Comparative analysis of the antibody response to the HTLV-I gag and env proteins in HTLV-I asymptomatic carriers and HAM/TSP patients: an isotype and subclass analysis

Validation of Multiplex Serology for human hepatitis viruses B and C, human T-lymphotropic virus 1 and Toxoplasma gondii

Multiplex Serology is a high-throughput technology developed to simultaneously measure specific serum antibodies against multiple pathogens in one reaction vessel. Serological assays for hepatitis B (HBV) and C (HCV) viruses, human T-lymphotropic virus 1 (HTLV-1) and the protozoan parasite Toxoplasma gondii (T. gondii) were developed and validated against established reference assays. For each pathogen, between 3 and 5 specific antigens were recombinantly expressed as GST-tag fusion proteins in Escherichia coli and tested in Monoplex Serology, i.e. assays restricted to the antigens from one particular pathogen. For each of the four pathogen-specific Monoplex assays, overall seropositivity was defined using two pathogen-specific antigens. In the case of HBV Monoplex Serology, the detection of past natural HBV infection was validated based on two independent reference panels resulting in sensitivities of 92.3% and 93.0%, and specificities of 100% in both panels. Validation of HCV and HTLV-1 Monoplex Serology resulted in sensitivities of 98.0% and 95.0%, and specificities of 96.2% and 100.0%, respectively. The Monoplex Serology assay for T. gondii was validated with a sensitivity of 91.2% and specificity of 92.0%. The developed Monoplex Serology assays largely retained their characteristics when they were included in a multiplex panel (i.e. Multiplex Serology), containing additional antigens from a broad range of other pathogens. Thus HBV, HCV, HTLV-1 and T. gondii Monoplex Serology assays can efficiently be incorporated into Multiplex Serology panels tailored for application in seroepidemiological studies.

The roles of acquired and innate immunity in human T-cell leukemia virus type 1-mediated diseases

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis in small subsets of HTLV-1 carriers. HTLV-1-specific T-cell responses play critical roles in anti-viral and anti-tumor host defense during HTLV-1 infections. Some HTLV-1 carriers exhibit selective loss or anergy of HTLV-1-specific T-cells at an asymptomatic stage. This is also observed in ATL patients and may therefore be an underlying risk factor of ATL in combination with elevated proviral loads. HTLV-1-specific T-cells often recognize the viral oncoprotein Tax, indicating expression of Tax protein in vivo, although levels of HTLV-1 gene expression are known to be very low. A type-I interferon (IFN) response can be induced by HTLV-1-infected cells and suppresses HTLV-1 expression in vitro, suggesting a role of type-I IFN response in viral suppression and pathogenesis in vivo. Both acquired and innate immune responses control the status of HTLV-1-infected cells and could be the important determinants in the development of HTLV-1-mediated malignant and inflammatory diseases.

IgE, CD8(+)CD60+ T cells and IFN-alpha in human immunity to parvovirus B19 in selective IgA deficiency

Although IgE is implicated in viral immunity, its role in parvovirus B19 immunity and its relationship to other immunological states has not been studied. Total serum immunoglobulin levels, IgG and IgE anti-parvovirus B19, blood lymphocyte numbers, and epsilon and cytokine specific mRNA were determined in pediatric patients with normal serum IgA levels (IgA+) and selective IgA deficiency (IgA-) on days 0 (initial diagnosis) and 14, and 3 years after recovery (nephelometry, Western blot test, flow cytometry, reverse transcriptase-polymerase chain reaction). We found that both patients had serum IgM, IgG, IgE, and IgA levels within normal ranges on day 0 to 3 years, excluding IgG(1) and IgA in the IgA- patient, which were elevated and negative, respectively, and IgE in the IgA+ patient, which was elevated (>100 IU/ml). The serum IgA+ and IgA- patients made IgE (and IgG) anti-parvovirus B19 at all time points. Excluding CD8(+)CD60+ T cells, determinations of T, B, and NK lymphocyte subsets always were within normal ranges. In both patients, CD8(+)CD60+ T-cell numbers were within normal ranges on day 0, but dramatically increased on day 14 (more than fivefold). At 3 years, they had returned to normal in the IgA+ patient, but remained high in the IgA- patient. On day 0 to 3 years, peripheral blood mononuclear cells of both patients expressed epsilon- and interferon (IFN)-alpha-specific mRNA. On day 0, the IgA+ patient expressed interleukin (IL)-4 and IL-10, but not IL-2, IFN-gamma, or IL-6 mRNA; the IgA- patient expressed IL-6 and IL-10 mRNA, but not IL-4, IL-2, or IFN-gamma mRNA. At 3 years, the IgA+ patient expressed mRNA for all cytokines, but the IgA- patient did not express mRNA for any of these cytokines. Our results suggest that IgE is important in parvovirus B19 immunity, and that IFN-alpha and CD8(+)CD60+ T cells may regulate IgE memory responses and isotype switching.

Detection of IgE anti-parvovirus B19 and increased CD23+ B cells in parvovirus B19 infection: relation to Th2 cytokines

The immune profile of a parvovirus B19-infected patient (male, 8 years old) was studied on day 0 (initial presentation) and on days 14 and 210 post symptom presentation (psp). Before infection, the patient was skin test positive to various allergens, including ragweed and tree and grass pollens, and had a serum IgE level of 150 IU/mL. On day 0, the patient was diagnosed as parvovirus B19 infected, as judged by the presence of IgG anti-parvovirus Abs in serum (EIA) and presentation of "slap cheek" rash. The patient's serum IgE level increased from 150 IU/mL before infection to 256 IU/mL on day 0, was 233 IU/mL on day 14, and returned to preinfection levels on day 210. In contrast, there was little change in the levels of serum IgM, IgG, or IgA (nephelometry). IgE anti-parvovirus B19 protein (VP-N) was detected in serum (Western blot) on days 0, 14, and 210, despite the decrease in total IgE on day 210. Although there was no increase in total numbers of blood CD23+ B cells on day 0, by day 14 the numbers of these cells increased dramatically (93%), remaining high on day 210. In contrast, there were virtually no changes in total numbers of CD4+ and CD8+ T cells or CD16/56+ NK precursor cells on days 0-210. On day 0, when IgG and IgE anti-parvovirus were detected in serum, patient's peripheral blood mononuclear cells (PBMC) expressed mRNA for the Th2 cytokines IL-4 and IL-10, but not for the Th1 cytokines IFN-gamma or IL-2. However, by day 14 psp, PBMC expressed mRNA for the Th1 cytokines IFN-gamma and IL-2, as well as for IL-4 and IL-10. This is the first demonstration of the existence of IgE anti-parvovirus B19 Ab. The presence of IgE anti-parvovirus B19 Ab in serum on day 0 and its persistence in serum 7 months psp suggests that IgE anti-parvovirus may be useful in prognosis of parvovirus B19 infection. Our results reinforce the idea that IgE, in general, may play a major role in anti-viral immunity, perhaps in conjunction with CD23+ cells. The results further suggest that clearance of this infection is accompanied by a switch to Th1 cytokines.

The HTLV-I orfI protein is recognized by serum antibodies from naturally infected humans and experimentally infected rabbits

The mechanism of T-cell transformation by human T-cell lymphotropic virus type I (HTLV-I), though not completely understood, appears to involve the interactions of several viral and cellular proteins. One of these viral proteins, p12(I), encoded by HTLV-I orfI, is a weak oncogene that binds the 16-kDa subunit of the vacuolar ATPase and interacts with the immature beta and gamma(c) chains of the IL-2 receptor. We have expressed the singly spliced orfI cDNA in the baculovirus system and used the recombinant protein as a tool to assess the presence of antibodies in naturally or experimentally infected hosts. In addition, rabbit antisera were raised against various p12(I) synthetic peptides and used to identify three antigenic regions within p12(I), one between the two putative transmembrane regions of p12(I) and two at the carboxy-terminus of the protein. More importantly, sera from a naturally infected human (1 of 32) and experimentally infected rabbits (9 of 20) recognized the rp12(I), demonstrating orfI expression and immunogenicity in vivo. Taken together these data provide the first evidence of orfI expression during HTLV-I infections.

Engineering of noninfectious HIV-1-like particles containing mutant gp41 glycoproteins as vaccine candidates that allow vaccinees to be distinguished from HIV-1 infectees

Many AIDS vaccine candidates under development may elicit immune responses similar to those observed in and used to screen human immunodeficiency virus type 1 (HIV-1)-infected individuals. Therefore, it is important to develop vaccine candidates that incorporate antigenic markers and allow vaccinees to be distinguished from HIV-1 infectees. To this end, we introduced a series of mutations into and in the vicinity of the major immunodominant region (MIR) of gp41 (residues 598-609), a domain recognized by almost all HIV-1 infectees, and evaluated whether HIV-1-like particles incorporating such mutant glycoproteins could be expressed in mammalian cells. Results indicated that although up to three consecutive amino acids could be replaced within MIR without significantly affecting particle formation or gp160 processing, deletions within MIR impaired envelope processing. Replacement of HIV-1 MIR by part or most of the corresponding domain from other lentiviruses markedly decreased or abolished gp160 processing. Synthetic peptides corresponding to a mutated MIR incorporating three amino acid replacements were not recognized by a panel of sera from HIV-1 infectees, suggesting that HIV-1-like particles with this type of mutation represent potential candidate vaccines that could allow vaccinees to be distinguished from HIV-1 infectees.

Protection against Schistosoma mansoni infection with a recombinant baculovirus-expressed subunit of calpain

Infections by human schistosomes, in particular Schistosoma mansoni, account for significant morbidity and mortality every year in tropical and sub-tropical areas. The eggs of the parasite induce pathological changes in the infected host; in chronic and heavy infections, these changes may lead to death. A well-designed anti-schistosomal vaccine, alone or in concert with existing control measures such as chemotherapy, may prove to be a safe, inexpensive, and effective means of reducing the occurrence of severe disease and death in S. mansoni infection. Previous studies have demonstrated the importance of the syncytial layer containing the apical plasma membrane (APM) of S. mansoni in both the survival of the parasite in the mammalian host and as a potential source of immunogens which may be utilized as vaccine candidates. In this paper, we present evidence for the protective capacity of several schistosomal antigen preparations, including a calcium binding protein of the APM, S. mansoni calpain (GenBank accession no. M74233). We have constructed and characterized expression of a recombinant baculovirus expressing the large subunit of S. mansoni calpain, Sm-p80. This recombinant Sm-p80 is recognized by IgA, IgM, IgG1, and IgG3 isotype antibodies found in S. mansoni-infected human sera and partially-purified recombinant Sm-p80 provided a 29-39% reduction in worm burden in immunized mice challenged with S. mansoni. Our data indicate that Sm-p80 may be a useful vaccine antigen for the reduction of the morbidity associated with S. mansoni infections of mammalian hosts.

Human T-lymphotropic virus type I excretion and specific antibody response in paired saliva and cervicovaginal secretions

Paired sera, salivas, and cervicovaginal secretions from 17 HTLV-I-infected women (10-75 years) were evaluated for total IgA, IgG, IgM, for IgA and IgG to whole HTLV-I lysate, for albumin, and for tax-rex proviral HTLV-DNA. IgG to HTLV-I were constantly detected, with much higher titers in serum (mean titer: 97,800) than in saliva (53) or in cervicovaginal secretions (216). IgA to HTLV-I were detected in only 12 (70%) sera, 6 (35%) salivas, and 8 (53%) cervicovaginal secretions, with higher titers in serum (75) than in saliva (8). Using the relative coefficient of excretion by reference to albumin, as well as the comparison of specific activities, the HTLV-I-specific IgG appeared primarily originating from serum, whereas IgA to HTLV-I were primarily locally produced. Salivary synthesis of IgG to HTLV-I occurred in both patients with a sicca syndrome attesting salivary glands impairment. Local excretions of total IgA, IgG, and IgM evaluated in body fluids were normal. HTLV DNA was detected in 4 (24%) salivas and in 3 (20%) cervicovaginal secretions, always in patients demonstrating local synthesis of HTLV-I-specific IgA or IgG. HTLV-I excretion elicits a weak local immune response to HTLV-I in saliva as well as in cervicovaginal secretions, which could be relevant for HTLV-I transmission via body fluids.