Prevalence of clinical remission in patients with sporadic idiopathic hypoparathyroidism

Background: Remission of disease activity is a characteristic feature of autoimmune endocrine disorders such as Graves' disease, Addison's disease and occasionally in patients with premature ovarian failure. Autoimmunity is also implicated in sporadic idiopathic hypoparathyroidism (SIH) with clinical remission of disease reported in three cases. Objective: To assess the rate of remission in patients with sporadic idiopathic hypoparathyroidism and review the cases reported so far. Subjects and methods: Subjects included 53 patients (M:F, 24:29) with SIH who had been symptomatic for at least 1 year (range 1-31 years). They were treated with calcium and 1-α -(OH)D3/cholecalciferol therapy and had a mean duration of follow up of 5.0 ± 3.2 years. Treatment was withdrawn in two stages in the patients who maintained normal levels of serum total calcium during the preceding year of treatment. In stage-1, the dose of therapy was reduced to half and subsequently all treatment was stopped (stage 2) in those patients who maintained normal serum total calcium levels on the reduced dose. Remission of SIH was defined as maintenance of normal serum total (≥ 2.12 mmol/l) and ionized calcium, inorganic phosphorus and serum intact parathyroid hormone (iPTH) for at least 3 months after withdrawal of calcium and 1-α -(OH)D3/cholecalciferol therapy. Calcium sensing receptor autoantibodies (CaSRAb) were determined by Western blot. Results: Two of the 53 patients (3.8%) with SIH stayed in remission for 1 year after complete withdrawal of therapy. CaSRAb was absent in both the cases. The clinical features, age at onset and duration of hypocalcaemic symptoms in cases with remission were comparable to those who did no show remission. Conclusion: Sporadic idiopathic hypoparathyroidism is not irreversible as is widely believed and spontaneous remission of disease may occur in 3.8% of patients

Novel K540N mutation in Plasmodium falciparum dihydropteroate synthetase confers a lower level of sulfa drug resistance than does a K540E mutation

Sulfadoxine (SDX) and sulfamethoxazole (SMX) each inhibit the Plasmodium falciparum dihydropteroate synthetase (PfDHPS), and certain point mutations in this enzyme yield the drug-resistant parasite. Using a simple Escherichia coli model system, we describe here the effect of the recently reported novel K540N mutation in PfDHPS on the level of SDX/SMX resistance. The survival rate of the transformed E. coli (DHPS-deficient strain) under different SDX or SMX concentrations revealed that the K540N mutation confers a lower level of drug resistance than its contemporary K540E mutation. Further, SMX was more effective than SDX in the E. coli system

Characteristics of Genetic Hitchhiking around Dihydrofolate Reductase Gene Associated with Pyrimethamine Resistance in Plasmodium falciparum Isolates from India▿ †

Sulfadoxine-pyrimethamine (SP) resistance in Plasmodium falciparum has been widespread across continents, causing the major hurdle of controlling malaria. Resistance is encoded mainly by point mutations in P. falciparum dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) target genes. To study the origin and evolution of pyrimethamine resistance on the Indian subcontinent, microsatellite markers flanking the pfdhfr gene were mapped. Here we describe the characteristics of genetic hitchhiking around the pfdhfr gene among 190 P. falciparum isolates. These isolates were collected from five different geographical regions of India (Uttar Pradesh, Madhya Pradesh, Assam, Orissa, and Andaman and Nicobar Islands) where malarial transmission rates and levels of drug resistance vary across regions. Among the isolates, we observed a significant reduction in genetic variation in the ±20-kb vicinity of the mutant pfdhfr alleles due to hitchhiking. This reduction in genetic diversity was more prominent around quadruple pfdhfr alleles (heterozygosity [He] = 0.23) than around double (He = 0.365) and single (He = 0.465) mutant alleles. Asymmetry in the selective sweep flanking the pfdhfr alleles was observed with regional isolates, emphasizing the drug usage with the parasite population. All the pfdhfr alleles share a single microsatellite haplotype and seem to have originated from a single progenitor similar to that of Southeast Asian (Thailand) pfdhfr mutants. Results of the present study also indicate that the emergence of drug-resistant alleles is a recent phenomenon in India compared to Southeast Asian countries

Multiple origins of Plasmodium falciparum dihydropteroate synthetase mutant alleles associated with sulfadoxine resistance in India

With the spread of Chloroquine (CQ) resistant malaria in India, Sulfdoxine - Pyrimethamine (SP) alone or in combination with Artesunate is used as an alternative antimalarial drug. Due to continuous drug pressure, the Plasmodium falciparum parasite is exhibiting resistance to antifolates because of mutations in candidate genes dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps). Our earlier study on flanking microsatellite markers of dhfr mutant alleles from India had shown single origin of the pyrimethamine resistance, with some minor haplotypes, which shared haplotypes with South East Asian (Thailand) strains. In the present study, we have analyzed 193 of these Indian P.falciparum isolates for 15 microsatellite loci around dhps to investigate the genetic lineages of the mutant dhps alleles in different part of the country. Eighty one of these samples had mutant dhps alleles, of which 62 were from Andaman and Nicobar Islands and remaining 19 from mainland India. Of 112 wild type dhps allele, 109 were from mainland India and only 3 from Andaman and Nicobar Islands. Consistent with the model of selection, the mean expected heterozygosity (H<SUB>e</SUB>) around mutant dhps alleles (H<SUB>e</SUB>= 0.55; n=81) associated with sulfadoxine resistance was lower (P≤ 0.05) compared to the mean H<SUB>e</SUB> around wild type dhps allele (H<SUB>e</SUB>=0.80; n=112). There was more genetic diversity in flanking microsatellites of dhps than dhfr among these isolates which confirms the assertion that dhps mutations are at a very early stage of fixation in parasite population. Microsatellite haplotypes around various mutant dhps alleles suggests that the resistant dhps alleles have multiple independent origins in India, especially in Andaman and Nicobar Islands. Determining the genetic lineages of the resistant dhps alleles on the Andaman and Nicobar Islands and mainland India is significant given the role of Asia in the intercontinental spread of chloroquine and pyrimethamine resistant parasite in the past

Emergence of an unusual sulfadoxine-pyrimethamine resistance pattern and a novel K<SUB>540</SUB>N mutation in dihydropteroate synthetase in Plasmodium falciparum isolates obtained from Car Nicobar Island, India, after the 2004 Tsunami

Background: Enormous amounts of drugs were used to contain the outbreak of infectious diseases in areas of India affected by the tsunami in December 2004. The impact of this drug use on the Plasmodium falciparum population needs to be investigated. Methods: The nucleotide sequence of the pfcrt, pfdhps and pfdhfr genes was determined for 229 clinical P. falciparum isolates collected from patients on Car Nicobar Island at 6 different time points between May 2004 and May 2008. Results: Over time, there was an increase in the proportion of the P. falciparum population that had mutations in the pfcrt, pfdhps and pfdhfr genes associated with higher levels of chloroquine, sulfadoxine, and pyrimethamine resistance, respectively. However, the parasites collected during October 2005 had mutations associated with a lower level of pyrimethamine resistance and a higher level of sulfadoxine resistance (a rare combination), as well as a novel K540N mutation in P. falciparum dihydropteroate synthetase (PfDHPS). The emergence of this parasite population coincided with the widespread use of an additional antifolate drug, trimethoprim-sulfamethoxazole, to treat other infections during January-March 2005. Molecular modeling revealed that the sulfadoxine binding affinity of the new PfDHPS triple mutant A<SUB>436</SUB> G<SUB>437</SUB> N<SUB>540</SUB>A<SUB>581</SUB>A<SUB>613</SUB> was similar to that of A<SUB>436</SUB> G<SUB>437</SUB> E<SUB>540</SUB>A<SUB>581</SUB>A<SUB>613</SUB> (bold type indicates mutated amino acids). Conclusions: The use of 2 antifolate drugs in combination should be avoided to prevent the selection of parasites with newer mutations and altered drug susceptibilities

Genetic variation in the Plasmodium falciparum circumsporozoite protein in India and its relevance to RTS,S malaria vaccine

Contains fulltext : 108006.pdf (publisher's version ) (Open Access)RTS,S is the most advanced malaria vaccine candidate, currently under phase-III clinical trials in Africa. This Plasmodium falciparum vaccine contains part of the central repeat region and the complete C-terminal T cell epitope region (Th2R and Th3R) of the circumsporozoite protein (CSP). Since naturally occurring polymorphisms at the vaccine candidate loci are critical determinants of the protective efficacy of the vaccines, it is imperative to investigate these polymorphisms in field isolates. In this study we have investigated the genetic diversity at the central repeat, C-terminal T cell epitope (Th2R and Th3R) and N-terminal T cell epitope regions of the CSP, in P. falciparum isolates from Madhya Pradesh state of India. These isolates were collected through a 5-year prospective study aimed to develop a well-characterized field-site for the future evaluation of malaria vaccine in India. Our results revealed that the central repeat (63 haplotypes, n = 161) and C-terminal Th2R/Th3R epitope (24 haplotypes, n = 179) regions were highly polymorphic, whereas N-terminal non-repeat region was less polymorphic (5 haplotypes, n = 161) in this population. We did not find any evidence of the role of positive natural selection in maintaining the genetic diversity at the Th2R/Th3R regions of CSP. Comparative analysis of the Th2R/Th3R sequences from this study to the global isolates (n = 1160) retrieved from the GenBank database revealed two important points. First, the majority of the sequences (~61%, n = 179) from this study were identical to the Dd2/Indochina type, which is also the predominant Th2R/Th3R haplotype in Asia (~59%, n = 974). Second, the Th2R/Th3R sequences in Asia, South America and Africa are geographically distinct with little allele sharing between continents. In conclusion, this study provides an insight on the existing polymorphisms in the CSP in a parasite population from India that could potentially influence the efficacy of RTS,S vaccine in this region

Global population structure of csp gene.

<p>A minimal spanning tree (MST) generated using BioNumerics software version 6.6 showing the relationship among all the 117 haplotypes based on the Th2R/Th3R sequences of the CSP from worldwide isolates [Asia, n = 974; South America, n = 181 and Africa, n = 184)]. Each circle represents an individual haplotype and the size of the circle is proportional to the number of isolates belonging to that haplotype (also shown as pie). The lines connecting the circles are branch length and are red if two haplotypes differ by only one mutation, blue if differ by 2 mutations, solid black if differ by 3 mutations, dashed black if differ by 4 mutations and gray if they differ by more than 4 mutations. Numbers outside the circles indicate haplotypes H1 to H117. The Dd2, 3D7, HB3, 7G8 and MAD20 type sequences are highlighted in bold. The haplotype pairs H55 & H58; H57 & H87; H60 & H106 and H97 & H98 are identical at amino acid level; but have one synonymous mutation. H1 to H24 are the same haplotypes we observed in our study sites and shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043430#pone-0043430-g003" target="_blank"><b>Fig </b><b>3B</b></a>. Please refer to <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043430#pone.0043430.s004" target="_blank">Table S1</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043430#pone.0043430.s006" target="_blank">Table S3</a></b> and <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043430#pone.0043430.s001" target="_blank">Fig S1</a></b> for more details on these sequence haplotypes and their country-wise distributions.</p

Sequence diversity in the N- and C-terminal non-repeat region of PfCSP.

<p>(<b>A</b>) Sequence alignment showing polymorphisms in the non-repeat N-terminal T cell epitope region (amino acid residue 84 to 104) of CSP in 161 samples. The shaded region (amino acid residue 93 to 97) is a conserved motif involved in sporozoite invasion of mosquito salivary gland as well as in binding to hepatocytes prior to invasion. (<b>B</b>) Sequence alignment showing polymorphisms in the non-repeat C-terminal T cell epitope regions (Th2R spanning from amino acid residues 311 to 327 and Th3R from amino acid residues 341 to 364) of CSP in 179 samples. The highly conserved sequences flanking the Th2R and Th3R domains are shaded grey. The eight laboratory-adapted strains are also included in this alignment. Numbers on the right indicate numbers of samples belonging to that particular haplotype. Dots represent amino acid positions identical to the 3D7 haplotype, whereas those different are indicated. C, community cohort; H, hospital cohort; T, total; WC, Wellcome.</p

Year-wise distribution of <i>P. falciparum</i> isolates collected from two sites for CSP sequence analysis.

<p>Year-wise distribution of <i>P. falciparum</i> isolates collected from two sites for CSP sequence analysis.</p