Sequence variations of the late upstream region of HPV16 in cervical intraepithelial neoplasm and invasive carcinoma

HPV16 is the most common type of human papillomavirus (HPV) seen in cervical squamous cell carcinoma. A 78-bp promotor element at nt 4118-4196 called late upstream region (LUR), critical for the expression of late genes, has been identified recently. Late genes encode viral capsid proteins that coat viral DNA to form particles and serve as antigen. To elucidate whether there are any sequence variations within LUR of HPV16 and any difference of these sequence variations between cervical invasive squamous cell carcinoma (CIC) and cervical intraepithelial neoplasia (CIN), we sequenced HPV16 LUR from 50 cases of HPV16-positive CIC and CIN. We found that variation frequency in the late upstream region ranged from 0 to 4.2 except for two cases in which variation frequency was as high as 22.8%. Eight of 24 CINs and 17 of 26 CICs contained two or more variations (33% vs. 65%, P < 0.025). The results suggested that the sequence variations occurred more often in LUR of HPV16 than in other regions of HPV16 and the variations in HPV16 LUR might play a role in the process of carcinogenesis of cervical carcinoma.

Oncogene lineages of human papillomavirus type 16 E6, E7 and E5 in preinvasive and invasive cervical squamous cell carcinoma

Human papillomavirus (HPV)16 accounts for about 60% of the HPV infections in invasive cervical cancer (ICC). There are many sequence variations within HPV16, some of which have been associated with different biological properties, although no definite correlations have yet been established. However, the definition 'variant' has been a source of confusion in research and diagnosis, since it is based on all sequence deviations from a randomly selected prototype. This study has sequenced the HPV16 oncogenes E6, E7 and E5 from 61 Swedish cases with cervical intraepithelial neoplasia grade III (CIN III) or ICC. Clustering the sequence variations at the three common sites of variation (nucleotide 350 in E6, which has previously been associated with the progression from CIN III to ICC, and nucleotides 3979 and 4042 in E5) resulted in the distinction of three major oncogene lineages encompassing more than 95% of the cases, and two minor oncogene lineages. Simple comparison of the distribution of the individual variations or oncogene lineages between CIN III and ICC showed no significant difference, but the number of variations in addition to the three common ones was significantly higher in ICC. This novel classification scheme, based on the variations in the E6, E7 and E5 region, is considered to be a major improvement over the classical 'prototype-variant' classification, and can help to clarify the interpretation of HPV sequence data in relation to the progression of cervical cancer.

Multidrug-resistant strains of Salmonella enterica serotype typhi are genetically homogenous and coexist with antibiotic-sensitive strains as distinct, independent clones

OBJECTIVE

The goal of this study was to report the molecular analysis of antibiotic-sensitive and multidrug-resistant (MDR) strains of Salmonella typhi, using pulsed-field gel electrophoresis (PFGE), with a particular emphasis on the coexistence of these strains in a typhoid-endemic region of Karachi, Pakistan.

METHODS

One hundred isolates of S. typhi in humans (50 MDR and 50 antibiotic-sensitive isolates) from sporadic cases of typhoid fever were analyzed by Vi-phage typing, antibiograms and PFGE.

RESULTS

The MDR S. typhi strains were resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole. Analysis by PFGE showed that 50 MDR isolates of S. typhi had a single, homogenous PFGE profile, which was distinctly different from that of 50 antibiotic-sensitive isolates obtained in the same time frame from the same area. This latter group of isolates showed much greater diversity of PFGE profiles, as has been observed in other endemic regions.

CONCLUSIONS

Multidrug-resistant and antibiotic-susceptible strains of S. typhi can coexist in endemic areas as epidemiologically independent pathogens and are not in competition for continued persistence and transmission.

HPV16 E6 gene variations in invasive cervical squamous cell carcinoma and cancer in situ from Russian patients

HPV16 is frequently seen in invasive cervical cancer (ICC) and cervical intraepithelial neoplasia (CIN). Its E6 gene has frequent sequence variations. Although some E6 variants have been reported to have different biochemical or biological properties, they do not show geographical identity. Moreover, the definition of 'variant' has been a source of confusion because it has been based on all departures from the 'prototype' once isolated randomly from an ICC case. We amplified the HPV16 E6 gene by PCR from fresh-frozen tissue of 104 cases of ICC and CIN from Russian patients and sequenced it in positive cases. We found that 32 of 55 (58.2%) ICC cases and 18 of 49 (36.7%) CIN cases were HPV 16-positive and we could identify 3 groups of E6 variants: group A was characterized by G at nt 350 where group B had T, and group M was a heterogeneous mixture of unique E6 variants; no significant difference existed in the distribution of the different groups between ICC and CIN; the clinically malignant (as defined by FIGO stage) order between the groups was M > A > B in ICC; in the cases with a single HPV16 E6 sequence, coexisting ICC, CIN and normal epithelium in the same patient shared the E6 variant; and 4 cases of ICC had double/multiple E6 variants. The results did not show any importance of E6 variants for ICC progression in Russian women. The results also indicated that the original HPV16 variant persisted during ICC progression, and that at a low frequency, double infections and/or mutation of variants might occur.

Calcineurin homologous protein as an essential cofactor for Na+/H+ exchangers

The Na+/H+ exchangers (NHEs) comprise a family of transporters that catalyze cell functions such as regulation of the pH and volume of a cell and epithelial absorption of Na+ and bicarbonate. Ubiquitous calcineurin B homologous protein (CHP or p22) is co-localized and co-immunoprecipitated with expressed NHE1, NHE2, or NHE3 independently of its myristoylation and Ca2+ binding, and its binding site was identified as the juxtamembrane region within the carboxyl-terminal cytoplasmic domain of exchangers. CHP binding-defective mutations of NHE1-3 or CHP depletion by injection of the competitive CHP-binding region of NHE1 into Xenopus oocytes resulted in a dramatic reduction (>90%) in the Na+/H+ exchange activity. The data suggest that CHP serves as an essential cofactor, which supports the physiological activity of NHE family members.

Comparison of safety and immunogenicity of a Vi polysaccharide typhoid vaccine with a whole-cell killed vaccine in Malaysian Air Force recruits

OBJECTIVE

To carry out a comparative study of the safety and immunogenicity of Vi polysaccharide vaccine against whole-cell killed (WCK) typhoid vaccine.

METHODS

The study was carried out on young adult recruits (aged 18-25 years) of the Malaysian Air Force. A total of 125 subjects received the Vi polysaccharide vaccine and 114 received the WCK vaccine.

FINDINGS

The Vi vaccine was significantly less reactogenic than the WCK vaccine with regard to systemic and local reactions. Following administration of the Vi vaccine, seroconversion rates (defined as the percentage of subjects with a 4-fold rise of baseline antibody level) of 75.5% and 67% were observed at 2 weeks and 6 weeks, respectively, after immunization, compared with 25% and 31.3% among recipients of the WCK vaccine. Of the 110 Vi vaccinees with serological data, 21 (19%) had high, seroprotective, pre-immunization levels of anti-Vi antibodies (> or = 1 microgram/ml). The majority of subjects in this group came from a region in Malaysia which is known to have high typhoid endemicity. Interestingly, these antibody levels were boosted considerably following administration of vaccine at a level that was 5-fold higher than in subjects with low pre-immunization levels. In contrast, the seroconversion rates in those receiving the Vi vaccine were higher in subjects with low pre-immunization levels of anti-Vi antibodies (76-84%), compared to those with protective levels of > or = 1 microgram/ml prior to immunization (48-57%).

CONCLUSIONS

The study reaffirms the safety and efficacy of the Vi polysaccharide vaccine and identifies a hitherto unrecognized advantage in its use, i.e. it is a potent immunogen that boosted considerably the protective antibody levels among a significant number of immunologically sensitized individuals living in typhoid-endemic regions.

Second mutations rescue point mutant of the Na(+)/H(+) exchanger NHE1 showing defective surface expression

We studied the effect of point mutation within the putative 11th transmembrane domain (TM11) of the Na(+)/H(+) exchanger NHE1 on the plasma membrane expression. Of the 19 mutants tested, two mutants (Tyr454 or Arg458 replaced by Cys) were retained in the endoplasmic reticulum. Interestingly, Y454C was expressed on the cell surface when one of the endogenous cysteine residues at position 8, 133, 421, or 477 was substituted with alanine. Random mutagenesis at Cys8 and its surrounding residues in the cytosolic N-tail revealed that replacement of Cys8 with Ala was the only identified single residue mutation that rescued Y454C. These results suggest that the abnormal conformation of the region of TM11 containing the Y454C mutation is compensated by the second mutation within other domains such as the N-tail. This approach may provide evidence for the interdomain interaction in NHE1.

Role of molecular typing in an outbreak of Salmonella paratyphi A

During the post monsoon season of 1996 an outbreak of human Salmonellosis caused by Salmonella serovar-paratyphi A occurred in New Delhi and had continued for over 2 months. A total of 36 clinically diagnosed enteric-fever cases were reported during this outbreak. The isolates were compared following their characterisation by biotyping, antibiogram-analysis, plasmid-profiling and IS200 probing, to study the relatedness in order to delineate a common source. The study included representative strains from both outbreak (15) and sporadic (7) cases for comparative analysis. Biotyping, antibiogram, whole cell protein-analysis and plasmid-profiling could not discriminate sporadic cases from outbreak strains, suggesting that a single clone/type (PT-1) may be prevalent in our region. In contrast, molecular-typing using IS200-probing revealed 2 clonally related strains circulating during the outbreak, as compared to the unrelated sporadic strains which exhibited considerable genetic diversity. Molecular analysis by IS200-probing, helped to assign an index case which provided a history of later outbreaks, since paratyphi A was repeatedly cultured in later outbreaks also. The study also suggests that genetic rearrangements can occur during the emergence of outbreaks. It reaffirmed the usefulness of IS200-probing in epidemiological investigations of Salmonella enterica serovars.

Localization and partial characterization of a molecule found in the plasma membrane of starfish and sea urchin embryos using a novel monoclonal antibody

A monoclonal antibody, P212, has been developed which reacts against 120 kD and 90 kD proteins, P212 antigens found in the plasma membranes of both starfish and sea urchin embryos. Immunocytochemical studies with colloidal gold tagged P212 showed that the P212 antigens are also found on the inner membranes of several different types of granules and vesicles located in the eggs and cytoplasm of embryonic cells, and in the trans region of the Golgi apparatus. One or both of the P212 antigens are also found in the cortical granules, granules which are exocytosed at fertilization. They are not found on intracellular membrane structures such as the rough endoplasmic reticulum, the nuclear membrane, or a number of deeper granular structures. The P212 antigens are probably located on the membranes of vesicles which are on the exocytosis-endocytosis pathway and may be involved in cell trafficking.

Genotypic characterization of Salmonella typhi by amplified fragment length polymorphism fingerprinting provides increased discrimination as compared to pulsed-field gel electrophoresis and ribotyping

Amplified fragment length polymorphism (AFLP) is a recently developed, PCR-based high resolution fingerprinting method that is able to generate complex banding patterns which can be used to delineate intraspecific genetic relationships among bacteria. In the present study, AFLP was evaluated for its usefulness in the molecular typing of Salmonella typhi in comparison to ribotyping and pulsed-field gel electrophoresis (PFGE). Six S. typhi isolates from diverse geographic areas (Malaysia, Indonesia, India, Chile, Papua New Guinea and Switzerland) gave unique, heterogeneous profiles when typed by AFLP, a result which was consistent with ribotyping and PFGE analysis. In a further study of selected S. typhi isolates from Papua New Guinea which caused fatal and non-fatal disease previously shown to be clonally related by PFGE, AFLP discriminated between these isolates but did not indicate a linkage between genotype with virulence. We conclude that AFLP (discriminatory index=0.88) has a higher discriminatory power for strain differentiation among S. typhi than ribotyping (DI=0.63) and PFGE (DI=0.74).

A novel topology model of the human Na(+)/H(+) exchanger isoform 1

The membrane topology of the human Na(+)/H(+) exchanger isoform 1 (NHE1) was assessed by substituted cysteine accessibility analysis. Eighty-three cysteine residues were individually introduced into a functional cysteineless NHE1, and these mutants were expressed in the exchanger-deficient PS120 cells. The topological disposition of introduced cysteines was determined by labeling with a biotinylated maleimide in the presence or absence of preincubation with the membrane-impermeable sulfhydryl reagent, 2-trimethylammoniumethyl-methanethiosulfonate in streptolysin O-permeabilized or nonpermeabilized cells. We proposed a new model for the topology of NHE1 that is significantly different from the model derived from hydropathy analysis. In this model, NHE1 is composed of 12 transmembrane segments (TMs) with the N and C termini located in the cytosol. The large, last extracellular loop in the membrane domain of the original model was suggested to comprise an intracellular loop, a new transmembrane segment (TM11), and an extracellular loop in the new model. Interestingly, cysteines at 183 and 184 and at 324 and 325 mapped to intracellular loops connecting TMs 4 and 5 (IL2) and TMs 8 and 9 (IL4), respectively, were accessible to sulfhydryl reagents from the outside. Furthermore, exchange activities of two mutants, R180C and Q181C, within IL2 were markedly inhibited by external MTSET. These data suggest that part of IL2 or IL4 may be located in a pore-lining region that is accessible from either side of the membrane and involved in ion transport.

Localization and partial characterization of a molecule found in the plasma membrane of starfish and sea urchin embryos using a novel monoclonal antibody

A monoclonal antibody, P212, has been developed which reacts against 120 kD and 90 kD proteins, P212 antigens found in the plasma membranes of both starfish and sea urchin embryos. Immunocytochemical studies with colloidal gold tagged P212 showed that the P212 antigens are also found on the inner membranes of several different types of granules and vesicles located in the eggs and cytoplasm of embryonic cells, and in the trans region of the Golgi apparatus. One or both of the P212 antigens are also found in the cortical granules, granules which are exocytosed at fertilization. They are not found on intracellular membrane structures such as the rough endoplasmic reticulum, the nuclear membrane, or a number of deeper granular structures. The P212 antigens are probably located on the membranes of vesicles which are on the exocytosis-endocytosis pathway and may be involved in cell trafficking.

Lithium activates mammalian Na+/H+ exchangers: isoform specificity and inhibition by genistein

Replacement of external NaCl with LiCl induced cytoplasmic alkalinization in CCL-39 cells and rat L6 myoblasts expressing the endogenous Na+/H+ exchanger isoform NHE1. This Li+-induced alkalinization is due to activation of the Na+/H+ exchanger because it was completely inhibited by 100 microM ethylisopropylamiloride (apparent Kd=1 microM) and because it did not occur in exchanger-deficient PS120 cells. The effect of Li+ was not mimicked by Na+, K+, Cs+ and choline+. Li+ caused cytoplasmic alkalinization in PS120 cells expressing NHE1 or NHE2, but not NHE3, when Li+ was added to cells at a concentration high enough to saturate their external transport sites as predicted from Li+ affinities. Li+ did not induce phosphatidylinositol (PI) turnover or intracellular Ca2+ mobilization. Li+-induced alkalinization was not affected by protein kinase C down-regulation, loss of glycogen synthase kinase 3beta caused by antisense oligonucleotide treatment, or pretreatment with calphostin C, pertussis toxin, MEK inhibitor PD98059 and PI3-kinase inhibitor LY294002. However, it was markedly suppressed by the tyrosine kinase inhibitor genistein (10 microM). Thus, externally added Li+ activates NHE1 and NHE2 via a mechanism possibly involving a tyrosine kinase, causing an increase in cytoplasmic pH that could potentially affect various cell functions.

Immunohistochemical and DNA sequencing analysis on human mismatch repair gene MLH1 in cervical squamous cell carcinoma with LOH of this gene

BACKGROUND

The human MLH1 gene (hMLH1) is one of the DNA mismatch repair genes. Defects in these genes are believed to be the underlying cause of microsatellite instability (MSI). MSI has been demonstrated in many human cancers such as colon cancer and some female-specific tumors. The hMLH1 gene can be inactivated by genetic mutation or by hypermethylation of its promoter region, which often causes cessation of hMLH1 protein production. We were prompted by our previous finding of 43% of cervical cancers and their precursors with a loss of heterozygosity (LOH) of the hMLH1 gene to investigate whether it is inactivated during the carcinogenesis of cervical cancer.

MATERIALS AND METHODS

hMLH1 protein production was assessed by immunohistochemistry, and nucleotide sequence analysis were performed on all exons of the hMLH1 gene.

RESULTS

In 11 cases of invasive cervical cancer, among which 7 had LOH of the hMLH1 gene, immunohistochemistry provided no evidence for cessation of hMLH1 protein production. In addition, no mutations were found in any of the 19 hMLH1 gene exons.

CONCLUSIONS

The activity of hMLH1 gene might not be disturbed in the development of cervical cancer although a proportion of the cases had lost one of its hMLH1 gene copies.

Convenient and versatile DNA extraction using agarose plugs for ribotyping of problematic bacterial species

We describe a convenient, versatile and safe method for preparing bacterial DNA for ribotyping analysis. In this method, extraction of bacterial DNA from Salmnonella typhi and Burkholderia pseudomallei. and subsequent restriction endonuclease digestion, was performed in agarose blocks/plugs thus minimizing shearing and loss of DNA, problems commonly associated with liquid phase phenol extraction. Digested DNA in the plugs was then electrophoresed directly, transferred to nylon membranes and hybridized with labeled rDNA probes in the usual manner to provide reproducible restriction patterns. This method is particularly useful for bacterial species where standard DNA extraction in the liquid phase using phenol has been problematic (e.g. B. pseudomallei) but can be used for any bacterial species. The DNA extracted within the agarose plugs can be stored for long periods and can be used in other, widely-used typing methods such as pulsed-field gel electrophoresis (PFGE) and PCR-based techniques. Embedding live cells directly in agarose plugs also minimizes the risk of exposure to these virulent human pathogens among laboratory workers.