Sinorhizobium meliloti CheA complexed with CheS exhibits enhanced binding to CheY1, resulting in accelerated CheY1 dephosphorylation.

Retrophosphorylation of the histidine kinase CheA in the chemosensory transduction chain is a widespread mechanism for efficient dephosphorylation of the activated response regulator. First discovered in Sinorhizobium meliloti, the main response regulator CheY2-P shuttles its phosphoryl group back to CheA, while a second response regulator, CheY1, serves as a sink for surplus phosphoryl groups from CheA-P. We have identified a new component in this phospho-relay system, a small 97-amino-acid protein named CheS. CheS has no counterpart in enteric bacteria but revealed distinct similarities to proteins of unknown function in other members of the α subgroup of proteobacteria. Deletion of cheS causes a phenotype similar to that of a cheY1 deletion strain. Fluorescence microscopy revealed that CheS is part of the polar chemosensory cluster and that its cellular localization is dependent on the presence of CheA. In vitro binding, as well as coexpression and copurification studies, gave evidence of CheA/CheS complex formation. Using limited proteolysis coupled with mass spectrometric analyses, we defined CheA(163-256) to be the CheS binding domain, which overlaps with the N-terminal part of the CheY2 binding domain (CheA(174-316)). Phosphotransfer experiments using isolated CheA-P showed that dephosphorylation of CheY1-P but not CheY2-P is increased in the presence of CheS. As determined by surface plasmon resonance spectroscopy, CheY1 binds ∼100-fold more strongly to CheA/CheS than to CheA. We propose that CheS facilitates signal termination by enhancing the interaction of CheY1 and CheA, thereby promoting CheY1-P dephosphorylation, which results in a more efficient drainage of the phosphate sink.

Distribution pattern of HCV genotypes & its association with viral load.

BACKGROUND & OBJECTIVES: Hepatitis C virus (HCV) has emerged as a leading cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma worldwide. Genotyping and assessment of the viral load in HCV patients is important for designing the therapeutic strategies. Thus the present study was designed to determine the distribution pattern of HCV genotypes in chronic hepatitis patients and their association with the viral load and biochemical profiles. METHODS: Seventy one HCV RNA positive patients were included in the study. HCV genotyping was carried out by restriction fragment length polymorphism (RFLP) followed by the direct sequencing of the core region. Viral load estimation was carried out by Taqman real time PCR system. RESULTS: Sixty three per cent (45/71) of cases were infected with genotype 3 followed by genotype 1 in 30.98 per cent (22/71) and genotype 2 in 5.63 per cent (4/71) of cases. Genotype 1 was associated with a significantly (P<0.001) higher viral load as compared to genotypes 3 and 2. There was no significant difference seen in the biochemical profile between the three groups of genotypes except in the levels of SGOT. The commonest mode of transmission was parenteral which accounted for 68 per cent of all the infected cases. INTERPRETATION & CONCLUSIONS: The present study revealed that HCV genotype 3 and 1 accounted for approximately 95 per cent of the HCV infection in Delhi and surrounding areas. Also two atypical subtypes like 3i and 3f were identified. Genotype 1 was associated with more severity of liver disease as compared to genotypes 3 and 2 as assessed by viral load.

Hepatitis C virus core antigen assay: can we think beyond convention in resource limited settings?

Hepatitis C virus infects over 15 million patients from India and 2.86 million from Brazil. Detection of anti-hepatitis C virus antibodies has limited sensitivity during acute phase: the pre-seroconversion window period. Hepatitis C virus-RNA detection techniques are used to overcome this shortfall, but are costly and unavailable widely in developing countries. Estimation of hepatitis C virus core-antigen, a protein with highly conserved sequence, by enzyme-immunoassays is an economic and simpler alternative to RNA detection. This study was conducted in Delhi, involving 300 acute and chronic liver disease patients, tested for anti-hepatitis C virus 3rd-generation ELISA, hepatitis C virus core-antigen-ELISA and hepatitis C virus-RNA reverse transcription-polymerase chain reaction. Among the acute patients, hepatitis C virus core-antigen assay could identify 13 out of 14 pre-seroconversion window period cases and 6 out of 8 seroconverted cases, with a pre-seroconversion window period sensitivity of 92.9% and specificity of 100%. In hepatitis C virus core-antigen-positive cases, the viral load was in the range of 4900 to 1.46×10(6)IU/mL, whereas in hepatitis C virus core-antigen-negative cases, the range of viral load was 100-4500IU/mL. The cost of the hepatitis C virus core-antigen-ELISA was estimated around 3-4 times lesser than the in-house reverse transcription-polymerase chain reaction and 9-10 times lesser than the United States Food and Drug Administration approved reverse transcription-polymerase chain reaction. With a good sensitivity and specificity in the acute phase of infection, hepatitis C virus core-antigen-ELISA can thus be a useful alternative in the developing nations.

Polymorphism of tumor necrosis factor-α and interleukin-10 gene promoter region in chronic hepatitis C virus patients and their effect on pegylated interferon-α therapy response.

The development and resolution of an inflammatory process is regulated by a complex interplay among cytokines that have pro- and anti-inflammatory effects. Regulatory mechanisms that control the production of cytokines include genetic polymorphism in particular promoter/leader region. Polymorphisms may directly or indirectly affect the binding of transcriptional factors, consequently increasing or decreasing the production of mRNA, thus regulating cytokine production. A total of 70 hepatitis C virus (HCV) RNA-positive patients and 70 healthy control subjects were included in the present study, who were attending the medical outpatient department (OPD) and wards of a tertiary care hospital in New Delhi during 2006-2008. This study was designed to determine the polymorphism of tumor necrosis factor-α and interleukin-10 genes in patients with chronic HCV infection patients and their effect on pegylated interferon-α therapy response. Polymorphism in the tumor necrosis factor-α G/G, G/A, and A/A genotype was significant between HCV patients and healthy controls. Interleukin-10 variants (G/G, G/A) were nonsignificant among HCV patients compared with healthy controls. As this is a preliminary study on small sample size, we believe that our findings may stimulate further studies on larger number of patients from this geographic region.

A Simple Method for the Efficient Isolation of Genomic DNA from Lactobacilli Isolated from Traditional Indian Fermented Milk (dahi).

A simple, inexpensive and effective genomic DNA isolation procedure for Lactobacillus isolates from traditional Indian fermented milk (dahi) is described. A total of 269 Lactobacillus isolates from fermented milk collected from four places in North and west India were tested for lysis by an initial weakening of the Gram positive cell wall with Ampicillin followed by Lysozyme treatment. The average genomic DNA yield was ~50 µg/ml log phase culture. Quality and repeatability of the method was found to be adequate for subsequent molecular applications. The quality of the genomic DNA isolated by this method was verified by restriction digestion and polymerase chain reaction (PCR). No inhibition was observed in subsequent PCR amplification and restriction digestion. The presented method is rapid, cheap and useful for routine DNA isolation from gram positive bacteria such as Lactobacillus.

Characterization of the luteinizing hormone beta (LH-beta) subunit gene in the Indian river buffalo (Bubalus bubalis).

The cDNA sequence of leuteinizing hormone (LH) beta subunit was determined to understand the molecular basis for silent oestrus behavior and poor response to superovulation in buffalo. The LH-beta cDNA contains an open reading frame 426 bp long. The deduced sequence of the LH-beta is 141 amino acids in length. The amino acid sequences of the Indian river buffalo LH-beta subunit showed overall similarity to those of other mammals. The nucleotide sequence variability of LH-beta was studied in more than approximately 350 Indian buffaloes covering five different breeds. The results of the sequence analysis showed that the buffalo LH-beta gene is not highly conserved and non-synonymous mutations are not rare, at least in the samples collected randomly from five different breeds and buffalo populations. A total of seven different variants were obtained. In spite of its crucial role in reproduction, variation of the LH-beta gene was found present in this species. The polymorphisms found were unique in the Indian river buffalo population.

Distribution pattern of HCV genotypes & its association with viral load.

Background & objectives: Hepatitis C virus (HCV) has emerged as a leading cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma worldwide. Genotyping and assessment of the viral load in HCV patients is important for designing the therapeutic strategies. Thus the present study was designed to determine the distribution pattern of HCV genotypes in chronic hepatitis patients and their association with the viral load and biochemical profiles. Methods: Seventy one HCV RNA positive patients were included in the study. HCV genotyping was carried out by restriction fragment length polymorphism (RFLP) followed by the direct sequencing of the core region. Viral load estimation was carried out by Taqman real time PCR system. Results: Sixty three per cent (45/71) of cases were infected with genotype 3 followed by genotype 1 in 30.98 per cent (22/71) and genotype 2 in 5.63 per cent (4/71) of cases. Genotype 1 was associated with a significantly (P<0.001) higher viral load as compared to genotypes 3 and 2. There was no significant difference seen in the biochemical profile between the three groups of genotypes except in the levels of SGOT. The commonest mode of transmission was parenteral which accounted for 68 per cent of all the infected cases. Interpretation & conclusions: The present study revealed that HCV genotype 3 and 1 accounted for approximately 95 per cent of the HCV infection in Delhi and surrounding areas. Also two atypical subtypes like 3i and 3f were identified. Genotype 1 was associated with more severity of liver disease as compared to genotypes 3 and 2 as assessed by viral load.