Prolonged viremic phase in children with measles

High CD4/CD45RO+ and CD8/CD45RO+ frequencies in children with vaccine-modified measles

BACKGROUND

Despite availability and wide vaccine coverage, measles infections still occur especially in developing countries. An outbreak of measles occurred among previously immunized older Ghanaian children who had milder clinical symptoms with measles-specific IgG antibodies that could have been attributed to secondary vaccine failure, suggesting that the infection was vaccine-modified measles (VMM).

METHODS

Two-color immunophenotyping of the peripheral blood mononuclear cells was performed at acute, recovery and convalescence phases for 19 VMM patients (mean age 6.2 +/- 3.5 years) using flow cytometry, and compared with that of 20 healthy, sex- and age-matched controls.

RESULTS

The results showed a significantly higher memory helper (CD4(+)/CD45RO(+)) cell frequency and increased suppressor cell (CD8(+)/CD45R0(+)) frequency in VMM patients compared to healthy controls. There were no complications and all the patients recovered completely.

CONCLUSIONS

These findings show that the mild symptoms in patients with VMM may have correlated with the increase of memory T cells, which is in sharp contrast with previous reports on acute measles infection. This may suggest that the intact immunologic memory cells could have been crucial for the resolution of VMM.

Vaccine-modified measles in previously immunized children in Accra, Ghana: clinical, virological and serological parameters

Despite rapidly increasing measles immunization coverage, epidemics of measles occurred from January to March 2000 in some parts of Accra, the capital of Ghana. 44 cases of acute measles were diagnosed at three health facilities during the outbreaks, which we examined clinically and serologically. The peak incidence occurred among 6-12-year-olds, clinical symptoms were milder than the typical symptoms of measles, and fever was significantly less common. None of the cases developed complications and all recovered completely. Thirty-eight (86.4%) were tested serologically; IgM antibodies were detected in 73.7% and IgG antibodies in 84.2% during the acute phase. Milder symptoms in a significant number of cases with measles IgG antibodies suggest that these are vaccine-modified measles, attributable to waning antibodies and low circulation of wild type virus in an area of high vaccine coverage. Serological confirmation will be required for accurate diagnosis, if measles is to be eradicated or kept under control. It also seems likely that multiple dose immunization schedules will be needed in the future to maintain protective antibody levels and to protect children against measles in Ghana. This will eliminate the frequent outbreaks of measles involving immunized children.

Suppression of antigen-specific T cell proliferation by measles virus infection: role of a soluble factor in suppression

Measles virus infection causes a profound immunosuppression. The basis for this immunosuppression is not known. This immunosuppression could be due to virus acting directly on lymphoid cells, the production of an immunosuppressive viral product, or a lymphoid product. We have developed an antigen-specific T cell system to study measles virus-T-cell interactions. We demonstrate that as few as five infectious viral particles added to 1000 T cells results in profound inhibition of antigen-specific T cell proliferation. Supernates taken from measles virus-infected T cells suppress the proliferation of uninfected T cells. Measles-virus-infected HeLa or Vero cells do not produce the factor. The antiproliferative effects of the supernates cannot be attributed to infectious virus, IL-10 or TGF-beta. The soluble factor appears to be larger than 100 kDa, yet retains antiproliferative activity following trypsin digestion with a size less than 10 kDa. Loss of activity is seen following heat treatment at 56 degrees C. The factor is lymphoid cell specific and exhibits cytokine-like behavior yet appears not to be a known cytokine. This soluble factor may be responsible for the overt clinical immunosuppression seen in man and a previously undescribed cytokine induced by measles virus infection of human lymphocytes.

Serum antibodies to HIV-1 are produced post-measles virus infection: evidence for cross-reactivity with HLA

Convalescent sera obtained from patients who were recently recovered from an acute measles virus infection were tested for the presence of anti-HIV-1 antibodies by Western blot analysis. While 16% (17/104) of control sera displayed reactive bands to a variety of HIV proteins, 62% (45/73) of convalescent sera demonstrated immunoreactive bands corresponding to HIV-1 Pol and Gag, but not Env antigens. This cross-reactivity appears to be the result of an active measles infection. No HIV-1 immunoblot reactivity (0/10) was observed in sera obtained from young adults several weeks after a combined measles, mumps, and rubella (MMR) vaccination. Interestingly, examination of anti-HLA typing sera specific for either class I and class II molecules revealed that 46% (19/41) of these sera contained cross-reactive antibodies to HIV-1 proteins. Absorption of measles sera with mixed lymphocyte reaction (MLR)-activated lymphocytes and/or HIV-1 recombinant proteins significantly decreased or removed the presence of these HIV-1-immunoreactive antibodies. Together, these findings suggest that the immune response to a natural measles virus infection results in the production of antibodies to HIV-1 and possibly autoantigens.

A rapid culture assay for examining measles virus infections from urine specimens

BACKGROUND

Large numbers of measles virus (MV) specimens are processed in our laboratory each year as part of a molecular epidemiological study of MV in South Africa. The development of a sensitive, rapid virus isolation system is needed to cope with the number of specimens processed.

OBJECTIVES

A comparison was made of centrifugation-enhanced shell vial culture and standard tissue culture using B95a cells for the isolation of MV from throat swabs and urine.

STUDY DESIGN

The rapid method was initially evaluated using Schwarz vaccine virus and then compared to standard culture using throat swab specimens.

RESULTS

The shell via assay proved to be ten times more sensitive than standard culture in the initial evaluation. Of 43 throat swab specimens, 37 (86%) were positive and 6 (14%) negative in standard culture using B95a cells. The specimens were removed after adsorption in standard culture, frozen and then used in the shell vial assay. It was found that 16/27 were positive in the shell vial assay (24 of these 27 being positive in standard culture,) and 8 negative and 8 specimens gave an indeterminate result. For the 45 urine specimens used in the shell vial assay, 71% were positive, 11% negative and 18% gave an indeterminate result, due to too few cells being present for antigen determination by indirect fluorescent antibody assay. Results were obtained in 4 days, as opposed to the average of 14 days for confirmed isolation in standard culture.

CONCLUSION

Rapid culture substantially reduced total test time, was less labour-intensive and was as sensitive as standard culture for the isolation of measles virus from clinical specimens.

Clinical features of measles in immunocompromised children

Measles is often fatal for immunocompromised hosts. Protective immunity against measles has been studied but is still not completely understood. Recently, five cases of measles were encountered in immunocompromised children. Two of these were allogeneic bone marrow transplanted cases (one common variable immunodeficiency and one severe aplastic anemia) in remission, one Wilms' tumor case in remission, one hepatoblastoma case after cytotoxic therapy at disease onset and one exaggerating hemophagocytic syndrome case with suppressed natural killer cell activity. Clinical symptoms, laboratory findings and the immunologic backgrounds of these five patients were investigated. One of the patients, an 8 year old boy with hemophagocytic syndrome, died of giant cell pneumonia which was confirmed in the section of necropsy lung specimen. Two other patients who received allogeneic bone marrow transplants were not immune to measles, despite their own and their donors' immunizations. Their clinical symptoms were rather severe but both patients recovered and have remained seropositive for as long as 13 months. This fatality from measles is the first reported in a patient with hemophagocytic syndrome. Suppressed natural killer cell activity may be a poor prognostic factor. Also, secondary immunization failure for measles can occur in bone marrow transplanted patients with rather severe clinical symptoms.

Markedly elevated levels of β2-microglobulin in urine with measles viruria in patients with measles

BACKGROUND

Measles is a highly contagious infectious disease in children. However, the pathogenesis has not yet been fully defined since susceptible cells to measles virus (MV) had not been developed. Recently, B95a cells, which are very susceptible to MV, have been reported.

OBJECTIVES

To evaluate measles viruria in patients with measles, isolation of MV from urine was performed using B95a cells.

STUDY DESIGN

Isolation of MV from supernates or sediments of urine in patients with measles was performed using B95a cells. The levels of beta2-microglobulin (MG) in urine and serum were also measured.

RESULTS

MV was isolated from either supernates or sediments of urine. MV was isolated from 10 of 11 samples (91%) within 2 days of the appearance of a rash. MV was isolated from supernates of urine for up to 4 days after the appearance of a rash, and from sediments for up to 5 days. The levels of urinary beta2-MG were elevated within 2 days of the appearance of a rash. The levels of urinary beta2-MG with measles viruria were significantly higher compared to those without measles viruria.

CONCLUSIONS

Measles viruria may occur early in all patients with measles and elevated levels of urinary beta2-MG in patients with measles may be the consequence of tubular injury.

Detection of measles virus genome directly from clinical samples by reverse transcriptase-polymerase chain reaction and genetic variability

A simple and sensitive method for the detection of measles virus genome was developed, amplifying the regions encoding the nucleocapsid (N) protein and hemagglutinin (H) protein of measles virus by reverse transcriptase-polymerase chain reaction (RT-PCR). We examined a variety of measles patients: 28 patients with natural infection, 4 with measles encephalitis and 1 with subacute sclerosing panencephalitis (SSPE). In 28 patients with natural measles infection a single step PCR amplifying the N region resulted in a high detection rate for all plasma samples (28/28) within 3 days of the onset of rash and 80% (20/25) even on day 7 of the onset of rash and later. Within 3 days of the onset of rash, 24/25 (96.0%) of nasopharyngeal secretions (NPS) and 27/28 (96.4%) of peripheral blood mononuclear cells (PBMC) were positive for the N region PCR and the positivity rate of PCR decreased in NPS and PBMC after 7 days of the rash. In acute measles infection, measles genome was detected in all cell fractions, CD4, CD8, B cells, and monocytes/macrophages by the H gene nested PCR. Measles genome was also detected from cerebrospinal fluids (CSF) in patients with measles encephalitis, SSPE, and acute measles by the H gene nested PCR. PCR products of the N and H regions were sequenced and we confirmed the presence of measles genome. Based on the sequence data, chronological sequence differences were observed over the past 10 years. The sequences obtained from the SSPE patient were closely related to those of the wild viruses that were circulating at the time when the patient initially acquired measles. RT-PCR for NPS, PBMC, CSF, and plasma provides a useful method for the diagnosis of measles and molecular epidemiological study in addition to virus isolation.