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S N Ghosh

Publications and source records attributed to S N Ghosh.

At least 19 recordsLinked to original sources
PubMed1998

Reduced DNA repair capacity in breast cancer patients and unaffected individuals from breast cancer families.

It has been suggested that increased fragile site expression in lymphocyte cultures can be used as a marker for genetic predisposition to cancer. We wished to determine whether aphidicolin (APC), an inhibitor of the DNA repair enzyme DNA polymerase alpha, could be used as a reliable biomarker in identification of DNA repair capacity in unaffected individuals at high risk from breast cancer families. PHA-stimulated lymphocyte cultures, with and without APC, were set up in 65 individuals, of whom 14 were breast cancer patients, 26 were unaffected individuals from breast cancer families, and 25 were controls. A significant proportion of breast cancer patients and unaffected individuals from familial breast cancer (FBC) families exhibited premature separation of centromeres (PSC) and aneuploidy in the untreated cultures. In the APC treated cultures, almost all such individuals exhibited a marked depression of mitotic index and increased aneuploidy, as compared to controls. Our results indicate that these individuals have defective DNA repair capacity. Such individuals could thus have a much higher risk of cancer as compared to persons exhibiting PSC and aneuploidy or DNA repair defects alone. We propose that APC may be a valuable biomarker in identifying individuals with genetic predisposition to cancer from FBC families.

Adult↗
PubMed1998

Natural killer cell function and genetic instability in unaffected individuals from breast cancer families.

Several recent reports highlight the importance of modifying factors in determining the risk for cancer of a person carrying a mutant allele of a tumour susceptibility gene. The study of two such risk modifying factors namely, natural killer (NK) cell function and constitutional cytogenetic anomalies in members of families with familial breast cancer is presented in this paper. We observed that, compared to healthy controls, a significant proportion of unaffected persons from breast cancer families not only display lower NK cell function or genetic instability alone, but also in conjunction. The significance of these observations is discussed. We propose that amongst the unaffected members, persons with lower NK cell function as well as constitutive cytogenetic anomalies may be at a higher risk for cancer. The need for a set of suitable biomarkers to identify individuals at high risk from familial breast cancer families has been recognized for many years. Constitutional cytogenetic anomalies, otherwise seen in breast tumours, have also been observed in lymphocyte cultures from unaffected persons from such families. Lowered NK cell function has previously been demonstrated in first degree relatives of cancer patients. Both these parameters have been implicated in determining the risk of developing malignancy. In the present study these aspects have been investigated simultaneously in order to assess their utility as potential biomarkers.

Adult↗
PubMed1996

Implication of involvement of rat chromosome #2 in spontaneous transformation of the rat-2 cell line.

Using an in vitro model for cell transformation, the relationship between specific chromosomal aberration and phenotypic changes was studied at different passages of Rat-2 cell line. A marker chromosome resulting from a translocation [t(2;7)] was found to be associated with focus formation in soft agar. Conversely, the loss of this marker chromosome was found to be associated with phenotypic reversion. These results suggest an association of this marker chromosome with phenotypic transformation for the Rat-cell line.

Animals↗
PubMed1996

Premature separation of centromere and aneuploidy: an indicator of high risk in unaffected individuals from familial breast cancer families?

It is estimated that one in every four women with a first-degree relative affected by breast cancer will develop the disease. Recent evidence suggests that susceptibility to breast cancer can be inherited. We have carried out cytogenetic analysis on PHA-stimulated lymphocyte cultures of breast cancer patients (familial and sporadic), patients with benign breast lesions, unaffected individuals from families with a history of breast cancer and healthy controls. A high incidence of premature separation of centromere (PSC) and aneuploidy was observed in a significant proportion of familial breast cancer patients and patients with fibrocystic disease as well as in some unaffected individuals from breast cancer families. These observations are also supported by cytogenetic analysis of EBV-transformed lymphoblastoid cell lines established from some of these individuals. No such aberrations were detected in the controls. Further, most of the affected and unaffected individuals with these two anomalies also exhibited structural chromosomal aberrations of 1q, 6q, 7q, 16q, 18q, or Xq. Based on these observations, we propose that the presence of both PSC and aneuploidy in lymphocyte cultures of unaffected individuals from breast cancer families can be used as an important predictive parameter to determine the risk of developing cancer.

Adult↗
PubMed1996

A simple technique for improving chromosome spreads from clumped metaphases.

A method has been described by which clumped metaphases either due to inadequate hypotonic KCl treatment or prolonged storage at 4 degrees C can be rescued. The cell pellet obtained from cell suspension following centrifugation was resuspended in freshly prepared Carnoy's fixative (1:3, acetic acid: methanol) at room temperature by vortexing. Twenty microliters of Triton X-100 at a concentration of 0.5% was added drop by drop while vortexing. Three changes with fixative containing 0.5% Triton X-100 were optimal for obtaining good metaphase spreads with complete removal of the cytoplasmic background. The advantage of this technique is that important patients' samples having clumped metaphases otherwise not useful for G-banding can be rescued and karyotyped by this method.

Chromosome Banding↗
PubMed1993

Analysis of computer-predicted antibody inducing epitope on Japanese encephalitis virus.

Theoretical methods to delineate antibody inducing epitopes have been employed to predict antigenic determinants on envelope glycoprotein (gpE) of Japanese encephalitis (JE), West Nile (WN) and Dengue (DEN) I-IV viruses. A predicted region on JE virus gpE 74CPTTGEAHNEKRAD87 was synthesized, conjugated to KLH (KLH-peptide) and used in immunization of mice. A mouse monoclonal antibody (MoAb IVB4) reactive to the peptide was also found to react with native JE virus gpE. Characterization of the idiotypic (ID) determinants with the help of polyclonal domain-specific anti-ID antibodies revealed that polyclonal anti-KLH-peptide antibodies and MoAb IVB4 are flavivirus-cross-reactive to Hx and NHx domains, respectively. The region 74-87 in JE virus gpE has been mapped as a linking area between Hx and NHx domains. Reactivity of the peptide with sera from JE patients and vaccinees also indicated the feasibility of using predicted peptides for diagnostic and prophylastic purposes.

Amino Acid Sequence↗
PubMed1993

Immunofluorescence studies on the replication of some arboviruses in nucleated and enucleated cells.

Porcine stable kidney (PS) or Vero cells infected with either flavi-(Japanese encephalitis--JE, West Nile--WN, and Dengue--DEN-2) or alphaviruses (Chikungunya--CHIK and Sindbis--SIN) were stained in indirect fluorescent antibody (FA) assay with anti-JE virus monoclonal (MoAb) Hx-3 (flavivirus cross-reactive) and polyclonal (immune PF) antibodies. By 48 hr post infection (p.i.), 15 to 20% of the three flaviviruses and CHIK virus infected cells, which revealed positive cytoplasmic immunofluorescence (IF), showed intranuclear IF. By 24 hr p.i., the intranuclear IF was not observed or became diminished. The enucleation of cells by cytochalasin B treatment prior to the infection with any of the three flaviviruses resulted in the loss of IF compared with the cells enucleated after the infection (18 hr p.i.) whereas SIN or CHIK virus-infected cells reacted similarly by the either method. These findings indicate an essential role of the nucleus in the replication of the flaviviruses only and while replicating in the infected cells, flaviviruses and CHIK virus might express viral specific proteins in the cell nuclei.

Alphavirus↗
PubMed1993

Detection of viral antigens on the surface of cells infected with Japanese encephalitis virus by modified immunofluorescent technique.

A modified immunofluorescent method employing anti-Japanese encephalitis (JE) virus monoclonal (MoAbs) and polyclonal (immune PF) antibodies was evaluated for the detection of viral antigens expressed on the surface of porcine stable kidney cells infected with JE virus (733913, India). The infected cells showed granular immunofluorescence on the surface with both the MoAbs, Hs-1 and Hx-3 and immune PF 24 hr and 48 hr post virus infection. Interestingly, two strains of JE virus viz. Yoken (Japan) and 755468 (India) which did not react with the MoAb Hs-1 in the standard indirect fluorescent antibody (FA) technique, were positive for surface immunofluorescence (IF) with the same MoAb. Thus, the modified technique will be useful for the detection of more labile and conformational-dependent epitopes which might get lost or denatured by prior fixation of infected cells with acetone.

Animals↗
PubMed1992

Monoclonal antibody to Japanese encephalitis virus cross-reacting with histones present in the cell nuclei.

An immunoglobulin G (IgG2b) class of monoclonal antibody (MoAb, NHA-1) raised against Japanese encephalitis virus (JEV) E glycoprotein, reacted with the viral antigen expressed in cytoplasm of the infected cells and also with the cell nuclei, by an indirect fluorescent antibody technique (FA). The NHA-1 reactivity to nuclei was found to be due to its recognizing a JEV cross-reactive epitope present on the nuclear histones. Adsorption with calf thymus histones (type II-AS) showed a drop in NHA-1 reactivity to both JEV and histones by an enzyme-linked immunosorbent assay (ELISA) and indirect FA; the drop was higher against the histones. The MoAb recognized specifically the viral antigens expressed on the infected porcine kidney cell surface by a modified indirect FA. ELISA carried out with glutaraldehyde-fixed antigens showed an almost 2-fold increase in the reactivity over unfixed JEV antigen but none for the histones. Thus, the results indicate that histones share a sequential homology with E glycoprotein of JEV, which might lead to an autoimmune disorder induced due to the molecular mimicry between these two antigens.

Animals↗
PubMed1991

Detection of virus specific IgG subclasses in Japanese encephalitis patients.

During the Japanese encephalitis (JE) epidemic in 1988 at Gorakhpur, Uttar Pradesh, 34 cerebrospinal fluid (CSF) samples with 16 matching sera from 34 anti JEV IgM positive (confirmed JE) and 24 CSF samples with 4 matching sera from 24 anti JEV IgM negative (clinical encephalitis) patients were collected and tested for presence of JEV specific IgG by ELISA. Eighteen CSF samples and 8 matching sera from confirmed JE and 5 CSF samples and one matching serum from clinical encephalitis patients positive for JEV specific IgG were further assayed for subclass specificity using specific murine monoclonal antibodies. Almost all the samples exhibited IgG1 as the virus specific subclass. In addition to IgG1, one serum and one CSF sample each from two different confirmed JE patients showed the presence of virus specific IgG4 and IgG3 respectively. Half of the confirmed JE and clinical encephalitis patients exhibited intrathecal synthesis as evident from either elevated IgG index or CSF IgG/CSF albumin ratio. Most of the patients who recovered had predominantly virus specific IgG1 in CSF. It seems likely that IgG1 might have a protective role in clearance of virus from the central nervous system.

Adolescent↗
PubMed1991

Nuclear immunofluorescence in porcine kidney cells infected with Japanese encephalitis virus.

Acetone-fixed porcine stable kidney (PS) cells infected with Japanese encephalitis (JE) virus were stained in indirect fluorescent antibody (FA) assay with anti-JE virus monoclonal (MoAb) and polyclonal (immune PF) antibodies. First positive immunofluorescence (IF) occurred in the cytoplasm with MoAb Hs-1 (anti-envelope, JE-specific) and immune PF after 7 hr post-infection (p. i.); it became prominent by 15 hr to 48 hr (maximum) when cells reacted strongly also with MoAb Hx-3 (flavivirus crossreactive epitope). In addition, 15 to 20% of the infected cells, which revealed positive cytoplasmic IF, showed intranuclear IF with Hs-1, Hx-3, and immune PF by 20 to 24 hr p.i. By 48 hr, the intranuclear IF was not observed or became diminished. These observations indicate that the JE virus specific epitope Hs-1 appeared first followed by the flavivirus cross-reactive epitope Hx-3. Nuclei of the infected cells seem to play some role in the replication of JE virus.

Animals↗
PubMed1991

Characterization of & induction of immune response to anti-idiotypic antibodies for JE virus.

Anti-idiotypic antibodies (anti-Ids, Ab2s) were prepared by immunizing rabbits with two murine monoclonal antibodies (Ab1) having specificities for two independent haemagglutinin (HA) epitopes on JE virus [viz., Hs-1, monoclonal antibody (MAb) specific for Japanese encephalitis virus (JEV) and Hx-1, MAb common to flaviviruses]. Anti-Hs-1 (S-Ab2) and Anti-Hx-1 (X-Ab2) reacted specifically with the immunizing Ab1. In addition, they could react with other MAbs whose reactivity was similar to their immunizing homologous Ab1. The paratope inhibition assay indicated that both anti-idiotypes recognized paratope related idiotopes on their respective Ab1 and could therefore be designated as Ab2 beta. Experimental animals (Swiss mice, Balb/c mice and guineapigs) immunized with S-Ab2 or X-Ab2 produced anti-JE virus antibodies (Ab3) which could be detected by enzyme linked immunosorbent assay, immunofluorescence, haemagglutination inhibition and neutralization tests. The anti-idiotypes were also found to stimulate a cellular immune response in vitro as assessed by 3H thymidine incorporation by lymphocytes from JE vaccinated individuals and experimentally immunized Balb/c mice. The findings of the present study suggest that both the anti-Id antibodies are homobodies which may act as surrogate antigens to manipulate the immune response against JEV.

Animals↗
PubMed1991

Circulating interferon-alpha in patients with Kyasanur forest disease.

Endogenous interferon (IFN) levels were monitored in acute (51) and convalescent phase (19) sera collected from patients suffering from Kyasanur forest disease (KFD). Levels of circulating IFN in the acute samples (GM 216.3 +/- 8.7) collected between 4 to 7 post onset day (POD) were significantly higher (P less than 0.001) than the convalescent samples (GM 13.19 +/- 1.6) collected between 30th to 90th POD. Interferonemia was concomitant with the viraemic phase. Neutralization studies indicated that the endogenous (circulating) IFN was antigenically similar to acid stable form of IFN-alpha.

Acute Disease↗
PubMed1990

Selection of a neutralization-escape variant strain of Japanese encephalitis virus using monoclonal antibody.

An Indian strain of Japanese encephalitis virus (JEV), 733913, a human isolate from Bankura, West Bengal in 1973, with all the functional epitopes designated by a panel of murine monoclonal antibodies (MAbs), was treated with one of the JEV specific HI reactive MAb(Hs-I). This led to selection of a neutralization-escape variant which showed loss of reaction to three different MAbs belonging to the same domain (Hs) and assumed similar characteristics to another JEV strain (755468) also isolated from Bankura in 1975 from mosquitoes. It is possible that selection of such variant might occur in presence of pre-existing JE antibody (Hs-I type) in pigs which are amplifying hosts of JEV. Subsequent dissemination of such variant virus could occur through mosquitoes.

Animals↗
PubMed1990

Protective effect of 6-MFA, a fungal interferon inducer against Japanese encephalitis virus in bonnet macaques.

6-MFA, an extract from the fungus Aspergillus ochraceus was administered to 8 bonnet macaques. An equal number of monkeys matched for age, sex and weight received placebo and served as controls. Twenty hours after the administration of the 6-MFA/placebo the monkeys were challenged with an Indian strain of Japanese encephalitis virus by the intranasal route. Signs and symptoms of the disease such as fever, tremors, loss of appetite, dehydration, flaccid paraplegia or quadriplegia were pronounced in all the control monkeys, while in the 6-MFA treated group only two developed symptoms. Virus could be isolated from only one of the 6-MFA treated monkeys on day 6, and from four control monkeys; one each from CSF, spinal cord, blood and from both nasal swab and blood of the fourth monkey. The appearance of HI and N antibodies in 6-MFA treated group was either delayed or completely suppressed. The results indicate that 6-MFA is a potential antiviral agent which can be used to reduce the morbidity and mortality in bonnet macaques (Macaca radiata) experimentally infected with Japanese encephalitis virus.

Animals↗
PubMed1989

Route-related variation in the immunogenicity of killed Salmonella enteritidis vaccine: role of antigen presenting cells.

In order to assess the role of the route of immunization on the immunogenicity of killed Salmonella vaccine, mice were immunized with killed S. enteritidis by intraperitoneal (i.p.) and intradermal (i.d.) routes. Whereas the former was non-immunogenic, the i.d. immunization generated an excellent delayed-type hypersensitivity response; further, i.p. immunization could even suppress the subsequent i.d. immunization. Since the peritoneal macrophages (MO) are known to be particularly low in Ia or MHC-class II antigens, so essential for antigen presentation, the non-immunogenicity by i.p. route was thought to be due to their poor presentation efficiency. Poly I: poly C, an interferon inducer, is known to enhance the MHC-class II expression; hence effect of poly I: poly C treatment on the immunogenicity of the killed vaccine by i.p. route was tested and indeed the non-immunogenicity was corrected. Poor efficiency of presentation of S. enteritidis antigen by peritoneal cells and its improvement by prior poly I: poly C treatment was further confirmed by in vitro lymphocyte transformation test using primed T cells and peritoneal cells from normal and poly I: poly C treated mice. Poly I: poly C treatment also enhanced expression of Ia antigens on peritoneal cells.

Animals↗
PubMed1989

Epitope analysis of strains of Japanese encephalitis virus by monoclonal antibodies.

Twenty one strains of Japanese encephalitis (JE) virus, including 16 from India, were compared antigenically on the basis of their reactivity in immunofluorescence (IF), haemagglutination inhibition (HI), ELISA with captured antigen (ECA), and neutralization (N) tests with JE monoclonal antibodies (MAbs). These MAbs represented three domains of distinct epitopes on the envelope protein, designated as Hs-1 to 4 (JE specific in HI), Hx-1 to 5 (flavivirus cross reactive in HI) and NHs-1 to 2 (non-HI JE virus specific). Fifteen of the 21 strains studied were placed in group I. These reacted with MAbs representing the three domains in all the tests indicating presence of the three types of epitopes with full functional activity. The remaining six strains were placed in group II and showed loss in HI reactivity with Hs MAbs but not with Hx MAbs. All the group II strains also reacted in IF and ECA with NHs-1. Hs epitopes in three strains, G9473 (Tamil Nadu), 641686 (Tamil Nadu) and 822199 (Karnataka), appeared to have mutated partially, indicating loss in HI reactivity with Hs MAbs only, while there was retention of other reactivities, viz., IF, ECA and to some extent N test with G9473 and 641686. The remaining three strains, 691004 (Sri Lankan), 755468 (West Bengal) and Yoken (Japan) of group II showed almost complete loss of Hs-1 and Hs-2 epitopes as there was absence of reactivity in IF, ECA and N test in addition to HI. However, Hs-3 MAb showed reactivity in IF with these strains.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗