Biological characterization of clones derived from the Edmonston strain of measles virus in comparison with Schwarz and CAM-70 vaccine strains

The sequence of vaccinations and increased female mortality after high-titre measles vaccine: trials from rural Sudan and Kinshasa

OBJECTIVE

West African studies have hypothesized that increased female mortality after high-titre measles vaccine (HTMV) was due to subsequent diphtheria-tetanus-pertussis (DTP) and inactivated polio vaccine (IPV) vaccinations. We tested two deductions from this hypothesis in HTMV studies from rural Sudan and Kinshasa; first, there should be no excess female mortality for HTMV recipients when DTP was not given after HTMV and second, excess female mortality should only be found among those children who received DTP after HTMV.

STUDIES

The Sudanese trial randomised 510 children to Edmonston-Zagreb (EZ) HTMV, Connaught HTMV or a control vaccine (meningococcal). Both the Connaught HTMV and the control group received standard measles vaccine at 9 months. In the Kinshasa study 1023 children received one dose of HTMV at 6 months or two doses at 312 and 912 months of age.

FINDINGS

First, the Sudan trial is one of the few randomised studies of measles vaccine; the EZ HTMV group had lower mortality between 5 and 9 months of age than controls, the mortality ratio (MR) being 0.00 (p = 0.030). This effect was not due to prevention of measles infection. Second, both studies provided evidence that HTMV per se was associated with low mortality. In a combined analysis comparing both HTMV groups with controls, the HTMV groups had a MR of 0.09 (0.01-0.71) between 5 and 9 months of age. In Kinshasa, the HTMV recipients who did not receive simultaneous DTP had an annual mortality rate of only 1.0% between 6 months and 3 years of age. Third, the female-male MR was related to subsequent DTP vaccinations. In Kinshasa, the female-male MR was only 0.40 (0.13-1.27) among the HTMV recipients who did not receive further doses of DTP. In Sudan, the female-male mortality ratio in the EZ group was 3.89 (95% CI 1.02-14.83) and the female-male MR increased with number of doses of DTP likely to have been given during follow-up (trend, p = 0.043). Fourth, in Kinshasa, mortality was higher among children who had received HTMV and DTP simultaneously than among children who had received HTMV alone (MR = 5.38 (1.37-21.2)).

CONCLUSIONS

Measles vaccine is associated with non-specific beneficial effects. When not given with DTP, HTMV per se was associated with low mortality. Increased female mortality was not found among children who did not receive DTP after HTMV. Hence, our deductions were supported and the sequence or combination of vaccinations may have an effect on sex-specific mortality patterns in low-income countries.

Comparative sequence analysis of the P-, M- and L-coding region of the measles virus CAM-70 live attenuated vaccine strain

Measles virus is a highly contagious agent which causes a major health problem in developing countries. The viral genomic RNA is single-stranded, nonsegmented and of negative polarity. Many live attenuated vaccines for measles virus have been developed using either the prototype Edmonston strain or other locally isolated measles strains. Despite the diverse geographic origins of the vaccine viruses and the different attenuation methods used, there was remarkable sequence similarity of H, F and N genes among all vaccine strains. CAM-70 is a Japanese measles attenuated vaccine strain widely used in Brazilian children and produced by Bio-Manguinhos since 1982. Previous studies have characterized this vaccine biologically and genomically. Nevertheless, only the F, H and N genes have been sequenced. In the present study we have sequenced the remaining P, M and L genes (approximately 1.6, 1.4 and 6.5 kb, respectively) to complete the genomic characterization of CAM-70 and to assess the extent of genetic relationship between CAM-70 and other current vaccines. These genes were amplified using long-range or standard RT-PCR techniques, and the cDNA was cloned and automatically sequenced using the dideoxy chain-termination method. The sequence analysis comparing previously sequenced genotype A strains with the CAM-70 Bio-Manguinhos strain showed a low divergence among them. However, the CAM-70 strains (CAM-70 Bio-Manguinhos and a recently sequenced CAM-70 submaster seed strain) were assigned to a specific group by phylogenetic analysis using the neighbor-joining method. Information about our product at the genomic level is important for monitoring vaccination campaigns and for future studies of measles virus attenuation.

Neutralization of measles virus infectivity and antibody-dependent cell-mediated cytotoxicity activity against an Epstein-Barr virus-infected cell line by intravenous immunoglobulin G [corrected]

Patients with antibody deficiency disorders are highly susceptible to microbial infections. Intravenous (i.v.) immunoglobulin concentrates were originally developed as replacement therapy for such patients. The present study assesses the measles virus neutralizing antibody titers and the antibody-dependent cell-mediated cytotoxicity (ADCC) capacities against Epstein-Barr virus (EBV)-infected cells of immunoglobulin G (IgG) preparations produced for i.v. use (i.v. IgG). The level of neutralizing antibodies against measles virus was determined by a syncytium neutralization test with Vero cells as targets. The measles virus neutralizing antibody titers of the i.v. IgG preparations were >3 x 10(2) and were an average of 1.0 log higher than the titers in pooled plasma from healthy subjects. The two IgG preparations tested showed similar ADCC activities against EBV-infected Raji cells, being active at concentrations of 3 mg/ml or higher. i.v. IgG bound to Raji cells but not to the EBV-negative Ramos cells, as evaluated by flow cytometry. Our in vitro findings may provide further support for the use of i.v. IgG for the prevention and treatment of infections caused by specific viral pathogens.

Infection of chicken embryonic fibroblasts by measles virus: adaptation at the virus entry level

Measles virus (MV) has a tropism restricted to humans and primates and uses the human CD46 molecule as a cellular receptor. MV has been adapted to grow in chicken embryonic fibroblasts (CEF) and gave rise to an attenuated live vaccine. Hallé and Schwarz MV strains were compared in their ability to infect both simian Vero cells and CEF. Whereas both strains infected Vero cells, only the CEF-adapted Schwarz strain was able to efficiently infect CEF. Since the expression of the human MV receptor CD46 rendered the chicken embryonic cell line TCF more permissive to the infection by the Hallé MV strain, the MV entry into CEF appeared to be a limiting step in the absence of prior MV adaptation. CEF lacked reactivity with anti-CD46 antibodies but were found to express another protein allowing MV binding as an alternative receptor to CD46.