Cord blood-derived mesenchymal stem cell does not stimulate nor inhibits T lymphocytes activation

The immune modulatory properties of mesenchymal stem cell (MSC) had brought a new insight in cell-based neotherapy. However, recent works of MSC are focused exclusively on bone marrow-derived MSC. We evaluated the immunogenicity of cord blood-derived MSC (CB-MSC) on T lymphocytes. Human peripheral blood mononuclear cells (PBMC) were prepared by density gradient separation and culture with the presence or absence of CB-MSC. PBMC were collected for activation analysis by flow cytometry at 24-, 48-, and 72- hours. The results showed that, CB-MSC does not stimulate nor inhibit T lymphocyte activation.

Mouse bone marrow mesenchymal stem cells acquire CD45-CD106+ immunophenotype only at later passages

Classically, MSC are identified by a CD45-CD106+ phenotype. In this study, we found that mouse MSC achieve this characteristic phenotype only at later passages. With increasing passages, CD45 (hematopoietic marker) expression shifts to negativity, whereas CD106 (vascular cell adhesion molecule-1) expression becomes increasingly positive. These results demonstrate that MSC cells cultured from mouse bone marrow acquire a classical MSC immunophenotype (CD45-CD106+) in later passages.

The effect of human mesenchymal stem cells on tumour cell proliferation

The therapeutic effect of mesenchymal stem cells (MSC) has been extensively investigated in recent decades, however this therapeutic effect has not been fully characterised. The aim of this study is to elucidate the inhibitory effect of MSC on haematopoietic tumour cells proliferation such as BV173 cell line. To this end, MSC generated from bone marrow, after immunophenotyping, they were co-cultured with tumour cell. The result shows that MSC profoundly inhibit the tumour cell proliferation via arresting the tumour cells at G0 and G1 phase of cell cycle.

Some characteristics of the larval breeding sites of Anopheles culicifacies species B and E in Sri Lanka.

BACKGROUND & OBJECTIVES: Anopheles culicifacies Giles, the major malaria vector in Sri Lanka, exists as a species complex comprising two sympatric sibling species--species B and E. Species E is reported to be the major vector of Plasmodium vivax and P. falciparum parasites in Sri Lanka, whilst species B is a poor or nonvector as in India. Knowledge of the breeding habits of the two sibling species can help in designing optimal vector control strategies. Hence, a survey was conducted in Sri Lanka to study the preferential breeding habitats of An. culicifacies species B and E. METHODS: Immature forms of An. culicifacies were collected from identified breeding sites in malarious districts. Collected larvae were typed for their sibling species status based on mitotic Y-chromosome structure. Data was analysed using Statistical Package for Social Science version 10.0. RESULTS: An. culicifacies immature forms were found in 23 collection sites. Among these samples 19 were found to have species E and four to have species B. All species B larvae were collected from Tonigala village in the Puttalam district. None of the 23 sites was found to have both species B and E. Species E, the major vector of malaria, appears to breed in variety of breeding sites which can be of an indication of its adaptive variation to exploit breeding sites with varying limnological characteristics. INTERPRETATION & CONCLUSION: The present findings have to be taken into account when formulating more effective larval control measures. They also show the need for a detailed study of possible different preferences for larval breeding sites between species B and E.

Expression & immunogenicity of malaria merozoite peptides displayed on the small coat protein of chimaeric cowpea mosaic virus.

BACKGROUND & OBJECTIVES: Foreign peptide sequences can be inserted into the betaB-betaC loop of the cowpea mosaic virus (CPMV) small coat protein (SCP) to yield functional chimaeric viruses. Immunisation with chimaeric CPMV elicits immune responses that protect against human immunodeficiency and mink enteritis viruses. The present study was undertaken to investigate the expression of a B cell epitope from the merozoite surface antigen-1 of the malaria parasite Plasmodium falciparum (PfMSP1) in CPMV for an epitope based vaccine. METHODS: DNA encoding a 19 aa sequence (VTHESYQEL VKKLEALEDA, termed P109), the N-terminus of the mature PfMSP1, was cloned into SCP gene yielding a chimaeric virus CPMV-P109. CPMV-P109 was propagated in cowpea plants. The immunogenicity of purified recombinant virus in rabbits was investigated. RESULTS: CPMV-P109 developed a systemically spreading infection in cowpea, with normal viral morphology. The P109 epitope was detected on CPMV-P109 by ELISA with an antiserum produced against homopolymeric P109. Immunisation of rabbits with CPMV-P109 yielded antibodies that, although were predominantly directed against virus-specific epitopes, also recognized the P109 peptide on the recombinant virus and free P109 peptide. These antibodies however, did not react with the native antigen on merozoite by immunofluorescence. INTERPRETATION & CONCLUSION: The results indicate that selecting immunodominant peptide epitopes and presenting them in a near native conformation are important for generating biologically relevant antibodies in the CPMV expression system. Further, the findings draw attention to the importance of measuring immune responses to the viral vector antigens, a preponderance of which can result in undesirable effects such as autoimmunity and hypersensitivity in immunized hosts.

Acute myeloid leukemia presenting as splenic rupture.

We describe a rare case of acute myeloid leukemia presenting primarily as an acute abdomen due to spontaneous splenic rupture in a 19 years male patient. He was treated with splenectomy after failure of conservative management for splenic preservation but later succumbed to an intracerebral haemorrhage.

Hepatic abscess complicating paratyphoid infection.

Salmonellosis is ubiquitous and is a world-wide public health concern. Liver abscesses are occasionally reported in Salmonella typhi infections, they are a very rare complication of Salmonella paratyphi infections. A 28 year old male patient without any prior medical history presented with fever, abdominal pain and a tender hepatomegaly. The imaging studies revealed multiple liver abscesses and an ultrasound (US) guided aspiration of the abscess yielded heavy growth of Salmonella paratyphi A. He was treated successfully by percutaneous drainage of the abscesses and appropriate antibiotics.

Isotypes of naturally acquired antibodies to a repetitive & non-repetitive epitope on Plasmodium falciparum surface proteins in an endemic area of Sri Lanka.

Isotypes of antibodies in adults and 7-15 yr old children living in a malaria endemic area of Sri Lanka were measured by radioimmunoassay against synthetic target antigens derived from two Plasmodium falciparum surface proteins. Greater than 50 per cent of the sample population possessed IgM antibodies while < or = 13 per cent developed each of the IgG antibody isotypes against a repetitive epitope present on the circumsporozoite protein (CS repeat). A more even distribution of IgM, IgG1, IgG2, IgG3 and IgG4 antibodies was seen against a non-repetitive epitope (P103) on a 45 kDa merozoite surface protein. This difference is attributed to a T-independent antibody response against the CS repeat.

Dynamics of natural antibody responses to malaria parasite surface proteins in the intermediate rainfall zone of Sri Lanka.

Antibodies against repetitive epitopes on Plasmodium falciparum and P. vivax circumsporozoite (CS) proteins and epitopes on the 45 kDa and 185-200 kDa P. falciparum merozoite surface proteins were measured by radioimmunoassay in a two year longitudinal study in Nikawehera village located in the intermediate rainfall zone of Sri Lanka. The prevalence and concentrations of specific antibodies were in many, but not all instances, greater in adults than in children who were aged 7-15 yr at the beginning of the study. The concentrations and prevalence of antibodies were associated with malaria transmission levels previously determined from entomological and hospital admission data in the area. Antibody responses to epitopes on different P. falciparum antigens, two different epitopes within the 185-200 kDa merozoite surface protein and between the P. falciparum and P. vivax CS repeats were significantly correlated. Antibody concentrations against a conserved epitope in the 185-200 kDa protein were significantly higher in P. falciparum infected individuals than in non-parasitaemic subjects. Antibody concentration and prevalences in Nikawehera were lower than at Weheragala, a site located 70 km away in the dry zone of Sri Lanka. It is postulated that lower levels of immunity in the population in areas such as Nikawehera, that are adjacent to more highly malaria endemic areas, may promote epidemics when conditions favour transmission.

Influence of N-terminal amino acids & conjugation position to carrier on specificities of antibodies elicited by malaria peptides.

The specificity of murine antibodies raised against structurally related peptides derived from a malaria parasite membrane protein was studied. The peptides were conjugated to bovine serum albumin (BSA) with 6-maleimido caproic acyl N-hydroxysuccinimide ester before immunization. Conjugation to BSA through a C-terminal or an internal cysteine residue elicited antibodies with noticeably different specificities. An N-terminal tripeptide sequence arginine-asparagine-asparagine had a dominant influence on the immunogenicity of the peptides. Such factors need to be taken into consideration while designing peptide-based immunogens.

Shortcomings of some currently available DNA probes for malaria detection.

A non-radioactive DNA probe based-method for detecting malaria will greatly aid epidemiological studies. Using putative Plasmodium falciparum and P. vivax-specific 18S ribosomal RNA directed oligonucleotides, different enzymatic and chemiluminescent detection methods were attempted without success. The sensitivity of the corresponding 32P-labelled probes was found to be inadequate. A published procedure based on chemiluminescent detection of repetitive DNA sequences of P. falciparum was found to be adequately sensitive but lacking in specificity.