HTLV-1 in Switzerland: low prevalence of specific antibodies in HIV risk groups, high prevalence of cross-reactive antibodies in normal blood donors

A retrospective analysis of false-positive infectious screening results in blood donors

BACKGROUND

False-positive infectious transfusion screening results remain a challenge with continued loss of both donors and blood products. We sought to identify associations between donor demographic characteristics (age, race, sex, education, first-time donor status) and testing false positive for viruses during routine blood donation screening. In addition the study assessed the prevalence of high-risk behaviors in false-positive donors.

STUDY DESIGN AND METHODS

Blood Systems, Inc. donors with allogeneic donations between January 1, 2011, and December 31, 2012, were compared in a case-control study. Those with a false-positive donation for one of four viruses (human immunodeficiency virus [HIV], human T-lymphotropic virus [HTLV], hepatitis B virus [HBV], and hepatitis C virus [HCV]) were included as cases. Those with negative test results were controls. For a subset of cases, infectious risk factors were evaluated.

RESULTS

Black race and Hispanic ethnicity were associated with HCV and HTLV false-positive results. Male sex and lower education were associated with HCV false positivity, and age 25 to 44 was associated with HTLV false positivity. First-time donors were more likely to be HCV false positive although less likely to be HBV and HTLV false positive. No significant associations between donor demographics and HIV false positivity were observed. A questionnaire for false-positive donors showed low levels of high-risk behaviors.

CONCLUSION

Demographic associations with HCV and HTLV false-positive results overlap with those of true infection. While true infection is unlikely given current testing algorithms and risk factor evaluation, the findings suggest nonrandom association. Further investigation into biologic mechanisms is warranted.

Can we improve the management of blood donors with nonspecific reactivity in viral screening and confirmatory assays?

Donors with nonspecific reactivity in viral screening or confirmatory assays are problematic for blood services because of donor management issues and product loss. Considerable experience has now accumulated in the use of screening and confirmatory assays; therefore, it is timely to examine the ways in which donors with nonspecific reactivity are managed. In this review, we summarize the causes and characteristics of nonspecific reactivity in blood donors and approaches for reducing the number of nonspecific reactive results and we offer some suggestions for improving the management of these donors.

The use of peptide arrays for the characterization of monospecific antibody repertoires from polyclonal sera of psychiatric patients suspected of infection by Borna Disease Virus

Borna Disease Virus (BDV) is suspected to infect humans and to be associated with psychiatric disorders. To this date, BDV-reactive antibodies provide the only reliable markers to diagnose human BDV infection. Their diagnostic value, however, was recently questioned by the observation that these antibodies recognize BDV antigen with only low avidity, a typical feature of cross-reacting antibodies. This raised the possibility that the human BDV-reactive antibodies were triggered by other pathogens than BDV. The recent establishment of a peptide array-based screening test allowed the further characterization of these antibodies. It revealed the presence of small amounts of BDV-reactive antibodies in crude human sera that specifically recognized various epitopes of three major BDV proteins. Most importantly, the purified epitope-specific antibodies were shown to bind to BDV antigen with high avidity when assayed by conventional immunofluorescence assay (IFA) or by Western blot. These results are compatible with the view that the presence of BDV-reactive antibodies in human sera reflects an infection with BDV, although the poor affinity maturation remains unexplained. Furthermore, it demonstrates that peptide array-based screening tests are a reliable system for identifying monospecific antibodies from human polyclonal sera with high specificity and sensitivity.

Prevalence of human T-cell leukemia virus types I and II in Switzerland

The retroviruses human immunodeficiency virus (HIV)-1/2 and human T-cell leukemia virus (HTLV)-I/II share modes of transmission, suggesting that efforts to monitor the current HIV-1 epidemic in Switzerland should be complemented by assessment of HTLV-I/II prevalence. This study presents an updated evaluation of HTLV-I/II infection among groups within the Swiss population polarized towards either low or increased risk of infection. Archived serum and peripheral blood mononuclear cell (PBMC) samples were examined for evidence of HTLV-I/II infection by enzyme-linked immunosorbant assay (ELISA), type-specific Western blot, type-specific polymerase chain reaction (PCR), DNA sequence analysis, and virus culture. Among blood donations obtained from low-risk Swiss donors, we report a complete lack of HTLV-II infection and the occurrence of HTLV-I infection limited to a prevalence of 0.079 per 100,000 (1/1,266,466). Among high-risk HIV-positive persons and HIV-negative persons at increased risk of HIV-infection, we report a focus of HTLV-I and HTLV-II infection at prevalence rates of 62 per 100,000 (1/1,620) and 309 per 100,000 (5/1,620), respectively. The finding of low HTLV-I/II prevalence among Swiss blood donors and containment of HTLV-I/II infection within known risk-groups does not support initiation of HTLV-I/II screening for Swiss blood, tissue, and organ donations.

Analysis of voluntary blood donors with biologic false reactivity on chemiluminescent immunoassays and implications for donor management

BACKGROUND

Biologic false-reactive (BFR) results in blood donors are problematic due to both component loss and donor-management issues. This report analyzes the results of a longitudinal study of BFR donors and the implications for donor management.

STUDY DESIGN AND METHODS

Donors who gave BFR results on HBsAg, HIV-1/HIV-2, HCV, or HTLV-I/HTLV/II chemiluminescent immunoassays (ChLIAs) (PRISM, Abbott) between May 1997 to March 1999 were analyzed. Donors were followed up for up to three donations after an index BFR episode. In addition, results of any negative donations before the index BFR result but within the study period were included in the analysis.

RESULTS

For donors who gave an index BFR result on the HBsAg ChLIA, 14.3 percent remained BFR at subsequent donations, whereas for the anti-HIV-1/HIV-2, anti-HCV, and anti-HTLV-I/HTLV-II ChLIAs, the figures were 66.0, 77.4, and 71.6 percent, respectively. For donors who gave a second BFR result, the percentage who remained BFR at subsequent donations was 75.0, 80.6, 84.6, and 74.5 percent for the four assays, respectively. The rate at which negative repeat donors became BFR during the study period was 0.02, 0.07, 0.12, and 0.02 percent for the HBsAg, anti-HIV-1/HIV-2, anti-HCV, and anti-HTLV-I/HTLV-II assays, respectively.

CONCLUSIONS

Our results indicate that donors who give an index BFR result on the ChLIAs (PRISM, Abbott) should be allowed to continue donating because most donors with a HBsAg BFR result were negative at subsequent donations, and between 22.6 and 34.0 percent of those with BFR results on the HIV-1/HIV-2, HCV, or HTLV-I/HTLV-II assays gave subsequent negative donations. However, donors who give a second BFR result should be counseled and deferred because they were very unlikely to give subsequent negative results.

High-avidity human serum antibodies recognizing linear epitopes of Borna disease virus proteins

BACKGROUND

The recent observation that Borna disease virus (BDV)-reactive antibodies from psychiatric patients exhibit only low avidity for BDV antigen called into question their diagnostic value and raised the possibility that antigenically related microorganisms or self antigens caused the production of these antibodies. We further characterized the specificity of these antibodies.

METHODS

We established a peptide array-based screening test that allows the identification of antibodies directed against linear epitopes of the two major BDV proteins, the nucleoprotein (N) and the phosphoprotein (P).

RESULTS

Initial tests employing sera of BDV-infected mice and rats or horses with Borna disease revealed a high specificity and sensitivity of this test. All sera recognized epitopes of N, P, or both. Sera of noninfected rats, mice, and horses showed no signals on either peptide array. Several human sera that recognized BDV antigen by indirect immunofluorescence contained antibodies that recognized various linear epitopes of one or even both BDV proteins. Remarkably, antibodies purified from such human serum by matrix-immobilized peptides showed high-avidity binding to BDV antigens when assayed by IFA or Western blotting.

CONCLUSIONS

These data suggest that reactive antibodies found in psychiatric patients indeed indicate infection with BDV or a BDV-like agent. However, the poor affinity maturation of BDV-specific human antibodies remains unexplained.

Low avidity of human serum antibodies for Borna disease virus antigens questions their diagnostic value

Borna disease virus (BDV) can induce neurological disease in animals. Since viral nucleic acid, infectious particles and antibodies recognizing BDV antigens were found at higher frequencies in psychiatric patients than in healthy controls, BDV is suspected to cause psychiatric disorders in humans. However, the human origin of these viruses has recently been questioned. To diagnose BDV infections, sera are usually analyzed for antiviral antibodies by indirect immunofluorescence (IFA) on virus-infected cells. This study reveals that the reactive antibodies in human sera mainly recognized the BDV phosphoprotein, whereas animal sera preferentially detected the viral nucleoprotein. Immunoglobulin (Ig) G in sera of experimentally or naturally infected animals bound to the viral antigen with high avidity, ie resisting 3 M urea, whereas reactive IgG in human sera did not. Longitudinal studies showed that reactive human antibodies persisted for many years without gaining high avidity for BDV antigens, indicating that they were probably not induced by BDV but rather by infection with an antigenically related microorganism of unknown identity or by exposure to other related immunogens.

Human retroviruses

It was only in 1980 that the first human retrovirus, HTLV-1, was isolated. Since then, HTLV-2, HIV-1 and HIV-2 have been identified. All four viruses are transmitted with varying efficiency sexually, vertically from mother to infant, and through blood by transfusion or contamination. HTLV-1 is endemic in populations in south-west Japan, Taiwan, sub-Saharan Africa, the Caribbean, southern USA, central and south America, Australia, Papua New Guinea, Solomon Islands and western Asia. There is now epidemic spread amongst IVDUs in north and south America and southern Europe. HTLV-1 is the aetiological agent of adult T-cell leukaemia/lymphoma (ATL) and tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). Other associations which may be causative are with polymyositis, infective dermatitis, gastrointestinal malignant lymphoma and chronic lymphatic leukaemia. ATL appears to be due to malignant transformation of HTLV-1 infected cells, and TSP/HAM to chronic activation of these cells. The epidemiology of HTLV-2 is being separated only recently from HTLV-1 through the application of PCR. It has a low level of endemicity in populations of central Africa, and central and south America. It is being spread epidemically amongst IVDUs in north America and southern Europe. Its association with any pathology in man remains uncertain. HIV-1 is epidemic and spreading rapidly throughout the world. In areas where homosexual contact was the predominant mode of transmission, heterosexual spread is becoming increasingly important. The areas where heterosexual contact is the predominant mode of transmission include the worst affected populations in the world, for example sub-Saharan Africa and some of the Caribbean. There have been recent and explosive increases of HIV-1 seroprevalence in IVDUs and female prostitutes in Asia, especially Thailand and India. Of the diverse pathology following infection, only the haematological consequences are reviewed in detail: these include anaemia, leucopenia, thrombocytopenia, disorders of coagulation and lymphomas. HIV-2, compared to HIV-1, is less infectious and causes less immunosuppression with more slowly progressive disease. It is prevalent in west Africa, but is spreading, albeit slowly, far beyond.

A registry-based case-control study of mycosis fungoides

The etiology of mycosis fungoides is unknown. Two possible causes (an unknown retrovirus with increased prevalence among never-married men, and prior malignancies) were investigated to determine whether they are associated with the incidence of mycosis fungoides. During 1973 to 1986, 953 case patients with mycosis fungoides or Sézary syndrome were registered by the Surveillance, Epidemiology, and End Results program. Each was matched by 5-year age group, sex, ethnicity, and geographic area to four control subjects, one each with cancer of the pancreas, brain, and stomach, and non-Hodgkin's lymphoma. For never-versus ever-married men, none of the relative risks differed significantly from those for women (odd ratios, .8-1.0). For any prior malignancy, the relative risks (and 95% confidence intervals) were 1.3 (.9-2.0), 1.2 (.8-1.8), 1.0 (.7-1.5), and 1.1 (.7-1.6). These data reject the previous relative risk estimate of 3.3 with greater than 99% power, and are consistent with only a small risk, if any, attributable to prior malignancy.

The epidemiology of HTLV-I infection

It has been 10 years since the discovery of the human T-cell lymphotropic virus type I (HTLV-I), the first human retrovirus. During the past decade, significant progress has been made in understanding the transmission of the virus and defining its geographic distribution. It has been shown conclusively that HTLV-I is a causal factor in the induction of both adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy. However, the pathogenesis of each of these conditions is not clear, and in the light of the evidence of immune dysfunction seen among carriers of the infection, it is likely that other associated diseases will be identified. The challenge in the next decade will be to develop and implement therapeutic interventions among carriers to prevent such diseases as well as to curtail transmission within endemic populations.

Evaluation of the human T-cell leukemia virus type I seropositivity of blood donors by the particle agglutination inhibition test

In the HTLV-I seroscreening of blood donor sera by gelatin particle agglutination (PA), more than 50% (55.6%) of the PA-positive sera were negative by immunofluorescence assay (IF). However, when donors were divided into age groups, there were increasing numbers of IF-positive/PA-positive donors with age. Among the PA-positive donors in the 50-64 age group, 65.9% were IF-positive compared to 16.0% in the 16-19 age group. The serological specificities of the IF-negative/PA-positive specimens were tested by using a newly developed PA inhibition (PAI) test. The HTLV-I specificity of the PAI test was confirmed by the observation that agglutinations with anti-HTLV-I p19 and gp21 monoclonal antibodies as well as IF-positive sera were specifically inhibited with HTLV-I preparations or HTLV-I-positive cell extracts and not with HTLV-I-negative cell extracts. Sixty of the 104 specimens collected randomly from the IF-negative/PA-positive donors were PAI-positive. The majority (80%) of such PAI-positive sera showed more than two bands of HTLV-I gag-encoded polypeptide, p19, p24, p28 and p53 on Western blotting. Some of the PAI-positive sera were also positive by enzyme immunoassay. These results indicate that at least some of the IF-negative/PA-positive donors possess HTLV-I-specific antibody and may be potential HTLV-I carriers who will become IF-positive at a later age.