Prevalence of antibodies against hepatitis A virus, hepatitis B virus, and Treponema pallidum in Mauritius.

A seroepidemiological study on the prevalence of antibodies against hepatitis A virus (HAV), hepatitis B virus (HBV) and Treponema pallidum was conducted in various groups of the population of the state of Mauritus (Islands of Mauritus and Rodrigues). 618 sera were tested. The overall prevalence of anti-HAV was 86.1% and yielded and age-dependent increase. Serological evidence for acute or chronic HBV infection was found in 3.8%; 4.5% were positive for anti-HBc alone, and in 12.6% past HBV infection was detected. No age- or sex-dependent increase in the prevalence of anti-HBc was found. There were differences in the anti-HBc prevalence among the various groups of population ranging from 5.9 (flight personnel) to 58.3% (prison inmates). Treponemal antibodies were detected in 6.0% and showed a fairly marked age-dependent increase. Our study suggests that vaccination programmes against HAV and HBV would be beneficial for the Mauritian population.

Use of pulsed field gel electrophoresis to characterize BCR gene involvement in CML patients lacking M-BCR rearrangement.

We studied the pattern of BCR involvement in 52 patients with chronic myeloid leukemia by Southern blotting. Of 33 Philadelphia (Ph)-positive patients, 30 had evidence of M-BCR rearrangement, two cases were difficult to interpret, and one clearly lacked evidence of M-BCR rearrangement. Of 19 Ph-negative patients, nine showed M-BCR rearrangement, nine showed no rearrangement, and one result was uncertain. We selected for more detailed study eight patients (three Ph-positive and five Ph-negative). Two of the Ph-positive patients, whose Southern blots were difficult to interpret, had rearranged bands when the BCR gene was studied by pulsed field gel electrophoresis (PFGE). Results of PFGE studies and in situ hybridization to metaphase chromosomes in the third Ph-positive patient, whose DNA clearly lacked M-BCR rearrangement on Southern analysis, were consistent with a breakpoint on chromosome 22 located 3' of all known exons of the BCR gene. However, mRNA studied with the polymerase chain reaction showed evidence of a classical b2-a2 linkage. The findings in this patient may be explained by an unusual genomic breakpoint downstream of the BCR gene associated with long range splicing that excluded all of the 3' BCR exons. Of the five patients with Ph-negative M-BCR non-rearranged CML studied by PFGE for BCR gene rearrangement, none had evidence of rearranged bands. We conclude that PFGE is a valuable adjunct to standard molecular techniques for the study of atypical cases of CML. Occasional patients with Ph-positive CML have breakpoints outside M-BCR. The BCR gene is probably not involved in patients with Ph-negative, M-BCR non-rearranged CML.

Use of a hypervariable minisatellite DNA probe (33.15) for evaluating engraftment two or more years after bone marrow transplantation for aplastic anaemia.

We have studied long-term engraftment in 24 multiply transfused patients transplanted for severe aplastic anaemia (SAA) 2-7 years previously from HLA identical sibling donors. All 24 patients had engrafted initially; nine (38%) developed grade II-IV a-GVHD, but only 5 (21%) developed chronic GVHD, which was mild, localized and transient. In 22 cases DNA 'fingerprint' analysis using a hypervariable minisatellite DNA probe (33.15) confirmed the donor/recipient origin of patient peripheral blood (PB) nucleated cells. Red cell antigens and PB lymphocyte chromosomes were also analysed in informative cases. In 19 patients (79%) PB cells were of donor origin confirming sustained engraftment, whereas five (21%) had PB cells of recipient origin. In four of these five cases complete autologous reconstitution was demonstrated. In one case DNA fingerprinting revealed mixed haemopoietic chimaerism. In three of the four cases of autologous reconstitution there had been a previous episode of late graft failure. The low incidence of chronic GVHD in the study group was not explained by autologous reconstitution or mixed chimaerism. We conclude that the hypervariable minisatellite probes are valuable in the study of engraftment after BMT, especially when patient and donor are HLA identical, of the same sex, and have the same ABO-Rh blood type. Pre-transplant specimens from the patient are not necessary for interpretation of the results provided that DNA from the donor is available.

Use of minisatellite DNA probes for recognition and characterization of relapse after allogeneic bone marrow transplantation.

Restriction fragment length polymorphisms can be used to distinguish blood and marrow cells from close relatives. We used two probes that recognize a series of dispersed and highly polymorphic tandem-repetitive minisatellite regions in the human genome that can be detected via a shared 10-15 base pair core sequence similar to the generalized recombination sequence (chi) of E. coli. We have studied the resulting individual-specific DNA fingerprints in 15 patients before and after allogeneic bone marrow transplantation performed for chronic myeloid leukaemia and in two patients transplanted for acute leukaemia. Early engraftment could be demonstrated at 3 weeks post-transplant based on the recognition of cells of donor origin. One patient who failed to engraft had only recipient type marrow cells 3 months post-transplant. Nine patients who relapsed after transplantation had only cells of recipient origin. In one patient who relapsed after transplantation with T-cell depleted donor marrow, fractionation studies showed that his T-cells at relapse were of recipient origin. We conclude that these minisatellite probes are valuable for characterizing the origin of different cell populations after marrow transplantation and could be useful for characterizing relapse when donor and recipient are of the same sex.

Molecular analysis of relapse in chronic myeloid leukemia after allogeneic bone marrow transplantation.

Four patients with Philadelphia (Ph') positive chronic myeloid leukemia (CML) were studied before, after, and on relapse following allogeneic bone marrow transplantation (BMT). Southern analysis of DNA from cells collected before and at relapse after BMT was performed in order to investigate the origin of the leukemia at relapse. Using minisatellite probes we showed that the relapse occurred in cells of host origin in all four patients and this was confirmed with a Y chromosome specific probe in two male patients who had a female donor. Furthermore, using two probes for the breakpoint cluster region (bcr) on chromosome 22, we showed that leukemic cells at relapse bore identical rearrangements to those in the disease at time of presentation of each patient. We conclude that relapse in all four patients is due to re-emergence of the original leukemic clone.