Prevalence of measles antibody among children under 15 years of age in Santa Cruz, Bolivia: implications for vaccination strategies.

We conducted a community-based survey in Santa Cruz city, Bolivia, to determine the age-specific prevalence of measles antibodies, determine factors associated with absence of detectable measles antibodies, and to compare results of salivary and serum measles immunoglobulin G (IgG) antibody assays. Serum samples from 1654 children were assayed for measles IgG antibody using the haemagglutination inhibition (HI) assay, and salivary samples were also obtained from 187 children and tested for measles IgG antibody using an antibody capture radioimmunoassay. Reported measles vaccine coverage in children aged 12-35 months was 77% (95% confidence interval [CI], 72-81%). Eighty-seven percent (95% CI 85-89%) had detectable HI antibody, but a high proportion had antibody levels below 200 miu (30-40% of 2-14 years old children). Measles seronegativity was associated with not being vaccinated against measles, a negative history of measles disease, living in the inner city, being a lifetime resident of Santa Cruz, and young age. Of 212 children without detectable measles antibody, 58% had a positive history of vaccination or measles disease, so that historical information was not sufficiently reliable to identify susceptibles. The salivary measles antibody assay was not sufficiently sensitive to be used for population screening; only 54% of 171 salivary samples from children who had detectable serum HI antibody were positive. A mass measles vaccination campaign of all children under 15 years of age is planned in Bolivia in 1994. Although only 7% of school-age children in Santa Cruz were seronegative, the effectiveness of a mass campaign in this age group depends in part on the response to revaccination of children with low, but detectable, antibody levels.

Response to measles revaccination among Bolivian school-aged children.

The response to measles revaccination was evaluated in 1994 among 202 Bolivian school-aged children whose antibody levels were below 200 miu (milli-international units) by haemagglutination inhibition (HI) in a large-scale serosurvey conducted in Santa Cruz one year earlier. Of the 202 revaccinated children, 164 (82%) had seroconverted between the 1993 serosurvey and the pre-revaccination blood sample. A measles outbreak occurred in Santa Cruz 6 months before the revaccination. Among the seroconvertors, only 6% gave a history of measles, and 15% a history of contact with a case of measles. All 20 children with undetectable HI antibody pre-revaccination, and all 6 children with levels below 100 miu, seroconverted after revaccination. The geometric mean titres by HI at 4 weeks after revaccination were 2018 miu (95% confidence limits [95% CL] 1143, 3564) and 398 miu (95% CL 254, 625) in the 2 groups, respectively. Six of 9 children with pre-revaccination antibody titres of 100-199 miu also seroconverted. No child demonstrated a measles-specific immunoglobulin M response. Among the 29 children who seroconverted and were followed up at one year after revaccination, 15(52%) showed a fourfold or greater decline in antibody levels, which in 8 fell to levels below 200 miu. This study confirmed the observation that revaccination is successful in producing an antibody response in children with low or undetectable pre-revaccination titres, but it also confirmed that vaccine-induced immunity wanes rapidly.

The water proton spin-lattice relaxation times in virus-infected cells.

The water proton spin-lattice relaxation times in HEp-2 cell cultures were determined immediately after 1 h of polio-virus adsorption. The shortening of the water T1 was closely related to the multiplicity of infection, allowing direct inspections of the virus--cell interaction since the first steps of the infectious cycle. Virus-induced structural and conformational changes of cell constituents were suggested to be detectable by NMR investigation of cell water.

Nuclear magnetic resonance investigation of virus-lymphomonocyte interactions.

The water protein spin-lattice relaxation time (T1) was measured in suspensions of human peripheral blood mononuclear cells (PBMC), uninfected or infected with type 1 herpes simplex virus, human cytomegalovirus and rubella virus. In the infected samples, T1 enhancements, which linearly depend on virus concentration, were observed. This T1 increase can be related to the early changes induced by the virus adsorption of the cells, not always confirmed by virus-induced cytopathic effect (CPE) in cocultures of infected PBMC and other sensitive cells. Compared with other conventional virological techniques, this NMR method seems to be rapid and sensitive. The NMR response was reproducible and specific, since neutralization of the viral infection by homologous antisera consistently matched the neutralization of the virus-induced NMR effects. These observations suggest that fast and sensitive 1H-NMR relaxation techniques can be implemented in virological diagnosis directly on pathological materials.

Expression of measles virus antigens in Streptococcus gordonii.

The measles virus proteins haemagglutinin (HA) and fusion protein (F), which together mediate attachment and penetration of the virus in the host cell and can elicit production of neutralising antibodies in the course of natural infection were expressed in the vaccine vector Streptococcus gordonii, a Gram-positive bacterium normally present in the human oral cavity. HA and F were expressed as fusion proteins attached to the bacterial surface, and were both found to be immunogenic when the recombinant S. gordonii were inoculated subcutaneously in mice.

[Capacity of clones of vaccinia virus to multiply at different temperatures and pH values]. / Capacità di moltiplicazione di cloni di virus caccinico a differenti temperature e valori di pH.

The study of the biological characteristics of ten clones, isolated from plaque, of vaccinia virus has made evident that two of these characteristics--the capacity to multiply at 40 degrees C and the type of CPE in animal cell cultures--can be used as genetic markers of neuropathogenicity, valued in relationship to the property to induce demyelinating encephalitis in mice injected intracerebrally or intravenously. The most neurovirulent clones demonstrated high capacity to multiply at 40 degrees C and lytic CPE; the clones, that did not have (or had at a very low level) encephalitogenic activity in mice, presented poor capacity to multiply at 40 degrees C and CPE of syncytial type. The variation of the pH of the cell culture medium enhances the difference of CPE induced by clones that had different levels of neuropathogenicity. The results are discussed in relation to their use in improving the smallpox vaccine.

NMR investigation of cell cultures: early detection of infection by Herpes simplex virus type 2 and transformation.

The water proton Nuclear Magnetic Resonance (NMR) spin-lattice relaxation rates were measured in suspension of uninfected and Herpes simplex virus type 2-infected WI-38 diploid cells and shown to allow reliable detection of (i) the early signs of productive infection, and (ii) the tendency to undergo either spontaneous or virus-induced transformation. In addition, NMR investigation of several transformed cell lines currently and previously established from WI-38 cells clearly indicated that the NMR relaxation parameter is a suitable tool for assessment of the level of malignancy, as revealed by in vivo oncogenicity tests in immunosuppressed mice.

Prevalence of measles antibodies before and after vaccination in previously unvaccinated children of the Cordillera Province (Santa Cruz Department, Bolivia).

A study was carried out in the Cordillera Health District (Santa Cruz Department, Bolivia) from October 1988 to April 1989 to determine the seroprevalence of measles antibodies and the seroconversion rates among a group of previously unvaccinated children (9-36 months of age) from the urban and rural area of the province, before and after immunization with a standard dose of Schwarz measles vaccine. Among 265 previously unvaccinated children, 77 (29%) had measles IgG antibodies prior to immunization; 141 out of 147 (96%) seronegative children at the time of vaccination seroconverted. No difference in seroprevalence and in seroconversion rates was found between the urban and rural groups.

[Evaluation of the specific immune response after anti-rubella vaccination]. / Valutazione della risposta immunitaria specifica dopo vaccinazione anti-rosolia.

A selective rubella immunization program was carried out in the Siena (Italy) area since 1984. 912 schoolgirls aged 10 to 18 were screened for rubella antibodies. Seropositivity rates, increasing with age, appeared quite heterogenous among subjects living in different villages. Seronegative girls were partly voluntarily immunized with RA 27/3 live attenuated rubella vaccine. Serological and clinical controls performed on 238 subjects one month after immunization showed a 99.6% vaccine-induced seroconversion rate and mild post-vaccinal reactions in 26% of vaccinees. Serological control performed, on 172 subjects, at 8-12 days after vaccination revealed that in most cases vaccine induced haemagglutination-inhibiting antibodies are not detectable at the time. The results are discussed in relation to a forthcoming introduction of compulsory rubella vaccination in our Country.

NMR parameters of local anesthetics as biological markers of the cell-virus interactions.

The selective proton NMR relaxation rates were measured in the system made by the local anesthetic procaine, human erythrocytes and the hemagglutinating Echo virus type 11. The NMR technique provided a very good tool for using drugs firmly bound to receptor membranes as biological "markers" of the virus-cell interaction.

Virus-cell interactions: nuclear magnetic resonance behaviour of intracellular water.

The water proton NMR spin-lattice relaxation time if measured in HEp-2 cells in relation to the infection by different viruses (Poliovirus type 1, Coxsackievirus B-3, human Adenovirus, Measles virus, Respiratory Syncytial virus, Herpes simplex virus, subtype 1, and Vaccinia virus). The NMR properties of intracellular water allow the early detection and identification of viruses. A close relationship is shown between the NMR behavior and the mode of virus-cell interaction.

Detection of human herpesviruses 6 and 7 in heart transplant recipients by a multiplex polymerase chain reaction method.

In order to evaluate the possible reactivation of human herpesviruses 6 (HHV-6) and 7 (HHV-7) after heart transplantation, buffy-coat and plasma specimens from 21 transplant patients and 56 healthy blood donors were examined for HHV-6 and HHV-7 DNA by polymerase chain reaction. Human herpesvirus 6 and HHV-7 infection or reactivation has been suggested to play a role in cytomegalovirus disease progression in renal transplant recipients. In the present study, however, no significant difference in the prevalence of HHV-6 and HHV-7 was found between the immunosuppressed and the healthy population; moreover, no viral reactivation was found in the heart transplant recipients.

Sarcoidosis and infections by human lymphotropic viruses.

In sera of 38 patients with sarcoidosis, assayed for antiviral antibody to Rubella, Measles, Cytomegalovirus (CMV), adenovirus, Epstein-Barr virus (EBV), human immunodeficiency virus (HIV), different incidence of seropositivity have been found, according to the virus assayed. Interestingly all patients were seropositive to rubella virus with high titres compared to data obtained from normal age matched population. These data indicate that in Sarcoidosis an altered antibody response of post-primary type can be found.

Live-cell immunofluorescence for detection of human immunodeficiency virus type 1 (HIV-1)-related antigens in peripheral blood mononuclear cells from HIV-1 seropositive individuals.

Live-cell indirect immunofluorescence was used to detect HIV-associated antigens in fresh uncultured peripheral blood mononuclear cells from 29 HIV-seropositive subjects. Conventional fixed-cell immunofluorescence and live-cell immunofluorescence were run in parallel on each sample using monoclonal antibodies directed against HIV gag and env gene products. Sera from the same patients were also tested for HIV antigen by a sandwich enzyme immunoassay. Results strongly indicate that nondenaturing live-cell immunofluorescence is much more sensitive for detection of HIV-associated antigens and may be useful in the diagnosis of HIV infection as well as in the study of pathogenesis.