Prevalence of hypertension and correlates among adults of 45-60 years in a rural area of Tamil Nadu.

Hypertension is one of the major causes of cardiovascular morbidity and mortality. Community based studies in the rural areas of Tamil Nadu on the prevalence of hypertension and its associated risk factors are scarce. A cross-sectional study was undertaken among a sample of 406 individuals (45-60 years) selected by the standard 30 cluster systematic random sampling technique to find out prevalence of hypertension and its associated risk factors in a rural area of Tamil Nadu. Chi-square test and multiple logistic regression were employed using SPSS package. The overall prevalence of hypertension was 33% and higher among sedentary type (41%). In bivariate analysis many of the independent variables correlated with hypertension, but in multivariate analysis, only body-mass index, family history and age remained significant.

Short Communication: detection of dengue virus antigens in desiccated mosquitoes: an improved tool for surveillance.

We developed a surveillance tool to monitor dengue virus (DENV) infection in vector mosquitoes using a dengue antigen-capture enzyme immunoassay (EIA) on desiccated specimens stored at room temperature (RT). We tested the effect of storage on the stability of DEN1, DEN2, DEN3 and DEN4 antigens. Although desiccated infected Aedes aegypti mosquitoes stored between 31 and 34 degrees C (RT) showed greater reactivity in the EIA than those stored at -80 degrees C, a significant difference between the two was observed only with DEN2. Storage between 31 and 34 degrees C for up to 4 weeks (the longest period tested) did not affect the reactivity in the EIA, indicating the stability of DENV antigens.

The 2001 dengue epidemic in Chennai.

UNLABELLED: Dengue is emerging as a serious public health problem in Tamil Nadu. The present surveillance system is unlikely to generate proper information on the epidemiology of the disease, which is essential for planning and development of relevant control/preventive measures against dengue. OBJECTIVE: Between November 2001 and January 2002, a descriptive study was undertaken on children with clinical dengue attending Kanchi Kamakoti Child Trust Hospital (KKCTH, a major private referral pediatric hospital in Tamil Nadu, India) to define the magnitude of dengue burden, the natural history of this disease in terms of clinical presentation, and outcome of the infections in hospitalized children (< 15) with clinical dengue. METHODS: The sera collected from patients analyzed for dengue specific IgM and IgG antibodies by IgM, IgG antibody capture enzyme linked immunosorbent assay (ELISA) using alternatively two commercial kits. World Health Organization clinical case definition was adopted to categorize the dengue confirmed children. RESULTS: Dengue was diagnosed in 74.5% (143) of the 192 hospitalized children with clinical dengue. A considerable proportion (20%) of the total dengue infections were constituted by infants less than 1 yr of age. DF [dengue fever], DHF [dengue hemorrhagic fever] and DSS [dengue shock syndrome] were diagnosed in 65%, 11.2% and 23.8% of 143 dengue confirmed patients respectively. Though severe dengue (DSS + DHF) was present in 35% of the patients, the mortality rate was low during the study period due to timely diagnosis and clinical management of the patients. CONCLUSION: In developing countries like India, building of laboratory capacity for diagnosis and combat-mode ready preparedness for the management of dengue cases in emergency situation may reduce dengue-related mortality. This can be achieved in a wider scale through an integrated approach through the community, professionals and the public health departments.

First time detection of Japanese encephalitis virus antigen in dry and unpreserved mosquito Culex tritaeniorhynchus Giles, 1901, from Karnal district of Haryana state of India.

Japanese encephalitis virus (JEV) antigen has been detected by antigen capture enzyme linked immunosorbentassay (ELISA) in dry specimens of the mosquito Culex tritaeniorhynchus Giles, 1901, collected from Karnal district of Haryana state in northern India. These mosquitoes were stored in dry condition for 20 months, at room temperature, before processing. The procedure of detecting JEV infection in long time stored, dry vector mosquitoes, has important application in the surveillance of Japanese encephalitis.

Dengue disease spectrum among infants in the 2001 dengue epidemic in Chennai, Tamil Nadu, India.

An investigation in a referral pediatric hospital has indicated that during a recent dengue outbreak in Chennai, Tamil Nadu, India, dengue in infancy constituted 20% of total dengue virus infections with low mortality rates in this hospital. In developing countries, strengthening of dengue management capabilities at hospitals can prevent dengue-related deaths in infants.

Longitudinal studies in South Indian villages on Japanese encephalitis virus infection in mosquitoes and seroconversion in goats.

Japanese encephalitis (JE) is endemic in Cuddalore district, Tamil Nadu, where Culex tritaeniorhynchus Giles was the major vector. We screened 45 100 adult female Cx. tritaeniorhynchus (902 pools) by enzyme-linked immunosorbent assay and isolated and confirmed JE virus (JEV) by using an insect bioassay system. We had 69 isolates of which 62 (90%) were identified as JEV. The average vector abundance per man hour for Cx. tritaeniorhynchus was 324.5 per month for the period June 1998-May 2000. The average minimum infection rate (MIR) per month in Cx. tritaeniorhynchus was 1.4 (range 0.0-5.6). Every year, a new batch of goats, 20 in the first year and 31 in the second year, born during the non-JE transmission period (January-June), aged <6 months and negative for haemagglutination inhibition (HI) antibodies were procured and placed in the villages as sentinels. Fortnightly, blood specimens were collected from these goats and tested for JE antibodies by HI test. Seroconversions (SCs) were recorded in 14 goats (70%) in the first year and 23 goats (74%) in the second year. JE HI antibody titres in goats were low (1:10-1:80) and these levels declined to undetectable levels in about 4 weeks following SCs. The time sequence of events indicated that four of five peaks of MIR in mosquitoes were followed 1-3 months later by peaks in the proportion of seroconverted goats. We suggest the screening of goats and cattle as a more feasible tool to stratify areas according to JE infection risk to the human population through the regular health system rather than screening mosquitoes using monoclonal antibodies, which is possible only in specialized laboratories.

A modified immunofluorescence assay for detection of Japanese encephalitis virus-infected cells.

Japanese encephalitis virus (JEV) infections are currently detected by indirect immunofluorescence (IF) assay using virus-specific antibodies on acetone-fixed smears. On few occasions, the acetone treatment was reported to damage certain epitopes on JE virus (JEV) glycoprotein. Here, we have made an attempt to adopt quick paraformaldehyde fixation followed by a short detergent treatment of cells in suspension for identification of JEV-infected brain cells of laboratory-reared Toxorhynchitis splendens mosquito larvae using virus-specific antibodies. JEV-positive cells could be scored by the presence of a well defined intracellular immunofluorescence staining against unstained uninfected antibody-treated cells. The advantage of this assay is that stained cell suspensions can be stored for up to 4 weeks, allowing analysis at convenience. Thus, the modified IF assay can be employed as an additional/alternate technique to standard IF assay for detection of JEV in cells and also to screen hybridoma cell lines for anti-JEV antibody production.

Cross-resistance to Bacillus sphaericus strains in Culex quinquefasciatus resistant to B. sphaericus 1593M.

Bacillus sphaericus 1593M resistant larvae of Culex quinquefasciatus were reared in the laboratory since 1995. Resistance in the larvae was monitored by subjecting selection pressure using B. sphaericus 1593M at every generation. Bioassays were conducted with different strains of B. sphaericus (Bs 2297, Bs 2362 and Bs IAB 59) and confirmed cross-resistance in the present study. The level ranged between 27.3 to 18.2 fold in comparison with susceptible larvae. But Bacillus thuringiensis var israelensis strains (Bti PG14 and Bti 426) did not show any cross-resistance in the larvae and it emphasized a need to study the mode of action of B. sphaericus toxin that induces cross-resistance in the larval strain.

Immune responses to chloroquine--sensitive and resistant populations of Plasmodium berghei in mice.

In order to elucidate the role of the host as a factor in the spread of chloroquine resistance, a study of the host's immune responses in chloroquine resistant (cqr) and chloroquine sensitive (cqs) Plasmodial infections is essential. Course of the infection and the nature of immune responses in mice infected with chloroquine resistant (R) and chloroquine sensitive (S) strains of Plasmodium berghei were compared. Crude parasite antigen activated T cells from both the groups of mice (R and S) and the parasite specific antibodies were detected in the sera of both the groups. The differences in immune responses between the control (uninfected) and infected mice were found to be significant. However, humoral and in vitro cellular responses obtained with T cells from chloroquine resistant P. berghei primed mice was lower in comparison with the responses obtained with T cells from the sensitive infections. Our studies therefore suggest that immunosuppression to parasite antigen is seen in mice primed with chloroquine resistant P. berghei, which may play a role in the development of resistance.

A longitudinal study of sero-reactivity to Plasmodium falciparum antigen in children and adult living in an endemic area of U.P.

Antibody levels of Pf RESA derived peptide R1 (EENVEHDA-C) from individuals living in malaria endemic areas correlated well with levels of endemicity. Serological and parasitological investigations were done in 32 adults (> 20 yrs) and 35 children (2-5 yrs) for three years; i.e. from 1992-95 periodically in village Piyawoli, U.P. Antibody levels against R1 peptide was estimated by ELISA, and blood smear for P. falciparum and P. vivax were screened using Jaswant Singh-Bhattacharya (JSB) staining. It appeared from our investigations that anti-R1 antibodies had a short span of life, i.e. 6-9 months. The longevity of these antibodies do not differ much in adults and children. The studies do not indicate any protective role for these antibodies. However, the levels of anti-R1 antibodies in a population living under malariogenic condition are related to Pf malaria endemicity.

T cell immunity in malaria.

Immunity to malaria is a complex process. In malaria endemic areas, sustained clinical immunity develops gradually. Protective immunity to malaria comprises both antibody-dependent and antibody-independent effector mechanisms. Although, the relative roles of B and T cells differ in different malaria systems and different stages of the parasite, T cells are essential for the induction and maintenance of immunity against malaria. T cell-derived soluble factors are believed to be important mediators of cellular effector mechanisms. The efficacy of an antigen as a malaria vaccine depends to a great extent on the T cell recognition sites and the nature of the responses induced by these determinants. In order to select suitable epitopes in an immunogen, an understanding of the definition of antigenic sites recognized by T cells and characterization of the nature of the T cell responses induced in malaria endemic populations is important.

Immunogenicity of the nonrepetitive regions of the circumsporozoite protein of Plasmodium knowlesi.

The circumsporozoite antigen (CS) of the simian malarial parasite Plasmodium knowlesi consists of tandemly repeated immunodominant peptide units that are variable and may play a role in evading the immune system. To study the immunogenicity of this antigen in the absence of the immunodominant repeats, the entire nonrepetitive region of the antigen was expressed in Escherichia coli as two fusion proteins with glutathione-S-transferase (GST) representing the amino terminal (GST-CSN) and the carboxy terminal domains (GST-CSC) of the CS antigen. The immunogenicity of these fusion proteins was studied in rabbits and different strains of mice. Antibody raised against both the CSN and CSC domains in both rabbits and every strain of mice recognized the native protein, as detected by immunofluorescence assay (IFA) using P. knowlesi sporozoites. A positive IFA reaction was also obtained with P. vivax sporozoites using antisera raised against the CSC domain. High titer antisera were raised in rabbits against both the domains, whereas mice showed comparatively low titers. On Western blots, mice showed specific response against the CSC domain. In both rabbits and mice, significant titers of antibodies were raised against region II, which has been shown to be the putative sporozoite binding site for hepatocytes in the case of P. falciparum.