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Papers by Amit Ghosh

PLoS ONE, 2014

Background: A live oral cholera vaccine VA 1.4 developed from a non-toxigenic Vibrio cholerae O1 ... more Background: A live oral cholera vaccine VA 1.4 developed from a non-toxigenic Vibrio cholerae O1 El Tor strain using ctxB gene insertion was further developed into a clinical product following cGMP and was evaluated in a double-blind randomized placebo controlled parallel group two arm trial with allocation ratio of 1:1 for safety and immunogenicity in men and women aged 18-60 years from Kolkata, India. Method: A lyophilized dose of 1.9610 9 CFU (n = 44) or a placebo (n = 43) reconstituted with a diluent was administered within 5 minutes of drinking 100 ml of a buffer solution made of sodium bicarbonate and ascorbic acid and a second dose on day 14. Result: The vaccine did not elicit any diarrhea related adverse events. Other adverse events were rare, mild and similar in two groups. One subject in the vaccine group excreted the vaccine strain on the second day after first dose. The proportion of participants who seroconverted (i.e. had 4-folds or higher rise in reciprocal titre) in the vaccine group were 65.9% (95% CI: 50.1%-79.5%) at both 7 days (i.e. after 1 st dose) and 21 days (i.e. after 2 nd dose). None of the placebo recipients seroconverted. Anti-cholera toxin antibody was detected in very few recipients of the vaccine. Conclusion: This study demonstrates that VA 1.4 at a single dose of 1.9610 9 is safe and immunogenic in adults from a cholera endemic region. No additional benefit after two doses was seen.

Nucleic Acids Research, 1984

The nucleotide sequence of black beetle virion (BBV) RNA2 has been determined. RNA2 is 1399 b lon... more The nucleotide sequence of black beetle virion (BBV) RNA2 has been determined. RNA2 is 1399 b long. Its 5' terminus is capped. Its 3' terminus has an unidentified moiety that renders the RNA resistent to polyadenylation and ligation. The first AUG codon at base 23 is followed by an open reading frame for a protein 107 amino acids long, the predicted size of coat protein precursor. A second open reading frame for a putative protein 72 amino acid residues long begins at base 1110. No other large open reading frames exist. The 5 1 half of the RNA can be folded into a long, imperfect hairpin of high predicted stability. The 3' half of the RNA can fold into a complex set of multiply bifurcated stem and loop regions.

Immunology Letters, 1999

The disease cholera is an important cause of mortality in many developing countries. Though it ca... more The disease cholera is an important cause of mortality in many developing countries. Though it can be controlled through improved sanitation, this goal is not easily attainable in many countries. Development of an efficacious vaccine offers the best immediate solution. A new oral candidate vaccine has been constructed from a non-toxigenic strain of Vibrio cholerae E1 Tor, Inaba, which is not only devoid of the cholera toxin (CT) virulence cassette but also is completely non-reactogenic in rabbit ileal loop assay. The strain, however, had toxR and tcpA genes. Through a series of manipulations, the ctxB gene of V. cholerae, responsible for the production of the 'B' subunit of the cholera toxin (CTB) was introduced into the cryptic hemolysin locus of the strain. The resulting strain, named vaccine attempt 1.3 (VA1.3), was found to be able to produce copious amounts of CTB. In the RITARD model this strain was found to be non-reactogenic and provided full protection against the challenge doses of both V. cholerae O1, classical and E1 Tor. In the immunized rabbit it invoked significant levels of anti-bacterial and anti-toxin immunity.

Microbiology, 1986

Alkaline phosphatase activity in Vibrio cholerae strain 569B grown in low-phosphate medium was st... more Alkaline phosphatase activity in Vibrio cholerae strain 569B grown in low-phosphate medium was stimulated if glucose or glycerol was used as the carbon source. No such stimulation was observed, however, if tricarboxylic acid cycle intermediates like succinate or citrate were used. Experiments using specific enzyme inhibitors strongly indicated that the metabolic reactions of the glycolytic pathway from glyceraldehyde 3-phosphate to 2-phosphoglycerate play a key role in the stimulation process.

Microbiology, 1995

General properties of the heat shock response in Vibrio cholerae were examined. Enhanced or de no... more General properties of the heat shock response in Vibrio cholerae were examined. Enhanced or de novo synthesis of 24 proteins was observed upon heat shock from 30 "C to 42 "C in cells labelled with [35S]methionine. A similar response could also be induced by a rise in temperature from 30 "C to 37 OC. Of these heat shock proteins, two were determined to be homologues of GroEL and DnaK, based upon their immunological cross-reactivity with antibodies raised against the Escherichia coli proteins. Three proteins, of molecular sizes 38,44 and 48 kDa, which were undetectable in the 30 "C grown culture, appeared de novo after the heat shock. As in other prokaryotic systems thermal induction of many of the proteins was transient, but both DnaK and GroEL remained induced for at least 28 min after heat shock. DNA hybridization studies revealed that genes analogous not only to dnaK and gmEL but also to dnal of Em coli exist in V. cholerae. Heat shock induced thermotolerance in V. cholerae but made the cells more sensitive to UV radiation. Unlike in E. coli, however, heat shock had no effect on the progeny virus yield in V. cholerae.

Problems of Particularly Dangerous Infections

The endemicity of cholera in India has been well researched. Among the other endemic areas, India... more The endemicity of cholera in India has been well researched. Among the other endemic areas, Indian subcontinent appears to be the cradle of Vibrio cholerae genovariants, which subsequently spread worldwide. In contrast, all the cholera cases recorded in Russia are of imported origin. In the past century, such importations might result in epidemics, which, however, ended with elimination of toxigenic V. cholerae (TVC) from the affected areas. Currently, the incidence of TVC in water reservoirs or infected returnees from Asian countries are rare events, mostly due to constant surveillance activities. Furthermore, the climatic conditions in the majority of Russian regions are unfavorable for longterm environmental survival of the pathogen. On the other hand, global shifts in climate accompanied by unexpected anomalies in previously stable climatic zones may promote dissemination of imported TVC and emergence of cholera. In some regions of Russia, seasonal weather patterns are pretty si...

Proceedings of the National Academy of Sciences, India Section B: Biological Sciences

ABSTRACT Microorganisms are extraordinarily diverse in their range of habitats. They are capable ... more ABSTRACT Microorganisms are extraordinarily diverse in their range of habitats. They are capable of growing wherever life is thermodynamically possible, making them capable of synthesizing myriad varieties of molecules, compounds, enzymes etc, which are yet beyond the reach of human capabilities. Hence it is being increasingly appreciated that in the search for new molecules etc., exploration of microbial biodiversity in search of the “right” microbe could be the first step. Earth consists a staggering number of microbes, a majority of which have remained unknown and unexamined not only because most of them are yet uncultivable but also because many habitats have remained unexplored. Efforts have been initiated globally including in India, to explore new habitats to look for microbes capable of making novel products and processes.

The Indian journal of medical research, 2011

Antimicrobial resistance poses a major threat in the treatment of infectious diseases. Though sig... more Antimicrobial resistance poses a major threat in the treatment of infectious diseases. Though significant progress in the management of diarrhoeal diseases has been achieved by improved hygiene, development of new antimicrobials and vaccines, the burden remains the same, especially in children below 5 yr of age. In the case of cholera, though oral rehydration treatment is the mainstay, antimicrobial therapy is mandatory at times to reduce the volume of stool and shorten the duration of the disease. Though for many pathogens, antimicrobial resistance emerged soon after the introduction of antibiotics, Vibrio cholerae remained sensitive to most of the antibiotics for quite a long period. However, the scenario changed over the years and today, V. cholerae strains isolated world over are resistant to multiple antibiotics. A myriad number of mechanisms underlie this phenomenon. These include production of extended-spectrum beta-lactamases, enhanced multi-drug efflux pump activity, plasmi...

The Indian journal of medical research, 1996

First attempt at cholera vaccination was made by Jaime Ferran in 1884. Since then, a variety of s... more First attempt at cholera vaccination was made by Jaime Ferran in 1884. Since then, a variety of strategies and methods have been evolved to create a safe, efficacious vaccine against cholera. For the first few years emphasis was on the development of parenteral vaccines. However, as a result of accumulation of a tremendous amount of knowledge, not only on Vibrio cholerae-the causative agent, but also on its interaction with the host, emphasis has shifted towards the development of oral vaccines. Two such vaccines, one killed, a whole cell/B subunit combination vaccine and the other a live attenuated one, have shown promise. The combination vaccine in its present state of development confers only a transient protection in young children, while the live attenuated one produces adverse reaction. To combat these, various strategies are being evolved. In one attempt, a potential candidate vaccine strain has been constructed from a non-reactogenic clinical isolate of V. cholerae, which is...

Mutation research, 1995

Wild-type Vibrio cholerae cells, when adapted by a stepwise treatment with sub-lethal concentrati... more Wild-type Vibrio cholerae cells, when adapted by a stepwise treatment with sub-lethal concentrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), acquired resistance to killing and mutagenesis by subsequent challenges with higher concentrations of MNNG. This was also seen in the rec isogenic strain indicating that the observed phenomenon was not due to the induction of SOS functions. Further, the adapted cells of both the wild-type and rec strains could reactivate lethally alkylated phages with equal efficiency. Increased resistance of adapted cells correlated with the induction of a 17-kDa DNA methyltransferase, capable of repairing O6-methylguanine lesions in DNA. This induced methyltransferase was found to be antigenically unrelated to the Escherichia coli methyltransferase (Ada protein) as determined by Western blotting with polyclonal antiserum raised against the E. coli protein. Even though no counterpart of the constitutively expressed methyltransferase (Ogt) of E. col...

Journal of virology, 1982

We show by sequence analysis of a 420-base-long region adjacent to the 3' polyadenylic acid o... more We show by sequence analysis of a 420-base-long region adjacent to the 3' polyadenylic acid of encephalomyocarditis viral RNA and by carboxy terminus analysis of protein E that the termination site of encephalomyocarditis virus polyprotein translation consists of two successive UAG codons located at positions 121 to 126 from the 3' polyadenylic acid.

Virology, 1982

Features of the primary structure and translation of the genomic RNAs of the cowpea and bean stra... more Features of the primary structure and translation of the genomic RNAs of the cowpea and bean strains of southern bean mosaic virus have been investigated in order to assess the similarity of the two viruses. The sequence of 400 bases at their 3' termini have been determined. These include the 3' noncoding regions and extend well into the coat protein cistrons. The noncoding regions (136 bases for the cowpea strain RNA and 129 bases for the bean strain RNA) show no obvious sequence homology. However, extensive base as well as amino acid sequence homology exists in the coding region. RNAs from both strains have a small protein attached to their 5' terminus-the protein in the cowpea strain being the smaller of the two. In vitro studies show that there are similarities in the overall mode of translation of the genomes of the two viruses. Although corresponding proteins are synthesized they differ in size.

Epidemiological and Molecular Aspects on Cholera, 2010

Page 1. Chapter 17 Integron-Mediated Antimicrobial Resistance in Vibrio cholerae Amit Ghosh and T... more Page 1. Chapter 17 Integron-Mediated Antimicrobial Resistance in Vibrio cholerae Amit Ghosh and T. Ramamurthy Abstract The disease cholera is the result of infection with the toxigenic strains of Vibrio cholerae. Even though ...

Virology, 1984

BBV (black beetle virus) RNAI, the subgenomic messenger RNA for BBV protein B and its double-stra... more BBV (black beetle virus) RNAI, the subgenomic messenger RNA for BBV protein B and its double-stranded form (dsRNA3) were purified from cells infected with BBV and were sequenced. RNA3 is 339 bases long. The sequence is homologous to that of the 3'terminal region of virion RNAl. RNA3 has a very limited homology to virion RNAt RNA3 is capped at its 5' terminus and has a structural feature at its 3' terminus that renders it inert to the action of the enzymes RNA ligase and poly(A) polymerase. RNA3 has two overlapping reading frames for putative proteins of size 10,763 and 11,633 Da. The positive and negative strands of dsRNA3 are not capped and correspond in length and sequence to RNA3 itself. Q 1986 Academic Press. 1nc.

Nucleic Acids Research, 1979

Voue7NmeI 99NcecAisRsac Southern bean mosaic viral RNA has a 5'-linked protein but lacks 3' termi... more Voue7NmeI 99NcecAisRsac Southern bean mosaic viral RNA has a 5'-linked protein but lacks 3' terminal poly(A)

MGG Molecular & General Genetics, 1985

Synthesis of tryptophanase, D-serine deaminase and alkaline phosphatase in Escherichia coli C was... more Synthesis of tryptophanase, D-serine deaminase and alkaline phosphatase in Escherichia coli C was repressed as the result of infection with the single-stranded DNA bacteriophage phi X174. However, the degree of repression differed, the more catabolite-sensitive the operon was, the more severe was the repression. For the catabolite-sensitive enzymes it was found that cyclic adenosine 3'5' monophosphate (cyclic AMP or cAMP) was unable to release or reduce the phage-induced inhibition. Experiments with amber mutants of phi X174 revealed that A, product of cistron A, was responsible for the inhibition. The cistron A product probably acted at the level of transcription. The possible role of A in the observed modulation of gene expression is discussed.

MGG Molecular & General Genetics, 1985

Two lines of evidence suggest that a gene analogous to the recA gene of Escherichia coli exists i... more Two lines of evidence suggest that a gene analogous to the recA gene of Escherichia coli exists in Vibrio cholerae and that its product serves a proteolytic function in the SOS response. Firstly, Southern blot hybridization using the recA gene of E. coli as a probe revealed a genomic sequence in V. cholerae which hybridized with the probe. Secondly, the SOS-like response in V. cholerae (as measured by beta phage induction) triggered by DNA damaging agents like Furazolidone could be blocked by Antipain, a protease inhibitor known to inhibit RecA protease action in E. coli. Maximal blocking effect of Antipain on beta phage induction occurred at 1 mM. At this concentration neither the viability of the host bacterium nor the lytic growth of a clear plaque mutant of the phage was affected by Antipain.

Microbiology, 1987

Low concentrations of urea, which did not inhibit the synthesis of the catabolite nonrepressible ... more Low concentrations of urea, which did not inhibit the synthesis of the catabolite nonrepressible enzyme alkaline phosphatase in Vibrio cholerae, or markedly affect its overall growth, specifically inhibited the expression of the tryptophanase operon in a temperature-dependent manner. However, in contrast to what is found in Escherichia coli, this urea-induced inhibition of tryptophanase synthesis in I/. cholerae could be almost completely relieved by exogenously added cyclic AMP. The possible mechanism of the process is discussed. I N T R O D U C T I O N Many enzymes responsible for the catabolism of carbon compounds in a variety of microorganisms are repressed by glucose or its degradation products. This phenomenon, known as catabolite repression (Magasanik, 1961), has been demonstrated in many organisms to be mediated through the intracellular level of cyclic 3' : 5'-adenosine monophosphate (CAMP) (Zubay, 1980). Enzymes whose synthesis is subject to catabolite repression are termed catabolite-repressible. In Escherichia coli various agents such as urea (Sanzey & Ullmann, 1976, 1980), nitrofurans (Herrlich & Schweiger, 1976), intercalating dyes (Sankaran & Pogell, 1973), gyrase-specific drugs (Sanzey, 1979) and phages (Ghosh et al., 19850) can preferentially inhibit the synthesis of catabolite-repressible enzymes. All these agents except urea, however, severely inhibit growth at the concentrations used. Urea, which exerts its effect at the level of transcription at the concentrations used, affects the expression of catabolite-repressi ble operons without interfering with overall cellular metabolism and thus truly mimics physiological catabolite repression (Sanzey & Ullmann, 1980). However, unlike physiological catabolite repression, the repression exerted by urea is not antagonized by cAMP (Sanzey & Ullmann, 1980). This observation, along with other observationsthat catabolite repression can persist in the presence of cAMP (Wanner et al., 1978) for example-has led to a reappraisal of the theory of catabolite repression (Ullmann & Danchin, 1983). Even though much information is available on the mechanism of catabolite repression in E. coli, very little is known about the process in other organisms. It has, however, been found that in many organisms catabolite repression is not mediated through cAMP (

Journal of Molecular Biology, 1985

The black beetle virus (BBV) is an isometric insect virus whose genome consists of two messenger-... more The black beetle virus (BBV) is an isometric insect virus whose genome consists of two messenger-active RNA molecules encapsidated in a single virion. The nucleotide sequence of BBV RNA1 (3105 bases) has been determined, and this, together with the sequence of BBV RNA2 (1399 bases) provides the complete primary structure of the BBV genome. The RNA1 sequence encompasses a 5' non-coding region of 38 nucleotides, a coding region for a protein of predicted molecular weight 101,873 (protein A, implicated in viral RNA synthesis) and a 3' proximal region encoding RNA3 (389 bases), a subgenomic messenger RNA made in infected cells but not encapsidated into virions. The RNA3 sequence starts 16 bases inside the coding region of protein A and contains two overlapping open reading frames for proteins of molecular weight 10,760 and 11,633, one of which is believed to be protein B, made in BBV-infected cells. A limited homology exists between the sequences of RNA1 and RNAB. Sequence regions have been identified that provide energetically favorable bonding between RNA2 and RNA1 possibly to facilitate their common encapsidation, and between RNA2 and negative strand RNA1 possibly to regulate the production of RNA3.

Journal of Infection, 1998

PLoS ONE, 2014

Background: A live oral cholera vaccine VA 1.4 developed from a non-toxigenic Vibrio cholerae O1 ... more Background: A live oral cholera vaccine VA 1.4 developed from a non-toxigenic Vibrio cholerae O1 El Tor strain using ctxB gene insertion was further developed into a clinical product following cGMP and was evaluated in a double-blind randomized placebo controlled parallel group two arm trial with allocation ratio of 1:1 for safety and immunogenicity in men and women aged 18-60 years from Kolkata, India. Method: A lyophilized dose of 1.9610 9 CFU (n = 44) or a placebo (n = 43) reconstituted with a diluent was administered within 5 minutes of drinking 100 ml of a buffer solution made of sodium bicarbonate and ascorbic acid and a second dose on day 14. Result: The vaccine did not elicit any diarrhea related adverse events. Other adverse events were rare, mild and similar in two groups. One subject in the vaccine group excreted the vaccine strain on the second day after first dose. The proportion of participants who seroconverted (i.e. had 4-folds or higher rise in reciprocal titre) in the vaccine group were 65.9% (95% CI: 50.1%-79.5%) at both 7 days (i.e. after 1 st dose) and 21 days (i.e. after 2 nd dose). None of the placebo recipients seroconverted. Anti-cholera toxin antibody was detected in very few recipients of the vaccine. Conclusion: This study demonstrates that VA 1.4 at a single dose of 1.9610 9 is safe and immunogenic in adults from a cholera endemic region. No additional benefit after two doses was seen.

Nucleic Acids Research, 1984

The nucleotide sequence of black beetle virion (BBV) RNA2 has been determined. RNA2 is 1399 b lon... more The nucleotide sequence of black beetle virion (BBV) RNA2 has been determined. RNA2 is 1399 b long. Its 5' terminus is capped. Its 3' terminus has an unidentified moiety that renders the RNA resistent to polyadenylation and ligation. The first AUG codon at base 23 is followed by an open reading frame for a protein 107 amino acids long, the predicted size of coat protein precursor. A second open reading frame for a putative protein 72 amino acid residues long begins at base 1110. No other large open reading frames exist. The 5 1 half of the RNA can be folded into a long, imperfect hairpin of high predicted stability. The 3' half of the RNA can fold into a complex set of multiply bifurcated stem and loop regions.

Immunology Letters, 1999

The disease cholera is an important cause of mortality in many developing countries. Though it ca... more The disease cholera is an important cause of mortality in many developing countries. Though it can be controlled through improved sanitation, this goal is not easily attainable in many countries. Development of an efficacious vaccine offers the best immediate solution. A new oral candidate vaccine has been constructed from a non-toxigenic strain of Vibrio cholerae E1 Tor, Inaba, which is not only devoid of the cholera toxin (CT) virulence cassette but also is completely non-reactogenic in rabbit ileal loop assay. The strain, however, had toxR and tcpA genes. Through a series of manipulations, the ctxB gene of V. cholerae, responsible for the production of the 'B' subunit of the cholera toxin (CTB) was introduced into the cryptic hemolysin locus of the strain. The resulting strain, named vaccine attempt 1.3 (VA1.3), was found to be able to produce copious amounts of CTB. In the RITARD model this strain was found to be non-reactogenic and provided full protection against the challenge doses of both V. cholerae O1, classical and E1 Tor. In the immunized rabbit it invoked significant levels of anti-bacterial and anti-toxin immunity.

Microbiology, 1986

Alkaline phosphatase activity in Vibrio cholerae strain 569B grown in low-phosphate medium was st... more Alkaline phosphatase activity in Vibrio cholerae strain 569B grown in low-phosphate medium was stimulated if glucose or glycerol was used as the carbon source. No such stimulation was observed, however, if tricarboxylic acid cycle intermediates like succinate or citrate were used. Experiments using specific enzyme inhibitors strongly indicated that the metabolic reactions of the glycolytic pathway from glyceraldehyde 3-phosphate to 2-phosphoglycerate play a key role in the stimulation process.

Microbiology, 1995

General properties of the heat shock response in Vibrio cholerae were examined. Enhanced or de no... more General properties of the heat shock response in Vibrio cholerae were examined. Enhanced or de novo synthesis of 24 proteins was observed upon heat shock from 30 "C to 42 "C in cells labelled with [35S]methionine. A similar response could also be induced by a rise in temperature from 30 "C to 37 OC. Of these heat shock proteins, two were determined to be homologues of GroEL and DnaK, based upon their immunological cross-reactivity with antibodies raised against the Escherichia coli proteins. Three proteins, of molecular sizes 38,44 and 48 kDa, which were undetectable in the 30 "C grown culture, appeared de novo after the heat shock. As in other prokaryotic systems thermal induction of many of the proteins was transient, but both DnaK and GroEL remained induced for at least 28 min after heat shock. DNA hybridization studies revealed that genes analogous not only to dnaK and gmEL but also to dnal of Em coli exist in V. cholerae. Heat shock induced thermotolerance in V. cholerae but made the cells more sensitive to UV radiation. Unlike in E. coli, however, heat shock had no effect on the progeny virus yield in V. cholerae.

Problems of Particularly Dangerous Infections

The endemicity of cholera in India has been well researched. Among the other endemic areas, India... more The endemicity of cholera in India has been well researched. Among the other endemic areas, Indian subcontinent appears to be the cradle of Vibrio cholerae genovariants, which subsequently spread worldwide. In contrast, all the cholera cases recorded in Russia are of imported origin. In the past century, such importations might result in epidemics, which, however, ended with elimination of toxigenic V. cholerae (TVC) from the affected areas. Currently, the incidence of TVC in water reservoirs or infected returnees from Asian countries are rare events, mostly due to constant surveillance activities. Furthermore, the climatic conditions in the majority of Russian regions are unfavorable for longterm environmental survival of the pathogen. On the other hand, global shifts in climate accompanied by unexpected anomalies in previously stable climatic zones may promote dissemination of imported TVC and emergence of cholera. In some regions of Russia, seasonal weather patterns are pretty si...

Proceedings of the National Academy of Sciences, India Section B: Biological Sciences

ABSTRACT Microorganisms are extraordinarily diverse in their range of habitats. They are capable ... more ABSTRACT Microorganisms are extraordinarily diverse in their range of habitats. They are capable of growing wherever life is thermodynamically possible, making them capable of synthesizing myriad varieties of molecules, compounds, enzymes etc, which are yet beyond the reach of human capabilities. Hence it is being increasingly appreciated that in the search for new molecules etc., exploration of microbial biodiversity in search of the “right” microbe could be the first step. Earth consists a staggering number of microbes, a majority of which have remained unknown and unexamined not only because most of them are yet uncultivable but also because many habitats have remained unexplored. Efforts have been initiated globally including in India, to explore new habitats to look for microbes capable of making novel products and processes.

The Indian journal of medical research, 2011

Antimicrobial resistance poses a major threat in the treatment of infectious diseases. Though sig... more Antimicrobial resistance poses a major threat in the treatment of infectious diseases. Though significant progress in the management of diarrhoeal diseases has been achieved by improved hygiene, development of new antimicrobials and vaccines, the burden remains the same, especially in children below 5 yr of age. In the case of cholera, though oral rehydration treatment is the mainstay, antimicrobial therapy is mandatory at times to reduce the volume of stool and shorten the duration of the disease. Though for many pathogens, antimicrobial resistance emerged soon after the introduction of antibiotics, Vibrio cholerae remained sensitive to most of the antibiotics for quite a long period. However, the scenario changed over the years and today, V. cholerae strains isolated world over are resistant to multiple antibiotics. A myriad number of mechanisms underlie this phenomenon. These include production of extended-spectrum beta-lactamases, enhanced multi-drug efflux pump activity, plasmi...

The Indian journal of medical research, 1996

First attempt at cholera vaccination was made by Jaime Ferran in 1884. Since then, a variety of s... more First attempt at cholera vaccination was made by Jaime Ferran in 1884. Since then, a variety of strategies and methods have been evolved to create a safe, efficacious vaccine against cholera. For the first few years emphasis was on the development of parenteral vaccines. However, as a result of accumulation of a tremendous amount of knowledge, not only on Vibrio cholerae-the causative agent, but also on its interaction with the host, emphasis has shifted towards the development of oral vaccines. Two such vaccines, one killed, a whole cell/B subunit combination vaccine and the other a live attenuated one, have shown promise. The combination vaccine in its present state of development confers only a transient protection in young children, while the live attenuated one produces adverse reaction. To combat these, various strategies are being evolved. In one attempt, a potential candidate vaccine strain has been constructed from a non-reactogenic clinical isolate of V. cholerae, which is...

Mutation research, 1995

Wild-type Vibrio cholerae cells, when adapted by a stepwise treatment with sub-lethal concentrati... more Wild-type Vibrio cholerae cells, when adapted by a stepwise treatment with sub-lethal concentrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), acquired resistance to killing and mutagenesis by subsequent challenges with higher concentrations of MNNG. This was also seen in the rec isogenic strain indicating that the observed phenomenon was not due to the induction of SOS functions. Further, the adapted cells of both the wild-type and rec strains could reactivate lethally alkylated phages with equal efficiency. Increased resistance of adapted cells correlated with the induction of a 17-kDa DNA methyltransferase, capable of repairing O6-methylguanine lesions in DNA. This induced methyltransferase was found to be antigenically unrelated to the Escherichia coli methyltransferase (Ada protein) as determined by Western blotting with polyclonal antiserum raised against the E. coli protein. Even though no counterpart of the constitutively expressed methyltransferase (Ogt) of E. col...

Journal of virology, 1982

We show by sequence analysis of a 420-base-long region adjacent to the 3' polyadenylic acid o... more We show by sequence analysis of a 420-base-long region adjacent to the 3' polyadenylic acid of encephalomyocarditis viral RNA and by carboxy terminus analysis of protein E that the termination site of encephalomyocarditis virus polyprotein translation consists of two successive UAG codons located at positions 121 to 126 from the 3' polyadenylic acid.

Virology, 1982

Features of the primary structure and translation of the genomic RNAs of the cowpea and bean stra... more Features of the primary structure and translation of the genomic RNAs of the cowpea and bean strains of southern bean mosaic virus have been investigated in order to assess the similarity of the two viruses. The sequence of 400 bases at their 3' termini have been determined. These include the 3' noncoding regions and extend well into the coat protein cistrons. The noncoding regions (136 bases for the cowpea strain RNA and 129 bases for the bean strain RNA) show no obvious sequence homology. However, extensive base as well as amino acid sequence homology exists in the coding region. RNAs from both strains have a small protein attached to their 5' terminus-the protein in the cowpea strain being the smaller of the two. In vitro studies show that there are similarities in the overall mode of translation of the genomes of the two viruses. Although corresponding proteins are synthesized they differ in size.

Epidemiological and Molecular Aspects on Cholera, 2010

Page 1. Chapter 17 Integron-Mediated Antimicrobial Resistance in Vibrio cholerae Amit Ghosh and T... more Page 1. Chapter 17 Integron-Mediated Antimicrobial Resistance in Vibrio cholerae Amit Ghosh and T. Ramamurthy Abstract The disease cholera is the result of infection with the toxigenic strains of Vibrio cholerae. Even though ...

Virology, 1984

BBV (black beetle virus) RNAI, the subgenomic messenger RNA for BBV protein B and its double-stra... more BBV (black beetle virus) RNAI, the subgenomic messenger RNA for BBV protein B and its double-stranded form (dsRNA3) were purified from cells infected with BBV and were sequenced. RNA3 is 339 bases long. The sequence is homologous to that of the 3'terminal region of virion RNAl. RNA3 has a very limited homology to virion RNAt RNA3 is capped at its 5' terminus and has a structural feature at its 3' terminus that renders it inert to the action of the enzymes RNA ligase and poly(A) polymerase. RNA3 has two overlapping reading frames for putative proteins of size 10,763 and 11,633 Da. The positive and negative strands of dsRNA3 are not capped and correspond in length and sequence to RNA3 itself. Q 1986 Academic Press. 1nc.

Nucleic Acids Research, 1979

Voue7NmeI 99NcecAisRsac Southern bean mosaic viral RNA has a 5'-linked protein but lacks 3' termi... more Voue7NmeI 99NcecAisRsac Southern bean mosaic viral RNA has a 5'-linked protein but lacks 3' terminal poly(A)

MGG Molecular & General Genetics, 1985

Synthesis of tryptophanase, D-serine deaminase and alkaline phosphatase in Escherichia coli C was... more Synthesis of tryptophanase, D-serine deaminase and alkaline phosphatase in Escherichia coli C was repressed as the result of infection with the single-stranded DNA bacteriophage phi X174. However, the degree of repression differed, the more catabolite-sensitive the operon was, the more severe was the repression. For the catabolite-sensitive enzymes it was found that cyclic adenosine 3'5' monophosphate (cyclic AMP or cAMP) was unable to release or reduce the phage-induced inhibition. Experiments with amber mutants of phi X174 revealed that A, product of cistron A, was responsible for the inhibition. The cistron A product probably acted at the level of transcription. The possible role of A in the observed modulation of gene expression is discussed.

MGG Molecular & General Genetics, 1985

Two lines of evidence suggest that a gene analogous to the recA gene of Escherichia coli exists i... more Two lines of evidence suggest that a gene analogous to the recA gene of Escherichia coli exists in Vibrio cholerae and that its product serves a proteolytic function in the SOS response. Firstly, Southern blot hybridization using the recA gene of E. coli as a probe revealed a genomic sequence in V. cholerae which hybridized with the probe. Secondly, the SOS-like response in V. cholerae (as measured by beta phage induction) triggered by DNA damaging agents like Furazolidone could be blocked by Antipain, a protease inhibitor known to inhibit RecA protease action in E. coli. Maximal blocking effect of Antipain on beta phage induction occurred at 1 mM. At this concentration neither the viability of the host bacterium nor the lytic growth of a clear plaque mutant of the phage was affected by Antipain.

Microbiology, 1987

Low concentrations of urea, which did not inhibit the synthesis of the catabolite nonrepressible ... more Low concentrations of urea, which did not inhibit the synthesis of the catabolite nonrepressible enzyme alkaline phosphatase in Vibrio cholerae, or markedly affect its overall growth, specifically inhibited the expression of the tryptophanase operon in a temperature-dependent manner. However, in contrast to what is found in Escherichia coli, this urea-induced inhibition of tryptophanase synthesis in I/. cholerae could be almost completely relieved by exogenously added cyclic AMP. The possible mechanism of the process is discussed. I N T R O D U C T I O N Many enzymes responsible for the catabolism of carbon compounds in a variety of microorganisms are repressed by glucose or its degradation products. This phenomenon, known as catabolite repression (Magasanik, 1961), has been demonstrated in many organisms to be mediated through the intracellular level of cyclic 3' : 5'-adenosine monophosphate (CAMP) (Zubay, 1980). Enzymes whose synthesis is subject to catabolite repression are termed catabolite-repressible. In Escherichia coli various agents such as urea (Sanzey & Ullmann, 1976, 1980), nitrofurans (Herrlich & Schweiger, 1976), intercalating dyes (Sankaran & Pogell, 1973), gyrase-specific drugs (Sanzey, 1979) and phages (Ghosh et al., 19850) can preferentially inhibit the synthesis of catabolite-repressible enzymes. All these agents except urea, however, severely inhibit growth at the concentrations used. Urea, which exerts its effect at the level of transcription at the concentrations used, affects the expression of catabolite-repressi ble operons without interfering with overall cellular metabolism and thus truly mimics physiological catabolite repression (Sanzey & Ullmann, 1980). However, unlike physiological catabolite repression, the repression exerted by urea is not antagonized by cAMP (Sanzey & Ullmann, 1980). This observation, along with other observationsthat catabolite repression can persist in the presence of cAMP (Wanner et al., 1978) for example-has led to a reappraisal of the theory of catabolite repression (Ullmann & Danchin, 1983). Even though much information is available on the mechanism of catabolite repression in E. coli, very little is known about the process in other organisms. It has, however, been found that in many organisms catabolite repression is not mediated through cAMP (

Journal of Molecular Biology, 1985

The black beetle virus (BBV) is an isometric insect virus whose genome consists of two messenger-... more The black beetle virus (BBV) is an isometric insect virus whose genome consists of two messenger-active RNA molecules encapsidated in a single virion. The nucleotide sequence of BBV RNA1 (3105 bases) has been determined, and this, together with the sequence of BBV RNA2 (1399 bases) provides the complete primary structure of the BBV genome. The RNA1 sequence encompasses a 5' non-coding region of 38 nucleotides, a coding region for a protein of predicted molecular weight 101,873 (protein A, implicated in viral RNA synthesis) and a 3' proximal region encoding RNA3 (389 bases), a subgenomic messenger RNA made in infected cells but not encapsidated into virions. The RNA3 sequence starts 16 bases inside the coding region of protein A and contains two overlapping open reading frames for proteins of molecular weight 10,760 and 11,633, one of which is believed to be protein B, made in BBV-infected cells. A limited homology exists between the sequences of RNA1 and RNAB. Sequence regions have been identified that provide energetically favorable bonding between RNA2 and RNA1 possibly to facilitate their common encapsidation, and between RNA2 and negative strand RNA1 possibly to regulate the production of RNA3.

Journal of Infection, 1998