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Biomedical subjects

R Ishak

Publications and source records attributed to R Ishak.

At least 37 records · Page 2Linked to original sources
PubMed1985

Examination of the immunological relationships between flaviviruses using yellow fever virus monoclonal antibodies.

Monoclonal antibodies prepared against vaccine strains of yellow fever (YF) virus were initially characterized by fluorescence microscopy of Vero cells infected with YF virus strain 17D. When similarly tested against representatives of all flavivirus subgroups, the antibodies produced a wide spectrum of reactions ranging from the monospecific to the broadly cross-reactive; at least five antigenic domains in the YF virus envelope glycoprotein were identified. Monoclonal antibodies differentiated between YF virus vaccine strains (17D, 17DD, FNV), wild-type viruses and plaque variants selected from a 17D pool. One isolate from a patient with YF was antigenically similar to the Brazilian vaccine strain 17DD. Several of the antibodies reacting with the YF viral envelope glycoprotein in biological tests identified the 54K envelope glycoprotein; 45K and 26K polypeptides in YF 17D virus-infected cells were also identified by radioimmunoprecipitation and polyacrylamide gel electrophoresis. Neither of these polypeptides was found in uninfected cells. They may represent short-lived precursors of the 54K protein, post-translational cleavage or breakdown products. Other antibodies reacted with a 48K polypeptide in virus-infected cell lysates. This may be the non-structural NV3 protein described for YF virus. Its appearance on the surface of unfixed infected cells, but not on released virions, was demonstrated by fluorescence microscopy.

Animals↗
PubMed1984

Absence of IgG Fc receptors on varicella-zoster virus-infected cells.

Herpesvirus-infected cells usually express receptors for the Fc portion of immunoglobulin G. Varicella-zoster virus has so far been the sole exception in the family. Both immunehemadsorption and immunofluorescence techniques failed to detect the expression of such receptors. This observation excludes the possibility of false-positive results in serological tests for antibodies to this virus. It is possible that the function of these receptors early in infection is not needed in the subsequent reactivation(s) of the virus. No variation has been shown to occur with different isolates.

Cells, Cultured↗
PubMedDate not supplied

Chlamydial infection in the Amazon region of Brazil.

The prevalence of antibodies to Chlamydia was determined in 9 population groups with different risk levels for sexually transmitted diseases in Belém, Pará state, Brazil. 583 serum samples were examined by the indirect immunofluorescence test. The prevalence rates varied from 33.3% in patients attending a sexually transmitted disease clinic to 97.1% in Parakana Indians. One or more pathogens were found in 55 of 86 patients presenting a clinical picture of urethritis; C. trachomatis was isolated from 11% (6/55) of these cases by inoculation to McCoy cell cultures, accounting for 30% (6/20) of the cases of non-gonococcal urethritis. C. trachomatis was isolated from one of 28 female patients (3.6%) attending gynaecology and obstetrics outpatient clinics. The positive patients had no symptom or complaint that would have suggested the diagnosis.

Adolescent↗
PubMedDate not supplied

[Retrospective seroepidemiology of HIV-1].

Serum samples collected between 1974 and 1980 out of populations from the States of Pará and Goiás, Brazil, were tested for antibodies against HIV-1 through ELISA, immunofluorescence, and immunoblot. The aim was to describe the possibility of the virus presence in this country before the present epidemic. Four samples from an epidemiologically closed community, the Xicrin indians, gave positive reaction in the ELISA test, but were negative in the confirmatory tests. The negative results suggest the absence of HIV-1, in the groups tested, prior to the 1980's.

Blood Donors↗
PubMedDate not supplied

[Biosafety in the laboratory].

The occurrence of laboratory-acquired infections have elicited in the last ten years an intense interest in methods and procedures for the safe handling of microbiological material. The major laboratory safety problem is aerial transmission, however, protection against airborne hazards is efficiently achieved by the use of microbiological safety cabinets. Biosafety rules should be strictly followed by all members of a laboratory. Evaluation of these procedures should be effectively performed by an independent biosafety committee. The upsurge of AIDS should stimulate the adoption of safe working procedures in the laboratory.

Accident Prevention↗
PubMedDate not supplied

Detection of HTLV-IIa blood donors in an urban area of the Amazon Region of Brazil (Belém, PA).

The human lymphotropic viruses type I (HTLV-I) and type II (HTLV-II) are members of a group of mammalian retroviruses with similar biological properties, and blood transfusion is an important route of transmission. HTLV-I is endemic in a number of different geographical areas and is associated with several clinical disorders. HTLV-II is endemic in several Indian groups of the Americas and intravenous drug abusers in North and South America, Europe and Southeast Asia. During the year of 1995, all blood donors tested positive to HTLV-I/II in the State Blood Bank (HEMOPA), were directed to a physician and to the Virus Laboratory at the Universidade Federal do Pará for counselling and laboratory diagnosis confirmation. Thirty-five sera were tested by an enzyme immune assay, and a Western blot that discriminates HTLV-I and HTLV-II infection. Two HTLV-II positive samples were submitted to PCR analysis of pX and env genomic region, and confirmed to be of subtype IIa. This is the first detection in Belém of the presence of HTLV-IIa infection among blood donors. This result emphasizes that HTLV-II is also present in urban areas of the Amazon region of Brazil and highlights the need to include screening tests that are capable to detect antibodies for both types of HTLV.

Adult↗
PubMedDate not supplied

Molecular evidence of mother-to-child transmission of HTLV-IIc in the Kararao Village (Kayapo) in the Amazon region of Brazil.

Blood samples from native Indians in the Kararao village (Kayapo), were analysed using serological and molecular methods to characterize infection and analyse transmission of HTLV-II. Specific reactivity was observed in 3/26 individuals, of which two samples were from a mother and child. RFLP analysis of the pX and env regions confirmed HTLV-II infection. Nucleotide sequence of the 5' LTR segment and phylogenetic analysis showed a high similarity (98%) between the three samples and prototype HTLV-IIa (Mot), and confirmed the occurrence of the HTLV-IIc subtype. There was a high genetic similarity (99.9%) between the mother and child samples and the only difference was a deletion of two nucleotides (TC) in the mother sequence. Previous epidemiological studies among native Indians from Brazil have provided evidence of intrafamilial and vertical transmission of HTLV-IIc. The present study now provides molecular evidence of mother-to-child transmission of HTLV-IIc, a mechanism that is in large part responsible for the endemicity of HTLV in these relatively closed populations. Although the actual route of transmission is unknown, breast feeding would appear to be most likely.

Base Sequence↗
PubMedDate not supplied

The thermal stability of yellow fever vaccines.

The assessment of yellow fever vaccine thermostability both in lyophilized form and after reconstitution were analyzed. Two commercial yellow fever vaccines were assayed for their thermal stability. Vaccines were exposed to test temperatures in the range of 8 degrees C to 45 degrees C. Residual infectivity was measured by a plaque assay using Vero cells. The titre values were used in an accelerated degradation test that follows the Arrhenius equation and the minimum immunizing dose was assumed to be 10(3) particles forming unit (pfu)/dose. Some of the most relevant results include that (i) regular culture medium show the same degradation pattern of a reconstituted 17D-204 vaccine; (ii) reconstituted YF-17D-204 showed a predictable half life of more than six days if kept at 0 degrees C; (iii) there are differences in thermostability between different products that are probably due to both presence of stabilizers in the preparation and the modernization in the vaccine production; (iv) it is important to establish a proper correlation between the mouse infectivity test and the plaque assay since the last appears to be more simple, economical, and practical for small laboratories to assess the potency of the vaccine, and (v) the accelerated degradation test appears to be the best procedure to quantify the thermostability of biological products.

Drug Stability↗
PubMedDate not supplied

A possible correlation between the host genetic background in the epidemiology of hepatitis B virus in the Amazon region of Brazil.

The Amazon region of Brazil is an area of great interest because of the large distribution of hepatitis B virus in specific Western areas. Seven urban communities and 24 Indian groups were visited in a total of 4,244 persons. Each individual was interviewed in order to obtain demographic and familial information. Whole blood was collected for serology and genetic determinations. Eleven genetic markers and three HBV markers were tested. Among the most relevant results it was possible to show that (i) there was a large variation of previous exposure to HBV in both urban and non-urban groups ranging from 0 to 59.2%; (ii) there was a different pattern of epidemiological distribution of HBV that was present even among a same linguistic Indian group, with mixed patterns of correlation between HBsAg and anti-HBs and (iii) the prevalence of HBV markers (HBsAg and anti-HBs) were significantly higher (P = 0.0001) among the Indian population (18.8%) than the urban groups (12.5%). It is possible that the host genetic background could influence and modulate the replication of the virus in order to generate HB carrier state.

Adolescent↗
PubMedDate not supplied

Serological evidence of HTLV-I and HTLV-II coinfections in HIV-1 positive patients in Belém, state of Pará, Brazil.

The occurrence of HTLV-I/II and HIV-1 coinfections have been shown to be frequent, probably in consequence of their similar modes of transmission. This paper presents the prevalence of coinfection of HTLV among HIV-1 infected and AIDS patients in Belém, State of Pará, Brazil. A group of 149 patients attending the AIDS Reference Unit of the State Department of Health was tested for the presence of antibodies to HTLV-I/II using an enzyme immunoassay and the positive reactions were confirmed with a Western blot that discriminates between HTLV-I and HTLV-II infections. Four patients (2.7%) were positive to HTLV-I, seven (4.7%) to HTLV-II and one (0.7%) showed an indeterminate pattern of reaction. The present results show for the first time in Belém not only the occurrence of HTLV-II/HIV-1 coinfections but also a higher prevalence of HTLV-II in relation to HTLV-I. Furthermore, it also enlarges the geographical limits of the endemic area for HTLV-II in the Amazon region of Brazil.

Adolescent↗
PubMedDate not supplied

[Chlamydia infection impact among native Indian groups of the Brazilian Amazon region].

Knowledge is limited on the spread of bacteria from genus Chlamydia in Brazil. This study included a sero-epidemiological survey of 2,086 samples from native Indian populations of the Brazilian Amazon region. Sera were screened using indirect immunofluorescence assay for detection of antibodies to C. trachomatis serotype L2, followed by microimmunofluorescence assay using fifteen C. trachomatis and C. pneumoniae serotypes as antigen substrates. Antibody prevalence was 48.6%, but there was a large prevalence range among the groups, including those that had never been challenged with the bacteria, as well as those in which almost all individuals had been infected. Titration of IgG antibodies and detection of specific IgM in high-titer samples showed the persistence of Chlamydia in 6.1% of the reactive individuals, who probably play an important role as reservoirs for dissemination of the bacteria. Specific seroreactivity to C. trachomatis showed the presence of serotypes A, B, Ba, D, E, G, H, I, and L1 in the geographic area surveyed. Furthermore, the survey showed that C. pneumoniae was also infecting these individuals. Both species may be involved in a significant human disease burden that merits further clarification.

Binomial Distribution↗