Enzyme immunoassay versus plaque neutralization and other methods for determination of immune status to measles and varicella-zoster viruses and versus complement fixation for serodiagnosis of infections with those viruses

Comparison of measles IgG enzyme immunoassays (EIA) versus plaque reduction neutralization test (PRNT) for measuring measles serostatus: a systematic review of head-to-head analyses of measles IgG EIA and PRNT

BACKGROUND

As countries move towards or achieve measles elimination status, serosurveillance is an important public health tool. However, a major challenge of serosurveillance is finding a feasible, accurate, cost-effective, and high throughput assay to measure measles antibody concentrations and estimate susceptibility in a population. We conducted a systematic review to assess, characterize, and - to the extent possible - quantify the performance of measles IgG enzyme-linked assays (EIAs) compared to the gold standard, plaque reduction neutralization tests (PRNT).

METHODS

We followed the PRISMA statement for a systematic literature search and methods for conducting and reporting systematic reviews and meta-analyses recommended by the Cochrane Screening and Diagnostic Tests Methods Group. We identified studies through PubMed and Embase electronic databases and included serologic studies detecting measles virus IgG antibodies among participants of any age from the same source population that reported an index (any EIA or multiple bead-based assays, MBA) and reference test (PRNT) using sera, whole blood, or plasma. Measures of diagnostic accuracy with 95% confidence intervals (CI) were abstracted for each study result, where reported.

RESULTS

We identified 550 unique publications and identified 36 eligible studies for analysis. We classified studies as high, medium, or low quality; results from high quality studies are reported. Because most high quality studies used the Siemens Enzygnost EIA kit, we generate individual and pooled diagnostic accuracy estimates for this assay separately. Median sensitivity of the Enzygnost EIA was 92.1% [IQR = 82.3, 95.7]; median specificity was 96.9 [93.0, 100.0]. Pooled sensitivity and specificity from studies using the Enzygnost kit were 91.6 (95%CI: 80.7,96.6) and 96.0 (95%CI: 90.9,98.3), respectively. The sensitivity of all other EIA kits across high quality studies ranged from 0% to 98.9% with median (IQR) = 90.6 [86.6, 95.2]; specificity ranged from 58.8% to 100.0% with median (IQR) = 100.0 [88.7, 100.0].

CONCLUSIONS

Evidence on the diagnostic accuracy of currently available measles IgG EIAs is variable, insufficient, and may not be fit for purpose for serosurveillance goals. Additional studies evaluating the diagnostic accuracy of measles EIAs, including MBAs, should be conducted among diverse populations and settings (e.g., vaccination status, elimination/endemic status, age groups).

Molecular Epidemiology of Measles in California, United States-2019

In 2019, the United States (US) experienced the highest number of measles importations and cases in the postelimination era. More than a quarter of imported cases entered the US through California. Measles surveillance efforts in California resulted in the identification of 26 importations, 6 outbreaks, and 72 cases in 2019. Only genotype B3 and D8 measles strains were detected. Genotype-specific differences were noted in the incidence of vaccine failures, hospitalizations, and severe complications among cases. A targeted whole genome sequencing approach provided higher-resolution discrimination between epidemiologically linked and sporadically introduced strains than conventional N450 sequencing. Our report underscores the importance of ensuring appropriate measles vaccination status, especially prior to international travel to measles-endemic regions, and highlights the value of a strong measles surveillance system in minimizing outbreaks and preserving measles elimination status in the US.

Subacute Sclerosing Panencephalitis: The Devastating Measles Complication That Might Be More Common Than Previously Estimated

Background

Subacute sclerosing panencephalitis (SSPE) is a fatal complication of measles. We reviewed California cases from 1998-2015 to understand risk factors for SPPE and estimate incidence.

Methods

SSPE cases had clinically compatible symptoms and measles antibody detection in cerebrospinal fluid (CSF) or medical record documentation of SSPE. Cases were identified though a state death certificate search, Centers for Disease Control and Prevention reports, or investigations for undiagnosed neurologic disease. Measles detection in CSF was performed by serology at the California Department of Public Health or at clinical laboratories.

Results

Seventeen SSPE cases were identified. Males outnumbered females 2.4:1. Twelve (71%) cases had a history of measles-like illness; all 12 had illness prior to 15 months of age. Eight (67%) children were exposed to measles in California. SSPE was diagnosed at a median age of 12 years (3-35 years), with a latency period of 9.5 years (2.5-34 years). Among measles cases reported to CDPH during 1988-1991, the incidence of SSPE was 1:1367 for children <5 years, and 1:609 for children <12 months at time of measles disease.

Conclusions

SSPE cases in California occurred at a high rate among unvaccinated children, particularly those infected during infancy. Protection of unvaccinated infants requires avoidance of travel to endemic areas, or early vaccination prior to travel at age 6-11 months. Clinicians should be aware of SSPE in patients with compatible symptoms, even in older patients with no specific history of measles infection. SSPE demonstrates the high human cost of "natural" measles immunity.

System-Wide Associations between DNA-Methylation, Gene Expression, and Humoral Immune Response to Influenza Vaccination

Failure to achieve a protected state after influenza vaccination is poorly understood but occurs commonly among aged populations experiencing greater immunosenescence. In order to better understand immune response in the elderly, we studied epigenetic and transcriptomic profiles and humoral immune response outcomes in 50-74 year old healthy participants. Associations between DNA methylation and gene expression reveal a system-wide regulation of immune-relevant functions, likely playing a role in regulating a participant's propensity to respond to vaccination. Our findings show that sites of methylation regulation associated with humoral response to vaccination impact known cellular differentiation signaling and antigen presentation pathways. We performed our analysis using per-site and regionally average methylation levels, in addition to continuous or dichotomized outcome measures. The genes and molecular functions implicated by each analysis were compared, highlighting different aspects of the biologic mechanisms of immune response affected by differential methylation. Both cis-acting (within the gene or promoter) and trans-acting (enhancers and transcription factor binding sites) sites show significant associations with measures of humoral immunity. Specifically, we identified a group of CpGs that, when coordinately hypo-methylated, are associated with lower humoral immune response, and methylated with higher response. Additionally, CpGs that individually predict humoral immune responses are enriched for polycomb-group and FOXP2 transcription factor binding sites. The most robust associations implicate differential methylation affecting gene expression levels of genes with known roles in immunity (e.g. HLA-B and HLA-DQB2) and immunosenescence. We believe our data and analysis strategy highlight new and interesting epigenetic trends affecting humoral response to vaccination against influenza; one of the most common and impactful viral pathogens.

Human leukocyte antigen associations with humoral and cellular immunity following a second dose of measles-containing vaccine: persistence, dampening, and extinction of associations found after a first dose

Previously we found human leukocyte antigen (HLA) associations with humoral immunity following a single dose of measles-containing vaccine. In this study, we sought to determine if HLA associations exist with humoral and cellular immunity following a second dose of measles-containing vaccine and if the associations we found with humoral immunity after the first dose persist following a second dose. We recruited a population-based sample of 346 schoolchildren, all who previously received two doses of a measles-containing vaccine. Molecular HLA classes I and II typing as well as humoral and cellular immune assays (measles-specific IgG antibody levels and lymphoproliferative response) were performed in these subjects. We found significant associations with class I HLA-B (p=0.05) as well as class II HLA-DPB1 (p=0.01) and -DPA1 (p=0.03) genes for measles vaccine-induced antibody levels after the second dose. Similarly, we found significant associations with class II HLA-DQB1 (p=0.05) and -DRB1 (p=0.01) genes for measles-specific lymphoproliferation after the second dose. While we found HLA associations after the second dose that we previously found after the first dose of measles containing vaccine, fewer alleles had statistically significant associations, suggesting that the second dose had a dampening or extinguishing effect on the HLA associations. It appears that the second dose overcomes HLA restriction through an as yet unknown mechanism. Future studies of HLA associations should consider both the effect of dose and the role that subsequent doses might play on genetic associations found with the response to a first dose.

[Measles, mumps and rubella virus infection in pregnancy. Possible adverse effects on pregnant women, pregnancy outcome and the fetus]

Measles, mumps and rubella are common childhood diseases. Therefore, frequent and intense contact with children of preschool age may be associated with a higher infection risk for childcare providers. This overview summarizes current knowledge on possible adverse effects of these infections on pregnant women, pregnancy outcome and the fetus. Acute rubella or mumps virus infections are apparently not more severe in pregnant than non-pregnant women. In contrast, measles virus infection in pregnancy is linked to a higher incidence of pneumonitis and hospitalization. Evidence of congenital defects due to fetal infection is only provided in case of rubella virus infection in early pregnancy. Following rubella virus infection in the first trimester an increased fetal loss rate was reported. In 1966, a prospective study showed also a significant association between maternal mumps in the first trimester and an increased risk of abortion. But other investigators could not confirm this association. Measles and rubella but not mumps virus infections are linked to an increased premature birth rate. Occurring in late pregnancy, all three infections can result in birth of an infected infant. But severe disease occurs rarely and is mostly reported for premature infants with early neonatal measles. Preventive measures, aimed to reduce the risk of infection or severe complications for pregnant childcare providers, should consider the individual history of the employee (e.g. previous immunizations or antibody test results), the current epidemiological situation and possible interventions like passive immunization in case of exposure to measles.

Pediatric encephalitis: what is the role of Mycoplasma pneumoniae?

BACKGROUND

Encephalitis is a complex, debilitating, and sometimes fatal neurologic condition to which children are especially prone. Mycoplasma pneumoniae, a common respiratory pathogen, has been implicated as an etiology of encephalitis. Evidence for recent or acute M. pneumoniae infection has been demonstrated in limited studies of both pediatric and adult patients with encephalitis.

PATIENTS AND METHODS

Unexplained encephalitis cases are referred to the California Encephalitis Project for diagnostic testing. Serum, cerebrospinal fluid, and respiratory specimens are tested by polymerase chain reaction and serology methods for the presence of multiple pathogens, including M. pneumoniae. M. pneumonia-associated cases of encephalitis were compared with other bacterial agents, herpes simplex virus 1, and enterovirus.

RESULTS

Of 1988 patients referred to the California Encephalitis Project, evidence of acute M. pneumoniae infection was found in 111 patients, of which 84 (76%) were pediatric patients. Eighty percent of the 84 patients were positive for M. pneumoniae by serology alone. Cerebrospinal fluid polymerase chain reaction for M. pneumoniae was rarely positive (2%). Patients with M. pneumoniae-associated pediatric encephalitis were a median of 11 years old, progressed rapidly (median: 2 days from onset to hospitalization), and were often in the ICU (55%). Symptoms included fever (70%), lethargy (68%), and altered consciousness (58%). Gastrointestinal (45%) and respiratory (44%) symptoms were less common. Compared with patients with other bacterial as well as viral agents, patients with M. pneumoniae-associated encephalitis had fewer seizures and less-severe hospital courses.

CONCLUSIONS

M. pneumoniae is the most common agent implicated in the California Encephalitis Project. Patients with M. pneumoniae-associated encephalitis are predominantly pediatric, and their presentations are clinically similar to enterovirus encephalitis, although they frequently require intensive care with prolonged hospitalizations. Given that M. pneumoniae infection is found more than any other pathogen, increased emphasis should be placed on elucidating the role and mechanism of M. pneumoniae in encephalitis.

Seroprevalence of antibody to varicella among Somali refugees

OBJECTIVES

To determine the seroprevalence of varicella antibody among recent Somali refugees living in Olmsted County, Minnesota, and to estimate the risk of varicella-zoster virus (VZV) infection in this group.

SUBJECTS AND METHODS

We obtained blood samples from the study subjects, along with demographic information, immunization records, and vaccine-preventable disease history. Serum samples were tested using a whole-virus IgG VZV-specific commercial enzyme-linked immunosorbent assay kit. This study was completed in 1998.

RESULTS

Overall, 200 Somali refugees, comprising 33 extended families, were interviewed, with 193 providing adequate blood samples. Thirty-five subjects (18%) were seronegative for varicelia. Males had a significantly higher seronegativity rate (25% [n = 23]) compared with females (12% [n = 12]; P = .02); however, this association disappeared after adjustment for age and varicella infection history. Five percent (5/92) of adults were seronegative compared with 30% (30/101) of all children (P < .001). Eight percent (5/61) of the adult females were seronegative, whereas none (0/31) of the adult males were seronegative. Conversely, 38% (23/60) of male children were seronegative compared with 17% (7/41) of female children (P < .001).

CONCLUSION

These results demonstrate a high prevalence of varicella seronegativity among Somali refugees who have immigrated to an endemic area. We recommend instituting improved education regarding varicella among Somali communities and increasing vaccine uptake or routine testing for serum varicella antibody to prevent VZV-related morbidity and mortality, particularly in adolescents, adult refugees, and women of childbearing age.

Beyond viruses: clinical profiles and etiologies associated with encephalitis

BACKGROUND

Encephalitis is a complex syndrome, and its etiology is often not identified. The California Encephalitis Project was initiated in 1998 to identify the causes and further describe the clinical and epidemiologic characteristics of encephalitis.

METHODS

A standardized report form was used to collect demographic and clinical data. Serum, cerebrospinal fluid, and respiratory specimens were obtained prospectively and were tested for the presence of herpesviruses, arboviruses, enteroviruses, measles, respiratory viruses, Chlamydia species, and Mycoplasma pneumoniae. The association between an identified infection and encephalitis was defined using predetermined, organism-specific criteria for confirmed, probable, or possible causes.

RESULTS

From 1998 through 2005, a total of 1570 patients were enrolled. Given the large number of patients, subgroups of patients with similar clinical characteristics and laboratory findings were identified. Ten clinical profiles were described. A confirmed or probable etiologic agent was identified for 16% of cases of encephalitis: 69% of these agents were viral; 20%, bacterial; 7%, prion; 3%, parasitic; and 1%, fungal. An additional 13% of cases had a possible etiology identified. Many of the agents classified as possible causes are suspected but have not yet been definitively demonstrated to cause encephalitis; these agents include M. pneumoniae (n=96), influenza virus (n=22), adenovirus (n=14), Chlamydia species (n=10), and human metapneumovirus (n=4). A noninfectious etiology was identified for 8% of cases, and no etiology was found for 63% of cases.

CONCLUSIONS

Although the etiology of encephalitis remains unknown in most cases, the recognition of discrete clinical profiles among patients with encephalitis should help focus our efforts toward understanding the etiology, pathogenesis, course, and management of this complex syndrome.

Extinction of the human leukocyte antigen homozygosity effect after two doses of the measles-mumps-rubella vaccine

We have reported associations between human leukocyte antigen (HLA) homozygosity and low measles antibody levels after one dose of the measles, mumps, and rubella (MMR) vaccine. Here, we examined associations between HLA homozygosity and immune responses to MMR after two doses of vaccine. We examined associations between HLA homozygosity and measles antibody levels in a group of 178 children (cohort 1) as well as associations between homozygosity and antibody levels and lymphoproliferative responses to MMR in 346 children (cohort 2). In cohort 1, HLA homozygotes and heterozygotes had similar increases in measles antibody levels after a second dose of measles vaccine. In cohort 2, HLA homozygosity was not associated with measles immune measures after two doses of vaccine. Homozygosity at the DPB locus was associated with increased rubella antibody levels, and homozygosity at the class IA alleles was associated with lower mumps lymphoproliferative response. Homozygosity at increasing numbers of loci was also associated with lower mumps antibody levels and lymphoproliferative response. Therefore, two doses of the MMR vaccine appear to induce sufficient antibody levels and lymphoproliferative responses against measles and rubella, regardless of HLA homozygosity status. However, children who are HLA homozygous may be less protected against mumps compared with children who are heterozygous.

Rhinovirus outbreak in a long term care facility for elderly persons associated with unusually high mortality

During a 6-week period in 2003, 56 residents and 26 staff developed respiratory illness in a long-term facility; 12 residents died. Seven of 13 respiratory specimens were culture-positive for rhinovirus; 6 of the isolates were serotype 82. In elderly populations, severe illness may be associated with organisms typically considered to be “benign,” such as rhinovirus.

Central memory CD4+ T cell responses in chronic HIV infection are not restored by antiretroviral therapy

A strong CD4(+) T cell response has been correlated with better control of HIV infection. However, the effect of HIV on the maintenance of Ag-specific memory CD4(+) T cells is not fully understood. We characterized the function and phenotype of memory CD4(+) T cells generated by mumps and influenza A or B viruses in HIV-infected individuals receiving highly active antiretroviral therapy (n = 21), HIV-infected long-term nonprogressors (n = 10), and HIV-seronegative volunteers (n = 10). We observed significantly decreased proliferation of the Ag-specific central memory CD4(+) T cell population (CD28(+)/CCR7(+)/CD45RA(-)) in the antiretroviral treated HIV-infected individuals compared with the seronegative controls. Restored CD4(+) T cell count and decreased HIV viral load while on highly active antiretroviral therapy did not result in increased proliferation, whereas nadir CD4(+) T cell count predicted the presence of Ag-specific proliferation. Our results indicate that HIV infection leads to impaired maintenance of virus-induced or vaccine-generated central memory CD4(+) T cells that is not restored by HAART.

SARS and common viral infections

In California, molecular testing was useful in decreasing suspicion for severe acute respiratory syndrome (SARS), by detecting common respiratory pathogens (influenza A/B, human metapneumovirus, picornavirus, Mycoplasma pneumoniae, Chlamydia spp., parainfluenza virus, respiratory syncytial virus, and adenovirus) in 23 (45%) of 51 patients with suspected SARS and 9 (47%) of 19 patients with probable SARS.

Whole blood samples as an alternative to serum for detection of immunity to measles virus by ELISA

The aim of this study was to evaluate enzyme linked immunosorbent assay (ELISA) as a testing strategy for detection of antibodies against measles virus from microquantities of blood soaked onto filter paper. We studied 165 healthy children in the age group of 1 to 2 years, attending the outpatient department of pediatrics. Two sets of samples were collected from each child. One by venipuncture and the other on Whatman filter paper-3 discs of 20 mm size by finger or heel prick so that each strip is completely soaked with blood on both sides. These were tested for measles virus antibodies by ELISA using Melotest measles IgG commercial ELISA kit manufactured by Melotec S. A. (Barcelona, Spain). The resulting sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the filter paper (FP) ELISA compared to serum ELISA was 100, 90, 97.8, and 100%, respectively. The correlation coefficient r = 0.93% (p < 0.001) and the agreement between the two techniques was 98% as calculated by the Kappa statistical method. The present study has found filter paper testing by ELISA to be a promising qualitative technique for detection of immunity against measles.

The challenges and strategies for laboratory diagnosis of measles in an international setting

Serum-based measles-specific IgM EIAs are the recommended laboratory assays for diagnosis of acute measles infections and appear to be sufficient for measles control programs. However, serum samples are not ideal for molecular characterization of measles virus. Although neither laboratory nor field-based diagnostic tests that rival the EIAs have been developed, laboratory surveillance could be improved if specimen collection were simplified. Ideally the collection method should be noninvasive, have no requirement for a cold chain, and/or have no requirement for technically sophisticated equipment. Two alternative specimen collection technologies appear promising and can be used for both diagnostics and for collecting pertinent genotyping information: oral fluid and filter paper collection methods. These methods are compared along with their respective utilities in supporting measles diagnosis and strain surveillance.

Frequency of measles virus-specific CD4+ and CD8+ T cells in subjects seronegative or highly seropositive for measles vaccine

The protective effect of measles immunization is due to humoral and cell-mediated immune responses. Little is known about cell-mediated immunity (CMI) to measles vaccine virus, the relative contribution of CD4(+) and CD8(+) T cells to variability in such immune responses, and the immunologic longevity of the CMI after measles vaccination in humans. Our study characterizes cellular immune response in subjects seronegative or highly seropositive for measles vaccine immunoglobulin G-specific antibody, aged 15 to 25 years, previously immunized with two doses of measles-mumps-rubella II vaccine. We evaluated the ability of subjects to respond to measles vaccine virus by measuring measles virus-specific T-cell proliferation. We examined the frequencies of measles virus-specific memory Th1 and Th2 cells by an ELISPOT assay. Our results demonstrated that proliferation of T cells in seronegative subjects was significantly lower than that for highly seropositive subjects (P = 0.003). Gamma interferon (IFN-gamma) secretion predominated over interleukin 4 (IL-4) secretion in response to measles virus in both groups. The median frequency of measles virus-reactive CD8(+) T cells secreting IFN-gamma was 0.09% in seronegative subjects and 0.43% in highly seropositive subjects (P = 0.04). The median frequency of CD4(+) T cells secreting IL-4 in response to measles virus was 0.03% in seronegative subjects and 0.09% in highly seropositive subjects (P = 0.005). These data confirm the presence of measles virus-specific cellular immune responses post-measles vaccine immunization in humans. The detection of measles virus-induced IFN-gamma and IL-4 production by ELISPOT can be used to identify measles virus-specific low-frequency memory T cells in subjects immunized with measles vaccine. These differences agree in directionality with the observed antibody response phenotype.

In search of encephalitis etiologies: diagnostic challenges in the California Encephalitis Project, 1998-2000

The California Encephalitis Project was initiated in June 1998 to identify the causes and characterize the clinical and epidemiologic features of encephalitis in California. Testing for >or=13 agents, including herpesviruses, enteroviruses, arboviruses, Bartonella species, Chlamydia species, and Mycoplasma pneumoniae, was performed at the Viral and Rickettsial Disease Laboratory (Richmond, California). Epidemiologic and clinical information collected for each case guided further testing. From June 1998 through December 2000, 334 patients who met our case definition of encephalitis were enrolled. A confirmed or probable viral agent of encephalitis was found in 31 cases (9%), a bacterial agent was found in 9 cases (3%), and a parasitic agent was found in 2 cases (1%). A possible etiology was identified in 41 cases (12%). A noninfectious etiology was identified in 32 cases (10%), and a nonencephalitis infection was identified in 11 (3%). Despite extensive testing and evaluation, the etiology of 208 cases (62%) remained unexplained.

Herpesviruses: emerging nosocomial pathogens?

BACKGROUND

Herpesviruses are ubiquitous pathogens that are known to cause infection in humans and animals. It is likely that more than 90% of adults have been infected by one or more herpesviruses. As hospitalized patients become increasingly immunosuppressed by virtue of illness or therapies, it is increasingly likely that human herpesvirus infection will become manifest in the hospital. Whether these manifestations represent manifestations of reactivated latent disease or true nosocomial infections is an open question.

METHODS

Review of the pertinent English-language literature.

RESULTS

There are eight known herpesviruses that cause disease in humans. Herpesviruses are double-stranded DNA viruses. The prototypical structure consists of an inner DNA core that is encased within a nucleocapsid that is icosahedral in configuration and consists of capsomere subunits. Herpesvirus infection generally occurs when virus is transmitted in oral secretions from an infected to a naive host. Clinical reactivation syndromes can occur in transplant patients, cancer chemotherapy patients, and patients with acquired immunodeficiency syndrome. Life-threatening infections are most closely associated with human herpesvirus-5 (cytomegalovirus), whereas the relationships between human herpesvirus-7 and clinical disease are largely undefined.

CONCLUSION

Clinical expressions of herpesvirus in surgical patients are not nosocomial infections, but are in the vast majority of cases the reactivation of latent infection. Reactivation disease can be lethal to the immunosuppressed host.

Identification of an association between HLA class II alleles and low antibody levels after measles immunization

This is the first large cohort study to report a genetic association between humoral antibody level after measles vaccine and the HLA class II genes. The WHO goal to eradicate measles world-wide magnifies the importance of data relating to the influence of immunogenetics on measles vaccine-induced antibody responses. We present here the analysis of 242 individuals who received one dose of measles-mumps-rubella-II (MMR-II) vaccine at the age of 15 months and were genotyped for HLA class II alleles. These subjects fit into one of three categories; 72 were classified as seronegative, 93 were seropositive and 77 were serohyperpositive. HLA-DRB1*03 (odds ratio (OR), 2.22) and HLA-DPA1*0201 (OR, 1.71) were significantly associated with measles vaccine seronegativity, while additional alleles provided suggestive evidence of association with seronegativity: DQA1*0201, DQB1*0201, and DQA1*0501. The alleles DRB1*03 and DQA1*0201 remained statistically significant after accounting for the effects of other alleles. These findings are crucial in designing both measles eradication by the use of vaccine, and future vaccines to be used in genetically heterozygous populations.

Vitamin A administered with measles vaccine to nine-month-old infants does not reduce vaccine immunogenicity

After a report of reduced seroconversion to measles in infants, aged 6 mo, given vitamin A with their measles vaccination, serious concerns were raised regarding the safety of the WHO's recommendation that infants be supplemented with vitamin A at the time of measles immunization. To determine the impact of coadministered vitamin A on the antibody response to measles vaccine given to infants aged 9 mo, the more common age for immunization in developing countries, we conducted a randomized, double-blind, placebo-controlled trial in an urban slum community in Delhi. Infants (618) were randomly allocated to receive 30 mg vitamin A or a placebo with the measles immunization. Antibodies to measles were measured by ELISA in serum samples obtained at before (baseline) and 12 wk after immunization. Overall, the seroconversion rates did not differ between vitamin A (89.5%) and placebo (87.6%) groups. There were no significant differences in the geometric mean titers in the two groups (ratio of geometric means, 1.19; 95% confidence interval, 0.97-1.46). Among malnourished infants, the geometric mean titer was significantly greater in the vitamin A group compared to the placebo group (ratio of geometric means, 1.57; 95% confidence interval, 1. 18-2.0), but seroconversion rates did not differ. There were no differences in seroconversion rates and geometric mean titers in the two study groups among the well-nourished children. These results indicate that 30 mg vitamin A does not reduce the immune response to the coadministered vaccine and, therefore, can be continued to be given safely in public health programs.

Response to measles revaccination among toddlers in Saudi Arabia by the use of two different trivalent measles-mumps-rubella vaccines

This trial confirmed the immunogenicity of a standard dose of measles vaccine Edmonston-Zagreb strain administered at the age of 6 months as evaluated serologically at 12 months of age in 94 healthy children in Saudi Arabia. The residual seropositivity rate for measles was 53.4 and 80.6% as measured by enzyme immunoassay (EIA) and plaque neutralization, respectively, and could be increased to virtually 100% seroprotection after immunization with 1 of 2 measles-mumps-rubella (MMR) vaccines (Triviraten Berna or MMR II MSD) at 12 months of age. In both groups, more than 90% of infants showed an immune response to the mumps and rubella vaccine strains at 14 months of age. There was a difference in the geometric mean titres of mumps antibodies in favour of MMR II (P < 0.001). The seroconversion rates for mumps antibodies differed between the 2 vaccines because of the different test systems and/or the different cut-off levels used. The study reconfirmed that for the assessment of Rubini mumps vaccine-induced antibodies the indirect immunofluorescence test is superior to the EIA. The systemic tolerability of both vaccines was excellent. Triviraten Berna is exclusively propagated on human diploid cell cultures and hence free of avian proteins.

Evaluation of hemagglutinin protein-specific immunoglobulin M for diagnosis of measles by an enzyme-linked immunosorbent assay based on recombinant protein produced in a high-efficiency mammalian expression system

Recombinant hemagglutinin (H) of the measles virus (MV) expressed in a mammalian high-expression system based on the Semliki Forest virus replicon was used in an enzyme-linked immunosorbent assay (ELISA) for the detection of specific immunoglobulin M (IgM) and IgG in patients with acute-phase measles. One hundred twelve serum specimens from 70 patients with measles were analyzed. Case definition was based on a commercial IgM ELISA that utilizes MV-infected cells (MV-ELISA) (Enzygnost; Behring Diagnostics); the clinical criteria of the Centers for Disease Control and Prevention (Atlanta, Ga.); and/or the increase in hemagglutinin test titers, neutralization test titers, and levels of MV-specific IgG whenever paired sera were available. The initial time courses of the IgM signal after the onset of rash are similar in the H- and MV-ELISAs. On days 0 to 19, both ELISAs detected IgM in 67 of 68 (98.5%) sera. Average maximal levels of IgM seem to persist, however, about 10 days longer in the MV-ELISA (up to day 25) than in the H-ELISA (day 15). From days 20 to 29 and 30 to 59, the H-ELISA detected only 64.3 (9 of 14) and 19.2% (5 of 26), respectively, of sera that were IgM positive by MV-ELISA. At least up to day 30, the performance of the H-ELISA seemed to be similar to that reported for commercial ELISAs based on whole MV. Our results demonstrate that MV H-specific IgM can be used to diagnose most measles cases from a single serum specimen collected within 19 days after the onset of rash and that the recombinant protein used in this study is suitable for this purpose.

A simplified immunoassay based on measles virus recombinant hemagglutinin protein for testing the immune status of vaccinees

Simplified tests based on recombinant antigens are considered to be important for monitoring immunity against measles virus (MV). The hemagglutinin protein (H) is the main target for neutralising and protective antibodies. We produced a recombinant MV-H protein, in a high-yield mammalian expression system based on the Semliki Forest virus replicon. The antigenicity of this recombinant protein was investigated with monoclonal antibodies and its suitability for measuring the immune status of vaccinees was tested in a large cohort by ELISA (H-ELISA). The results were evaluated against neutralisation (NT) and hemagglutination inhibition (HI) titers and MV-specific IgG measured in a commercial whole-virus based ELISA (MV-ELISA, Enzygnost). The H-ELISA correlated better with HI (r=0.78) and NT titers (r=0.80), than the MV-ELISA (HI, r=0.58; NT, r=0.59). In contrast to the MV-ELISA, the H-ELISA detected no false-positive sera (P < 0.02) and the number of false-negative sera was significantly lower in the H-ELISA than in the MV-ELISA (4/378 vs. 15/378; P < 0.025). The performance of the H-ELISA did not deteriorate significantly when, instead of background corrected net values, uncorrected raw O.D. values of the H-antigen were considered, or when early time points (30 min) were evaluated. These results demonstrate that the recombinant H-ELISA detects efficiently non-immune individuals among vaccinees, despite their relatively low MV-antibody levels. A simplified format with single value measurements did not result in loss of sensitivity or specificity and its performance compared favorably with commercial ELISAs based on whole virus.

Immunosorbent assay based on recombinant hemagglutinin protein produced in a high-efficiency mammalian expression system for surveillance of measles immunity

Recombinant hemagglutinin (H) protein of the measles virus (MV) was produced in mammalian cells with a high-yield expression system based on the Semliki Forest virus replicon. Crude membrane preparations of H protein-transfected BHK-21 cells were used to coat microtiter plates to measure specific immunoglobulin G antibodies in 228 serologically defined serum samples mainly from measles late-convalescent adults. The titers by the enzyme-linked immunosorbent assay for the H protein (H-ELISA) closely correlated with neutralization test (NT) titers (R2 = 0.66), hemagglutination inhibition test (HI) titers (R2 = 0.64), with the titers from a certified commercial ELISA based on whole MV-infected cells (MV-ELISA; R2 = 0.45). The correlations described above were better than those of the commercial MV-ELISA titers with the NT (R2 = 0.52) or HI (R2 = 0.48) titers. By using the 2nd International Standard for anti-measles serum, the detection level of the assay corresponds to 215 mIU/ml for undiluted serum, which corresponds to the estimated threshold for protective immunity. The specificity, accuracy, and positive predictive value were, in general, better for the H-ELISA than for a commercial MV-ELISA, independent of whether HI, NT, or HI and NT were used as "gold standards." In contrast, the H-ELISA proved to be slightly less sensitive than the MV-ELISA (sensitivities, 98.6 versus 99.5%, respectively; P was not significant). The assays did not differ significantly in the number of serum samples with positive HI and NT results (n = 212) which measured false negative (H-ELISA, 2 of 212 [0.94%]; MV-ELISA, 1 of 212 [0.47%]), but the H-ELISA detected significantly more measles-susceptible individuals than the MV-ELISA (10 of 11 versus 3 of 11, respectively; P < 0.05) among the individuals whose sera had negative HI and NT results. Our data demonstrate that the H-protein preparation that we describe could be a cost-effective alternative to current whole-virus-based ELISAs for surveillance for immunity to measles and that such an assay could be more efficient in detecting susceptibility to measles. Furthermore, unlike whole MV-based antigens, H-protein would also be suitable for use in the development of a simple field test for the diagnosis of measles.

Measles virus fusion protein- and hemagglutinin-transfected cell lines are a sensitive tool for the detection of specific antibodies by a FACS-measured immunofluorescence assay

A FACS-measured immunofluorescence assay was developed for the detection of antibodies directed against the hemagglutinin (H) and fusion (F) glycoproteins of measles virus (MV). Human melanoma cell lines transfected with either the MV H or F genes, which showed a high surface expression of the respective proteins in their native conformation, were used as target cells. The cells were incubated with diluted plasma samples, and stained subsequently with FITC-conjugated secondary antibodies. The FACS-measured fluorescence signals correlated directly with the amount of specific immunoglobulins over a wide concentration range. The use of different conjugates enabled the separate detection of MV-specific IgG, IgM, IgA and IgG subclasses, with relatively low backgrounds. Hemagglutinin-specific IgG, IgM and IgA fluorescence signals were shown to correlate well with MV-specific IgG ELISA titers and MV-specific IgM or IgA capture ELISA OD450-values, respectively. The polyclonal conjugates with specificity for human immunoglobulins offered sufficient cross-reactivity to detect MV-specific IgG, IgM and IgA in plasma samples of cynomolgus macaques, making this technique a useful tool for studying serological responses in vaccination and challenge experiments in non-human primate models.

Safety and characterization of the immune response engendered by two combined measles, mumps and rubella vaccines

We performed a randomized trial to compare the safety and immunogenicity of two combined measles, mumps and rubella vaccines in healthy children 14-24 months of age. Triviraten Berna Vaccine (Swiss Serum and Vaccine Institute), contains the Edmonston Zagreb 19 strain of measles virus, the Rubini mumps virus strain and the Wistar RA 27/3 rubella strain while MMR-Vax (Merck, Sharp & Dohme, West Point, PA) contains the Enders attenuated Edmonston measles strain, the Jeryl Lynn mumps strain and the Wistar RA 27/3 rubella strain. Immunization with Triviraten Berna was associated with a significantly lower incidence of swelling and redness at the injection site in addition to a reduced rate of fever compared with MMR-Vax. Seroconversion rates for the measles and rubella vaccine components were comparable in all tests used. However, seroconversion for the mumps vaccine component was test-dependent. Using an ELISA, the seroconversion rate following immunization with MMR-Vax was significantly (P < 0.01) higher than for Triviraten Berna. In contrast, nearly identical rates were obtained using an indirect immunofluorescence test. Both vaccines were equally effective at engendering antibodies capable of neutralizing wild type mumps virus. Geometric mean ELISA antibody titers against measles and mumps virus were higher following immunization with MMR-Vax while that for rubella was higher after immunization with Triviraten Berna. A small number (N = 13) of adolescents immunized either with MMR-Vax or Triviraten Berna were reimmunized with Triviraten Berna and various humoral and cellular response parameters to the measles and mumps vaccine components analyzed. While few subjects mounted a humoral antibody response to measles, most likely due to elevated baseline titers, there was a marked lymphoproliferative response. Anti-mumps virus ELISA antibody titers were higher both at baseline and after reimmunization in subjects who received MMR-Vax for primary immunization. However, there was no difference in either neutralizing titer or proliferative response in subjects primed with MMR-Vax or Triviraten Berna either before or after reimmunization.

Subacute sclerosing panencephalitis manifesting as viral retinitis: clinical and histopathologic findings

PURPOSE AND METHODS

To describe the clinical and histopathologic features of a patient with viral retinitis secondary to subacute sclerosing panencephalitis.

RESULTS

The patient was a human immunodeficiency virus-negative intravenous drug abuser with an acute retinitis that later progressed to encephalitis despite aggressive treatment for possible viral, protozoal, bacterial, and rickettsial infections. The patient had many of the characteristic findings of subacute sclerosing panencephalitis, including a history of measles in early childhood, myoclonus, periodic complexes on electroencephalographic testing, persistently elevated serum and cerebrospinal fluid antimeasles immunoglobulin G (IgG) titers, and a cerebrospinal fluid oligoclonal IgG gammopathy. Ultrastructural examination demonstrated numerous filamentous microtubular intranuclear viral inclusions in the nuclear layers of the retina consistent with the measles virus. This case is unusual in that our patient developed subacute sclerosing panencephalitis later in life and because there was an 8-year period between presumed viral infections in the two eyes.

CONCLUSIONS

An acute retinitis in an intravenous drug abuser is not always caused by human immunodeficiency virus-related infections; not all viral retinitis responds to therapy; and mortality as well as the usual morbidity may be associated with viral retinitis. One might consider the diagnosis of subacute sclerosing panencephalitis in a young person with an acute retinitis with little or no vitreal inflammation and lack of response to anticytomegalovirus and antitoxoplasmosis therapy.

A study of maternally derived measles antibody in infants born to naturally infected and vaccinated women

Maternal, cord and infant measles antibody levels were measured and compared in a group of 411 vaccinated mothers and 240 unvaccinated mothers, and their babies, between 1983 and 1991. Maternal and cord sera were tested by haemagglutination inhibition and/or enzyme-linked immunosorbent assay, and plaque reduction neutralization tests were also used to test infant sera. Geometric mean titres were significantly higher in the unvaccinated than in the vaccinated mothers (P < 0.001). Infants born to mothers with a history of measles had higher antibody levels at birth than infants of vaccinated mothers and, although the difference narrowed over time, continued to have higher levels up to 30 weeks of age. Between 5 and 7 months of age significantly more of the children of vaccinated mothers had plaque reduction neutralization antibody levels below that which would interfere with vaccination. As the boosting effect of circulating natural measles disappears, earlier measles vaccination may need to be considered, perhaps as part of a two-dose policy.

Assays for antibodies to varicella-zoster virus

Anti-varicella-zoster virus serum antibody assays and their use in vaccine development are described. Of particular interest are FAMA and neutralization assays and the gpELISA. These and other assays are compared and summarized in terms of characteristics including biologic relevance, sensitivity, specificity, and suitability for different laboratory and clinical applications.

Comparative analysis of the attachment protein gene (H) of dolphin morbillivirus

DMV, dolphin morbillivirus, a paramyxovirus of uncertain origin recently emerged in Mediterranean dolphins. This study presents the complete nucleotide sequence of the hemagglutinin (H) gene including the gene boundaries. The single open reading frame of the DMV H gene encodes a protein of 604 residues which exhibits overall sequence characteristics similar to the H genes of other morbilliviruses. When compared to its closest homologues, measles virus (MV) and rinderpest virus (RPV), DMV has, respectively, 44 and 46% of amino acid residues in identical positions. The primary sequence of the DMV H protein is markedly less conserved than that of the fusion protein. The comparative data at the genomic level correspond with cross-neutralization studies with different morbilliviruses. Retrospective serogical studies dating back to 1983 indicate DMV-like infections in whales of the eastern Atlantic. The presented data support and extend previous studies suggesting that this novel morbillivirus is one of the phylogenetically oldest morbilliviruses known to circulate today. The relationship of DMV and established morbilliviruses to the newly emerged candidate morbillivirus infecting horse and man is discussed.

Combined use of complement and anti-immunoglobulin in an enhanced neutralization assay for antibodies to varicella-zoster virus

An enhanced neutralization assay was developed to permit the sensitive, specific, and reproducible measurement of antibodies to varicella-zoster virus (VZV). Optimal neutralization was achieved using a combination of guinea pig complement (C') and rabbit anti-human IgG. This provided 625-, 160- and 13- to 64-fold increases in dilution endpoints of human post-zoster serum, varicella-zoster immune globulin and representative sera from recipients of live attenuated varicella vaccine, respectively, above those measured in the absence of C' and anti-IgG. The specificity of the assay was shown by the absorption of serum neutralization capacity with VZV-specific antigen and the lack of concordance between antibody titers to VZV with those to either herpes simplex virus type-2 or cytomegalovirus. The antibody status of recipients of live attenuated varicella vaccine was established from the amount of neutralizing activity produced at a single optimal serum dilution.

Comparison of commercial enzyme immunoassay kits with plaque reduction neutralization test for detection of measles virus antibody

Four commercially available enzyme immunoassay (EIA) kits were evaluated in comparison with the plaque reduction neutralization (PRN) test for detection of measles virus antibody. The EIA kits, Enzygnost (Behring), Diamedix, Vidas (bioMerieux Vitek), and Measlestat (Biowhittaker), were assessed with two PRN cutoff titers: a PRN titer of 8, the lowest detectable antibody level by the PRN test under the test conditions, and a titer of 120, which has been shown to be the minimum protective antibody titer. At a PRN cutoff titer of 8, the sensitivity was 88.2, 91.1, 74.6, and 69.8% for Behring, Diamedix, Vidas, and Biowhittaker EIA tests, respectively, with negative predictive values ranging from 22.7 to 45.5%. The specificity was 93.8% for Diamedix and 100% for the rest. At a PRN cutoff titer of 120, the sensitivity and specificity, respectively, were 100 and 90.7% (Behring), 98.2 and 58.8% (Diamedix), 90.6 and 94.5% (Vidas), and 85.7 and 96.4% (Biowhittaker). At this PRN cutoff titer, the negative predictive values of all EIA tests improved considerably, ranging from 70.7 to 100%. The EIA results showed an excellent association with PRN results when the PRN titers of the test samples were either < 8 or > 1,052. Discrepancies occurred especially when testing samples having PRN titers in the range of 8 to 120, indicating lack of sensitivity of the EIA tests in detecting measles virus antibody at low levels. Maternally derived measles virus antibody at this level has been shown to interfere with measles vaccine response in children and hence has implications from the standpoint of measles immunization. The ready availability, ease of operation, and rapid turnaround time are strong plus points of the EIA kits, and they could be useful in a clinical laboratory setting for routine application, but they may have limited use in vaccine-related studies and seroepidemiological surveys.

Measles serodiagnosis: standardization and evaluation of a Dot-ELISA

A Dot-ELISA using a measles virus (MV) antigen obtained by sodium deoxycholate treatment was standardized and evaluated for IgM and IgG antibody detection in measles patients and measles-vaccinated subjects. A total of 192 serum samples were studied, comprising 47 from patients with acute and convalescent measles, 55 from 9-month old children prior to measles vaccination and 41 from children of the same age after vaccination, and 49 from patients with unrelated diseases. The diagnostic performances of the IgG Dot-ELISA and IgG immunofluorescence test (IFT) were found to be close, varying from 0.97 to 1.00 in sensitivity and the specificities were maximum (1.00). Nevertheless, the sensitivity of the IgM Dot-ELISA (0.85) was higher than that (0.63) of the IgM IFT, although both assays had comparably high (1.00) specificities. The IgM Dot-ELISA in particular proved to be more sensitive in relation to other assays studied by revealing antibodies in 80.0% (12/15) of vaccinated children on the 15th day after immunization. In contrast, the IgM IFT, failed to detect antibodies in the same group of vaccinated children. The stability of the MV antigen was longer than that of the IFT antigen, and the reproducibility of the Dot-Elisa was satisfactory.

Modified seroneutralization assay for measles virus antibody detection

We describe a simple, inexpensive, sensitive and specific modified seroneutralization assay for use on a wide scale to screen for the presence of measles antibodies. After only one reaction (1 h) and a 3-day incubation period at 37 degrees C, the test can be easily read using a rapid, inexpensive methylene blue/phenol staining procedure. The determination of protective antibody titres by modified and standard seroneutralization methods was strongly correlated (corr. coff. = 0.98).

The risk of measles, mumps, and varicella among young adults: a serosurvey of US Navy and Marine Corps recruits

OBJECTIVES

To assess the risk of epidemic transmission and to guide immunization policy, the seroprevalence of antibody to measles, mumps, and varicella was determined in a group of young adults.

METHODS

A cross-sectional study of 1533 US Navy and Marine Corps recruits was conducted in June 1989. Antibody status was determined with commercially available enzyme-linked immunosorbent assays.

RESULTS

Direct sex and race adjustment to the 15- to 29-year-old US population resulted in seronegativity rates of 17.8% for measles, 12.3% for mumps, and 6.7% for varicella. Measles and mumps seronegativity rates were higher among Whites whereas varicella seronegativity was higher among non-Whites. Recruits enlisting from outside the 50 US states, especially those from island territories, were more likely to lack varicella antibody. The sensitivity of a positive history of vaccination or disease in predicting antibody status was less than 90% for all diseases.

CONCLUSIONS

These results suggest a continued potential for epidemics, especially of measles, and the need for mandatory immunization policies. Immigrants to the United States, especially those from island territories, may be a high-risk group that could benefit from varicella vaccination.

Passive hemagglutination assays for the detection of antibodies to herpes viruses

A simple and effective method for the detection of antibodies to herpes simplex virus (HSV), human cytomegalovirus (HCMV) and varicella-zoster virus (VZV), has been established using the passive hemagglutination assay (PHA) in combination with viral specific glycoproteins. The results obtained with the PHA were compared with those from neutralization (NT) and complement fixation (CF) tests. The PHA test for each of the herpes viruses appears to compare favorably with the other assays tested. The specificity and sensitivity of HSV PHA to NT were 100%, whereas the specificity and sensitivity of HSV CF test to NT were 98% and 100%, respectively. For HCMV, the specificity and sensitivity of PHA to NT and PHA to CF were 100%. Similarly, the specificity and sensitivity of VZV PHA to NT were 100%. Because of the low sensitivity of the VZV CF, the sensitivity of CF to NT was 83%. Furthermore, the range of antibody titers and their absolute levels obtained in the PHAs were significantly greater than those in the NT and CF tests.

Subacute sclerosing panencephalitis (SSPE) in Papua New Guinea: a high incidence in young children

Eighty-seven cases of subacute sclerosing panencephalitis (SSPE) were diagnosed from September 1988 to April 1991 in Papua New Guinea (PNG), by demonstration of high-titre measles-specific antibodies in cerebrospinal fluid (CSF). For 1990 the annual incidence of SSPE, for the study provinces, was calculated to be 56 cases per million under 20 years of age and it is expected that this figure will be higher in 1991. The mean age of presentation was 4.9 years, with a male to female ratio of 1.8:1. An elevation in the ratio of immunoglobulin G as a percentage of total protein in CSF and an increase in the CSF:serum immunoglobulin G ratio was shown in SSPE patients. The dramatic appearance and high frequency of the disease in PNG might relate to the early age of measles infection encountered in children in this country.

Measles immunity among community hospital employees

OBJECTIVE

To define measles immunity rates among employees at 2 hospitals during a community outbreak in 1990.

DESIGN

Cohort survey using enzyme-linked immunosorbent assay (ELISA) and questionnaire.

SETTING

Two community hospitals.

PARTICIPANTS

Seventy-six percent of 2,060 employees.

RESULTS

Seven percent (115/1566) of participants lacked ELISA-defined measles immunity. Among employees whose ages were known, 14% (64/467) of those born after 1956 and 5% (50/1086) of those born before 1957 lacked serologic evidence of immunity. Fifty-eight percent of the susceptible persons had substantial patient contact. With ELISA results as the reference for immunity, the predictive value of an undocumented positive history of measles disease or vaccination was 95%; the predictive value of a negative history of both was 52%. Measles developed in 7 employees.

CONCLUSIONS

A substantial number of hospital employees lacked ELISA-defined measles immunity, including many who had patient contact or who had been born before 1957. Undocumented disease and vaccination histories were not adequate predictors of serologic status. This study supports the recommendations and suggestions of the Immunization Practices Advisory Committee that hospitals should require documented evidence of measles immunity from employees who have patient contact.

Evaluation of monoclonal antibody-based capture enzyme immunoassays for detection of specific antibodies to measles virus

Monoclonal antibodies to the hemagglutinin protein, fusion protein, phosphoprotein, matrix protein, and nucleoprotein of measles virus were evaluated as detector antibodies in capture enzyme immunoassays (EIAs) for the detection of specific serum immunoglobulin G (IgG), IgA, and IgM antibodies to measles virus. A pool of monoclonal antibodies to hemagglutinin protein and nucleoprotein proved optimal and was further evaluated. Specific IgM was detected in 97% of adolescents with clinical measles, 97% of infants 3 weeks postvaccination, and less than 1% of normal serum specimens. Specific IgA antibodies were found in 97% of adolescents with clinical measles, 97% of infants 3 weeks postvaccination, and less than 1% of normal serum specimens. Specific IgA antibodies were found in 97% of clinical measles cases and vaccinees, in 26% of healthy persons, and in 36% of infants 8 months postvaccination; consequently, IgA antibodies were not a useful indicator of recent measles infection. A significant increase in IgG antibodies between paired specimens was detected in 92% of clinical cases and all vaccinees. Only 59% of infant specimens had persistent IgG antibodies as detected by capture EIA at 8 months postvaccination, whereas all specimens had antibodies as detected by hemagglutination inhibition and plaque neutralization. An alternative indirect EIA, in which antigen was directly absorbed to the solid phase, was more sensitive than the capture design, detecting IgG antibodies in all infants postvaccination. When standardized with a microneutralization assay for the detection of persistent antibodies, the indirect IgG EIA gave predictive values for positive and negative tests exceeding 90%. Our capture IgM and indirect IgG EIAs provide a practical combination of serologic tests for the determination of acute measles virus infection and past exposure to measles virus or vaccine, respectively.

Comparison of indirect immunofluorescence test for measles antibodies with haemagglutination inhibition and plaque neutralization tests

Indirect Immunofluorescence (IFA), Plaque Reduction Neutralization (PRN) and Haemagglutination Inhibition (HI) tests for measles antibodies were carried out in 197 sera obtained from umbilical cord and vaccinated children. The IFA was also applied to blood samples collected with filter paper. IFA results demonstrated that the test is relatively simple to perform, with good reproducibility for different antigen lots. Good correlation was obtained between IFA, PRN and HI antibody titers. Better correlation was demonstrated with IFA and PRN than with HI and PRN tests. Sensitivity of IFA in detecting antibody was less effective than PRN, however more effective than HI using rhesus monkey red blood cells. PRN antibody titers over 100 were detected by IFA but not by HI (9.7% with negative results). IFA may be of considerable practical use and able to substitute HI in seroepidemiological surveys and to evaluate vaccine efficacy. It also can be simplified by employing filter paper collected samples.

Determination of immune status to measles, rubella, and varicella-zoster viruses among medical students: assessment of historical information

We examined the serological susceptibility of entering medical students to measles, rubella, and varicella-zoster (VZV) viruses over a four-year period. Serological results were then compared to historical information to ascertain whether undocumented histories of disease or vaccination could be used to identify students who may not need serological testing. For measles, historical information was of no benefit in predicting immunity. For VZV and, to a greater extent, rubella, a higher seropositive rate was seen in students claiming a positive history.

Screening of antibodies to varicella-zoster virus in leukemic patients: comparison of commercial methods of enzyme-immunoassay and fluoroimmunoassay

Commercial methods of enzyme immunoassay and fluoroimmunoassay for the detection of varicella-zoster antibodies were compared using serum samples from individuals in a program of bone marrow transplantation. The correlation was 93.4%. Enzyme immunoassay showed to be more sensitive. Both methods are applicable to the detection of varicella-zoster antibodies. However, when fluoroimmunoassay is used, we recommend the confirmation of negative results by a sensitive enzyme immunoassay.

Passive hemagglutination test for measles immunity and serodiagnosis

A passive hemagglutination (PHA) test for measles was evaluated in comparison with hemagglutination inhibition (HI) and neutralization (NT) tests. The PHA test determines exclusively the level of antibody directed to the hemagglutinin protein of measles virus. The ratio of PHA to HI titer was 1 to 32 (geometric mean, 6.5) for the first 5 weeks of infection but declined to near unity thereafter. It gradually increased again to 4 to 32 (geometric mean, 11.7) over several years. The initial high PHA titer relative to the HI titer was most likely due to the presence of the immunoglobulin M antibody known to be efficient in agglutination, because 2-mercaptoethanol (2ME) treatment of sera reduced the PHA titer to a level similar to that of the HI titer. The PHA titer in sera obtained after the convalescent phase was insensitive to 2ME, and the relative increase in the PHA over the HI titer was presumably a result of increased antibody avidity. In some individuals, the HI titer fell to below detectable levels several years after either natural infection or vaccination, but the PHA as well as the NT titer remained positive. The PHA titer was therefore a more reliable and more sensitive indicator of immune status against measles than the HI titer. The decrease in PHA titer by 2ME treatment provided evidence of a current or very recent infection. PHA was found to be useful both for assessing immunity status and for serodiagnosis.

Varicella in hospital personnel: a challenge for the infection control practitioner

Five unrelated cases of chickenpox (varicella) occurred in a 1-month period involving one physician, two house staff members, one medical student, and a nursing assistant at a large Veterans Administration medical center. This required immediate identification of susceptible employees and patients to prevent transmission to other personnel and patients. Negative history is not a reliable predictor of susceptibility. Of the fifty contacts reporting negative histories, only five persons (10%) were actually negative by antibody testing. No secondary cases of varicella occurred. These incidents suggested that more rapid prescreening of key hospital personnel with negative histories who have direct patient contact might be helpful in identifying susceptible employees in the future.

Radioimmunoassay for the detection of IgG antibodies to herpes simplex virus and its use as a prognostic indicator of HSV excretion in transplant recipients

We report the development of a solid-phase radioimmunoassay for the detection of IgG antibodies to herpes simplex virus (HSV), using a mouse monoclonal antibody specific for the Fc portion of human IgG as the radiolabelled detecting antibody. The binding ratio to test antigen at a single serum dilution, 1:100, correlated significantly with the endpoint titre by radioimmunoassay and with neutralising antibody titre. When compared to neutralisation the radioimmunoassay had a sensitivity of 100% and a specificity of 93%. We believe that the anomalous results are not false positives but represent an increased sensitivity of the radioimmunoassay. We found, by either radioimmunoassay or neutralisation, that high levels of antibody prior to transplantation were associated with a significantly increased risk of HSV excretion post-transplantation in both renal and bone marrow transplant recipients. Thus the radioimmunoassay is a sensitive, specific, and rapid test that can be used as a prognostic indicator of HSV excretion in transplant recipients.

Long-term antibody response after measles vaccination in an isolated arctic society in Greenland

Scoresbysund is an isolated district on the east coast of Greenland with 500 inhabitants, mainly Polar Eskimos, which had never been exposed to natural measles. In 1968 more than 90% of the population were vaccinated with the Schwarz live further-attenuated measles vaccine and subsequently children born after 1968 likewise received the measles vaccination. Upon the initial measles vaccination no clinical cases of measles have been observed. The immunity status of the isolated population has been followed for 16 years after vaccination by IgM, IgA, and IgG ELISA tests and by HI test on a series of serum samples taken at intervals. Immunoblotting was performed on sera obtained 16 years after the vaccination. In general, antibody studies have demonstrated some decline in antibody titres after the initial measles vaccination. However, a temporary moderate increase in measles antibodies occurred in some individuals 2-4 years after vaccination, probably due to a reinfection of vaccinees. Most of these individuals did not have demonstrable IgA antibodies prior to the supposed reinfection.