Use of dried blood spots for the detection and confirmation of HTLV-I specific antibodies for epidemiological purposes

No significant HTLV seroprevalence in German people who inject drugs

Background

Although human T-lymphotropic virus (HTLV) is transmitted via the same routes as human immunodeficiency virus (HIV), its worldwide seroprevalence differs drastically because HTLV is transmitted mainly via infected cells rather than free virus. The sharing of needles and other equipment places people who inject drugs (PWID) at particularly high-risk for such blood-borne diseases.

Methods

To validate the methodology used to process and analyze the dried blood spots (DBS) utilized in the study, dried serum spots (DSS) with dilutions of sera from known HTLV infected individuals were analyzed by ELISA and Western blot. DBS collected between 2011 and 2015 from 2,077 PWID in eight German cities recruited by respondent-driven sampling were tested for HTLV-specific antibodies.

Results

The validation demonstrated that the use of DSS allowed identification of samples with even low titers of HTLV-specific antibodies, although a confirmatory Western blot with an additional venous blood sample would often be required. Despite numerous HIV and HCV positive individuals being identified within the study population, none tested positive for HTLV.

Conclusion

While the HIV and HCV prevalences in German PWID are comparable to those in other European countries, the very low prevalence of HTLV reflects the situation in the general population.

Serological and Molecular Methods to Study Epidemiological Aspects of Human T-Cell Lymphotropic Virus Type 1 Infection

We estimated that at least 5-10 million individuals are infected with HTLV-1. Importantly, this number is based on the study of nearly 1.5 billion people living in known human T-cell lymphotropic virus type 1 (HTLV-1) endemic areas, for which reliable epidemiological data are available. However, for some highly populated regions including India, the Maghreb, East Africa, and some regions of China, no consistent data are yet available which prevents a more accurate estimation. Thus, the number of HTLV-1 infected people in the world is probably much higher. The prevalence of HTLV-1 prevalence varies depending on age, sex, and economic level in most HTLV-1 endemic areas. HTLV-1 seroprevalence gradually increases with age, especially in women. HTLV-1 has a simian origin and was originally acquired by humans through interspecies transmission from STLV-1 infected monkeys in the Old World. Three main modes of HTLV-1 transmission have been described; (1) from mother-to-child after prolonged breast-feeding lasting more than six months, (2) through sexual intercourse, which mainly, but not exclusively, occurs from male to female and lastly, (3) from contaminated blood products, which contain HTLV-1 infected lymphocytes. In specific areas, such as Central Africa, zoonotic transmission from STLV-1 infected monkeys to humans is still ongoing.The diagnostic methods used to study the epidemiological aspects of HTLV-1 infection mainly consist of serological assays for the detection of antibodies specifically directed against different HTLV-1 antigens. Screening tests are usually based on enzyme-linked immunoabsorbent assay (ELISA), chemiluminescence enzyme-linked immunoassay (CLEIA) or particle agglutination (PA). Confirmatory tests include mostly Western blots (WB)s or innogenetics line immunoassay (INNO-LIA™) and to a lesser extent immunofluorescence assay (IFA). The search for integrated provirus in the DNA from peripheral blood cells can be performed by qualitative and/or quantitative polymerase chain reaction (qPCR). qPCR is widely used in most diagnostic laboratories and quantification of proviral DNA is useful for the diagnosis and follow-up of HTLV-1 associated diseases such as adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). PCR also provides amplicons for further sequence analysis to determine the HTLV-1 genotype present in the infected person. The use of new generation sequencing methodologies to molecularly characterize full and/or partial HTLV-1 genomic regions is increasing. HTLV-1 genotyping generates valuable molecular epidemiological data to better understand the evolutionary history of this virus.

An overview of the clinical use of filter paper in the diagnosis of tropical diseases

Tropical infectious diseases diagnosis and surveillance are often hampered by difficulties of sample collection and transportation. Filter paper potentially provides a useful medium to help overcome such problems. We reviewed the literature on the use of filter paper, focusing on the evaluation of nucleic acid and serological assays for diagnosis of infectious diseases using dried blood spots (DBS) compared with recognized gold standards. We reviewed 296 eligible studies and included 101 studies evaluating DBS and 192 studies on other aspects of filter paper use. We also discuss the use of filter paper with other body fluids and for tropical veterinary medicine. In general, DBS perform with sensitivities and specificities similar or only slightly inferior to gold standard sample types. However, important problems were revealed with the uncritical use of DBS, inappropriate statistical analysis, and lack of standardized methodology. DBS have great potential to empower healthcare workers by making laboratory-based diagnostic tests more readily accessible, but additional and more rigorous research is needed.

Detection of infections with hepatitis B virus, hepatitis C virus, and human immunodeficiency virus by analyses of dried blood spots--performance characteristics of the ARCHITECT system and two commercial assays for nucleic acid amplification

BACKGROUND

Nowadays, dried blood spots (DBS) are primarily used to obtain diagnostic access to risk collectives such as intravenous drug users, who are prone to infections with hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV). Before DBS analyses can be used in this diagnostic context, however, a comprehensive evaluation of its performance characteristics must be conducted. To the best of our knowledge, the current study presents for the first time such essential data for the Abbott ARCHITECT system, which is currently the worldwide leading platform in this field of infection diagnostics.

METHODS

The investigation comprised 1,762 paired serum/DBS samples and a total of 3,524 determinations with the Abbott ARCHITECT HBsAg, anti-HBc, anti-HBs, anti-HCV and HIV-1-p24-antigen/anti-HIV 1/2 assays as well as with the artus HBV LC PCR and VERSANT HCV RNA qualitative (TMA) tests.

RESULTS

In the context of DBS testing, a specificity of 100% was recorded for the seven serological and molecular biological assays. The analytical sensitivity of HBsAg, anti-HBc, anti-HBs, anti-HCV, HIV-1-p24-antigen/anti-HIV 1/2, HBV DNA, and HCV RNA detections in DBS eluates was 98.6%, 97.1%, 97.5%, 97.8%, 100%, 93%, and 100%, respectively.

DISCUSSION/CONCLUSIONS

The results obtained indicate that it is today possible to reliably detect HBsAg, anti-HBc, anti-HBs, anti-HCV and HIV-1-p24 antigen/anti-HIV 1/2 with state-of-the-art analytical systems such as the Abbott ARCHITECT in DBS eluates even when a comparatively high elution volume of 1,000 μl is used. They also provide evidence for the inherent analytical limits of DBS testing, which primarily concern the anti-HBc/anti-HBs system for individuals with HIV infections and nucleic acid tests with relatively low analytical sensitivity.

The use of dried blood spots for assessing antibody response to hepatitis A virus after natural infection and vaccination

During recent years, vaccination against hepatitis A has been implemented in several countries. It is expected that the increase in mass vaccination against hepatitis A will eventually result in a decreased prevalence of anti-HAV antibodies in the general population. For this reason, a suitable clinical sample for diagnosis of hepatitis A must be sufficiently sensitive to enable detection of lower antibodies titers. In this study, the feasibility of using dried blood spots (DBS) was assessed for the detection of anti-HAV antibodies after a natural infection and vaccination. Seventy-four DBS and paired plasma samples were obtained from a group of college students for a cross-sectional hepatitis A seroepidemiological study. Forty-six students seronegative for anti-HAV were selected randomly and immunized with an inactivated hepatitis A vaccine using an 0-6 month schedule. Seroconversion was monitored in paired plasma and DBS samples 6 months after the first dose followed by a period of 8 and 24 months after the second dose. A strong correlation between OD/CO rates of paired plasma and DBS samples for the detection of anti-HAV was observed. The sensitivity and specificity of the DBS compared with plasma for the detection of anti-HAV antibodies after natural infection was 100%. The sensitivity of DBS in samples collected 24 months after the second dose of hepatitis A vaccine was 95.4%. The results showed that DBS samples can be used for the detection of anti-HAV antibodies both after natural infection or vaccination.

Newborn screening archives as a specimen source for epidemiologic studies: feasibility and potential for bias

PURPOSE

To evaluate the feasibility of obtaining dried blood spots (DBS) from newborn screening archives for subjects in epidemiologic studies and using these specimens for genotyping, and to evaluate the potential for bias in their use.

METHODS

We attempted to locate DBS at Washington State's archives for 230 participants in a previous case-control study of childhood cancer, who were born 1978-1990. We compared characteristics of children for whom we did and did not locate specimens and attempted genetic polymorphism analyses (11 polymorphisms, 82-480 bp amplicons).

RESULTS

We retrieved specimens for 203 (88%) children, including 199 (94%) born in months when a DBS catalog was available. Among the latter, the proportion with specimens located varied by birth place (e.g., hospital, home), maternal education, and prenatal smoking, but did not vary significantly by race/ethnicity. All genotyping assays were completed for all specimens, and among controls genotype distributions were in Hardy-Weinberg equilibrium and similar to previous reports.

CONCLUSIONS

Newborn screening archives have potential to provide specimens for epidemiologic studies conducting genotyping and perhaps other assays, but the possibility that reliance on these resources could bias risk estimates must be considered.

Use of dried spots of whole blood, plasma, and mother's milk collected on filter paper for measurement of human immunodeficiency virus type 1 burden

We studied the use of dried spots of bodily fluids (plasma, whole blood, and mother's milk) on filter paper as a means of sample collection and storage for human immunodeficiency virus type 1 (HIV-1) viral load testing under stringent field conditions. Plasma placed directly in lysis buffer, which is customarily used for viral load assays, was used for comparison in all our experiments. Utilizing reconstruction experiments, we demonstrate no statistical differences between viral loads determined for plasma and mother's milk spotted on filter paper and those for the same fluids placed directly in lysis buffer. We found that the addition of whole blood directly to lysis buffer was unreliable and could not be considered a feasible option. However, viral load measurements for whole blood spotted onto filter paper correlated with plasma viral load values for both filter spots and lysis buffer (Pearson correlation coefficients, 0.7706 and 0.8155, respectively). In conclusion, dried spots of plasma, whole blood, or mother's milk provide a feasible means for the collection, storage, and shipment of samples for subsequent viral load measurement and monitoring. Virus material spotted and dried on filter paper is a good inexpensive alternative for collecting patient material to monitor the HIV-1 viral load. Measuring the HIV-1 burden from whole blood dried on filter paper provides a suitable alternative for low-technology settings with limited access to refrigeration, as can be found in sub-Saharan Africa.

Comparison of available methods to elute serum from dried blood spot samples for measles serology

Six existing protocols for the extraction of serum from blood spots dried onto filter paper were compared. Assessment criteria included: detection of measles IgM and IgG by the Dade Behring Enzygnost immunoassays, volumes of recovered eluates, reproducibility, processing time and throughput, difficulty of protocol, equipment required, safety and estimated costs. Detection of measles IgM in eluates obtained by four of these protocols was as in serum, and significant differences were only observed in eluates from the two remaining protocols (p < 0.05). Significant differences were found between extraction protocols regarding measles-specific IgG detection when an IgG indeterminate DBS was analyzed (p < 0.05), but not when an IgG positive and negative DBS were studied. Sufficient eluate volumes were recovered for testing in the IgM Behring assay following all protocols but two. Sufficient eluate was recovered for testing in the IgG Behring assay following all six protocols. While all protocols were relatively easy to perform, only two protocols required less than 2h for completion. In general, compared protocols performed well on the extraction of antibodies from DBS for serology with differences being observed with eluate volume recovery, turn around time, required equipment and cost. An easy-to-implement protocol is proposed for the rapid extraction of serum for measles/rubella serology in outbreak situations for use in the World Health Organization Global Measles and Rubella Laboratory Network.

Human T cell leukaemia/lymphoma virus infection in pregnant women in the United Kingdom: population study

OBJECTIVE

To assess the prevalence of human T cell leukaemia/lymphoma virus (HTLV) infection in pregnant women in the United Kingdom.

DESIGN

Population study.

SUBJECTS

Guthrie card samples from babies born in 1997-8. Samples were linked to data on mother's age and ethnic status and parents' country of birth and then anonymised.

SETTING

North Thames Regional Health Authority.

MAIN OUTCOME MEASURES

Presence of antibodies against HTLV in eluates tested by gelatin particle agglutination assay and results confirmed by immunoblot.

RESULTS

Of 126 010 samples tested, 67 had confirmed antibodies to HTLV (59 HTLV-I, 2 HTLV-II, 6 untyped) and six had indeterminate results. Seroprevalence was 17.0 per 1000 (95% confidence interval 9.2 to 28.3) in infants whose mothers were born in the Caribbean, 3.2/1000 (1.5 to 5.9) with mothers born in west and central Africa, and 6.8/1000 (3.1 to 12.9) in infants of black Caribbean mothers born in non-endemic regions. In infants with no known risk (both parents born in non-endemic regions and mother not black Caribbean) seroprevalence was 0.06-0.12 per 1000. Mother's country of birth, father's country of birth, and mother's ethnic status were all independently associated with neonatal seroprevalence. An estimated 223 (95% confidence interval 110 to 350) of the 720 000 pregnant women each year in the United Kingdom are infected with HTLV.

CONCLUSIONS

The prevalence of HTLV and HIV infections in pregnant women in the United Kingdom are comparable. The cost effectiveness of antenatal HTLV screening should be evaluated, and screening of blood donations should be considered.

The use of the dried blood spot sample in epidemiological studies

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Detection of antibodies to hepatitis C virus in dried blood spot samples from mothers and their offspring in Lahore, Pakistan

Dried blood spot samples from mothers and their offspring attending the obstetric and pediatric departments of two hospitals in Lahore, Pakistan, were tested for antibodies to hepatitis C virus (HCV). The seroprevalence of HCV in the women was 6.7% (95% confidence interval [CI], 4.3 to 9.1), and that in the children was 1.3% (95% CI, 0.34 to 2.26). Four anti-HCV immunoglobulin G (IgG)-positive children had mothers that were anti-HCV IgG negative, which suggested that their infection was community acquired.

Neonatal cytokines and coagulation factors in children with cerebral palsy

We explored the association of inflammatory mediators and markers of autoimmune and coagulation disorders with cerebral palsy (CP), examining 53 analytes in dried neonatal blood of 31 children with spastic CP, most born at term, and 65 control children. Ultramicroanalysis was performed by recycling immunoaffinity chromatography coupled with laser-enhanced fluorescence and chemiluminescence detection. Reactive antibodies to lupus anticoagulant, anticardiolipin, antithrombin III, and the translational product of the factor V Leiden mutation were isolated by recycling immunoaffinity chromatography and measured by capillary electrophoresis with chemiluminescence-enhanced immunoassay. Higher concentrations of interleukins (ILs) 1, 8, 9, tumor necrosis factor-alpha, and RANTES were observed in these children with CP than in any control child. There were also substantial elevations of IL-6, 11, 13, and other chemokines and colony-stimulating factors in children with CP. Antiphospholipid antibody was present in a titer of 1:100 or greater in 4 children with CP and no control child. Using cuts empirically chosen by recursive partitioning, we found higher concentrations of antibody to antithrombin III, to a translational product of factor V Leiden mutation, and to proteins C and S in children with CP than in controls. We conclude that inflammation and these coagulation abnormalities, which have interacting pathways, are important in the etiology of CP.

A method for the detection and confirmation of antibodies to hepatitis C virus in dried blood spots

This study describes the development and evaluation of a cost effective test rationale for the detection of anti-HCV in dried blood spots. Samples were screened using an 'in house' IgG ELISA that incorporated the recombinant proteins c22-3, c200 and NS5. Confirmation of specific antibody to HCV was by a modification of the immunoblot RIBA 3.0. An extensive panel of well evaluated anti-HCV positive and negative samples from the UK and South Africa were used to assess the sensitivity and specificity of the two tests. One third of the anti-HCV positive samples had been typed. All anti-HCV positive samples were detected by the 'in house' screening EIA. Test/negative optical density ratios showed that more than 95% of reactive samples produced values greater than 5.0. Antibodies to HCV could be detected in a wide range of samples derived from asymptomatic and symptomatic patients and of different genotypes, with similar sensitivity. The presence of anti-HCV could be confirmed by RIBA 3.0 in samples with low reactivity but not in anti-HCV negative samples. Furthermore the immunoblot assay successfully increased specificity by screening out false reactive EIA samples that might occur in an epidemiological survey of a multi-ethnic population.

Dried sera for confirming blood-borne virus infections (HCV, HTLV-I, HIV & HBsAg)

For safe blood transfusion, developing countries face considerable problems including serological screening and confirmation of blood-borne virus infections (HCV, HTLV-I, HIV and HBsAg). Confirmation tests are not only costly but also require sophisticated techniques and expertise. In order to provide this support we have attempted to perform a virus antibody confirmation test on samples dried on blotting paper (BP). Forty-nine sera derived from selected patients and donors from Bombay, and nine donors' sera from Bellarussia were transported on BP. In control experiments, dilutions of antibody-positive sera (HIV, HTLV-I & HCV) and 'blinded' HTLV-I antibody-positive and antibody-negative donors were applied on BP. Eluates from snipped BP were tested initially by screening tests, and the reactives were subjected to confirmatory tests for three types of virus antibody tests (HCV, HTLV-I & HIV) by blotting methods and neutralisation tests for HBsAg. There was considerable reduction of titres in dry sera but all BP-derived dry specimens gave excellent qualitative concordance with their liquid-equivalent sera, and the HTLV-I-positive donor was identified and reconfirmed correctly. Presence of only HCV antibody was confirmed in all the nine selected Bellarussian donors. Blood donors in Bombay had 3% HIV antibody, 6% HBsAg and none had HCV antibody, while selected patients showed substantially higher levels of these markers: HIV-antibody 64%, HBsAg 57% and HCV-antibody 17% confirmed positive. The cause of this high level remains to be established. Dry samples received by post seem to be an economical approach to a first step in providing some levels of independent confirmation of reactives in developing countries.

Seroepidemiology of HTLV-I in relation to that of HIV-1 in the Gauteng region, South Africa, using dried blood spots on filter papers

The seroprevalence of human T-lymphotropic virus type I (HTLV-I), in relation to that of human immunodeficiency virus type I (HIV-1), was determined in a comparative unlinked anonymous antenatal and neonatal (for indirect measurement of maternal antibodies) serosurvey in the Gauteng region of South Africa, using dried blood spots (DBS) and modified particle agglutination assays. Samples were confirmed to be antibody positive by western blot. A total of 2582 DBS collected during 1993 and 1994 from subjects of African, European and coloured origin were tested. Ten were confirmed as positive for HTLV-I and 128 for HIV-1. No antibodies to HTLV-I or HIV-1 were demonstrated in the 221 women of European and coloured origin who were screened. The HTLV-I seroprevalence rate in subjects of African origin appeared to increase from 0% in 1993 to 0.49% in 1994, while HIV-1 seroprevalence rates of 5.2% and 5.4% were recorded for 1993 and 1994 respectively. No significant differences in HTLV-I and HIV-1 seroprevalence rates were noted for the two areas investigated. These results indicate that HTLV-I should be included in infection control programs, and provide baseline data for monitoring the possible spread of HTLV-I in the heterosexual population in this region.

The epidemiology of HTLV-I in Europe

Although human T-lymphotropic virus type I (HTLV-I) infection in Europe is thought to be unusual except amongst people who have immigrated from countries where HTLV-I is endemic, the screening of blood donors has revealed a low seroprevalence across Europe, not only in donors originating from endemic areas but also in the indigenous population. Data from blood donors should not be extrapolated to other groups because blood donors are selected to be at low risk of parenterally transmissible infections. Unfortunately only small studies have been conducted in other population groups, including women attending antenatal clinics, despite the importance of breast-feeding in vertical transmission. Data from metropolitan areas of the United Kingdom and France suggest that the seroprevalence of HTLV-I in pregnant women is up to 100 times higher than in blood donors. HTLV-I infection is also more common in patients attending sexually transmitted disease clinics, whilst HTLV-II is endemic in many cities amongst intravenous drug users. There are few incidence data for diseases associated with HTLV-I, even though cases of adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy have been described in many European countries. Data on the seroprevalence of HTLV-I in central and eastern Europe are scanty but the few published studies suggest a higher rate than has been documented in western Europe.