Biomedical subjects

Vandana Kalia

Publications and source records attributed to Vandana Kalia.

8 recordsLinked to original sources

PubMed2006

Differentiation of memory B and T cells.

In the past few years progress has been made in understanding the molecular mechanisms that underlie the initial generation, and the ensuing differentiation and maintenance, of humoral and cellular immunity. Although B and T cell immunological memory contribute to protective immunity through fundamentally distinct effector functions, interesting analogies are becoming apparent between the two memory compartments. These include heterogeneity in function, anatomical location and phenotype, which probably relate to differential environmental cues during the early priming events as well as the later differentiation phases. Detailed definition of the molecular and cellular signals involved in the development of immunological memory, and the relative contributions of different memory subsets to protective immunity, remains an important goal.

Animals↗

PubMed2005

Antibody neutralization escape mediated by point mutations in the intracytoplasmic tail of human immunodeficiency virus type 1 gp41.

The persistence of human immunodeficiency virus type 1 (HIV-1) infection in the presence of robust host immunity has been associated in part with variation in viral envelope proteins leading to antigenic variation and escape from neutralizing antibodies. Previous studies of natural neutralization escape mutants have predominantly focused on gp120 and gp41 ectodomain sequence variations that alter antibody binding via changes in conformation or glycosylation pattern of the Env, likely due to the immune pressure exerted on the exposed ectodomain component of the glycoprotein. Here, we show for the first time a novel mechanism by which point mutations in the intracytoplasmic tail of the transmembrane component (gp41) of envelope can render the virus resistant to neutralization by monoclonal antibodies and broadly neutralizing polyclonal serum antibodies. Point mutations in a highly conserved structural motif within the intracytoplasmic tail resulted in decreased binding of neutralizing antibodies to the Env ectodomain, evidently due to allosteric changes both in the gp41 ectodomain and in gp120. While receptor binding and infectivity of the mutant virus remained unaltered, the changes in Env antigenicity were associated with an increase in neutralization resistance of the mutant virus. These studies demonstrate the structurally integrated nature of gp120 and gp41 and underscore a previously unrecognized potentially critical role for even minor sequence variation of the intracytoplasmic tail in modulating the antigenicity of the ectodomain of HIV-1 envelope glycoprotein complex.

Antibody Specificity↗

PubMed2004

Effect of Symplocos racemosa Roxb. on gonadotropin release in immature female rats and ovarian histology.

In the present study we are reporting in vivo effect of aqueous extracts of Symplocos racemosa Roxb. (Fam. Symplocaceae) on serum FSH and LH levels in immature female Sprague-Dawley rats under basal conditions. Symplocos racemosa is used in Indian System of Medicine (ISM) for various female disorders. Aqueous extract on oral administration significantly stimulated serum FSH level (P < 0.016) along with the rise in serum LH level (P < 0.001). Moreover, histopathological studies revealed enhanced folliculogenesis, presence of mature follicles and detached oocytes, which are result of increased FSH and LH levels. Further, an increase in the ovary weight of treated animals was found due to observed FSH surge. These results are in concordance with the traditional use of the drug for female disorders.

Animals↗

PubMed2004

Luteinizing hormone estimation.

Luteinizing hormone (LH) is an important hormone of the reproductive system, which has found application in diagnosis and therapeutic medicine. It plays a vital role in the development and functioning of the reproductive system. Determination of LH concentration is important for detection of dysfunction of the pituitary-ovarian axis, diagnosis of reproductive disorders, monitoring of antifertility programmes and in therapeutic preparations. On the basis of heterogeneity and various biological effects served by the hormone, different assay systems have been developed for its estimation. Initially, LH was quantified on the basis of in vivo and in vitro endocrine activity. However, with the advancement in biotechnology, various immunoassays have been designed for performing most of the physiological and clinical studies on serum LH. The immunoassays offer improvement in sensitivity, precision and convenience over bioassays. However, these immunoassays have their own limitations and results obtained in different laboratories are often not comparable. This review makes an attempt to enumerate and compare various assay methods used in the serum LH measurement in varied clinical conditions.

Animals↗

PubMed2003

Caspase-mediated apoptosis and cell death of rhesus macaque CD4+ T-cells due to cryopreservation of peripheral blood mononuclear cells can be rescued by cytokine treatment after thawing.

Cryopreservation of peripheral blood mononuclear cells (PBMC) from animal model studies and clinical trials is utilized as a primary method for long-term storage of PBMC for future in vitro and in vivo applications. The objective of this study was to define the mechanistic pathways involved in cryopreservation-induced apoptosis of CD4+ T-cells in PBMC, and to evaluate a cytokine treatment of the cryopreserved samples to rescue apoptosis for the potential future use of the cryopreserved PBMC. Using cryopreserved PBMC samples isolated from naïve and Simian immunodeficiency virus (SIV)-infected rhesus macaques as a model, frozen PBMC showed significantly increased levels of apoptosis-induced CD4+ T-cell death compared to fresh PBMC over a 5-day culture period as detected by Annexin V/PI and trypan blue staining. Mechanistic studies using a broad-spectrum caspase inhibitor z-VAD demonstrated a crucial involvement of caspases in cryopreservation-induced apoptosis of CD4+ T-cells. Furthermore, the ability of z-VAD to inhibit both mitochondrial membrane perturbation and apoptotic cell death implicated the involvement of caspase-mediated mitochondrial membrane damage in cryopreservation-induced apoptosis of CD4+ T-cells. Due to their known properties to promote T-cell survival and inhibit apoptosis, we evaluated the ability of IL-2, IL-4, and IL-7 combination cytokine treatment of the cryopreserved cells to rescue apoptosis of the CD4+ T-cells. The cytokine treatment resulted in a significant inhibition (p<0.01) of apoptosis-induced cell death and rescued CD4+ T-cell survival (p<0.01) in the cryopreserved cells. Efficient rescue of cryopreserved CD4+ T-cells has clinical significance in immune function analysis of longitudinal samples and in various long-term protocols requiring cryopreservation, including bone marrow and stem cell transplantation.

Animals↗

PubMed2003

Expression of IFN-gamma induced CXCR3 agonist chemokines and compartmentalization of CXCR3+ cells in the periphery and lymph nodes of rhesus macaques during simian immunodeficiency virus infection and acquired immunodeficiency syndrome.

Dysregulation of cytokines and chemokines during human immunodeficiency virus 1 (HIV-1) and simian immunodeficiency virus (SIV) infection is thought to be critical in the progression of acquired immunodeficiency syndrome (AIDS). To evaluate the potential role of Th1-agonist chemokines in disease progression during AIDS, we assessed CXCL9/MIG and CXCL10/IP-10 expression simultaneously in the periphery and lymphoid tissues of SIV-infected animals at a single-cell level by flow cytometry. We optimized intracellular staining and analysis of CXCL9/MIG and CXCL10/IP-10 production in human leukocyte antigen (HLA)-DR+ macaque cells by flow cytometry using cross-reactive antibodies against human chemokines. We observed an upregulation of CXCL9/MIG and CXCL10/IP-10 production in both the periphery and lymph nodes of infected animals compared with naïve controls. Animals with higher viral loads had higher levels of CXCL9/MIG and CXCL10/IP-10 producing cells compared with animals with low viral loads. Analysis of cells bearing the receptor (CXCR3) for CXCL9/MIG and CXCL10/IP-10 revealed increased number of CXCR3+ cells in the lymph nodes of infected animals. Importantly, an inverse correlation (P < 0.05) between CXCL9/MIG and CXCL10/IP-10 production, both in the periphery and lymph nodes, and peripheral CD4+ T-cell numbers was observed. These findings provide further evidence that dysregulation of Th1 agonist chemokines might contribute to the ultimate immunopathology during AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed2003

Rational site-directed mutations of the LLP-1 and LLP-2 lentivirus lytic peptide domains in the intracytoplasmic tail of human immunodeficiency virus type 1 gp41 indicate common functions in cell-cell fusion but distinct roles in virion envelope incorporation.

Two highly conserved cationic amphipathic alpha-helical motifs, designated lentivirus lytic peptides 1 and 2 (LLP-1 and LLP-2), have been characterized in the carboxyl terminus of the transmembrane (TM) envelope glycoprotein (Env) of lentiviruses. Although various properties have been attributed to these domains, their structural and functional significance is not clearly understood. To determine the specific contributions of the Env LLP domains to Env expression, processing, and incorporation and to viral replication and syncytium induction, site-directed LLP mutants of a primary dualtropic infectious human immunodeficiency virus type 1 (HIV-1) isolate (ME46) were examined. Substitutions were made for highly conserved arginine residues in either the LLP-1 or LLP-2 domain (MX1 or MX2, respectively) or in both domains (MX4). The HIV-1 mutants with altered LLP domains demonstrated distinct phenotypes. The LLP-1 mutants (MX1 and MX4) were replication defective and showed an average of 85% decrease in infectivity, which was associated with an evident decrease in gp41 incorporation into virions without a significant decrease in Env expression or processing in transfected 293T cells. In contrast, MX2 virus was replication competent and incorporated a full complement of Env into its virions, indicating a differential role for the LLP-1 domain in Env incorporation. Interestingly, the replication-competent MX2 virus was impaired in its ability to induce syncytia in T-cell lines. This defect in cell-cell fusion did not correlate with apparent defects in the levels of cell surface Env expression, oligomerization, or conformation. The lack of syncytium formation, however, correlated with a decrease of about 90% in MX2 Env fusogenicity compared to that of wild-type Env in quantitative luciferase-based cell-cell fusion assays. The LLP-1 mutant MX1 and MX4 Envs also exhibited an average of 80% decrease in fusogenicity. Altogether, these results demonstrate for the first time that the highly conserved LLP domains perform critical but distinct functions in Env incorporation and fusogenicity.

Cell Fusion↗

PubMed2002

Detailed analysis of CD4+ Th responses to envelope and Gag proteins of simian immunodeficiency virus reveals an exclusion of broadly reactive Th epitopes from the glycosylated regions of envelope.

Ag-specific CD4(+) Th cells play a key role in the development, maturation, and maintenance of pathogen-specific humoral and cellular immune responses. To define the fine specificity of broadly reactive Th responses associated with mature immunity in a lentiviral system, we analyzed peptide-specific Th responses in eight macaques chronically infected with a reference live attenuated SIV at 12-14 mo postinoculation. All macaques had stable immunocompetent Th cells at the time of analysis, and a unique array of Th responses to 20-mer overlapping peptides from envelope (Env) and Gag was identified for each macaque, which were then used to define a set of 31 broadly reactive peptide epitopes. Only 5 of the 31 broadly reactive Th epitope peptides mapped to the surface (SU) domain of Env. Interestingly, these were all confined to two conserved nonglycosylated regions toward the carboxyl terminus of SU, suggesting a structural influence of glycosylation on development of Th responses. Gag and the Env transmembrane proteins contained the majority of broadly reactive peptide epitopes (12 and 14 peptides, respectively), which were uniformly distributed throughout their sequence. This study defines for the first time broadly reactive Th epitope peptides of SIV Env and Gag proteins that are associated with enduring broadly protective vaccine immunity to attenuated SIV, which may be used for the design and evaluation of experimental vaccines. Moreover, the data suggest that extensive glycosylation of SU may provide yet another immune escape mechanism developed by lentiviruses to restrict the breadth of Th repertoire to SU, a major immunologically exposed protein of the virus.

Aging↗