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Biomedical subjects

G Sridharan

Publications and source records attributed to G Sridharan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Correlation of CD4(+) T-Cell counts estimated by an immunocapture technique (Capcellia) with viral loads in human immunodeficiency virus-seropositive individuals.

As antiretroviral therapy becomes more affordable, valid, reliable, and inexpensive laboratory tests are also needed to monitor the progression of disease in people with human immunodeficiency virus (HIV) infection. The CD4(+) T-cell counts estimated by Capcellia, an immunocapture method, and flow cytometry were compared and were correlated with HIV type 1 (HIV-1) load. There was a significant negative correlation between the HIV-1 load and CD4(+) T-cell counts estimated by flow cytometry (r = -0.63, P = <0.001) as well as between the HIV-1 load and CD4(+) T-cell counts estimated by Capcellia (r = -0.61, P = <0.001). Capcellia is a cost-effective, user-friendly assay that correlated well with HIV-1 load determinations for individuals both with and without treatment.

Adult↗
PubMed2001

A pilot study on the role of cytomegalovirus & human herpesvirus-6 infections in Indian bone marrow transplant recipients.

BACKGROUND & OBJECTIVES: Studies from Western transplant centers have shown the importance of cytomegalovirus (CMV) in infections among immunosuppressed post-transplant patients (both solid and bone marrow transplant recipients). Human herpesvirus-6 (HHV-6) infection is also important. Since such data are lacking from India, we carried out a pilot study to investigate the role of these two viruses in infections among Indian allogeneic bone marrow transplant (BMT) recipients. METHODS: A total of 21 BMT patients who developed acute graft versus host disease (GVHD), two patients who developed chronic GVHD, and eight recipients who did not develop GVHD but had skin rash/elevated liver enzymes, persistent cytopaenia or interstitial pneumonitis with a high clinical suspicion of possible CMV association were studied for markers of CMV and HHV-6 infections. RESULTS: CMV DNAemia was documented in 9 (42.8%) and CMV IgM in 4(19%) of the 21 patients with acute GVHD. HHV-6 DNAemia was not seen in any patient with acute GVHD but 2 (9.5%) had HHV-6 IgM. Of the 2 patients with chronic GVHD, 1 was positive for CMV DNA and IgM, and both were negative for HHV-6 markers. The lower incidence of CMV DNAemia in our recipients may be attributable to the presence of neutralizing antibody (anti gB/AD-1) among the 17 CMV and HHV-6 DNAemia negative recipients, 4(23.5%) had neutralizing antibodies (S/N ratio > or = 5). Of the 13 CMV DNAemia positive recipients, only one (7.7%) was positive for neutralizing antibodies. Among the 5 neutralizing antibody (S/N ratio > or = 5) positive recipients, 4 (80%) were negative for CMV DNAemia. The one nPCR positive was revealed only at high DNA (> 0.1 microgram) input indicating low CMV signal strength. INTERPRETATION & CONCLUSION: The present study shows the use of DNAemia in detecting CMV infections among BMT recipients. All recipients had high avidity CMV IgG (AI > 50%) confirming CMV reactivation or reinfection in these patients. There was evidence from this study suggesting that neutralizing antibodies may play a role in controlling CMV reactivation. We found no significant HHV-6 association with GVHD in Indian allogeneic BMT recipients.

Adolescent↗
PubMed2001

Characterization of antibody response to human cytomegalovirus in Indian renal transplant patients.

BACKGROUND & OBJECTIVES: Cytomegalovirus (CMV) disease in seroendemic transplant populations is due to reactivation of the virus, or reinfection. In this context, the antibody response is likely to influence presentation, clinical severity and outcome of the disease, and may provide a diagnostic and prognostic marker. This study was carried out in Indian renal transplant patients and healthy adults to characterize the antibody response to cytomegalovirus. METHODS: Thirty three transplant recipients with CMV illness (symptomatology with IgM and/or nPCR positive status), 20 recipients who were asymptomatic in the 6 months of follow up after transplantation and 62 healthy controls were investigated for markers of CMV infection. These individuals were tested for IgG avidity and neutralizing antibody by ELISA techniques. RESULTS: All 53 transplant recipients were found to have an IgG avidity index of > 50 per cent. Antibody to a CMV envelope glycoprotein gB/AD-1 (putative neutralizing antibody) was expressed as S/N ratio and was > or = 5 in asymptomatic (65%) and symptomatic (27%) immunosuppressed renal transplant recipients. However, none of the 53 CMV IgG positive healthy controls were positive for neutralizing antibodies S/N ratio > or = 5 (S/N ratio = sample mean OD/mean OD of 3 negative controls in each run). We observed the simultaneous presence of CMV PCR signal in leukocytes and neutralizing antibody (S/N ratio > or = 5) in the plasma in 22 (41.5%) of the 53 renal transplant recipients. INTERPRETATION & CONCLUSIONS: In this study among the immunosuppressed transplant patients we observed an association between symptomatic disease and the relative absence of neutralizing antibodies. The neutralizing antibodies are less frequently demonstrable among controls; while appearance in a higher proportion of asymptomatic recipients especially in association with high IgG avidity (> 90%) is suggestive of its role in control of CMV disease despite reactivation as evidenced by DNAemia while on immunosuppressive therapy.

Adult↗
PubMed2001

A study on some phenotypic virulence markers of enteropathogenic Escherichia coli.

BACKGROUND & OBJECTIVES: The problem of enteropathogenic Escherichia coli (EPEC) causing diarrhoea in infants exists in India. But often the enteropathogenic status is not based on adequate characterization. Hence there is a need for evaluating the serotyping being used to identify EPEC for its validity in the light of recent knowledge on phenotypic markers of virulence. This study was done to evaluate the EPEC isolates for two potential virulence factors namely entero-adhesiveness with subsequent actin accumulation and verotoxin production. METHODS: Fifty consecutive EPEC strains identified by serotyping from stool samples of children with diarrhoea during January 1997 to June 1999 were studied for HEp-2 cell adherence, the fluorescent actin staining (FAS) characteristics of Hep-2 cells and vero cytotoxin production. RESULTS: Serotypes O55, O125 and O126 accounted for most of the isolates. In the Hep-2 assay, 72 per cent of the strains showed localised pattern of adherence and 22 per cent showed a mixed pattern of localised and diffuse adherence. In the FAS test 96 per cent strains showed typical staining while none of the strains produced verotoxin. INTERPRETATION & CONCLUSION: 'O' serogrouping appears to be still the simplest and an useful test for presumptive identification of EPEC. The FAS test for confirmation of EPEC was found to be very consistent in indicating EPEC.

Animals↗
PubMed2000

Peripheral CD4+/CD8+ T-lymphocyte counts estimated by an immunocapture method in the normal healthy south Indian adults and HIV seropositive individuals.

BACKGROUND: Flow cytometry is the standard method for the estimation of CD4/CD8 counts, but the high initial investment for this instrument and costly reagents make it unaffordable to most of the centers in a developing country like India. OBJECTIVES: To evaluate the feasibility of an alternate system for the estimation of CD4 and CD8 counts in normal south Indian adults and validate the usefulness of this assay to monitor the counts in HIV seropositive individuals. STUDY DESIGN: Forty-six normal healthy adults and 68 HIV seropositive individuals both belonging to south Indian linguistic groups were enrolled in this cross-sectional study. The HIV seropositive individuals included 54 HIV-1, 9 HIV-2 and 5 HIV 1&2 infected individuals serologically confirmed by one of the commercial Immunoblot kits. The Capcellia CD4/CD8 whole blood assay, an immuno-capture ELISA based kit from Sanofi DIAGNOSTICS Pasteur, (France) was used with a few modifications in the procedure to measure the CD4 and CD8 counts. RESULTS: The mean CD4 cell counts were 1048 (central 95 centile only), 746 and 424 for the normal healthy adults, asymptomatic HIV seropositives and symptomatic HIV patients, respectively, and the mean CD8 counts were 595, 889 and 732, respectively. Statistically significant differences were observed in the CD4 cell counts between HIV seronegative healthy adults and asymptomatic (P < 0.001) as well as asymptomatic and symptomatic (P < 0.05) HIV infected individuals. The mean CD4 counts of asymptomatic HIV-2 infected individuals was significantly higher than the counts of asymptomatic HIV-1 infected individuals (P < 0.05). CONCLUSIONS: This is an user friendly test and can be an alternate to flow cytometry for the estimation of peripheral T-lymphocyte subsets in developing countries. The assay system has certain limitations inherent to ELISA techniques.

Adult↗
PubMed2000

Molecular confirmation of human immunodeficiency virus (HIV) type 2 in HIV-seropositive subjects in south India.

Nested PCRs for human immunodeficiency virus type 1 (HIV-1) and HIV-2 were compared with immunoblot test results. Twelve of 13 immunoblot-positive HIV-2 samples were positive by PCR. There were five INNO-LIA (Innogenetics, Zwijnaarde, Belgium) and/or HIVBLOT 2.2 (Genelabs, Singapore) samples that tested positive for dual infection. HIV-1 PCR was positive in all samples, while HIV-2 PCR was positive in two and RIBA (Chiron Corporation, San Diego, Calif.) was positive for HIV-2 in three samples. Thus the prevalence of HIV-2 is accurately estimated by the use of immunoblotting, but that of HIV-1 and -2 dual infection may be overestimated.

Female↗
PubMed2000

Hospital-based evaluation of two rapid human immunodeficiency virus antibody screening tests.

Two rapid human immunodeficiency virus (HIV) screening assays, HIV TRI-DOT and HIV-SPOT were compared with standard enzyme-linked immunosorbent assays according to a testing algorithm. Sensitivities and specificities in the real-time evaluation were 99.5 and 99.9% for TRI-DOT and 98.2 and 99.7% for HIV-SPOT, respectively. These two tests are suitable for use where facilities and laboratory expertise are limited.

AIDS Serodiagnosis↗
PubMed2000

Cytomegalovirus infection in a seroendemic renal transplant population: a longitudinal study of virological markers.

BACKGROUND/AIMS: The detection of viremia by polymerase chain reaction (PCR) in cytomegalovirus (CMV) infection in renal allograft recipients has been shown to have a predictive value for disease. However, its diagnostic utility in a population with high background seropositivity has not been defined. This prospective study was undertaken to assess the relationship of CMV DNAemia, and/or IgM seropositivity to CMV disease in a seroendemic transplant population. METHODS: Consecutive patients undergoing renal transplantation between August 1997 and February 1998 were enrolled. Blood was sampled before transplantation from the donors and recipients for CMV serology and nested PCR for CMV DNA, and after transplantation from the recipients only at monthly intervals until 6 months. Patients were observed for the development of any CMV-like illness during follow-up. CMV DNA was quantitated using limiting dilution PCR on samples obtained from symptomatic patients at the time of illness and from asymptomatic patients at the end of their 6-month follow-up. RESULTS: A total of 57 recipient-donor pairs were recruited. Immunosuppression was cyclosporine-based in 55 of 57 (95. 6%). The CMV serologic status was D+R+ in 55 of 57 and D+R- in 2 of 57 pairs. PCR positivity indicating viremia increased from 5% before transplantation to 95% at 6 months after transplantation. Similarly IgM positivity reached 80% at 3 months and thereafter; positivity for any marker was 100% by 6 months. Viremia was sustained in over half the patients. The incidence of CMV-attributable disease peaked at 3 months, and was predominantly mild and self-limiting. Tissue-invasive disease appeared later in 4 patients (7%). Asymptomatic viremia was seen in 60-70% of patients at each sampling point. The positive predictive value (PPV) of PCR positivity for disease was 35-40%, and the negative predictive value (NPV), 90-100%. However, the high NPV was of use only in the early post-transplant period, negativity for markers declining rapidly with time. Quantitative assay showed significantly higher levels of CMV DNA in symptomatic patients (p = 0.01). A cutoff of 0.001 microg had a specificity of 95% and a PPV of 92.3% for symptomatic CMV disease. CONCLUSION: Qualitative tests to detect CMV DNAemia and IgM, although useful markers of viremia and active infection, have limited utility for the diagnosis of disease in a seroendemic transplant population. Quantitation of CMV DNAemia may play an important role in diagnosis in such a setting.

Adolescent↗
PubMed2000

Increase in plasma IL-10 levels and rapid loss of CD4+ T cells among HIV-infected individuals in south India.

Increased levels of immune activation among HIV patients from developing countries are believed to accelerate and/or enhance the shift to a Th2 cytokine environment, which in turn may result in a more rapid progression to AIDS. In support of this hypothesis, we present data from a cohort of 35 HIV+ individuals in southern India. Among asymptomatic individuals in this cohort, a dramatic increase in plasma interleukin (IL)-10 coincided with rapid decrease in CD4 counts and progression to AIDS. Serum IL-10 levels were significantly higher after 6 months of follow up (P=0.01), while CD4 counts declined at a rate of 280 cells/ul per year, roughly 3 times the rate of decline reported for HIV+ asymptomatic subjects in developed countries. Changes in serum IL-10 levels and CD4 counts fell short of statistically significant correlation (P=0.1). Among AIDS patients in this cohort, the mean period from diagnosis of AIDS to death was <5 months and is in agreement with an earlier report of rapid progression in India.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Role of molecular techniques in the detection of HBV DNA & HCV RNA among renal transplant recipients in India.

In this study we have investigated the occurrence of hepatitis B virus (HBV), hepatitis C virus (HCV) and hepatitis D virus (HDV) infections among 68 renal transplant recipients. Replicative HBV and replicative HCV infections were seen in 12 (17.6%) and 38 (55.9%) patients respectively, the difference was statistically significant (P < 0.001). Among the 38 HCV RNA+ individuals, anti-HCV was present only in 23. Anti-HCV in the absence of HCV RNA was detected in one patient. Anti-HDV antibody was seen in 2 (15.4%) of the 13 HBV infected individuals. Nine (13.2%) of the 68 individuals had replicative dual infection with HBV and HCV. Triple infection (HBV DNA+, HCV RNA+, anti-HDV+) was seen in 2 transplant recipients. There was significantly higher demonstration of replicative HCV (P < 0.001) in transplant recipients having elevated liver enzymes (n = 34) as compared to transplant recipients having normal liver enzyme levels (n = 34). Though not significant, a higher detection rate was also seen with replicative HBV infection and replicative dual infection among transplant recipients with elevated liver enzymes. The higher detection of HCV in renal transplant recipients by molecular techniques, emphasizes the need for HCV RNA testing. Further deliberate attempts to change practices to reduce this problem may also improve graft and patient survival in recipients.

Adolescent↗
PubMed2000

Vaccinia reactive antibodies in a south Indian population.

The prevalence of vaccinia virus antibodies was determined in both urban and rural populations in southern India. The study sample consisted of 211 adults and 52 children. The antibody titre was measured in all sera by virus neutralisation and by indirect immunofluorescence assay (IFA). A small panel of sera was tested by Western blotting. There was no significant difference in detection rates between the tests. Generally, seropositivity correlated with a previous history of vaccination. All children were negative for vaccinia antibodies. Among adults overall, 54% had neutralising antibodies whereas 60% were positive for antibodies detected by IFA, however, the prevalence of vaccinia antibody by either method was significantly higher (P < 0.001) among rural subjects than in urban subjects. This higher antibody prevalence among the rural population could be due to exposure to other indigenous orthopoxviruses, possibly buffalopox.

Adult↗
PubMed2000

Prevalence of enterically transmitted hepatitis viruses in patients attending a tertiary--care hospital in south India.

The prevalance of enterically transmitted hepatitis viruses, namely, hepatitis A virus (HAV) and hepatitis E virus (HEV) were studied in 404 patients with acute hepatitis attending a tertiary-care hospital in south India. Presence of current HAV/HEV infection was ascertained by the demonstration of IgM antibodies. In 381 patients tested for both agents, HAV IgM was present in 51(13.3%) and HEV IgM present in 66(17.3%). There was dual infection in 3 males (0.8%). HEV infection was seen mostly in older children and adults with only 5.5% occurring in children < 12 years of age. HAV infection was commonly seen to occur in < 12 years of age group (52.7%). One hundred and twenty-six patients were from the Vellore region, among whom HAV and/or HEV aetiology was observed in 28.5%. In this region there did not appear to be any correlation between occurrence of acute hepatitis due to these viruses and rainfall or environmental temperature. Acute hepatitis due to enteric hepatitis viruses was seen throughout the year.

Adolescent↗
PubMed1999

Improved sensitivity of reverse transcriptase polymerase chain reaction for hepatitis C virus using random hexamer primers.

The use of specific primers and random primers for the detection of hepatitis C virus RNA by reverse transcriptase-polymerase chain reaction was compared. The cDNA obtained from using both methods was amplified by the same protocol. Of the 30 plasma specimens tested, 6 (20%) were hepatitis C virus RNA-positive using specific primers and 19 (63%) were positive using random primers, demonstrating that the use of random hexamer-primed reverse transcriptase-polymerase chain reaction significantly improves the sensitivity (p < 0.01).

DNA Primers↗
PubMed1999

Comparison of two different methodologies for the detection of hepatitis B virus DNA in plasma.

In this study, two different methodologies were compared for the detection of hepatitis B virus (HBV) DNA in the plasma of 28 patients and 36 controls. Method 1 was a nested polymerase chain reaction (PCR) followed by product detection in an ethidium bromide stained gel, whereas method II was a commercial single step PCR with digoxigenin labeled product captured by a probe and then detected in a digoxigenin-antidigoxigenin enzyme-linked immunosorbent assay (DIG ELISA). The results indicate that both methods are comparable showing a concordance of 98.4%, there was no statistically significant difference in the detection rates. We feel that any one of these assays may be suitable in a clinical laboratory setting, though the commercial assay may offer some advantages to laboratories without sufficient skilled staff in trouble-shooting PCR related problems.

DNA, Viral↗
PubMed1999

Cytotoxicity of non O1, non O139 Vibrios isolated from fresh water bodies in Vellore, south India.

The samples of plankton, soil sediment and water from a pond, a lake and a moat respectively in and around Vellore were studied for environmental vibrios. Vibrios were isolated from all these specimens after enrichment in alkaline peptone water and subculture on selective media. Non O1, non O139 Vibrio cholerae, Aeromonas spp. and Plesiomonas spp. were isolated. There were no isolates of V. cholerae serogroup O1 and O139. Representative strains of non O1 and non O139 V. cholerae from environmental sources were tested for toxin production in Chinese hamster ovary (CHO) and Vero cell monolayer in microtitre plates. Thirty-three (91.7%) of the 36 strains tested demonstrated cytopathic effect (CPE) in both cell lines indicating their toxigenicity. PCR done on representative strains of non O1 and non O139 V. cholerae showed that none of the strains were positive for ctx A, tcp A-E and tcp C genes. These results indicate that these non agglutinating environmental vibrios produced cytotoxins other than the cholera toxin.

Aeromonas↗
PubMed1998

A novel factor produced by placental cells with activity against HIV-1.

The factors controlling the dynamics of HIV-1 transmission from mother to infant are not clearly known. Previous studies have suggested the existence of maternal and placental protective mechanisms that inhibit viral replication in utero. Preliminary studies from our laboratory revealed that supernatant from placental stromal cells protected HIV-1-infected PBMC from virus-induced apoptosis and suppressed virus production. We have attempted to characterize the antiviral activity of this placental factor (PF) and delineate the stages of HIV-1 replication affected. This activity was not due to the presence of any known cytokine reported to have anti-HIV effect. Direct exposure to PF had no suppressive effect on the infectivity of cell-free HIV-1, and envelope-mediated membrane fusion appeared to be unaffected. Western blot analysis of HIV-1 from infected PBMC treated with PF revealed that expression of all viral proteins was reduced proportionately, both intracellularly and in released virions. However, exposure of HIV-1-infected cells to PF resulted in production of virions with 10-100-fold-reduced infectivity. PF-treated virions contained two- to threefold reduced ratios of cyclophilin A:Gag protein as compared with untreated virus. Reduced cyclophilin A content resulting in decreased binding of cyclophilin A to Gag could account, in part, for the observed reduction in infectivity. Our results suggest that placental cells produce an antiviral factor that protects the fetus during gestation and may have therapeutic potential.

Anti-HIV Agents↗