Search PubMed⌕ Search

Biomedical subjects

G M Shearer

Publications and source records attributed to G M Shearer.

At least 19 recordsLinked to original sources
PubMed2000

Semi-allogeneic cell hybrids stimulate HIV-1 envelope-specific cytotoxic T lymphocytes.

OBJECTIVE: The present study was designed to determine whether the HLA allogeneic T helper response stimulated by semi-allogeneic cell lines could be used as an in vitro model of immune-based therapy to stimulate HIV-specific cytotoxic T lymphocytes. DESIGN AND METHODS: Semi-allogeneic cell hybrids were obtained by the fusion of peripheral blood mononuclear cells from HIV-infected patients with the allogeneic beta2-microglobulin-deficient FO1-12 melanoma cell line. These hybrids were used as antigen presenting cells for HIV envelope peptide (env)-specific cytotoxic assays. RESULTS: The hybrid cell lines express HLA class I and II antigens from both parental cells, as well as the CD86 costimulatory molecule. HIV-specific cytotoxic T lymphocyte activity was obtained when patients' peripheral blood mononuclear cells were costimulated with env peptides plus semi-allogeneic hybrids, in contrast with stimulation with either env or hybrid cells alone. Thus, the semi-allogeneic hybrids enhanced HIV-specific killing of target cells. CONCLUSIONS: Irradiated, semi-allogeneic cell hybrids engineered for individual AIDS patients provide efficient and simultaneous co-recognition of HLA allogeneic determinants and viral antigenic determinants presented by self-HLA molecules on the same antigen presenting cells and results in the generation of enhanced HIV-specific cytotoxic T lymphocyte activity.

HIV Envelope Protein gp120↗
PubMed2000

Influence of human immunodeficiency virus-infected maternal environment on development of infant interleukin-12 production.

Monocyte-derived cytokine production by cord blood mononuclear cells (CBMC) from infants born to human immunodeficiency virus (HIV)-positive and -negative women was measured to determine whether monocyte dysfunction could contribute to the accelerated HIV disease of pediatric patients. Production of interleukin (IL)-12, but not that of tumor necrosis factor-alpha and IL-10, was reduced, compared with adult peripheral blood mononuclear cells (PBMC). This deficiency was more pronounced in infants of HIV-positive women, whose IL-12 production was also deficient. CBMC IL-12 levels were increased by interferon-gamma and CD40 ligand but remained deficient, compared with PBMC. IL-12 production was undetectable in 7 of 8 HIV-positive infants, in contrast to 21 of 26 uninfected infants. Uninfected infants of infected women exhibited an intermediate profile. These findings suggest that the maternal environment and/or exposure in utero to HIV products influence the newborn's immune response and that the differences between infants born to HIV-positive and -negative women may persist.

Adult↗
PubMed2000

Effects of total pathogen burden on coronary artery disease risk and C-reactive protein levels.

Infection and inflammation have been suggested to play roles in coronary artery disease (CAD). We hypothesized that: (1) CAD risk is associated with the aggregate number of pathogens (pathogen burden), and (2) increased pathogen burden is associated with elevated levels of C-reactive protein (CRP), a marker of inflammation. We evaluated 233 patients for CAD. Blood samples from each patient were tested for immunoglobulin-G (IgG) antibodies to cytomegalovirus (CMV), Chlamydia pneumoniae, hepatitis A virus (HAV), herpes simplex virus type 1 (HSV-1) and HSV type 2 (HSV-2), and for the CRP levels. Of the 233 study subjects, 68% had evidence of CAD by coronary angiography. Although the prevalence of seropositivity for each pathogen tended to be higher in the patients with CAD than those without, only the association between CAD and seropositivity to HAV was significant in multivariate analysis. Over 75% of study subjects had been exposed to > or =3 of the 5 pathogens tested, and analysis determined that increasing pathogen burden was significantly associated with increasing CAD risk, even after adjustment for traditional CAD risk factors. The prevalence of CAD was 48%, 69%, and 85% in individuals with antibodies to < or =2 pathogens, to 3 or 4 pathogens, and to 5 pathogens, respectively. A similar association between increasing pathogen burden and CRP levels was also found. The pathogen burden remained a significant predictor of CRP levels after multivariate analysis. Our data suggest that infection does play a role in the genesis of atherosclerosis. However, the risk posed by infection is related to the pathogen burden that may contribute to CAD through inflammatory responses.

Adult↗
PubMed2000

Beta-chemokines inhibit activation-induced death of lymphocytes from HIV-infected individuals.

The present study investigates the role of the HIV-suppressive beta-chemokines macrophage inflammatory protein (MIP)-1alpha, MIP-1 and RANTES in activation-induced cell death (AICD). A pool of these beta-chemokines reduced anti-CD3-induced apoptosis of T cell blasts from healthy blood donors in a dose-dependent manner. Although the pooled beta-chemokines were more effective, the inhibitory effect could also be mediated by each of the individual chemokines and was blocked by neutralizing anti-chemokine antibodies. The beta-chemokines also inhibited pokeweed mitogen/staphylococcal enterotoxin B-induced T lymphocyte apoptosis in 33/49 HIV-infected (HIV+) individuals. This anti-apoptotic effect was not correlated with the patients' CD4 T cell counts. beta-chemokines did not lead to altered secretion of IL-2, IL-4, IFN-gamma or IL-10 in response to activation stimuli in either normal T cell blasts or peripheral blood mononuclear cells from HIV+ individuals. Co-incubation with beta-chemokines did not inhibit anti-CD3-induced expression of cell surface Fas ligand, nor did it alter levels of the death receptor Fas or Bcl-2 in T cell blasts, suggesting that the beta-chemokines are blocking AICD downstream of Fas. These observations indicate that beta-chemokines may play a novel role as modulators of AICD, in addition to their known role as chemoattractants and inhibitors of HIV replication.

Antigens, CD↗
PubMed2000

Alloantigenic stimulation bypasses CD28-B7 costimulatory blockade by an interleukin-2-dependent mechanism.

Allogeneic leukocytes have been used as biological adjuvants for T cell-specific responses to tumor and recall antigens, but the mechanisms underlying this effect have not been fully understood. The present study investigates whether alloantigen stimulation of human T cells would bypass an in vitro T cell costimulatory dysfunction induced by CTLA4Ig blockage of CD28-B7 interaction. Here, we demonstrate that costimulation with intact allogeneic leukocytes plus viral antigen circumvented the inhibition of this costimulatory pathway via interleukin-2 (IL-2) production, resulting in the generation of influenza-specific cytotoxic T lymphocytes (CTL). The alloantigen-induced help for influenza-specific CTL generation did not require cell-to-cell contact between responding and allogeneic stimulator cells. These results suggest that alloantigens can be used to bypass defects in the CD28-B7 costimulatory pathway and, therefore, may contribute to understanding the mechanisms of alloantigen-induced restoration of T cell-mediated immunity.

Abatacept↗
PubMed2000

Immune-based approaches for control of HIV infection and viral-induced immunopathogenesis.

Due to the limited efficacy of the current antiretroviral drug regimens in completely eradicating HIV and reconstituting the immune system, AIDS research is turning toward immune-based therapy to complement highly active antiretroviral therapy. Here we review potential mechanisms of protective cellular immunity and current HIV-specific immune-based strategies and discuss the rationale for novel hypothetical immunologic approaches for modulation of host antiviral immunity. One of the mechanisms by which the immune system exerts antiviral effects is via leukocyte generation of anti-HIV factors. Recent observations in this area of research suggest that non-HIV antigens can stimulate the in vitro production of anti-HIV activity by leukocytes from healthy uninfected individuals and HIV-infected patients. These findings may provide insights for the design of novel therapeutic or prophylactic approaches, which might contribute to modulating immune system control of HIV infection.

Antiretroviral Therapy, Highly Active↗
PubMed2000

Effect of aging on cytokine production in normal and experimental systemic lupus erythematosus-afflicted mice.

Aging mice of strains susceptible to the induction of experimental systemic lupus erythematosus (SLE) develop a milder disease than young animals. To find out whether the decrease in susceptibility to disease is due to age-associated changes in cytokine profile, we first examined the secretion of cytokines by healthy mice aged 2-15 months. A gradual age-related decline in the levels of interleukin (IL)-2 and interferon (IFN) gamma, and an increase in IL-4, IL-10, IL-1, and tumor necrosis factor (TNF) alpha were observed. Experimental SLE was induced in 2- and 10-month-old mice by immunization with the monoclonal anti-DNA antibody bearing the 16/6 Id. Early increased production of pro-inflammatory cytokines (TNFalpha and IL-1), followed by a peak of the Th1-type cytokines (IL-2, IFNgamma) were observed in young mice. The Th2-type cytokines (IL-4, IL-10) peaked later. In contrast, only a mild increase in all of the above cytokines was determined in 10-month immunized mice. It thus appears that the decline in susceptibility to SLE induction in older mice may be related to changes in the capacity to produce cytokines.

Aging↗
PubMed2000

Inhibition of human immunodeficiency virus type 1 replication prior to reverse transcription by influenza virus stimulation.

It is now recognized that, in addition to drug-mediated therapies against human immunodeficiency virus type 1 (HIV-1), the immune system can exert antiviral effects via CD8(+) T-cell-generated anti-HIV factors. This study demonstrates that (i) supernatants from peripheral blood mononuclear cells (PBMC) stimulated with influenza A virus inhibit replication of CCR5- and CXCR4-tropic HIV-1 isolates prior to reverse transcription; (ii) the HIV-suppressive supernatants can be generated by CD4- or CD8-depleted PBMC; (iii) this anti-HIV activity is partially due to alpha interferon (IFN-alpha), but not to IFN-gamma, IFN-beta, the beta-chemokines MIP-1alpha, MIP-1beta, and RANTES, or interleukin-16; (iv) the anti-HIV activity is generated equally well by PBMC cultured with either infectious or UV-inactivated influenza A virus; and (v) the antiviral activity can be generated by influenza A-stimulated PBMC from HIV-infected individuals. These findings represent a novel mechanism for inhibition of HIV-1 replication that differs from the previously described CD8 anti-HIV factors (MIP-1alpha, MIP-1beta, RANTES, and CD8 antiviral factor).

Antibodies↗
PubMed1999

HIV-specific immunity following immunization with HIV synthetic envelope peptides in asymptomatic HIV-infected patients.

OBJECTIVE: A phase I trial was conducted to evaluate the safety and immunogenicity of an HIV synthetic peptide vaccine in HIV-seropositive individuals. The immunogens used in this study were PCLUS 3-18MN and PCLUS 6.1-18MN envelope peptides. METHODS: Eight HIV-infected patients received six subcutaneous injections of 160 microg PCLUS 3-18MN in Montanide ISA 51 and were followed longitudinally for a year after the first immunization. Peripheral blood mononuclear cells (PBMC) were tested for peptide-specific T helper and cytotoxic T cell (CTL) responses, HIV-1MN neutralizing antibodies and antibodies against HIV PCLUS 3 and P18 MN peptides. RESULTS: PCLUS 3-1 8MN-specific T helper responses were significantly increased at 36 weeks (P < 0.05, after adjustment for multiple comparisons) following initial immunization with PCLUS 3-18MN. A P18MN-specific CTL response, not present prior to vaccination, was observed after immunization in one patient. Serum HIV-1 MN-neutralizing antibody titers increased in each of the three patients who had low titers prior to immunization. Plasma HIV RNA levels and CD4 cell counts did not change appreciably during the study period. CONCLUSIONS: This trial demonstrates that both peptides can be safely administered to HIV-infected individuals and that PCLUS 3-18MN induces increases in HIV peptide-specific immune responses.

AIDS Vaccines↗
PubMed1999

Infection of HIV-1 transgenic mice with Mycobacterium avium induces the expression of infectious virus selectively from a Mac-1-positive host cell population.

Infection of HIV-1-transgenic mice with Mycobacterium avium, a common opportunistic pathogen in AIDS patients, was shown to result in increased tissue expression of viral specific transcripts. Moreover, by coculturing splenocytes from the transgenic animals with human T cells it was possible to demonstrate that the elevation in HIV-1 mRNA triggered by M. avium infection reflects increased production of infectious virions. Viral immune activation was also shown to correlate with a marked elevation of p24 in supernatants of ex vivo-cultured tissues and, more importantly, in systemic increases in the HIV-1 protein in plasma. Interestingly, these tissue and systemic p24 responses were found to be differentially regulated. Thus, while in vitro p24 production by cultured splenocytes increased concurrently with bacterial loads during the first 6 wk of infection, levels of the Ag in plasma actually decreased. In situ localization experiments together with FACS analysis of HIV-1-expressing splenocytes indicated that virus production is restricted largely to cells of the monocyte/macrophage lineage. Indeed, in vitro p24 expression by cells from noninfected transgenic mice was up-regulated by polyclonal stimulation of macrophages but not T cells. Together these results underscore the importance of the macrophage reservoir in persistent virus expression and establish a convenient and relevant animal model for studying the factors responsible for immune activation of HIV-1 induced by mycobacterial as well as other common coinfections encountered by AIDS patients.

Animals↗
PubMed1999

Normal immune function of monocyte-derived dendritic cells from HIV-infected individuals: implications for immunotherapy.

Dendritic cells (DC) are the most potent cells involved in the generation of primary and secondary immune responses. To assess the feasibility of using autologous DC as immunotherapy for HIV disease, we analyzed a variety of immune parameters using DC isolated from HIV-infected (HIV+) individuals, as well as DC obtained from HIV-uninfected (HIV-) individuals infected in vitro with HIV. After stimulation with recombinant CD40 ligand (CD40LT), cytokine and beta-chemokine production were similar by DC from HIV- donors infected in vitro with the CCR5-using HIV Ba-L strain (n = 8) compared with uninfected DC from the same donors. Production of beta-chemokines, but not of cytokines, was increased by a CXCR4-using IIIB strain-infected DC (n = 7). Stimulation of HIV-infected DC with CD40LT decreased infection in Ba-L-infected DC, but had no effect on IIIB-infected DC. Consistent with this finding, CD40LT down-regulated CCR5 and up-regulated CXCR4 expression on DC. Monocyte-derived DC were also propagated from 15 HIV+ and 13 HIV- donors. They exhibited similar expression of costimulatory molecules and produced similar amounts of IL-12, IL-10, and beta-chemokines, following stimulation. By contrast, stimulated PBMC from HIV+ patients exhibited decreased IL-12 and increased IL-10 production. In summary, phenotype, cytokine secretion, and beta-chemokine production by DC from HIV+ individuals were normal. These cells may prove useful in boosting cellular immune responses in HIV+ individuals.

Adoptive Transfer↗
PubMed1999

Incorporation of zidovudine into leukocyte DNA from HIV-1-positive adults and pregnant women, and cord blood from infants exposed in utero.

OBJECTIVE: The nucleoside analog 3'-azido-3'-deoxythymidine (ZDV) has widespread clinical use but also is carcinogenic in newborn mice exposed to the drug in utero and becomes incorporated into newborn mouse DNA. This pilot study was designed to determine ZDV incorporation into human blood cell DNA from adults and newborn infants. DESIGN: In this prospective cohort study, peripheral blood mononuclear cells (PBMC) were obtained from 28 non-pregnant adults and 12 pregnant women given ZDV therapy, six non-pregnant adults with no exposure to ZDV, and six non-pregnant adults who last received ZDV > or = 6 months previously. In addition, cord blood leukocytes were obtained from 22 infants of HIV-1-positive, ZDV-exposed women and from 12 infants unexposed to ZDV. There were 11 mother-infant pairs involving HIV-1 -positive women. METHODS: DNA was extracted from PBMC obtained from non-pregnant HIV-1-positive adults taking ZDV, pregnant HIV-1-positive women given ZDV during pregnancy, and from adults not taking ZDV. Cord blood leukocytes were examined from infants exposed to ZDV in utero and from unexposed controls. DNA samples were assayed for ZDV incorporation by anti-ZDV radioimmunoassay (RIA). RESULTS: The majority (76%) of samples from ZDV-exposed individuals, pregnant women (8 of 12), non-pregnant adults (24 of 28), or infants at delivery (15 of 22), had detectable ZDV-DNA levels. The range of positive values for ZDV-treated adults and infants was 25-544 and 22-452 molecules ZDV/10(6) nucleotides, respectively. Analysis of 11 mother-infant pairs showed variable ZDV-DNA incorporation in both, with no correlation by pair or by duration of drug treatment during pregnancy. Two of the 24 samples from individuals designated as controls were positive by anti-ZDV RIA. The 20-fold range for ZDV-DNA values in both adults and infants suggested large interindividual differences in ZDV phosphorylation. CONCLUSIONS: Incorporation of ZDV into DNA was detected in most of the samples from ZDV-exposed adults and infants. Therefore, the biologic significance of ZDV-DNA damage and potential subsequent events, such as mutagenicity, should be

Adult↗
PubMed1999

Human glioma-induced immunosuppression involves soluble factor(s) that alters monocyte cytokine profile and surface markers.

Patients with gliomas exhibit deficient in vitro and in vivo T cell immune activity, and human glioblastoma culture supernatants (GCS) inhibit in vitro T lymphocyte responses. Because APC are essential for initiating and regulating T cell responses, we investigated whether GCS would affect cytokines produced by monocytes and T cells from healthy donors of PBMC. Incubation of PBMC with GCS decreased production of IL-12, IFN-gamma, and TNF-alpha, and increased production of IL-6 and IL-10. The GCS-induced changes in IL-12 and IL-10 occurred in monocytes, and involved changes in IL-12 p40 and IL-10 mRNA expression. Incubation with GCS also resulted in reduced expression of MHC class II and of CD80/86 costimulatory molecules on monocytes. The immunosuppressive effects were not the result of IL-6 or TGF-beta1 that was detected in GCS. However, it was due to a factor(s) that is resistant to pH extremes, differentially susceptible to temperature, susceptible to trypsin, and has a minimum molecular mass of 40 kDa. Our findings show that glioblastoma-generated factors that are known to suppress T cell responses alter the cytokine profiles of monocytic APC that, in turn, inhibit T cell function. This model indicates that monocytes can serve as an intermediate between tumor-generated immune-suppressive factors and the T cell responses that are suppressed in gliomas.

Antibodies, Monoclonal↗
PubMed1999

Human herpesvirus 8 cellular immune responses in homosexual men.

Little is known about cellular immunity to human herpesvirus 8 (HHV-8), the virus associated with Kaposi's sarcoma (KS). T cell proliferative responses to purified HHV-8 were measured in homosexual men, a group with elevated HHV-8 seroprevalence and high risk of KS. None of 20 blood donor controls had T cell responses to HHV-8. Among human immunodeficiency virus (HIV)-negative homosexual men, 8 (42%) of 19 HHV-8 seropositive men responded as did 4 (16%) of 25 HHV-8 seronegative men. Among HIV-positive homosexual men, however, none of 21 HHV-8 seropositives had T cell responses to HHV-8, even though most responded to common recall antigens, and 10 had >/=400 CD4 cells/mm3. The results suggest that HHV-8 T cell proliferative responses are common in HIV-negative homosexual men and that HIV infection may be associated with diminished HHV-8 cellular immunity, possibly before there is substantial depletion of CD4 cells. If correct, this could explain why KS occurs relatively early in HIV infection/AIDS.

Antibodies, Viral↗
PubMed1999

Effect of zidovudine postexposure prophylaxis on the development of HIV-specific cytotoxic T-lymphocyte responses in HIV-exposed healthcare workers.

We evaluated the effects of zidovudine postexposure prophylaxis (PEP) on the development of human immunodeficiency virus (HIV) envelope-specific cytotoxic T-lymphocyte responses in 20 healthcare workers with occupational exposures to HIV. Seven healthcare workers were treated with zidovudine PEP. Only 1 of 7 treated, versus 6 of 13 not treated, developed an HIV envelope-specific cytotoxic T-lymphocyte response. These data suggest that zidovudine abrogated HIV-specific cytotoxic T-lymphocyte responses. HIV-specific cytotoxic T-lymphocyte responses may be useful as a surrogate marker of HIV replication in the evaluation of new regimens for PEP of occupational HIV exposures.

Anti-HIV Agents↗