The binding of rabbit IgG and its enzymatically derived fragments to homologous peritoneal macrophages.

Rabbit IgG and its Fab, Fc and pFc' fragments, prepared by papain or peptic digestion, were assayed for binding to homologous peritoneal macrophages. The binding affinity of IgG for the peritoneal macrophages (Ka = 5.9 +/- 1.6 x 10(5) L/M) was comparable to that recorded with alveolar macrophages (7.6 +/- 1.8 x 10(5) L/M, Arend & Mannik, 1973) but the number of receptor sites per peritoneal cell (4.6 +/- 2.1 x10(6)) was about four-fold greater than on the latter. Of the fragments, only Fc bound to macrophages with an affinity comparable to intact IgG; pFc' bound weakly and Fab was totally inactive. These data, taken with a recent study involving rabbit IgG and guinea-pig macrophages (Ovary, Saluk, Quijada & Lamm, 1976), indicate that the primary IgG binding site for macrophages is located in the C gamma 2 domain.     

Complement activation by malignant B cells from patients with chronic lymphocytic leukaemia (CLL).

It has previously been reported that the expression of the complement receptors CR1 (CD35) and CR2 (CD21) on malignant B cells in CLL is reduced compared with the expression on normal B cells, while deposition of complement C3 fragments, as a consequence of alternative pathway (AP) activation of complement, is observed on mononuclear cells from patients with B CLL. Following our demonstration that normal B cells are capable of activating the AP of complement in a CR2-dependent fashion, we have chosen to re-examine the complement-activating ability of B CLL cells in relation to their altered phenotype with respect to CR2 and the complement regulatory membrane proteins, CR1, decay accelerating factor (DAF) (CD55) and membrane cofactor protein (MCP) (CD46). Flow cytometry was used to measure expression of complement receptors and regulatory proteins on CD5+ B cells from CLL patients, as well as the deposition of C3 fragments occurring both in vivo and after in vitro AP activation. We have confirmed the reduced expression of CR1 and CR2 on CLL cells and have shown that AP activation in the presence of homologous, normal serum was reduced on B CLL cells compared with normal B cells. The degree of AP activation correlated directly with CR2 expression. In addition, we observed that CLL cells bear in vivo-deposited C3d,g, although at a significantly lower level than normal B cells.     

In vivo expression and immunological studies of the 42-kilodalton carboxyl-terminal processing fragment of Plasmodium falciparum merozoite surface protein 1 in the baculovirus-silkworm system

The 42-kDa carboxyl-terminal processing fragment of Plasmodium falciparum merozoite surface protein 1 (MSP-1(42)) is an anti-erythrocytic stage malaria vaccine candidate. In this study, MSP-1(42) was expressed by using the Bombyx mori nuclear polyhedrosis virus-silkworm expression system, and the antigenicity and immmunogenicity of the recombinant protein, Bmp42, were evaluated. The average yield of Bmp42, as determined by a sandwich enzyme-linked immunosorbent assay (ELISA), was 379 microg/ml of infected silkworm hemolymph, which was >100-fold higher than the level attainable in cell culture medium. N-terminal amino acid sequencing revealed that Bmp42 was correctly processed in silkworm cells. Data from immunoblotting, as well as from the inhibition ELISA, suggested that the conformational B-cell epitopes of MSP-1(42) were recreated in Bmp42. Immunization of rabbits with Bmp42 in complete Freund's adjuvant generated high-titer antibody responses against the immunogen. Specificity analyses of the anti-Bmp42 antibodies using several recombinant MSP-1(19) proteins expressing variant and conserved B-cell epitopes suggested that the anti-Bmp42 antibodies recognized primarily conserved epitopes on MSP-1(19). Furthermore, the anti-Bmp42 antibodies were highly effective in inhibiting the in vitro growth of parasites carrying homologous or heterologous MSP-1(42). Our results demonstrated that the baculovirus-silkworm expression system could be employed to express biologically and immunologically active recombinant MSP-1(42) at elevated levels; thus, it is an attractive alternative for producing a protective MSP-1(42) vaccine for human use.     

Bacteriological and molecular analysis of rifampin-resistant Mycobacterium tuberculosis strains isolated in Australia

To develop a better understanding of the epidemiology and molecular biology of rifampin-resistant Mycobacterium tuberculosis strains in Australia, 50 clinical isolates (33 rifampin-resistant and 17 rifampin-sensitive strains) cultured between 1990 and 1997 were analyzed by a number of bacteriological and molecular techniques. Examination of the drug resistance profiles of the 33 rifampin-resistant isolates revealed that 91% were resistant to rifampin in combination with resistance to isoniazid, 88% were resistant to rifampin on first isolation, and 81% showed cross-resistance with rifabutin. On the basis of the demographic data provided for the patients infected with the rifampin-resistant strains, 90% of the patients were born overseas. Of these patients, 64% developed clinical symptoms within 5 years of residence in Australia. On a molecular level, analysis of the rpoB gene revealed that 97% of the rifampin-resistant isolates had missense mutations within a conserved region of the gene, and eight types of missense mutations were detected. Of the 31 rifampin-resistant isolates that were typed by restriction fragment length polymorphism (RFLP) analysis, 28 distinct patterns were obtained by RFLP analysis with IS6110, and three clusters of genetically related isolates were identified. All isolates within the clusters were from patients who were born overseas and who had the same country of origin. The results from this study provide an overview of the current situation of rifampin resistance in Australia and can serve as a basis for continued monitoring of drug-resistant M. tuberculosis strains isolated within the country.     

Quantitative studies of Fc receptors on human monocytes: characterization by binding of homologous and heterologous monomeric IgG and soluble immune complexes of different composition

The binding of 125I-labelled monomeric human and rabbit IgG (H-IgG, R-IgG) and rabbit IgG immune complexes (IC) to monocyte-enriched human peripheral blood cells had been investigated quantitatively. Scatchard plots at 4 degrees demonstrated that R-IgG bound to the same number of Fc receptors per cell (19,000) as H-IgG, but with a lower affinity (2.4 +/- 0.9 X 10(8)/l/mol and 3.5 +/- 1.1 X 10(8)l/mol, respectively). Inhibition studies demonstrated that the two ligands could mutually inhibit each other, H-IgG having higher inhibitory efficiency versus R-IgG than the reverse. It seems likely that R-IgG reacts with the Fc receptor for the homologous IgG, although with lower affinity. Binding of soluble R-IgG anti-bovine serum albumin (BSA) IC, prepared at molar antigen:antibody (Ag:Ab) ratio of 2:1 and 12:1, showed quite different behaviour, the IC binding with association constants almost 10-fold lower than the affinity of monomeric R-IgG, but binding six- to seven-fold as many IgG molecules per cell at saturation.     

Associations between Self-Reported Daily Affect Ratings and Sleep Duration during the First Two Weeks of Antidepressant Therapy

ABSTRACT

Background: In the context of a randomized controlled trial evaluating the efficacy of augmenting fluoxetine treatment in young adults with major depressive disorder (MDD) using a modified repeated partial sleep deprivation protocol contrasting 2 weeks of restricted time in bed (i.e., 6 h TIB) to no time in bed restriction (i.e., 8 h TIB) the study examines whether sleep duration and the timing of repeated partial sleep deprivation predicts patient-reported affect ratings.

Participants: Participants included 58 young adults with DSM-IV-diagnosed MDD.

Methods: Daily ratings of affect and sleep were collected during the first 2 weeks of initiating fluoxetine treatment, yielding 630 person-days. Actigraphy monitoring was employed to assess compliance with time in bed condition.

Results: Negative affect ratings and positivity ratios in the morning were more improved among participants assigned to the 6 h TIB condition compared to the 8 h TIB group. Participants whose bedtime was delayed by 2-h nightly demonstrated the most significant improvement in negative affect and positivity ratio during the first 2 weeks of fluoxetine therapy. Moreover, the trajectory of morning negative affect ratings in the first 2 weeks was predictive of remission after 4 weeks of fluoxetine therapy.

Conclusions: These findings suggest that monitoring changes in daily affect may be a valuable marker of early treatment response in young adults with MDD.     

Longitudinal reliability of focus glycoprotein G-based type-specific enzyme immunoassays for detection of herpes simplex virus types 1 and 2 in women

Serologic assays that utilize herpes simplex virus (HSV) type-specific glycoproteins G-1 (HSV-1) and G-2 (HSV-2) to discriminate between antibodies against HSV-1 and HSV-2 are sensitive and specific. However, the high rates of seroreversion, defined as the change in an individual's antibody status from positive to negative over time, previously reported in longitudinal evaluations of glycoprotein G type-specific tests suggests that their use in HSV acquisitional studies would be problematic. To further explore the reliability of the glycoprotein G-based serologic tests, we evaluated HSV-1 and HSV-2 enzyme immunoassays from Focus Technologies in a longitudinal cohort of 1207 young women from Pittsburgh, Pa. On enrollment of the women in the study, HSV-1 and HSV-2 antibodies were detected in 46.6 and 24.9% of the women, respectively. Among the women with at least three visits, 3.4% (15 of 447) of those who were HSV-1 antibody positive had a subsequent negative result while fewer than 1% (2 of 227) of those who were HSV-2 antibody positive seroreverted. The median of mean positive index values for women who seroreverted to HSV-1 antibody was lower than that for women who remained seropositive (1.25 versus 7.06; P < 0.001). Similarly, the median of mean positive index values for women whose HSV-2 antibody status reverted from positive to negative was lower than that for those women who did not serorevert (1.83 versus 7.46; P = 0.02). Comparative Western blot analysis demonstrated that the lower positive index values, seen more often among the HSV seroreverters, often signified false-positive immunoassay results. Overall, the seroreversion rates were low; the use of glycoprotein G-based serologic tests for the measurement of HSV-1 and HSV-2 antibodies in incidence studies therefore appears warranted.     

No evidence for triallelic inheritance of MKKS/BBS loci in Amish Mckusick-Kaufman syndrome

It has been hypothesized that two mutations in one gene are not sufficient and that three mutations between two genes are required for penetrance in some cases of Bardet-Biedl syndrome (the so-called "triallelic inheritance" model). McKusick-Kaufman syndrome (MKS) is allelic to one form of Bardet-Biedl syndrome (BBS). We describe an Amish family with MKS, where three children were affected with homozygous MKKS (BBS6) mutations (H84Y and A242S on both alleles), their father was a carrier, and their mother was homozygous for the same MKKS mutations, but she was non-penetrant. Genotyping and/or sequencing of BBS1, BBS2, BBS3, BBS4, BBS5, BBS7, and BBS8 excluded "triallelic inheritance" for each gene either by an incompatible inheritance pattern or an absence of mutations in the coding region and the intronic splice junctions of these genes. We conclude that the "triallelic" model does not explain the incomplete penetrance of MKS.