Structural and immunochemical characterization of a Neisseria gonorrhoeae epitope defined by a monoclonal antibody 2C7; the antibody recognizes a conserved epitope on specific lipo-oligosaccharides in spite of the presence of human carbohydrate epitopes

Lipo-oligosaccharides (LOS) produced by Neisseria gonorrhoeae are important antigenic and immunogenic components of the outer membrane complex. Previously, we showed that murine monoclonal antibody (mAb) 2C7 did not cross-react with human glycosphingolipids but identified the LOS epitope that is widely expressed in vivo and in vitro (Gulati, S., McQuillen, D. P., Mandrell, R. E., Jani, D. B., and Rice, P. A. (1996) J. Infect. Dis. 174, 1223-1237). In the present study, we analyzed the structure of gonococcal strain WG LOS containing the 2C7 epitope and investigated the structural requirements for expression of the epitope. We determined that the WG LOS components are Hep[1]-elongated forms of 15253 LOS that have a lactose on both Hep[1] and Hep[2] (Yamasaki, R., Kerwood, D. E., Schneider, H., Quinn, K. P., Griffiss, J. M., and Mandrell, R. E. (1994) J. Biol. Chem. 269, 30345-30351). In addition, we found that expression of the 2C7 epitope within the LOS is blocked when the Hep[2]-lactose is elongated. Based on the structural data of these LOS and the results obtained from immunochemical analyses, we conclude the following: 1) mAb 2C7 requires both the 15253 OS minimum structure and the N-linked fatty acids in the lipoidal moiety for expression of the epitope; 2) mAb 2C7 binds to the LOS that elongates the lactose on Hep[1] of the 15253 OS, but not the one on Hep[2]; and 3) the 2C7 epitope is expressed on gonococcal LOS despite the presence of human carbohydrate epitopes such as a lactosamine or its N-acetylgalactosaminylated (globo) form. Our study shows that the conserved epitope defined by mAb 2C7 could potentially be used as a safe site for the development of a vaccine candidate.

Biotyping of Acinetobacter species isolated from clinical samples

We used the biotyping scheme using carbohydrate substrate utilization test with 14 carbon sources to speciate Acinetobacter isolates from blood and cerebrospinal fluid cultures of patients admitted to the postoperative neurosurgery ICU during January to November 1996. Sixty one patients culture positive for Acinetobacter sp. from blood or cerebrospinal fluid were followed up prospectively. Among these patients, 40 patients had clinically diagnosed infections like bacteriemia or meningitis while in 21 patients the isolation was regarded as contaminants. A. baumanniii was the most common isolate associated with clinical infections while A. lwoffii was more likely to be an environmental contaminant.

Acute renal failure in an intensive care unit in India--prognostic factors and outcome

We prospectively analyzed 70 consecutive patients who developed acute renal failure (ARF) in the intensive care unit (ICU) during a six year period to define prognostic factors and outcome. Age, sex, preexisting chronic diseases, systemic infections, number of organs failing during the disease course, need and mode of renal replacement therapy (RRT), and length of stay in ICU were recorded. Analysis of factors in survivors (n=7, Gp A) and nonsurvivors (n=63, Gp B) was done by univariate and multivariate analysis. The mean age of patients was 28.6 years. Forty nine (70%) patients developed ARF following surgery, whereas 21 (30%) developed ARF in a medical setting. Cardiovascular surgery (39) and pancreatic surgery (7) were important causes in the surgical group, whereas in the medical group acute pancreatitis (11) was the main causative factor. One patient had ARF only, while in the rest, other organs were also involved. In more than 80% of these patients, organ failure and sepsis were present before the onset of ARF. Fifty two (74.3%) patients required dialytic support. The overall mortality was 90%. Number of organs failing, (1.5 +/-9 in Gp A vs 3.6 +/- 8 in Gp B), presence of systemic infection (1 in Gp A vs 55 in Gp B), prolonged stay in ICU (3.7 +/- 1.1 days in Gp A vs 8.0 +/- 5.4 in Gp B) and need for RRT (2 in Gp A vs 50 in Gp B) correlated with the mortality. Using multiple logistic regression analysis, only multiple organ failure (3 or more) correlated with the mortality. We conclude that multiple organ failure is a poor prognostic factor in patients with ARF in the setting of the ICU.

Changing trends of histopathology in childhood nephrotic syndrome

This study was conducted to analyze the trend of histopathologic subtypes in idiopathic nephrotic syndrome (INS) in a homogenous racial group in India population. A prospective analysis of 400 consecutive children with INS was performed. Kidney biopsies were performed according to standard indications. Steroids were administered following the Arbeitsgeminschaft fur Padiatrische Nephrologie protocol. Cyclophosphamide was administered to children in the frequent-relapser, steroid-dependent, and steroid-nonresponder categories. Of the various histopathologic subtypes, focal segmental glomerulosclerosis (FSGS) was the most common (87 of 222 subtypes; 39.1%). Children who underwent biopsy between July 1992 and December 1996 (group B, n = 157) were compared with our initial published data of biopsies performed between January 1990 and June 1992 (group A, n = 65), with similar indications for biopsy in both groups. The incidence of FSGS was significantly greater in biopsies performed in the recent period (group B, 47% versus group A, 20%; P = 0.0002). The different clinical and biochemical parameters were also analyzed to differentiate FSGS from the other 2 subtypes. Hypertension (P = 0. 005), renal insufficiency at presentation (P = 0.001), and steroid resistance (P = 0.0006) were significantly greater in children with FSGS. On follow-up (mean, 5.4 years), children with FSGS were at a significantly greater risk for developing renal insufficiency (P = 0. 0001). We conclude there is a shift toward an increasing prevalence of FSGS over the years in the Indian population. This trend has immense therapeutic and prognostic significance.

The contrasting mechanisms of serum resistance of Neisseria gonorrhoeae and group B Neisseria meningitidis

Neisseria gonorrhoeae and Neisseria meningitidis have evolved intricate mechanisms to evade complement-mediated killing. Sialylation of gonococcal lipooligosaccharide (LOS) results in conversion of previously serum sensitive strains to unstable serum resistance, which is mediated by factor H binding. Porin (Por) is also instrumental in mediating stable serum resistance in gonococci. The 5th loop of certain gonococcal PorlAs binds factor H, which efficiently inactivates C3b to iC3b. Factor H glycan residues may be essential for factor H binding to certain Por1A strains. Por1A strains can also regulate the classical pathway by binding to C4b-binding protein (C4bp) probably via the 1st loop of the Por molecule. Certain serum resistant Por1 B strains can also regulate complement by binding C4bp through a loop other than loop 1. Purified C4b can inhibit binding of C4bp to Por 1B, but not Por1A, suggesting different binding sites on C4bp for the two Por types. Unlike serum resistant gonococci, resistant meningococci have abundant C3b on their surface, which is only partially processed to iC3b. The main mechanism of complement evasion by group B meningococci is inhibition of membrane attack complex (MAC) insertion by their polysaccharide capsule. LOS structure may act in concert with capsule to prevent MAC insertion. Meningococcal strains with Class 3 Por preferentially bind factor H, suggesting Class 3 Por acts as a receptor for factor H.

Etiology and outcome of chronic renal failure in Indian children

A prospective analysis of all new pediatric cases of chronic renal failure (CRF) was performed at our hospital over a 1-year period. The diagnosis of CRF was based on serum creatinine >2 mg/dl with supportive clinical, laboratory, and radiological findings. There were a total of 48 patients with CRF with a median age of 13 years (range 10 days to 16 years). The causes of CRF included glomerulonephritis (37.5%), obstruction and interstitial (52%), hereditary (6.3%), and undetermined (4.2%). Patients were symptomatic for a mean of 33.2 months (range 10 days to 11 years) at presentation. Eight patients (16.7%) had acute reversible deterioration of renal function at presentation. This was due to accelerated hypertension in 2, infection in 3, volume depletion in 2, and nonsteroidal antiinflammatory drugs in 1 patient. At presentation, 22 (46%) children had mild to moderate renal failure and 26 (54%) had end-stage renal disease. Twenty-one children (43. 7%) had associated illness at presentation. Mean follow-up was 22.9 weeks (range 2-126 weeks). At the end of the study period, 10 (21%) patients were on conservative treatment, 7 (14.6%) on maintenance dialysis, 8 (16.7%) patients had functioning allografts, 4 (8.3%) patients had died, and 19 (39.6%) opted against further therapy. We conclude that CRF in Indian children carries a poor prognosis due to late referral and the limited availability and high cost of renal replacement therapy.

Posttranscriptional regulation of mammalian methionine synthase by B12

Methionine synthase is one of two key enzymes involved in the removal of the metabolite, homocysteine. Elevated homocysteine levels constitute a risk factor for cardiovascular diseases and for neural tube defects. In cell culture, the activity of methionine synthase is enhanced several-fold by supplementation with its cofactor, B12. The mechanism of this regulation is unknown, although it has been ascribed to a shift from apoenzyme to holoenzyme. Using sensitive assay techniques as well as a combination of Northern and Western analyses, we demonstrate that the effect of B12 on induction of methionine synthase activity is paralleled by an increase in the level of the enzyme. These studies exclude conversion of apoenzyme to holoenzyme as a basis for activation that had been described previously. Since the mRNA levels do not change during the same period that the methionine synthase levels increase, regulation of this protein by its cofactor must be exerted posttranscriptionally.

An essential saccharide binding domain for the mAb 2C7 established for Neisseria gonorrhoeae LOS by ES-MS and MSn

A study of bacterial surface oligosaccharides were investigated among different strains of Neisseria gonorrhoeae to correlate structural features essential for binding to the MAb 2C7. This epitope is widely expressed and conserved in gonococcal isolates, characteristics essential to an effective candidate vaccine antigen. Sample lipooligosaccharides (LOS), was prepared by a modification of the hot phenol-water method from which de-O-acetylated LOS and oligosaccharide (OS) components were analyzed by ES-MS-CID-MS and ES-MSnin a triple quadrupole and an ion trap mass spectrometer, respectively. Previously documented natural heterogeneity was apparent from both LOS and OS preparations which was admixed with fragments induced by hydrazine and mild acid treatment. Natural heterogeneity was limited to phosphorylation and antenni extensions to the alpha-chain. Mild acid hydrolysis to release OS also hydrolyzed the beta(1-->6) glycosidic linkage of lipid A. OS structures were determined by collisional and resonance excitation combined with MS and multistep MSn which provided sequence information from both neutral loss, and nonreducing terminal fragments. A comparison of OS structures, with earlier knowledge of MAb binding, enzyme treatment, and partial acid hydrolysis indicates a generic overlapping domain for 2C7 binding. Reoccurring structural features include a Hepalpha(1-->3)Hepbeta(1-->5)KDO trisaccharide core branched on the nonreducing terminus (Hep-2) with an alpha(1-->2) linked GlcNAc (gamma-chain), and an alpha-linked lactose (beta-chain) residue. From the central heptose (Hep-1), a beta(1-->4) linked lactose (alpha-chain), moiety is required although extensions to this residue appear unnecessary.

Complement processing and immunoglobulin binding to Neisseria gonorrhoeae determined in vitro simulates in vivo effects

Local inflammation elicited by Neisseria gonorrhoeae correlates closely with sensitivity to killing by normal human serum. Serum-sensitive (SS) isolates are rendered resistant in vitro by lipooligosaccharide sialylation. Differences in C3b processing on N. gonorrhoeae in vitro were found to match findings at the cervical level in vivo. Nonsialylated SS gonococci bound 5-fold more C3b than did stably serum-resistant (SR) gonococci; most was processed to iC3b, yet significant C3b persisted. Sialylated SS gonococci bound 4-fold less total C3 antigen than did SR gonococci, which was promptly converted to iC3b. C3b bound later on stably SR gonococci but again was processed swiftly to iC3b. In vivo, the iC3b/C3 ratio of SS isolates more closely resembled nonsialylated SS isolates in vitro, implying heterogeneous sialylation or desialylation in vivo. In vitro, total IgM bound was unchanged by sialylation of SS isolates, but total C4 bound decreased by 75%, suggesting that sialylation may indirectly regulate the classical complement pathway.

Outbreak of nosocomial Acinetobacter baumannii bacteremia in a high risk ward

Acinetobacter baumannii is emerging as a major cause of nosocomial infections particularly in high risk patients. Being resistant to adverse environmental conditions, it can stay for prolonged periods in the hospital environment. We report an outbreak in the medical oncology ward where nine patients suspected of bacteraemia were blood culture positive for A. baumannii from the two samples each, one collected through the i.v. cannula and another through the peripheral veneous puncture. The bacteria was also isolated from the environmental sources from the various samples collected. The biotype, antibiogram, cellular protein profiles on SDS-PAGE and the restriction enzyme analysis patterns of the patient isolates and the environmental isolates were similar. This points to the environment as a source of infection. With reinforcement of proper barrier nursing and use of disposable heparine ampoules it was possible to control the outbreak.

Acute clonorchiasis in a child

Clonorchiasis usually presents with chronic gastrointestinal disturbances or cholangiocarcinoma. We describe a rare acute presentation of clonorchiasis in a child with diarrhea and liver abscess.

Dental and skeletal changes after intraoral molar distalization with sectional jig assembly

The present study was conducted on 10 subjects to evaluate dental and skeletal changes after intraoral molar distalization. The maxillary molars were distalized with a sectional jig assembly. Sentalloy open coil springs were used to exert 150 gm of force for a period of 12 weeks. A modified Nance appliance was the main source of anchorage. The pre- and postdistalization records included dental study casts, clinical photographs, and cephalograms. A total of 665 readings recorded from lateral cephalograms and dental casts were subjected to statistical analysis. The mean distal movement of the first molar was 2.78 mm, which was highly significant (o < 0.001). It moved distally at the rate of 0.86 mm/month. There was clinically some distal tipping (3.50 degrees) and distopalatal rotation (2.40 degrees). These changes were statistically significant (p < 0.001). The second molars accompanied the first molars and moved distally by nearly the same amount. There was 1.00 mm increase in the overjet and 2.60 degrees mesial tip of second premolar. The changes in the facial skeleton and dentition bases were minimal and statistically not significant. However, there was clockwise rotation of the mandible of 1.30 degrees that was statistically significant. This was the result of molar extrusion (1.60 mm).

Binding of complement factor H to loop 5 of porin protein 1A: a molecular mechanism of serum resistance of nonsialylated Neisseria gonorrhoeae

Neisseria gonorrhoeae isolated from patients with disseminated infection are often of the porin (Por1A) serotype and resist killing by nonimmune normal human serum. The molecular basis of this resistance (termed stable serum resistance) in these strains has not been fully defined but is not related to sialylation of lipooligosaccharide. Here we demonstrate that Por1A bearing gonococcal strains bind more factor H, a critical downregulator of the alternative complement pathway, than their Por1B counterparts. This results in a sevenfold reduction in C3b, which is >75% converted to iC3b. Factor H binding to isogenic gonococcal strains that differed only in their porin serotype, confirmed that Por1A was the acceptor molecule for factor H. We identified a surface exposed region on the Por1A molecule that served as the binding site for factor H. We used gonococcal strains with hybrid Por1A/B molecules that differed in their surface exposed domains to localize the factor H binding site to loop 5 of Por1A. This was confirmed by inhibition of factor H binding using synthetic peptides corresponding to the putative exposed regions of the porin loops. The addition of Por1A loop 5 peptide in a serum bactericidal assay, which inhibited binding of factor H to the bacterial surface, permitted 50% killing of an otherwise completely serum resistant gonococcal strain. Collectively, these data provide a molecular basis to explain serum resistance of Por1A strains of N. gonorrhoeae.

Disruption of a regulatory system involving cobalamin distribution and function in a methionine-dependent human glioma cell line

Cobalamin metabolism and function were investigated at the levels from transcobalamin II (TCII) receptor to the cobalamin-dependent enzymes, methionine synthase and methylmalonyl-CoA mutase, in a methionine-dependent (P60) and a methionine-independent (P60H) glioma cell line. Using P60H as reference, the P60 cells cultured in a methionine medium had slightly lower TCII receptor activity and normal total cobalamin content, a moderately reduced microsomal and mitochondrial cobalamin(III) reductase activity but only trace amounts of the methylcobalamin and adenosylcobalamin cofactors. When transferred to a homocysteine medium without methionine, P60H cells showed a slightly enhanced TCII receptor activity, but the other cobalamin-related functions were essentially unchanged. In contrast, the methionine-dependent P60 cells responded to homocysteine medium with a nearly 6-fold enhancement of TCII receptor expression and a doubling of both the hydroxycobalamin content and the microsomal reductase activity. The mitochondrial reductase and the cobalamin-related processes further down the pathway did not change markedly. In both cell lines, TCII receptor activity was further increased when growth in homocysteine medium was combined with N2O exposure. These data suggest that low methionine and/or high homocysteine exert a positive feedback control on TCII receptor activity. The concurrent increase in hydroxycobalamin content and in microsomal reductase activity are either subjected to similar regulation or secondary to increased cobalamin transport. This regulatory network is most prominent in the methionine-dependent P60 cells harboring a disruption of the network in the proximity of cobalamin(III) reductase.

Portal hypertension in north Indian children

Etiological factors associated with portal hypertension in children influence the decision about therapy and the prognosis. This cross-sectional observational study was performed at a tertiary care centre in northern India from January, 1990 to December, 1994. Children below the age of 14 years with suspected portal hypertension were prospectively assembled into a cohort to determine the etiology and clinical profile of portal hypertension. Of the 115 patients with portal hypertension, 76.5% had extrahepatic portal hypertension (EHPH). Remaining 23.5% of the cases had intrahepatic and post-hepatic causes of portal hypertension. Children with EHPH had a significantly earlier onset of symptoms as compared to those with intrahepatic portal hypertension (p = 0.002) and bled significantly more frequently (p = 0.00). Forty per cent of patients with chronic liver disease (CLD) never had jaundice. History suggestive of potential etiological factors could be elicited in only 7% of EHPH patients. The commonest site of block in splenoportal axis was at the formation of the portal vein. An inverse relation of bleeding rates with duration of illness was seen in EHPH. Of the 10 CLD patients in whom liver biopsy could be done, cirrhosis was present in 6 patients. Understanding the natural history of EHPH and portal hypertension due to other etiologies may have significant implications in choosing the appropriate intervention and predicting the outcome.

A novel sialic acid binding site on factor H mediates serum resistance of sialylated Neisseria gonorrhoeae

Factor H (fH), a key alternative complement pathway regulator, is a cofactor for factor I-mediated cleavage of C3b. fH consists of 20 short consensus repeat (SCR) domains. Sialic acid binding domains have previously been localized to fH SCRs 6-10 and 13. To examine fH binding on a sialylated microbial surface, we grew Neisseria gonorrhoeae in the presence of 5'-cytidinemonophospho-N-acetylneuraminic acid, which sialylates lipooligosaccharide and converts to serum resistance gonococci previously sensitive to nonimmune serum killing. fH domains necessary for binding sialylated gonococci were determined by incubating organisms with recombinant human fH (rH) and nine mutant rH molecules (deletions spanning the entire fH molecule). rH and all mutant rH molecules that contained SCRs 16-20 bound to the sialylated strain; no mutant molecule bound to serum-sensitive nonsialylated organisms. Sialic acid was demonstrated to be the fH target by flow cytometry that showed a fourfold increase in fH binding that was reversed by neuraminidase-mediated cleavage of sialic acid off gonococci. Functional specificity of fH was confirmed by decreased total C3 binding and almost complete conversion to iC3b on sialylated gonococci. Sialic acid can therefore bind fH uniquely through SCRs 16-20. This blocks complement pathway activation for N. gonorrhoeae at the level of C3.

Renal artery stenosis in aortoarteritis: spectrum of disease in children and adults

Nonspecific aortoarteritis is the commonest cause of renovascular hypertension (RVH) accounting for 87% of the patients in the present study. We compared the clinical and radiographic features and outcome in children (n = 16) and adult (n = 24) patients with aortoarteritis. Children have a shorter duration of disease and present more commonly with constitutional symptoms. All the patients were hypertensive; however, malignant hypertension and hypertensive encephalopathy were more common in children. Abdominal bruit and asymmetry of pulses were present only in 75 and 35% of the patients, respectively. Asymmetric kidney size on ultrasound was present in 15 of 24 adults, whereas 9 of 16 children had equal sized kidneys. Captopril renography had a better sensitivity for detection of RVH in children (13 of 16 in children vs. 12 of 24 in adults showing positive results). On intra-arterial digital substraction angiography, abdominal aortic involvement was invariable, whereas the thoracic aorta was involved less frequently in both age groups. Angiographic scores for the severity of vascular involvement was significantly lesser in children (6.87+/-4.8) as compared to adults (11.32+/-4.5). Thirteen of the 15 children were found suitable for revascularization, whereas 12 of 24 adults were not considered for revascularization as their kidneys were small and contributed to less than 10% of total function. Six of the adult patients underwent nephrectomy for the control of blood pressure. Results of angioplasty were also better in children than adults. We conclude that children present earlier with less severe vascular disease and respond better to revascularization, as compared to adults.

Tuberculosis in childhood nephrotic syndrome in India

We studied the prevalence, clinical features, and impact of tuberculosis (TB) on children with nephrotic syndrome (NS). Of the 300 children with NS, 28 (9.3%) were diagnosed as having TB. This occurred following the initiation of immunosuppressive therapy in 27 children, and in 1 child it preceded the onset of NS. Pulmonary involvement was the commonest (22/28), followed by tubercular lymphadenitis (2/28), meningitis (2/28), and occult TB (2/28). Of the various diagnostic criteria, history of previous cough, fever, or exposure to a case of TB (23/28) and chest skiagram (21/28) were the most useful. The occurrence of TB did not induce a relapse or affect the subsequent response to steroid therapy (as is often seen with other infections) or have a deleterious effect on renal function. Patients who received higher doses of steroids (frequent relapsers, steroid dependent, initial non-responders, and subsequent non-responders) had a significantly higher prevalence of TB (19/148) than those who received lower doses (infrequent relapsers 8/151) (P = 0.04). We thus found TB to be an important complication of children with NS in our country. The conventional diagnostic tests, such as Mantoux and acid-fast bacilli isolation, are often unhelpful in these children, and a high index of suspicion is required, especially in children who require frequent courses of steroid therapy.

Hereditary palmoplantar keratodermas in South India

Thirty-one patients with inherited palmoplantar keratodermas (PPKs) were screened from 59,490 cases who visiting the OPD of JIPMER, Pondicherry. The prevalence rate was 5.2 per 10,000 population (1:2000 approx.). PPKs were more common in males (25 patients) than females (6 patients); the overall male to female ratio was 4.2:1. The incidence was highest in the group from 0-10 years of life (67.7% of cases). Unna-Thost syndrome topped the list with 38.7% of cases and its prevalence 1:6000 (approx.), followed by Greither's disease (22.9%) and others-Vohwinkel (3 cases), idiopathic punctate (2 cases), ichthyosis vulgaris associated PPK (2 cases) etc. This study has for the first time reported the prevalence and patterns of hereditary PPKs in South India.

Chronic renal failure in India

A prospective study of all new cases of chronic renal failure (CRF) including inservice referrals was done at our hospital over a period of 1 year from May 1994 to April 1995. The diagnosis of CRF was based on clinical, laboratory, and radiological features. Kidney biopsies were done when indicated. The patients were subdivided into various etiologic groups of primary renal disease according to standard criteria. There were a total of 835 cases of CRF with a median age of 43 years (range 10 days to 90 years); 67.8% of them were men. Glomerulonephritis (28.6%), diabetic nephropathy (23.2%), and interstitial nephritis (16.5%) were the most common causes of CRF, followed by obstructive nephropathy (6.4%), benign nephrosclerosis (4.1%), and polycystic kidney disease (2%). However, in patients more than 40 years of age, diabetic nephropathy was the most common cause (36.8%). The cause of CRF was unknown in 16.2% of the cases. One hundred twenty-one patients (14.5%) had an acute deterioration of their underlying renal dysfunction at presentation. This was most commonly due to accelerated hypertension (26.1%), infection (22.4%), volume depletion (20.1%), and drugs (14.9%). Anti-inflammatory drugs were the most common drugs responsible for the acute decline in renal function. One year after their initial presentation, of the 512 patients (61.3%) with end stage renal disease, 12.5% had died, 17% had received a kidney allograft, 12.7% were on some form of maintenance dialysis, and 295 patients were lost to follow-up. Of the 323 patients with less severe illness, 7 died, 209 were on outpatient treatment, and 107 patients were lost to follow-up. We conclude that the pattern of CRF in India does not differ greatly from that in the developed countries. However, it carries a poorer prognosis due to late referral and limited availability and affordability of renal replacement therapy in India.