Predictive value of CD19 measurements for bacterial infections in children infected with human immunodeficiency virus

We investigated the predictive value of CD19 cell percentages (CD19%) for times to bacterial infections, using data from six pediatric AIDS Clinical Trials Group protocols and adjusting for other potentially prognostic variables, such as CD4%, CD8%, immunoglobulin (IgA) level, lymphocyte count, prior infections, prior zidovudine treatment, and age. In addition, we explored the combined effects of CD19% and IgG level in predicting time to infection. We found that a low CD19% is associated with a nonsignificant 1.2-fold increase in hazard of bacterial infection (95% confidence interval: 0.97, 1.49). In contrast, a high IgG level is associated with a nonsignificant 0.87-fold decrease in hazard of infection (95% confidence interval: 0.68, 1.12). CD4% was more prognostic of time to bacterial infection than CD19% or IgG level. Low CD19% and high IgG levels together lead to a significant (P < 0. 01) 0.50-fold decrease in hazard (95% confidence interval: 0.35, 0. 73) relative to low CD19% and low IgG levels. Similarly, in a model involving assay result changes (from baseline to 6 months) as well as baseline values, the effect of CD19% by itself is reversed from its effect in conjunction with IgG. In this model, CD19% that are increasing and high are associated with decreases in hazard of infection (P < 0.01), while increasing CD19% and increasing IgG levels are associated with significant (at the P = 0.01 level) fourfold increases in hazard of infection relative to stable CD19% and decreasing, stable, or increasing IgG levels. Our data suggest that CD19%, in conjunction with IgG level, provides a useful prognostic tool for bacterial infections. It is highly likely that T-helper function impacts on B-cell function; thus, inclusion of CD4% in such analyses may greatly enhance the assessment of risk for bacterial infection.

Receptor-mediated maternofetal transfer of immunoglobulins. Inhibition of transport of anti-HIV-1 immunoglobulin by generic immunoglobulins in the in vitro perfused placenta

OBJECTIVES

The passage of immunoglobulin G (IgG) across the placenta is thought to involve Fc' receptors on the syncytiotrophoblast. To confirm the receptor dependency of this process we have studied the changes in the tissue content and transfer kinetics of immunoglobulins and hyperimmune serum to HIV (HIVIG) during in vitro dual placental perfusion.

METHODS

Isolated lobules of term placentae from normal pregnancies were perfused in a model of maternal and fetal circulation. The perfused tissue was compared to fresh tissue samples from the same placenta for the content of IgG, IgG subclasses, IgM, cytokeratin, human placental lactogen and SP1 antigen by immunohistochemistry and by protein elution.

RESULTS

The immunoglobulin staining faded by an average of 40% during the 1st hour of perfusion. In contrast, staining for cytokeratin, human placental lactogen and SP1 remained unchanged. During a 4-hour recycling of endogenous immunoglobulins in the maternal circulation, IgG and HIVIG crossed to the fetal side in a steady rate. The transport of HIVIG could be inhibited by preperfusion with an intravenous gammaglobulin preparation (IVIG).

DISCUSSION

The transfer of IgG across the placenta occurs in a steady state rate consistent with a receptor-mediated mechanism. Furthermore, inhibition of HIVIG maternofetal transfer by IVIG further establishes the receptor-mediated transfer of immunoglobulins through the placenta.

Artifactual staining of monoclonal antibodies in two-color combinations is due to an immunoglobulin in the serum and plasma

Two-color whole blood lysis is the assay of choice for lymphocyte immunophenotyping because of the additional information it provides. Recently, artifactual double-staining of some specimens has been observed with this assay. In these cases, the samples appear to be uncompensated for spectral overlap or to inappropriately coexpress two antigens simultaneously. This artifact can result in the apparent coexpression of CD4 and CD8 (observed in lymphoblastic processes) or of CD5 and CD20 (characteristic of chronic lymphocytic leukemia) in normal persons, leading to an erroneous diagnosis. Using plasma, serum, or immunoglobulin preparations from donors who exhibit this artifact we sought to determine 1) the source of the artifact and 2) ways to overcome it. This staining is apparently due to an immunoglobulin in the donors' serum and plasma which does not have specific reactivity with mouse immunoglobulin. Washing whole blood samples or blocking with mouse immunoglobulin is a convenient way of avoiding this artifact.

Maternofetal transmission of human immunodeficiency virus-1: the role of antibodies to the V3 primary neutralizing domain

The increase in the number of human immunodeficiency virus-1 (HIV-1)-infected children is a direct consequence of the heterosexual spread of the disease to women and the growing number of HIV-positive i.v. drug users. It is not known how the majority of infants born to HIV-1-infected women escape HIV-1 infection, and, for those infected, the timing of HIV-1 transmission has yet to be determined. In addition, the role of maternal antibodies in the prevention of HIV-1 transmission to the fetus is unclear. We have previously demonstrated a correlation between vertical transmission and the absence of high-affinity/avidity antibodies to a peptide, KRI-HIGPGRAFYT, which corresponds to a region of the primary neutralizing domain of the gp120 V3 loop of HIVMN (MN-PND). The present study examines the correlation between the presence of these high affinity antibodies in women completing a pregnancy or undergoing an elective abortion and the detection of HIV-1 infection in their aborted fetuses. In several instances, transmission occurred despite high-affinity antibodies to the MN-PND. We have, therefore, evaluated the reactivity of sera to different MN-PND variants. In one infant born to a mother with high-affinity/avidity antibodies to KRI-HIGPGRAFYT (classic MN-PND), the infected baby developed antibodies to an MN-PND variant peptide against which his mother did not mount a humoral immune response during pregnancy. This finding indicates that fetal infection with MN-PND escape mutants arising during pregnancy may occur during a period when the mother is serologically negative.

Alterations in human fetal hematopoiesis are associated with maternal HIV infection

In the majority of adult and pediatric patients with AIDS, hematologic abnormalities including leukopenia, anemia, and thrombocytopenia are commonly observed. In addition to these findings, changes in hematopoietic progenitor cells occur, including a reduction of multipotential-forming units, granulocyte-macrophages, macrophage as well as eosinophil colony-forming units, and bone marrow erythroid burst-forming units. This study examined alterations in human fetal liver hematopoiesis in 2nd trimester abortuses from human immunodeficiency virus (HIV)-seropositive women. The differentiation and growth potential of hematopoietic cells in vitro were monitored. Upon initial isolation, some populations of liver hematopoietic cells from abortuses of HIV-seropositive women were significantly decreased when compared to age-matched samples from fetuses of normal females including the percentage of early T cells [cluster of differentiation (CD)2], B cells (CD19), and early monocytes (CD14). A decrease in multipotent progenitors (CD34), myelomonocytes (CD33), and panleukocytes (CD45) was also observed. In contrast, after 21 d in culture, cells from HIV abortuses demonstrated an increase in the percentage of CD14 cells when stimulated with erythropoietin and granulocyte-monocyte colony-stimulating factor, as well as an increase in CD45 phenotype after exposure to granulocyte-monocyte colony-stimulating factor alone. These samples showed a persistence of erythropoietic elements (transferrin and CD36 phenotype) when compared to normal controls. No significant difference in the in vitro growth of hematopoietic progenitors (bone marrow erythroid burst-forming units, granulocyte-macrophage colony-forming units, and multipotential forming units) between these samples and normal controls was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Persistent productive HIV-1 infection of a CD4- human fetal thymocyte line

Human fetal thymuses were obtained from abortuses of HIV-1 seronegative females. Thymocytes were isolated and cultured for 2 days with PHA. Thereafter, the culture was divided and half of the cells were exposed to the HIV-1 RF isolate for 4 h. After this incubation period, the HIV-1 exposed and nonexposed control cells were cultured in RPMI 1640 supplemented with IL-2 for 30 days and subsequently maintained in RPMI without the addition of growth factors. Long term culture of both HIV-1 exposed and control thymocytes has yielded two cell lines that have been maintained for more than 3 yr without the addition of growth factors. Flow cytometry using mAb that recognize T cell differentiation markers was used to analyze cell phenotypes. The HIV-1 exposed thymocyte cell line (E88/RF) was shown to be HIV-1 infected by p24 ELISA, reverse transcriptase activity, immunocytochemistry, in situ hybridization, polymerase chain reaction, electron microscopy, and to produce infectious particles by a syncytial forming assay. The non-HIV-1-exposed thymocyte cell line (T412) has remained negative by all criteria for HIV-1 infection. Flow cytometry showed the T412 cells to be positive for the T cell markers CD45, CD38, and CD4 but negative for all other markers tested. The E88/RF cells are positive for CD45 and CD38 but negative for CD4 and other markers. These data report the isolation of two human fetal thymocyte cell lines; one uninfected and susceptible to HIV-1 infection, and the other persistently and productively infected with HIV-1 with little cytopathology. These findings suggest that HIV-1 can persistently infect early T cells and may alter T cell differentiation.

Persistent productive HIV-1 infection of a CD4- human fetal thymocyte line

Human fetal thymuses were obtained from abortuses of HIV-1 seronegative females. Thymocytes were isolated and cultured for 2 days with PHA. Thereafter, the culture was divided and half of the cells were exposed to the HIV-1 RF isolate for 4 h. After this incubation period, the HIV-1 exposed and nonexposed control cells were cultured in RPMI 1640 supplemented with IL-2 for 30 days and subsequently maintained in RPMI without the addition of growth factors. Long term culture of both HIV-1 exposed and control thymocytes has yielded two cell lines that have been maintained for more than 3 yr without the addition of growth factors. Flow cytometry using mAb that recognize T cell differentiation markers was used to analyze cell phenotypes. The HIV-1 exposed thymocyte cell line (E88/RF) was shown to be HIV-1 infected by p24 ELISA, reverse transcriptase activity, immunocytochemistry, in situ hybridization, polymerase chain reaction, electron microscopy, and to produce infectious particles by a syncytial forming assay. The non-HIV-1-exposed thymocyte cell line (T412) has remained negative by all criteria for HIV-1 infection. Flow cytometry showed the T412 cells to be positive for the T cell markers CD45, CD38, and CD4 but negative for all other markers tested. The E88/RF cells are positive for CD45 and CD38 but negative for CD4 and other markers. These data report the isolation of two human fetal thymocyte cell lines; one uninfected and susceptible to HIV-1 infection, and the other persistently and productively infected with HIV-1 with little cytopathology. These findings suggest that HIV-1 can persistently infect early T cells and may alter T cell differentiation.

Neopterin concentrations in pediatric human immunodeficiency virus infection as predictor of disease activity

Neopterin concentrations in 50 children with human immunodeficiency virus infection were correlated with disease course. The neopterin concentrations ranged from 4 to 70 nM with a mean of 34.7 +/- 25.1 (SD) nM compared with a mean of 6.1 +/- 1.6 nM in the human immunodeficiency virus-negative control group. Elevated neopterin concentrations above the upper range of the control group were detected as early as 5 months of age. Nineteen of 20 patients (95%) with neopterin concentrations above 20 nM either died or have severe clinical disease. Increasing neopterin concentrations were also associated with poor prognosis even though the first value was below 20 nM. Conversely neopterin concentrations less than 20 nM or declining concentrations were associated with a stable clinical course, except in terminal illness. With stepwise logistic regression analysis neopterin concentrations were predictive for disease progression. This predictive value was further improved by the addition of CD4 cell counts.

Clinical and immunologic effects of lipid-based parenteral nutrition in AIDS

The effect of lipid-based parenteral nutrition was assessed in eight patients with AIDS and weight loss of 10% or greater. All patients received home parenteral nutrition consisting of a lipid-based system with 50% of nonprotein calories given as fat. Measurements were made of body weight, serum albumin, and immune function as assessed by mitogen responses, P24 antigen levels and T-cell counts. Over a period of 2 months, weight gain and improved well-being were noted in all patients. An improved in vitro lymphocyte mitogenic response to phytohemagglutinin and to concanavalin A was also noted. No change in T-cell subsets was observed. Viral cultures and P24 serum levels also remained unchanged. Lipid-based parenteral nutrition is safe and probably efficacious in AIDS.

Immune complexes in pediatric human immunodeficiency virus infection

Circulating immune complexes (CIC) were analyzed in a cohort of 30 children infected with the human immunodeficiency virus. Elevated CIC were detected by the C1q assay in 70% (21/30) of all patients and by the Raji cell assay in 93% (28/30) of all patients. While only less than one third of patients with elevated CIC had free serum antibodies to Epstein-Barr virus, 80% (16/20) of them had detectable antibodies to Epstein-Barr virus associated with CIC. Enriched CIC in human immunodeficiency virus-infected children contained low levels of complement. These findings document that, as an expression of the humoral immunodeficiency, CIC in human immunodeficiency virus-infected children are deficient in complement and can thus be underestimated if complement-precipitating methods are used for their detection.

HL-T, a new cell line derived from HL-60 promyelocytic leukemia cell cultures expressing terminal transferase and secreting suppressor activity

A cell line with immature blast cell morphology was isolated from HL-60 promyelocytic leukemia cell cultures and designated HL-T. This new cell type is biphenotypic, expressing terminal transferase (TdT) together with myelomonocytoid immunologic features. TdT enzymatic activity, undetectable in HL-60, was determined to be 140 to 180 units/10(8) HL-T cells by the dGTP-assay, approximately 20% of the activity found in lymphoblastoid cell lines. HL-T predominantly synthesize the known 58-kDa TdT-protein plus a minor 54/56-kDa doublet. The 58-kDa steady state form is nonglycosylated and is phosphorylated. Precursor antigens S3.13 and MY-10, absent on HL-60, are expressed by HL-T; however, the cells are negative for HLA-Dr. Southern blot analysis by hybridization with immunoglobulin heavy chain (JH) and T cell-receptor chain gene (T beta) probes shows JH to be in the germ-line configuration in both cell lines and the T beta gene to be in germ-line in HL-60 but to be rearranged in HL-T. Truncation of the gene encoding the granulocyte-macrophage-colony-stimulating factor (GM-CSF), as found in HL-60, is not observed in HL-T. HL-T are resistant to differentiation-induction by retinoic acid and 1,25-dihydroxyvitamin D3. Cytogenetically HL-T share with HL-60 a deletion of the short arm of chromosome 9 at breakpoint p13, an aberration frequently found in patients with T cell leukemia. In addition, HL-T display t(8;9)(p11;p24) and trisomy 20. Tetraploidy is observed in 80% of HL-T metaphases with aberrations identical to those in the diploid karyotype. Like HL-60, the new line shows some surface-antigenic-T cell characteristics. Despite an antigenic pattern most consistent with that of helper-inducer T cells (T4+, D44+/-, 4B4+, 2H4-, TQ1+/-), HL-T cells and their conditioned culture medium suppress antigen, mitogen, and mixed-leukocyte-culture-mediated lymphocyte proliferation.