HTLV type 1 infection in squirrel monkeys (Saimiri sciureus): a promising animal model for HTLV type 1 human infection

We show that the squirrel monkey Saimiri sciureus is susceptible to experimental infection with either syngeneic or allogeneic HTLV-1-immortalized cells. As in humans, such experimental inoculation leads to chronic infection, and HTLV-1 provirus was detected in PBMCs by PCR. Chronically infected monkeys developed high titers of antibodies against the structural proteins of the virus, as do HTLV-1-infected humans. Furthermore, in serially sacrificed squirrel monkeys infected with HTLV-1, proviral DNA was detected at primary phases of infection in PBMCs, spleens, and lymph nodes. Tax/rex mRNA was also detected by RT-PCR in the PBMCs of two monkeys at 12 days after inoculation and in the spleen and lymph nodes of the monkey sacrificed on Day 12. In this animal, scattered HTLV-1-tax/rex mRNA-positive lymphocytes were detected by in situ hybridization in frozen sections of the spleen. These results indicate that PBMCs, spleen, and lymph nodes serve as major reservoirs for HTLV-1 during the early phase of infection. To evaluate the relationship between viral expression and the immune response during infection, humoral and cytotoxic T cell responses (CTL) were studied at various times after inoculation. Antibodies to HTLV-1 were detected 3 weeks after infection and anti-p40Tax and anti-Env CTL activity was detected 2 months after infection and remained detectable thereafter. Our results indicate that the squirrel monkey provides a useful animal model for studying the pathogenesis of HTLV-1 and for evaluating new candidate vaccines.

Lymphoid organs as a major reservoir for human T-cell leukemia virus type 1 in experimentally infected squirrel monkeys (Saimiri sciureus): provirus expression, persistence, and humoral and cellular immune responses

The aim of this study was to investigate the distribution of human T-cell leukemia virus type 1 (HTLV-1) in various organs of serially sacrificed squirrel monkeys (Saimiri sciureus) in order to localize the reservoir of the virus and to evaluate the relationship between viral expression and the humoral or cellular immune response during infection. Six squirrel monkeys infected with HTLV-1 were sacrificed 6, 12, and 35 days and 3, 6, and 26 months after inoculation, and 20 organs and tissues were collected from each animal. PCR and reverse transcription-PCR (RT-PCR) were performed with gag and tax primers. Proviral DNA was detected by PCR in peripheral blood mononuclear cells (PBMCs) of monkeys sacrificed 6 days after inoculation and in PBMCs, spleens, and lymph nodes of monkeys sacrificed 12 and 35 days and 3, 6, and 26 months after inoculation. Furthermore, tax/rex mRNA was detected by RT-PCR in the PBMCs of two monkeys 8 to 12 days after inoculation and in the spleens and lymph nodes of the monkey sacrificed on day 12. In this animal, scattered HTLV-1 tax/rex mRNA-positive lymphocytes were detected by in situ hybridization in frozen sections of the spleen, around the germinal centers and close to the arterial capillaries. Anti-HTLV-1 cell-mediated immunity was evaluated at various times after inoculation. Anti-p40(Tax) and anti-Env cytolytic T-cell responses were detected 2 months after infection and remained detectable thereafter. When Tax peptides were used, this response appeared to be directed against various Tax epitopes. Our results indicate that squirrel monkeys represent a promising animal model for studying the early events of HTLV-1 infection and for evaluating candidate vaccines against HTLV-1.

First seroepidemiological study and phylogenetic characterization of human T-cell lymphotropic virus type I and II infection among Amerindians in French Guiana

We investigated the serological, epidemiological and molecular aspects of human T-cell lymphotropic virus type I and II (HTLV-I/II) infection in the Amerindian populations of French Guiana by testing 847 sera. No HTLV-II antibodies were detected, but five individuals (0.59%) were seropositive for HTLV-I. Analysis of the nucleotide sequences of 522 bp of the env gene and the compete LTR showed that all of the strains from French Guiana belonged to the cosmopolitan subtype A. The similarities were greater between Amerindian and Creole strains than between Amerindian and Noir-Marron strains or than between Creole and Noir-Marron strains. Phylogenetic analysis showed two clusters: one of strains from Amerindians and Creoles, which belong to the transcontinental subgroup, and the other of strains from Noirs-Marrons, belonging to the West African subgroup. Our results suggest that the Amerindian HTLV-I strains are of African origin.

Mayaro virus fever in French Guiana: isolation, identification, and seroprevalence

This paper reports the first isolation of Mayaro (MAY) virus from a patient infected in French Guiana. The identification was initially performed using immunofluorescent antibody testing with specific mouse antibody, and confirmed by plaque-reduction neutralization testing and reverse transcription-polymerase chain reaction. To determine if MAY virus infection is widespread in French Guiana, a serosurvey was performed to determine the prevalence of antibody to this virus in various ethnic groups and areas of French Guiana. Human sera (n = 1,962) were screened using the hemagglutination inhibition (HI) test. To determine whether MAY virus circulates in the rain forest, a serosurvey in monkey populations was performed. Monkey sera (n = 150) were also screened for antibody to MAY virus using HI testing. Of the human sera tested, 6.3% were positive for anti-MAY virus antibodies. Significant differences in MAY virus seroprevalence between different age groups were observed. Seroprevalence rates increased with age, with a large increase in people 10-19 years of age in comparison with those less than 10 years of age. After adjustment for age, significant differences were also found between places of residence. The prevalence of anti-MAY virus antibody was higher in people living in contact with the forest, especially in the Haut Oyapock area (odds ratio [OR] = 97.7, 95% confidence interval [CI] = 48.2-197.9) and along the Maroni River (OR = 39.7, 95% CI = 20.6-76.6). The ethnic differences observed in this study were probably due to differences in residence. Among monkeys, higher seroprevalence rates were found in Alouatta seniculus (66.0%) than in Saguinus midas (18.2%). Among Alouatta, the seroprevalence increased significantly with weight (and therefore with age). This study indicates that MAY virus is present in French Guiana, and human infections occur in areas where people live near the tropical rain forest.

Antinuclear autoantibodies in human T-cell leukemia/lymphoma virus type I carriers in French Guiana

To compare the rate of antinuclear antibodies (ANA) in HTLV-I carriers and negative individuals in French Guiana, 350 sera (175 HTLV-I carriers, either symptomatic or not, and 175 controls) were screened for ANA, using an immunofluorescence assay. All positive sera were tested for autoantibodies against extractable nuclear antigens, histones and double stranded DNA. ANA were detected in 9.71% of the HTLV-I carriers and 3.43% of the control group (p < 0.05). There was no difference in ANA distribution by age, sex, or ethnic group. Neither was there any difference between asymptomatic and symptomatic HTLV-I individuals. However, ANA of medical interest were significantly higher (p < 0.04) in HTLV-I seropositive Creoles than in seropositive Noir-Marrons.

Role of the genetic background of rats in infection by HTLV-I and HTLV-II and in the development of associated diseases

Three aspects of the rat model of HTLV-I/II infection were investigated. (i) The efficacy of HTLV-I-transformed rat cell lines in infecting different strains of rats: WKY and Lewis HTLV-I-transformed cell lines were injected into adult WKY, Lewis and Brown Norway rats, representing syngeneic and allogeneic combinations. The HTLV-I provirus was not detected in peripheral-blood mononuclear cells (PBMC) from these rats 18 weeks after inoculation, showing that HTLV-I-transformed rat cells are not suitable for virus challenge in vaccination experiments. Rats inoculated with Lewis HTLV-I-transformed cells produced an antibody response to HTLV-I, which was higher in allogeneic (WKY and Brown Norway) than in syngeneic rats. (ii) The susceptibility of rats to HTLV-II infection: After human HTLV-II-producing cells (MO) were injected into adult WKY rats, the HTLV-II provirus was detected in PBMC 12 weeks later. Sequencing of a portion of this provirus confirmed its identity with the HTLV-II from MO cells. (iii) The role of MHC haplotype in susceptibility to neurological disease in rats inoculated as newborns with HTLV-I: The hypothesis that the RT-Ik haplotype confers susceptibility was tested by inoculating newborn OKA (RT-Ik), WKY (RT-Il), Lewis (RT-Il) and Fischer 344 (RT-I lvl) rats with human HTLV-I-producing cells (MT-2). Eighteen months later, only the WKY rats showed histological abnormality of the spinal cord, without clinical paralysis. Fischer 344 rats developed cutaneous tumors and OKA rats mammary tumors. The HTLV-I provirus was not detected in these tumors.

Prevalence of antibodies to hepatitis A, C, and E viruses in different ethnic groups in French Guiana

In order to determine the prevalence of antibodies to hepatitis A, C, and E viruses (HAV, HCV, and HEV) in the various ethnic groups and areas of French Guiana, sera (996 for HCV and HEV, 941 for HAV) were tested for antibodies to these viruses using ELISAs. Differences in HAV seroprevalence were found for different age groups, with a large increase in people aged 20-30 years in comparison with those under 20. After logistic analysis, significant differences were found between places of residence; the prevalence of anti-HAV was higher along the Maroni and Oyapock rivers than in the littoral area. The ethnic differences that were observed were generally due to differences in residence. Of all sera, 5.3% were positive for anti-HCV in preliminary tests, but only 1.5% remained positive after confirmation. Brazilians were significantly more frequently infected by HCV than other ethnic groups (4.7%). Sixty-four sera (6.4%) had antibodies to HEV, and differences were found between ethnic groups. Persons of ethnic groups who had emigrated recently to French Guiana had significantly higher seroprevalence rates: 14.6% for Chinese and Hmongs [odds ratio (OR), 4.4; 95% confidence interval (CI), 1.8-10.7], 13.5% for Brazilians (OR, 4.1; CI, 1.8-9.4), and 10.6% for Haitians (OR, 3.1; CI, 1.1-8.7).

HTLV-I infection in squirrel monkeys (Saïmiri sciureus) using autologous, homologous, or heterologous HTLV-I-transformed cell lines

Peripheral blood mononuclear cells (PBMC) from three adult male squirrel monkeys (Saïmiri sciureus) were transformed by human T-cell leukemia/lymphoma virus type I (HTLV-I) by cocultivation with lethally irradiated human MT-2 cells. Three permanent monkey T-cell lines producing HTLV-I were obtained and characterized. Six weeks after inoculation seroconversion was observed in three of three monkeys inoculated with autologous transformed T cells and in two of three monkeys receiving homologous cells. Proviral DNA was detected in their PBMC at various times after inoculation, with the highest proviral load and antibody titers being found in monkeys infected with homologous cells. Monkeys inoculated with heterologous MT-2 cells did not seroconvert, and HTLV-I provirus was detected only transiently in their PBMC. To determine whether in vitro and in vivo HTLV-I infection of squirrel monkey cells led to a selection of monkey-adapted viral mutants, comparative sequencing of the proviral gp21 env between ex vivo monkey HTLV-I-infected PBMC, the inoculum, and MT-2 cells was done and no significant differences were detected. The squirrel monkey, which is naturally free of simian T-cell leukemia/ lymphoma virus, thus appears to be a suitable model for evaluating HTLV-I candidate vaccines and for studying the pathogenesis of HTLV-I.

Expression and immunogenicity in rats of recombinant adenovirus 5 DNA plasmids and vaccinia virus containing the HTLV-I env gene

The complete human T-cell leukemia virus type I (HTLV-I) env gene was inserted into an expression cassette containing the adenovirus 5 major late promoter (Ad5-MLP). Recombinant Ad5-HTLV-I-env was obtained by homologous recombination in 293 cells simultaneously transfected by the expression cassette and the genomic DNA of Ad5. In vitro expression of the HTLV-I-env gene in the recombinant vector was detected by immunofluorescence and Western blotting. Functional expression of HTLV-I-env was confirmed by syncitium formation specifically in HeLa cells infected with Ad5-HTLV-I-env. Two immunization regimens against HTLV-I were tested in WKY and Fischer F-344 rats. The first involved WKY rats primed with Ad5-HTLV-I-env or naked DNA plasmids containing the HTLV-I-env gene and boosted with Ad5 containing the HTLV-I-env gp46 gene or with baculovirus-derived recombinant gp46. No antibody against HTLV-I was detected, while HTLV-I-specific cytotoxic T lymphocytes were recovered from all immunized groups but not from controls. The second approach involved Fischer F-344 rats primed and boosted with recombinant vaccinia virus containing the HTLV-I-env gene. Such rats developed antibodies against the HTLV-I env gp21 and gp46 (non-neutralizing). After challenge with human HTLV-I-producing cells (MT-2), both immunization regimens were found to induce partial protection.

Evidence in Gabon for an intrafamilial clustering with mother-to-child and sexual transmission of a new molecular variant of human T-lymphotropic virus type-II subtype B

Following the observation of an HTLV-II seropositive 60-year-old woman living in Gabon (Central Africa), a serologic and molecular study of her family members was conducted in an attempt to determine the duration of the HTLV-II infection and the modes of transmission of the virus. Among 41 family members, five were HTLV-I seropositive and 7 exhibited specific HTLV-II antibodies in their sera as demonstrated by high immunofluorescence titers on C19 cells and/or specific Western-blot pattern. The second husband of the index case and two of his sisters were infected by the virus, suggesting the presence of HTLV-II in this family over two generations. Sequence analysis of an amplified fragment of 172 nucleotides within the gp21 of the env region (6469-6640) of four HTLV-II infected individuals revealed a new HTLV-II molecular variant of the subtype b diverging from the prototypes NRA and G12 by seven (4.1%) and five (2.9%) bases substitutions, respectively. Molecular analysis of the total env gene (1462 bp) and fragments of the pol and pX regions confirmed that this new African variant was the most divergent HTLV-II subtype b yet described, exhibiting 2.3% of nucleotide substitutions in the env gene (33 bases) as compared to the two HTLV-II b prototypes. These data demonstrate, for the first time in Africa, intrafamilial both mother-to-child transmission and sexual transmission between spouses of an HTLV-II b molecular variant, and also suggest that this virus has been present in Gabon for a long period of time.

An HTLV-I/II vaccine: from animal models to clinical trials?

A human T-lymphotropic virus type I/II (HTLV-I/II) vaccine is necessary in view of two etiologically related, life-threatening diseases, namely, adult T-cell leukemia/lymphoma and tropical spastic paraparesis/HTLV-I-associated myelopathy. When the risk of developing autoimmune diseases such as uveitis, polymyositis, and arthritis is included, one can estimate the life-long risk of infected individuals to develop an HTLV associated pathology as approximately 10%. The populations at risk are, in a large majority, from developing countries but the epidemic of HTLV-II infection in intravenous drug users (IVDU) represents a possible reservoir for dissemination in the general population. The number of HTLV-I-infected individuals (15 to 25 million), together with the severity of associated disease, justifies the development of a vaccine. Different vaccine preparations have been developed, using mostly recombinant pox and adenoviruses, but DNA plasmid technology will soon become a feasible approach. Various animal models exist for experimental viral infections, involving rats, rabbits, or monkeys, but up to now, neither hematological nor neurological disorders have been induced by HTLV infection in such animal models. For long-term protection from HTLV-I-associated diseases, vaccination should induce both neutralizing antibodies and specific cell-mediated immunity. This will require the incorporation of both env and gag coding sequences in the vaccine preparations. Preventive clinical trials may involve different cohorts of seronegative young girls from endemic areas prior to sexual activity and IVDU in the industrialized world. In parallel, one should consider therapeutic vaccine trials in HTLV-I-positive mothers and IVDU to protect them against disease development. The observed rate of seroconversion in these different cohorts makes such trials feasible.

Immune responses and protective effect in mice vaccinated orally with surface sporozoite protein of Eimeria falciformis in ISCOMs

Immunostimulating complexes (ISCOMs) were built after treatment of a purified surface protein from Eimeria falciformis sporozoites with a palmitic acid derivation, leading to a high ratio (33-64%) of P27 incorporation in these cage-like structures. P27 kept its antigenicity after incorporation in ISCOMs, which induced, after iterative intubations by the oral route to groups of mice, a systemic IgG response, a local IgA response, and a local enhanced cellular response as demonstrated by lymphoproliferation of mesenteric lymph node cells upon in vitro stimulation with antigen. This immunization (120 micrograms in six oral doses at 2-day intervals) afforded mice a partial protection (60%) against a subsequent 400 oocyst challenge. The reduction in daily oocyst excretion was corroborated by significantly different weight losses between immunized and control mice on days 9 and 10 postinfection and the subsequent death of these control mice. These observations provide the first application of ISCOMs to parasitic intestinal diseases.

The immunodominant Eimeria acervulina sporozoite antigen previously described as p160/p240 is a 19-kilodalton antigen present in several Eimeria species

A lambda Zap II cDNA expression library, constructed from Eimeria acervulina (PAPa46 strain) sporulated oocyst stage, was screened with sera raised to E. acervulina or Eimeria tenella oocysts in order to isolate clones coding for antigens common to the two species. Most of the clones isolated were derived from the same gene. Antisera raised to a recombinant glutathione-S-transferase fusion protein 1P reacted with an antigen of 19 kDa in immunoblot of E. acervulina sporulated and unsporulated oocysts. Immunofluorescence of E. acervulina sporozoites indicated that the antigen is located in the cytoplasm. The anti-1P antisera reacted on immunoblots of E. tenella with a 19-kDa antigen and by immunofluorescence on E. tenella, Eimeria maxima and Eimeria falciformis sporozoites, indicating that the antigen is conserved in Eimeria species. DNA sequencing indicated that the sequence was almost identical to that of clone cSZ1 previously described by Jenkins et al. using E. acervulina strain #12. The 1P insert hybridized to a 1150-nt mRNA from E. acervulina PAPa46 strain and strain #12, a size consistent with the observed molecular weight of the protein.

Production and characterization of monoclonal antibodies directed against Eimeria falciformis and cross-reactive with sporozoites from two species of avian coccidia

Monoclonal antibodies (mAbs) were obtained against the surface antigens of the Eimeria falciformis sporozoite by immunizing mice with whole homogenized sporozoite. The hybridomas were selected by their reactivities against oocyst extracts, then against glutaraldehyde-treated sporozoites. Three mAbs recognized both the surface of E. falciformis, E. tenella, and E. acervulina and their refractile bodies, whereas a fourth mAb recognized only one epitope on the refractile bodies. All mAbs bound to the same immunoaffinity-purified antigens in Western-blot analysis (P27 for E. falciformis and P25 for E. tenella and E. acervulina). Thus, the mAbs define at least two shared epitopes between sporozoite antigens from different eimerian species. Two of these mAbs are involved in the in vitro phagocytosis of E. falciformis sporozoites by macrophages and also in their lysis by neutrophils. Altogether, these properties showed that the four mAbs came from different activated B-cells. The P27 antigen recognized by our mAbs represents a major target of the in vitro destructive immune response.

Protective oral immunization of chickens against Eimeria tenella with sporozoite surface antigens

Antigens were extracted from the surface of Eimeria tenella sporozoites with a solution containing Triton X 100 (1%), sodium dodecyl sulphate (0.5%) Na deoxycholate (1%) and EDTA (1 mM). After removal of the detergents, these surface antigen preparations conferred an immunity that protected chickens against a subsequent infection (10(4) sporulated oocysts). The best results were obtained after two 250 micrograms injections of Al(OH)3 adsorbed antigens (oocyst output per g caecal material on Day 7 post infection: 2.39 x 10(7) +/- 0.32 x 10(7) oocysts for controls and 7.37 +/- 10(6) +/- 3.19 x 10(6) oocysts for vaccinated birds) and after four gastric intubations of liposome entrapped antigens (oocysts output on Day 7 postinfection: 2.75 x 10(6) +/- 2.02 x 10(6) g-1 caecal material). These results represented respectively 70 and 88% protection indexes. Studies on the systemic and local antibody response after one or several infections of chickens with the parasite indicated at least 20 different molecules in the detergent antigens which are classified after immunoblotting according to their properties.

In vitro interactions between murine neutrophils and Eimeria falciformis sporozoites

The in vitro interactions between elicited mouse peritoneal neutrophils, antibodies and newly excysted sporozoites of Eimeria falciformis resulted in lysis of the parasite. This lysis required the presence of a heat-labile component of normal mouse serum, and was antibody- and cell-concentration-dependent. Under optimal conditions (serum dilution = 1/192, effector cell/sporozoite = 10/1) this lysis, which began after incubation at 37 degrees C for 4 h, was nearly complete after 18 h. It began by opsonization of the sporozoites by antibodies and complement. Inhibition studies performed with inhibitors of neutrophil function did not enable us to determine the mechanism of this extracellular lysis (oxidative respiratory burst or enzyme release), since only metal chelators, lysosomotropic reagents and compounds known to interfere with adenylate cyclase activity were truly inhibitory.