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E van der Ryst

Publications and source records attributed to E van der Ryst.

31 records · Page 2Linked to original sources
PubMed1997

Characterization and titration of an HIV type 1 subtype E chimpanzee challenge stock.

A subtype E human immunodeficiency virus type 1 (HIV-1) isolate from the Central African Republic (E/90CR402) was adapted to growth on chimpanzee peripheral blood mononuclear cells (PBMCs) by cocultivation of irradiated, infected human PBMCs with chimpanzee PBMCs. The resulting virus was passaged in chimpanzee PBMCs to generate a stock of chimpanzee-adapted virus. Although its V3 region sequence was identical to that of the parental isolate, the chimpanzee-adapted virus had a syncytium-inducing phenotype as opposed to the non-syncytium-inducing phenotype of the parental virus. After demonstrating in one animal each that the passaged virus could infect chimpanzees following intravenous (i.v.) or cervical inoculation, the i.v. infectious titer of the stock was determined. Exposure of three chimpanzees to different doses of the virus indicated that the titer was between 2 and 5 TCID50. Thus, the HIV-1 E/90CR402 chimpanzee challenge stock established persistent infections in chimpanzees by both the i.v. and genital routes and should be valuable for future HIV-1 vaccine studies to evaluate cross-protection between HIV-1 subtypes.

Animals↗
PubMed1997

Rift Valley fever virus: a seroepidemiologic study of small terrestrial vertebrates in South Africa.

Epizootics of Rift Valley fever (RVF) are often associated with periods of heavy rainfall, which are favorable for mosquito vectors. However, in seasons with normal or low rainfall, enzootic circulation occurs, suggesting the existence of a natural host that can act as a cryptic carrier during interepizootic periods. To confirm the role of heavy rainfall in epizootic circulation, and to identify a possible natural host of RVF virus, serum samples from small terrestrial mammals in the Free State and Northern Cape regions of South Africa were collected before and after the 1988 floods. These areas are known to support epizootic circulation of RVF virus. The samples were tested for the presence of RVF virus-specific IgG using an ELISA and positive sera were confirmed by a neutralization test. Forty-seven (15%) of 312 Aethomys namaquensis (Namaqua rock rat) had antibodies to RVF virus. Of these positive sera, nine (6%) of 141 were collected before the floods of 1988 and 38 (22%) of 171 were collected afterwards (P = 0.001). Naive A. namaquensis were inoculated with RVF virus and developed a viremia, but no clinical symptoms, suggesting that they can act as temporary asymptomatic carriers of the virus. These results suggest a role for A. namaquensis as a cryptic carrier for RVF virus during interepizootic periods and support the results of other studies suggesting an amplifying role for heavy rainfall in the circulation of RVF virus.

Animals↗
PubMed1997

The binding potential of commercial antibody conjugates with sera of various small terrestrial mammals.

Infectious diseases of wild animals are of increasing importance, both from an economic viewpoint and because several of these diseases are pathogenic to man. However, serosurveys to determine the circulation of infectious organisms in wildlife are complicated by the fact that antibodies to species-specific immunoglobulins are not available for use in serological assays such as enzyme-linked immunosorbent assays (ELISAs) or immunofluorescence assays. To determine the binding potential of four commercially available antibody conjugates with the sera of wild animals, sera from 27 species of small terrestrial mammals were allowed to react with alkaline phosphatase-labelled protein A, anti-rabbit IgG, anti-mouse IgG and anti-human IgG by by the use of an ELISA. It was found that sera from some species of the order Lagomorpha bound optimally to anti-rabbit IgG, while anti-mouse IgG could be used for most species of Rodentia. For all Carnivora, Insectivora, Macroscelidea, Hyracoidea and other Rodentia, staphylococcal protein A demonstrated optimal binding. None of the sera that was tested bound to anti-human IgG. These results demonstrate that commercial conjugates can be used in serological assays in which wild animal sera are used, and should be useful for future serosurveys to determine the circulation of infectious agents in small terrestrial mammals.

Animals↗
PubMed1996

Comparison of the polymerase chain reaction and serology for the diagnosis of HTLV-I infection.

Human T-lymphotropic virus type I (HTLV-I) is associated with tropical spastic paraparesis (TSP) and adult T-cell leukaemia/ lymphoma (ATL). HTLV-I seroconversion may not take place for many years after infection and some patients develop relatively low concentrations of antibodies that are difficult to detect by means of conventional assays. Some serologic tests also yield high rates of false-positive results. We therefore decided to determine whether the polymerase chain reaction (PCR) might be more sensitive than serology for the diagnosis of HTLV-I infection. Samples of serum and of peripheral blood mononuclear cells were obtained from 50 patients with spastic myelopathy and nine with T-cell neoplasia. The serum samples of serum were tested for the presence of HTLV-I antibodies by means of an enzyme-linked immunosorbent assay (ELISA). Positive results were confirmed by Western blot (WB) assay. DNA was extracted from the peripheral blood mononuclear cells and a PCR performed by use of two primer pairs from the env and pol regions of the proviral genome. Seven of the 50 patients with myelopathy and none of those with T-cell neoplasia had detectable antibodies to HTLV-I and all seven were PCR positive. One patient with an indeterminate WB result and one who was HTLV-I antibody-negative, both with myelopathy, were also PCR-positive. In this study, PCR was found to be more sensitive than serology for the diagnosis of HTLV-I infection. PCR should therefore be considered for selected HTLV-I antibody-negative patients with unexplained spastic myelopathy or T-cell neoplasia.

Adolescent↗
PubMed1996

Failure of a human immunodeficiency virus type 1 (HIV-1) subtype B-derived vaccine to prevent infection of chimpanzees by an HIV-1 subtype E strain.

Generation of an effective vaccine against human immunodeficiency virus type 1 (HIV-1) must overcome problems associated with extensive genetic diversity. Although we previously reported vaccine-induced protection of chimpanzees against infection with an HIV-1 strain different from the one used to make the immunogens, both the HIV-1 vaccine and challenge strains were classified within subtype B. To determine whether the HIV-1-specific immunity elicited might also prevent infection by a strain of HIV-1 from a different clade, the same chimpanzees were given booster inoculations with the rgp160-MN/LAI (recombinant hybrid gp160 molecule) and V3-MN immunogens and then were challenged by intravenous inoculation of a comparable dose of a subtype E HIV-1 from the Central African Republic. Both animals became infected with the subtype E virus, indicating that intraclade vaccine-mediated protection does not predict interclade protection, at least in the context of intravenous challenge and the HIV-1 strains used. This study has important implications for planned phase III efficacy trials of similar vaccine preparations in Thailand where HIV-1 subtype B and E strains cocirculate.

AIDS Vaccines↗
PubMed1996

HTLV-I infection in the Free State region of South Africa: a sero-epidemiologic study.

Human T-lymphotropic virus type I (HTLV-1) is associated with tropical spastic paraparesis (TSP) and adult T-cell leukemia/lymphoma. HTLV-I infection is endemic in certain parts of the Natal/KwaZulu region of South Africa. No studies on the seroprevalence of HTLV-I infection in the Free State (FS) have been published. This study was designed to determine the prevalence of HTLV-I antibodies among different patient groups in the FS. Sera from 863 patients were analyzed. There were: 178 asymptomatic rural Blacks, 200 asymptomatic urban Blacks, 50 asymptomatic Whites, 60 patients with spastic myelopathy, 70 patients with other neurologic disorders, 12 patients with T-cell haematologic malignancies and 293 human immunodeficiency virus (HIV) seropositive patients. Sera were tested for the presence of HTLV-I/II antibodies using an enzyme linked immunosorbent assay (ELISA). Positive results were confirmed using a modified Western blot assay. None of the asymptomatic Whites were HTLV-I antibody positive (95 pc confidence interval (CI): 0 to 7 pc), while 2 pc (95 CI: 0.5 to 5 pc) of asymptomatic urban Blacks and 1.1 pc (95 pc CI: 0.14 to 4 pc) of asymptomatic rural Blacks had HTLV-I antibodies. Of the group of patients with spastic myelopathy 33.3 pc (95 pc CI: 21.7 to 46.7 pc had HTLV-I antibodies, while none of the patients with T-cell haematologic malignancies (95 pc CI: 0 to 26.5 pc) or other neurologic disorders (95 pc CI: 0 to 5 pc) had HTLV-I antibodies. Of the HIV seropositive patients 6.1 (95 pc CI: 4 to 9.5) were co-infected with HTLV-I. HTLV-I infection is present in the Free State. It is strongly associated with spastic myelopathy in this region. HIV seropositive patients have a high rate of HTLV-I co-infection.

Adult↗