to reverse the HIV-1-suppressive activity. These results show that inactivated HIV-1-pulsed autologous DCs can stimulate splenic resident human CD4(+) T cells in hu-PBL-SCID-spl mice to produce a yet-to-be-defined, novel soluble factor(s) with protective properties against R5 HIV-1 infection.     

Pathogenicity of Helicobacter rodentium in A/JCr and SCID mice

Helicobacter rodentium was first recognized as a potential pathogen when it was isolated, along with Helicobacter bilis, from a colony of scid/Trp53 knockout mice with diarrhea. Clinical disease in these mice was more severe than that previously reported in mice infected with H. bilis alone, thus suggesting that H. rodentium contributed to the pathogenesis of enteritis. The purpose of the study reported here was to address two questions: is H. rodentium pathogenic in mice, and when co-infection with a pathogenic helicobacter occurs, does H. rodentium augment disease? To this end, A/JCr and C.B-17/IcrCrl-scidBr mice were inoculated with H. rodentium and/or H. hepaticus. Twelve weeks after inoculation, mice were euthanized. The cecum and liver were evaluated microscopically for evidence of disease. Cecal interferon-inducible protein 10 (IP-10), macrophage inflammatory protein 1alpha (MIP-1alpha), interleukin 10 (IL-10), and interferon gamma (IFN-gamma) mRNA values were measured as an indicator of mucosal immune response. Hepatic lesions were not identified in mice mono-infected with H. rodentium; likewise, cecal lesion scores were not significantly different from those of uninfected controls. With the exception of an increased IL-10 mRNA value in SCID mice, mean immune-related gene expression in H. rodentium mono-infected and uninfected control mice was not significantly different. In contrast, all mice infected with H. hepaticus developed moderate to severe hepatitis, significant increase in cecal lesion scores, and increased immune-related gene expression. The C.B-17/IcrCrl-scidBr mice co-infected with H. hepaticus and H. rodentium had liquid cecal contents and low terminal body weight. Further, compared with mice infected with H. hepaticus alone, co-infection was associated with significant increases of IL-10, MIP-1alpha, and IP-10 mRNA values in C.B-17/IcrCrl-scidBr and IFN-gamma and MIP-1alpha mRNA values in A/JCr mice. These results suggested that H. rodentium alone does not cause hepatitis or enteritis in A/JCr or C.B-17/IcrCrl-scidBr mice; however, co-infection with H. hepaticus and H. rodentium was associated with augmented cecal gene expression and clinical manifestation of disease in immunodeficient mice.     

Contribution of the sympathetic nervous system on the burn-associated impairment of CCL3 production

Previously, we have reported that the susceptibility of burned patients to infectious complications is increased when the production of CC-chemokine ligand 3 (CCL3) is impaired. In this study, the role of the sympathetic nervous system on impaired CCL3 production and antibacterial resistance following burn injuries was investigated. Normal mice were resistant (65% survival) to cecal ligation and puncture (CLP)-induced sepsis, while the same CLP killed 90% of thermally injured mice (TI-mice). However, TI-mice resisted CLP-induced sepsis (60% survival) when they were previously treated with CCL3 or sympathectomized with 6-hydroxydopamine (6-OHDA). Augmentation of host resistance against CLP-induced sepsis by 6-OHDA was abrogated by anti-CCL3 mAb treatment. Norepinephrine (NE) production was increased in circulation of TI-mice, and treatment of TI-mice with 6-OHDA resulted in the inhibition of NE secretion. CCL3 production was impaired in cultures of T cells from TI-mice or normal T cells treated with NE, even when stimulated with anti-CD3 mAb. However, CCL3 was produced by mAb-stimulated T cells from TI-mice previously treated with 6-OHDA. These results indicated that by inhibiting CCL3 production the sympathetic nervous system contributes to the increased susceptibility of TI-mice to sepsis.     

Antibody-mediated coengagement of FcγRIIb and B cell receptor complex suppresses humoral immunity in systemic lupus erythematosus

Engagement of the low-affinity Ab receptor FcγRIIb downregulates B cell activation, and its dysfunction is associated with autoimmunity in mice and humans. We engineered the Fc domain of an anti-human CD19 Ab to bind FcγRIIb with high affinity, promoting the coengagement of FcγRIIb with the BCR complex. This Ab (XmAb5871) stimulated phosphorylation of the ITIM of FcγRIIb and suppressed BCR-induced calcium mobilization, proliferation, and costimulatory molecule expression of human B cells from healthy volunteers and systemic lupus erythematosus (SLE) patients, as well as B cell proliferation induced by LPS, IL-4, or BAFF. XmAb5871 suppressed humoral immunity against tetanus toxoid and reduced serum IgM, IgG, and IgE levels in SCID mice engrafted with SLE or healthy human PBMC. XmAb5871 treatment also increased survival of mice engrafted with PBMC from a unique SLE patient. Unlike anti-CD20 Ab, coengagement of FcγRIIb and BCR complex did not promote B cell depletion in human PBMC cultures or in mice. Thus, amplification of the FcγRIIb inhibitory pathway in activated B cells may represent a novel B cell-targeted immunosuppressive therapeutic approach for SLE and other autoimmune diseases that should avoid the complications associated with B cell depletion.     

Deficiency in early development of the thymus-dependent cells in irradiation chimeras attributable to recipient's environment.

Allogeneic bone marrow chimeras were prepared using reciprocal combinations of AKR and C3H mice. When C3H mice were recipients, the number of thymocytes recoverable from such chimeras (C3H recipient chimeras) was small as compared with that from chimeras for which AKR mice were used as recipients (AKR recipient chimeras) regardless of donor strain. The thymocytes from C3H recipient chimeras showed a profound deficiency in generating proliferative responses to stimulation by anti-CD3 mAb (2C11) or anti-TCR (alpha, beta) mAb (H57-597), even though the expression of CD3 and TCR molecules fell within the same range as that in AKR recipient chimeras. Furthermore, after stimulation with immobilized 2C11, the proportion of IL-2R+ cells in the thymocytes from C3H recipient chimeras was much less than that in AKR recipient chimeras. However, no significant difference in proliferative responses to 2C11 plus PMA, in influx of Ca2+ after stimulation with 2C11 or IL-2 production in response to 2C11 plus PMA or PMA plus A23187 was demonstrated between C3H and AKR recipient chimeras. These findings suggest that the thymocytes from C3H recipient chimeras have a deficiency in the signal transduction system as compared with chimeras for which AKR mice are the recipients. The thymic stromal component involved in this difference in the C3H recipient chimeras is discussed.     

Influence of calcium ions in the flow cytometric analysis of human CD8-positive cells.

BACKGROUND: The CD8 co-receptor is an important marker used to identify various lymphocyte subsets. A significant decrease in CD8alpha staining intensity was observed in the presence of divalent cation chelators. METHODS: Peripheral blood mononuclear cells (PBMC) obtained from healthy volunteers were treated with calcium chelators, stained with different anti-human CD8 mAbs, and analyzed by flow cytometry. RESULTS: Calcium chelators caused a dose-dependent decrease in fluorescence intensity, using specific anti-human CD8alpha mAbs. This phenomenon was not due to CD8 internalization and could be reversed by the addition of calcium ions. In contrast, calcium depletion increased staining intensity with one anti-CD8beta mAb. CONCLUSIONS: Divalent cation chelators are used as cell anti-clumping agents in MACS or FACS applications. Researchers should be aware that such treatment could lead to the almost complete loss of fluorescence with selected anti-human CD8alpha mAbs. Since CD8 staining is used in conjunction with tetramer staining to identify antigen-specific cytotoxic human T cells, the effect of calcium depletion should be taken into account in experimental design.     

Influence of a Small Number of Mature T Cells in Donor Bone Marrow Inocula on Reconstitution of Lymphoid Tissues and Negative Selection of a T Cell Repertoire in the Recipient

Allo-chimerism and clonal elimination of self antigen (Ag) (Ia + Mls-1^a) reactive Vβ6+ T cells were analyzed and compared between allogeneic bone marrow (BM) chimeras reconstituted with BM cells which had been treated with anti-Thy-1 monoclonal antibody (mAb) plus complement (C) (T^– chimeras) and BM chimeras which had been reconstituted with BM cells pretreated with anti-Thy-1 mAb alone (T⁺ chimeras). When lethally irradiated AKR (Mls-1^a) mice were reconstituted with BM cells from B10 or B10 H-2 congenic mice, both T⁺ and T^– chimeras were entirely free of signs of graft-versus-host reaction (GVHR). However, complete replacement of the AKR lymphoid tissues by donor BM cells was accomplished at an early stage in T⁺ chimeras but not in T^– chimeras. On the other hand, clonal elimination of Vβ6⁺ T cells reactive to the recipient Ag (Mls-1^a) was abolished in T⁺ chimeras but successfully induced in T^– chimeras. The Vβ6⁺ T cells not eliminated in T⁺ chimeras showed depressed responses against Mls-1^a antigens. The findings herein demonstrate that T cells which contaminate a BM inoculum survive in recipient mice after treatment with anti-Thy-1 mAb without C in vitro followed by BMT. The surviving T cells have been estimated to represent fewer than 0.5% of the BM cells inoculated. These cells appear to accelerate the full replacement of recipient lymphoid tissues by donor cells. Furthermore, the T cells which survive in the marrow inoculum influence eventually the development of a tolerant state in the T cell repertoire of the donor.     

M2b monocytes predominated in peripheral blood of severely burned patients

Severely burned patients were shown to be carriers of M2 monocytes, and all of the monocytes isolated from peripheral blood of severely burned patients (19 of 19 patients) were demonstrated as M2b monocytes (IL-12(-)IL-10(+)CCL1(+) monocytes). Low levels of M2a (IL-12(-)IL-10(+)CCL17(+) monocytes) and M2c monocytes (IL-12(-)IL-10(+)CXCL13(+) monocytes) were demonstrated in peripheral blood of severely burned patients (M2a, 2 of 19 patients; M2c, 5 of 19 patients). M2b, M2a, and M2c monocytes were not detected in peripheral blood of healthy donors. However, M2b monocytes appeared when healthy donor monocytes were cultured in media supplemented with burn patient serum (15%). CCL2 was detected in sera of all burn patients, and M2b monocytes were not generated from healthy donor monocytes cultured with media containing 15% burn patient sera that were previously treated with anti-CCL2 mAb. In addition, M2b monocytes were generated from healthy donor monocytes in cultures supplemented with rCCL2. These results indicate that M2b monocytes are predominant in peripheral blood of severely burned patients who are carriers of CCL2 that functions to stimulate monocyte conversion from resident monocytes to M2b monocytes.     

CD8+ T cells are a biologically relevant source of macrophage inflammatory protein-1 alpha in vivo

Chemokines are small proteins that direct the migration of leukocytes to inflammatory foci. Many cell types, including macrophages, fibroblasts, endothelial cells, and lymphocytes, produce chemokines in vitro, but biologically relevant sources of chemokines in vivo have not been well characterized. To investigate the pertinent sources of macrophage inflammatory protein-1 alpha (MIP-1 alpha) in vivo, we used MIP-1 alpha-deficient (MIP-1 alpha-/-) mice as donors and as recipients in adoptive transfer experiments after a lethal infection with Listeria monocytogenes (LM). Unexpectedly, we found that the production of MIP-1 alpha by CD8+ T cells was critical in this system, as the cells from MIP-1 alpha-/- mice primed with LM were significantly less effective in protecting naive mice against a lethal infection by LM than were the CD8+ T cells from wild-type (wt) mice. This requirement for donor T cell production of MIP-1 alpha was confirmed by the observation that wt donor T cells do not mediate protection when coadministered with an anti-MIP-1 alpha polyclonal antiserum. Production of MIP-1 alpha by the recipient mice was not required for protection, because wt and MIP-1 alpha-/- recipients were equally well protected by wt T cells. A 2- to 3-fold decrease in the number of transferred lymphocytes was seen in the spleens of mice receiving T cells from MIP-1 alpha-/- mice compared with those receiving wt T cells. In addition, CD8+ T cells from MIP-1 alpha-/- mice had a reduced ability to kill LM-infected target cells in vitro. These findings demonstrate that T cell production of MIP-1 alpha is required for clearance of an intracellular pathogen in vivo.     

The chemokine macrophage-inflammatory protein-1 alpha and its receptor CCR1 control pulmonary inflammation and antiviral host defense in paramyxovirus infection

In this work, we explore the responses of specific gene-deleted mice to infection with the paramyxovirus pneumonia virus of mice (PVM). We have shown previously that infection of wild type mice with PVM results in pulmonary neutrophilia and eosinophilia accompanied by local production of macrophage-inflammatory protein-1 alpha (MIP-1 alpha). Here we examine the role of MIP-1 alpha in the pathogenesis of this disease using mice deficient in MIP-1 alpha or its receptor, CCR1. The inflammatory response to PVM in MIP-1 alpha-deficient mice was minimal, with approximately 10-60 neutrophils/ml and no eosinophils detected in bronchoalveolar lavage fluid. Higher levels of infectious virus were recovered from lung tissue excised from MIP-1 alpha-deficient than from fully competent mice, suggesting that the inflammatory response limits the rate of virus replication in vivo. PVM infection of CCR1-deficient mice was also associated with attenuated inflammation, with enhanced recovery of infectious virus, and with accelerated mortality. These results suggest that the MIP-1 alpha/CCR1-mediated acute inflammatory response protects mice by delaying the lethal sequelae of infection.     

Tumour necrosis factor alpha production by polymorphonuclear neutrophils treated with mouse anti-human CD19 monoclonal antibody

Polymorphonuclear neutrophils (PMNs) play pivotal roles as phagocytic cells in immune defence against bacteria and parasites, exerting their effects by production of reactive oxygen species, several cytokines, chemokines and by phagocytotic reaction. In our investigation of properties of activated PMNs, we discovered that one of the two kinds of mouse anti-human CD19 monoclonal antibodies (mAbs) clone SJ25-C1, weakly binds to freshly prepared PMNs. Moreover, the treatment of freshly prepared PMNs with anti-CD19 mAb (clone SJ25-C1) at 37 degrees C for 6 h induces the production and the secretion of tumour necrosis factor alpha (TNF alpha) by PMNs in vitro which was detectable in culture supernatants by bioassay using mouse cell line L929 cells. The concentration of TNF alpha secreted into the culture supernatant of PMNs cultured in the presence of anti-CD19 mAb (clone SJ25-C1) was higher than those of PMNs treated at 37 degrees C for 6 h with various PMN activators, such as anti-CD24 mAb, granulocytes-macrophage colony stimulation factor (GM-CSF) or interferon gamma (IFN gamma). In contrast, another clone of anti-CD19 mAb, HD37, did not bind to freshly prepared PMNs and failed to produce TNF alpha. To confirm that anti-CD19 mAb (clone SJ25-C1)-treated PMNs definitely produce TNF alpha, we measured the levels of intracellular expression of TNF alpha in PMNs permeabilized by saponin. These cells were treated with fluorescence-conjugated mouse anti-human TNF alpha mAb for detection of intracellular TNF alpha expression. Consequently, large amounts of intracellular TNF alpha were detected in PMNs treated with anti-CD19 mAb (clone SJ25-C1) but not in those treated with anti-CD19 mAb (clone HD37).     

The role of macrophage inflammatory protein-1 alpha/CCL3 in regulation of T cell-mediated immunity to Cryptococcus neoformans infection

Macrophage inflammatory protein-1alpha (MIP-1alpha/CCL3) is a CC chemokine required for optimal recruitment of leukocytes in response to cryptococcal Ags. MIP-1alpha is expressed in the lungs by day 6 post Cryptococcus neoformans infection and could play a role in the development of cell-mediated immunity. To address this possibility, wild-type (MIP-1alpha(+/+)) mice and MIP-1alpha knockout (MIP-1alpha(-/-)) mice were infected intratracheally with a highly virulent strain of C. neoformans (145A). MIP-1alpha message was detected in the lungs on days 3, 7, and 14 in MIP-1alpha(+/+) mice, but it was undetectable in MIP-1alpha(-/-) mice. On day 16, MIP-1alpha(-/-) mice had a 7-fold increase in C. neoformans burden in the lungs, but no decrease in pulmonary leukocyte recruitment. MIP-1alpha(+/+) and MIP-1alpha(-/-) mice had similar numbers of recruited lymphocytes and monocytes/macrophages. Notably, MIP-1alpha(-/-) mice had a significantly greater number of eosinophils. MIP-1alpha(-/-) mice had extremely high levels of serum IgE. This switch of immune response to a T(2) phenotype was associated with enhanced IL-4 and IL-13 expression in the lungs of MIP-1alpha(-/-) mice compared with MIP-1alpha (+/+) mice. Progression of pulmonary cryptococcosis in the presence of nonprotective T(2) immunity resulted in profound lung damage in MIP-1alpha(-/-) mice (eosinophilic crystal deposition, destruction of lung parenchyma, and pulmonary hemorrhage). Twelve-week survival was dramatically decreased in MIP-1alpha(-/-) mice. These studies, together with our previous studies, demonstrate that MIP-1alpha plays a role in both the afferent (T(1)/T(2) development) and efferent (T(1)-mediated leukocyte recruitment) phases of cell-mediated immunity to C. neoformans.     

The importance of IL-1 beta and TNF-alpha,and the noninvolvement of IL-6, in the development of monoclonal antibody-induced arthritis

Injection of anti-type II collagen Ab and LPS induces arthritis in mice. The levels of IL-1 beta, IL-6, and chemokines (macrophage inflammatory protein (MIP)-1 alpha, MIP-2, and monocyte chemoattractant protein-1) in the hind paws increased with the onset of arthritis and correlated highly with arthritis scores. The level of TNF-alpha was also elevated, but only transiently. Quantitative real-time PCR analysis revealed increases in cytokine and chemokine mRNA. To elucidate the contribution of inflammatory cytokines and chemokines in arthritis development more directly, recombinant proteins, neutralizing Abs, and knockout mice were used. The injection of rIL-1 beta or TNF-alpha, but not IL-6 or chemokines, induced arthritis when mice were i.v. preinjected with anti-type II collagen Ab. However, a single injection of recombinant cytokines or chemokines into the hind paws did not induce swelling. Arthritis development was inhibited by neutralizing Ab against IL-1 beta, TNF-alpha, or MIP-1 alpha. In contrast, the inhibitory effect by anti-MIP-2 Ab was partial and, surprisingly, Abs to IL-6 and monocyte chemoattractant protein-1 showed no inhibitory effect. Furthermore, arthritis development in IL-1R(-/-) mice and TNFR(-/-) mice was not observed at all, but severe arthritis was developed in IL-6(-/-) mice. These results suggest that IL-1 beta and TNF-alpha play more crucial roles than IL-6 or chemokines in this model. Because arthritis was also developed in SCID mice, the development of arthritis in the Ab-induced mice model is due to a mechanism that does not involve T or B cells.     

Analysis of cell-free human alpha1 integrin with a monoclonal antibody to the I-domain: detection in ocular fluid and function as an adhesion substrate

The alpha1 beta1 integrin, an inserted (1) domain containing collagen receptor, is expressed in the cell surface membrane of normal and malignant cells, and may play a role in their migration through tissues or in metastatic spread. Here we report that a functional anti-human alpha1beta1 integrin monoclonal antibody (mAb) (1B3.1) directly and specifically binds plastic bound recombinant human alpha1 I-domain protein containing the collagen binding site. Detection was diminished by acidification of the I-domain protein but was enhanced by increasing concentrations of Mg2+ cation. Furthermore, we detected binding of the mAb to proteins from the ocular fluids of 6 patients, with the highest concentration, corresponding to 22.1 ng/ml of I-domain, found in a sample from the eye of a patient with metastatic lung adenocarcinoma. Interestingly, we found that both SKNSH neuroblastoma cells and virally transformed human T cells adhered specifically to plastic wells coated with either immobilized collagen IV or alpha1 I-domain. MAb I B3.1 inhibited adhesion to collagen IV but not to immobilized I-domain. These results suggest a novel function for cell free alpha1 I-domain as a substrate for cellular adhesion, which may have relevance in tumor spread in vivo.     

Infectious Cellular Load in Human Immunodeficiency Virus Type 1 (HIV-1)-Infected Individuals and Susceptibility of Peripheral Blood Mononuclear Cells from Their Exposed Partners to Non-Syncytium-Inducing HIV-1 as Major Determinants for HIV-1 Transmission in Homosexual Couples

To study risk factors for homosexual transmission of human immunodeficiency virus type 1 (HIV-1), we compared 10 monogamous homosexual couples between whom transmission of HIV-1 had occurred with 10 monogamous homosexual couples between whom HIV-1 transmission had not occurred despite high-risk sexual behavior. In the group of individuals who did not transmit virus, peripheral cellular infectious load was lower and the CD4⁺ T-cell counts were higher than in the group of transmitters. HIV-1 RNA levels in serum did not differ between transmitters and nontransmitters. Compared with peripheral blood mononuclear cells (PBMC) from normal healthy blood donors, 8 of 10 nonrecipients and only 3 of 8 recipients had PBMC with reduced susceptibility to in vitro infection with non-syncytium-inducing (NSI) HIV-1 variants isolated from either their respective partners or an unrelated individual. No difference in susceptibility was observed for infection with a syncytium-inducing variant. Among the individuals who had PBMC with reduced susceptibility, five nonrecipients and one recipient had PBMC that were equally or even less susceptible to NSI variants than PBMC that had low susceptibility and that were derived from healthy blood donors that were heterozygous for a 32-bp deletion in the CCR5 gene (CCR5 Δ32). Three of these individuals (all nonrecipients) had a CCR5 Δ32 heterozygous genotype themselves, confirming an association between low susceptibility to NSI variants and CCR5 Δ32 heterozygosity. All three recipients with less susceptible PBMC had partners with a high infectious cellular load; inversely, both nonrecipients with normally susceptible PBMC had partners with a very low infectious cellular load. These results suggest that a combination of susceptibility of target cells and inoculum size upon homosexual exposure largely determines whether HIV-1 infection is established.     

Essential role for the p40 subunit of interleukin-12 in neutrophil-mediated early host defense against pulmonary infection with Streptococcus pneumoniae: involvement of interferon-gamma

Interleukin (IL)-12 is a critical cytokine in the T helper (Th)1 response and host defense against intracellular microorganisms, while its role in host resistance to extracellular bacteria remains elusive. In the present study, we elucidated the role of IL-12 in the early-phase host defense against acute pulmonary infection with Streptococcus pneumoniae, a typical extracellular bacterium, using IL-12p40 gene-disrupted (IL-12p40KO) mice. IL-12p40KO mice were highly susceptible to S. pneumoniae infection, as indicated by the shortened survival time, which was completely restored by the replacement therapy with recombinant (r) IL-12, and increased bacterial counts in the lung. In these mice, recruitment of neutrophils in the lung was significantly attenuated when compared to that in wild-type (WT) mice, which correlated well with the reduced production of macrophage inflammatory protein (MIP-2) and tumor necrosis factor (TNF)-alpha in the infected tissues at the early phase of infection. In vitro synthesis of both cytokines by S. pneumoniae-stimulated lung leukocytes was significantly lower in IL-12p40KO mice than in WT mice, and addition of rIL-12 or interferon (IFN)-gamma restored the reduced production of MIP-2 and TNF-alpha in IL-12p40KO mice. Neutralizing anti-IFN-gamma monoclonal antibody (mAb) significantly decreased the effect of rIL-12. Anti-IFN-gamma mAb shortened the survival time of infected mice and reduced the recruitment of neutrophils and production of MIP-2 and TNF-alpha in the lungs. Our results indicated that IL-12p40 plays a critical role in the early-phase host defense against S. pneumoniae infection by promoting the recruitment of neutrophils to the infected tissues.