Dynamics of T- and B-lymphocyte turnover in a natural host of simian immunodeficiency virus

Increased lymphocyte turnover is a hallmark of pathogenic lentiviral infection. To investigate perturbations in lymphocyte dynamics in natural hosts with nonpathogenic simian immunodeficiency virus (SIV) infection, the nucleoside analog bromodeoxyuridine (BrdU) was administered to six naturally SIV-infected and five SIV-negative sooty mangabeys. As a measure of lymphocyte turnover, we estimated the mean death rate by fitting a mathematical model to the fraction of BrdU-labeled cells during a 2-week labeling and a median 10-week delabeling period. Despite significantly lower total T- and B-lymphocyte counts in SIV-infected sooty mangabeys than in SIV-negative mangabeys, the turnover rate of B lymphocytes and CD4⁺ and CD8⁺ T lymphocytes was not increased in the SIV-infected animals. A small, rapidly proliferating CD45RA⁺ memory subset and a large, slower-proliferating CD45RA⁻ central memory subset of CD4⁺ T lymphocytes identified in the peripheral blood of sooty mangabeys also did not show evidence of increased turnover in the context of SIV infection. Independently of SIV infection, the turnover of CD4⁺ T lymphocytes in sooty mangabeys was significantly higher (P < 0.01) than that of CD8⁺ T lymphocytes, a finding hitherto not reported in rhesus macaques or humans. The absence of aberrant T-lymphocyte turnover along with an inherently high rate of CD4⁺ T-lymphocyte turnover may help to preserve the pool of central memory CD4⁺ T lymphocytes in viremic SIV-infected sooty mangabeys and protect against progression to AIDS.     

Selective downregulation of rhesus macaque and sooty mangabey major histocompatibility complex class I molecules by Nef alleles of simian immunodeficiency virus and human immunodeficiency virus type 2

Human immunodeficiency virus type 1 (HIV-1) Nef downregulates HLA-A and -B molecules, but not HLA-C or -E molecules, based on amino acid differences in their cytoplasmic domains to simultaneously evade cytotoxic T lymphocyte (CTL) and natural killer cell surveillance. Rhesus macaques and sooty mangabeys express orthologues of HLA-A, -B, and -E, but not HLA-C, and many of these molecules have unique amino acid differences in their cytoplasmic tails. We found that these differences also resulted in differential downregulation by primary simian immunodeficiency virus (SIV) SIV(smm/mac) and HIV-2 Nef alleles. Thus, selective major histocompatibility complex class I downregulation is a conserved mechanism of immune evasion for pathogenic SIV infection of rhesus macaques and nonpathogenic SIV infection of sooty mangabeys.     

Clinical significance of promoter hypermethylation of RASSF1A, RARbeta2, BRCA1 and HOXA5 in breast cancers of Indian patients

Promoter hypermethylation of genes is implicated in the pathogenesis of many cancers, including breast cancer. Herein, we analyzed the promoter methylation status of a panel of critical growth regulatory genes, RASSF1A, RARbeta2, BRCA1 and HOXA5, in 54 breast cancers and 5 distant normal breast tissues of Indian patients. The methylation data were correlated with clinicopathological characteristics and hormone receptor status to determine the impact of methylation in breast carcinogenesis. Promoter hypermethylation of RASSF1A was observed in 39/54 (72%), HOXA5 in 36/54 (67%), BRCA1 in 15/54 (28%) and RARbeta2 in 8/54 (15%) breast cancers. Our most significant findings were the association of RASSF1A methylation with nodal metastasis (p=0.05); and RARbeta2 methylation with age (all tumors in patients in the older age group were methylated, p=0.04). Further, the interactions between DNA methylation and hormone receptor biology in breast cancer cells are beginning to be clearly understood. In this context the association of HOXA5 methylation with loss of ERalpha (p=0.009) is noteworthy.     

Crystal structure of the peptidoglycan recognition protein at 1.8 A resolution reveals dual strategy to combat infection through two independent functional homodimers

The mammalian peptidoglycan recognition protein-S (PGRP-S) binds to peptidoglycans (PGNs), which are essential components of the cell wall of bacteria. The protein was isolated from the samples of milk obtained from camels with mastitis and purified to homogeneity and crystallized. The crystals belong to orthorhombic space group I222 with a = 87.0 Å, b = 101.7 Å and c = 162.3 Å having four crystallographically independent molecules in the asymmetric unit. The structure has been determined using X-ray crystallographic data and refined to 1.8 Å resolution. Overall, the structures of all the four crystallographically independent molecules are identical. The folding of PGRP-S consists of a central β-sheet with five β-strands, four parallel and one antiparallel, and three α-helices. This protein fold provides two functional sites. The first of these is the PGN-binding site, located on the groove that opens on the surface in the direction opposite to the location of the N terminus. The second site is implicated to be involved in the binding of non-PGN molecules, it also includes putative N-terminal segment residues (1-31) and helix α2 in the extended binding. The structure reveals a novel arrangement of PGRP-S molecules in which two pairs of molecules associate to form two independent dimers. The first dimer is formed by two molecules with N-terminal segments at the interface in which non-PGN binding sites are buried completely, whereas the PGN-binding sites of two participating molecules are fully exposed at the opposite ends of the dimer. In the second dimer, PGN-binding sites are buried at the interface while non-PGN binding sites are fully exposed at the opposite ends of the dimer. This form of dimeric arrangement is unique and seems to be aimed at enhancing the capability of the protein against specific invading bacteria. This mode of functional dimerization enhances efficiency and specificity, and is observed for the first time in the family of PGRP molecules.     

Isolation of 24-epibrassinolide from leaves of <Emphasis Type="Italic">Aegle marmelos</Emphasis> and evaluation of its antigenotoxicity employing <Emphasis Type="Italic">Allium cepa</Emphasis> chromosomal aberration assay

Brassinosteroids are of universal occurrence in plants. They have been reported to affect plant growth and development through a spectrum of physiological responses. Recently they are reported to confer resistance in plants against a number of biotic and abiotic stresses. In the present study, a brassinosteroid was isolated from Aegle marmelos Correa. (Rutaceae) which was characterized to be 24-epibrassinolide (EBL) using various spectroscopic techniques (TLC and ESI-MS analysis). It was evaluated for the antigenotoxicity against maleic hydrazide (MH) induced genotoxicity in Allium cepa chromosomal aberration assay. It was shown that the percentage of chromosomal aberrations induced by maleic hydrazide (0.01%) declined significantly with 24-epibrassinolide treatment. EBL (10⁻⁷ M) proved to be the most effective concentration with 91.8% inhibition. This is the first report on the isolation of 24-epibrassinolide from Aegle marmelos and its antigenotoxic effects against MH employing Allium cepa chromosomal aberration assay.     

Regulation of cellulase production in two thermophilic fungi Melanocarpus sp. MTCC 3922 and Scytalidium thermophilum MTCC 4520

This paper reports regulation of cellulase production in two thermophilic fungi, Melanocarpus sp. MTCC 3922 and Scytalidium thermophilum MTCC 4520. The expression of endoglucanase (EG), avicel adsorbable endoglucanase (AAEG) and β-glucosidase in both fungi was inducible. Of the different carbon sources tested, rice straw induced maximal levels of cellulase in both fungi. While, the addition of fructose (1%, w/v) to the carboxymethylcellulose (CMC) medium resulted in two-fold increase in endoglucanase production in Melanocarpus sp., however, the addition of ethanol (1%, v/v) resulted in eight-fold-increased expression of endoglucanase in S. thermophilum. The expression profiles of different components of cellulase complex were shown to be co-regulated in S. thermophilum but independently regulated in Melanocarpus sp.     

Effect of Carbon Source on Production of Lytic Enzymes by the Sclerotial Parasites Trichoderma atroviride and Coniothyrium minitans

Three isolates of Trichoderma atroviride and two isolates of Coniothyrium minitans known to efficiently degrade sclerotia of Sclerotinia sclerotiorum were cultured on minimal medium with sucrose, carboxymethyl cellulose (CMC), xylan, laminarin, colloidal chitin or powdered sclerotia as carbon source. The activity of endochitinase, endo‐β‐1,3‐glucanase, endoxylanase and endocellulase in culture filtrates was determined after 7 and 15 days of culture using dye‐labelled substrates. The strongest inducers of chitinase were colloidal chitin and sclerotia powder. Chitinase activity appeared to be faster induced in the isolates of T. atroviride than in the isolates of C. minitans, but the maximum level of activity present in culture filtrates of the two species was similar. With CMC and xylan as carbon source, concurrent production of the corresponding enzymes was observed for the Trichoderma isolates. The isolates of C. minitans produced cellulase on xylan but not on CMC, whereas xylanase was produced on both carbon sources. Laminarin induced the formation of glucanases in the three isolates of T. atroviride but not the isolates of C. minitans. However, in the sclerotia‐containing cultures of C. minitans glucanase activity was even higher than in the respective cultures of the Trichoderma isolates. During the 31‐day study period, the pattern of enzyme production in shake cultures containing sclerotia powder was very similar for the isolates of T. atroviride and C. minitans. Glucanase activity generally reached a peak 24 days after inoculation of the flasks, whereas the activity of chitinase, cellulase and xylanase remained fairly constant throughout the experiment.     

Production of Ligninolytic Enzymes by Phlebia Floridensis

Summary The present work reports the production of laccase, lignin peroxidase and manganese peroxidase by the little studied white-rot fungus Phlebia floridensis under a variety of nutritional and physicochemical conditions. Among the different media and supplements the highest yields of laccase, lignin peroxidase and manganese peroxidase were recorded in the presence of sugarcane bagasse, wheat straw and rice straw, respectively. Laccase and manganese peroxidase activities were best expressed at a pH of 4.5 while lignin peroxidase was optimally active at a lower pH. Laccase proved to be much more thermostable as compared to the other two enzymes.