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M F Barros

Publications and source records attributed to M F Barros.

10 recordsLinked to original sources
PubMed2004

Detection of hepatitis B virus core mutants by PCR-RFLP in chronically infected patients.

HBV chronic infection is an important health problem. The HBV core antigen carries several epitopes for T and B cell recognition and the immune response is crucial for determining the outcome of viral infection. Using PCR-RFLP several point mutations were detected in the HBV core ORF of HBV extracted from the serum of 140 chronically infected patients and 86 samples from another 37 patients followed-up in a longitudinal study. Mutations at position 2248 and 2147 (A3) and at 2038 (M2) were found most frequently. The wild type core genotype was found in about 50% of the samples. PCR-RFLP results were confirmed by direct sequencing of amplified products from HBV DNA present in chronically infected patients. The method is rapid and reliable and may be particularly useful for a rapid detection of viral mutants in a large number of patients.

Adolescent↗
PubMed1986

Single-stranded deoxyribonucleic acid nuclease induced by African swine fever virus and associated to the virion.

Infection of Vero cells with African swine fever (ASF) virus resulted in a marked increase of DNase active on single-stranded DNA (ss-DNase). No increase was observed for double-stranded DNA-specific nuclease activity. In contrast to uninfected cell ss-DNase, which has a pH optimum at pH range 8.5-9, virus-induced ss-DNase is most active at pH 7. Differences in sensitivity to several ions and other modifications of the reaction mixture and considerable difference in reaction kinetics suggest that the increase in nuclease activity is due to a new virus-induced enzyme. This is strengthened by the fact that anti-ASF virus antiserum inhibits the activity of ss-DNase from infected cells but not from uninfected cells. Exclusion chromatography of the digests shows that virus-specific ss-DNase is exclusively or predominantly an endonuclease. The increase in nuclease activity of infected cells is proportional to the multiplicity of infection. Virus-specific ss-DNase is synthesized at late times after infection and its synthesis is dependent on viral DNA replication since it is not induced when infected cells are treated with cytosine arabinoside. Most of ss-DNase activity in infected cells is associated to an insoluble cytoplasmic fraction, presumably virosomes. The enzyme can also be detected in partially stripped purified virions which hydrolyze 6.9 ng DNA per microgram viral protein.

African Swine Fever Virus↗
PubMed1975

[Separation of antirubella IGM antibodies by affinity chromatography].

The separation of IgM globulins by affinity chromatography has been used for serodiagnosis of primary infections with rubella or measles virus. IgM antibody activity levels are similar to those obtained when the separation has been performed by ultracentrifugation. The results of 50 cases examined by the two separation methods are in agreement. However, affinity chromatography is more specific than gel filtration methods and requires a smaller amount of serum. The anti-human IgM globulins, covalently bound to activated Sepharose, maintain their binding capacity to IgM for a long period; and the same gel could be used more than 40 times. Due to its specificity, sensitivity and reliability, affinity chromatography is an efficient tool for routine laboratory diagnosis of a recent primary infection.

Antibodies, Anti-Idiotypic↗
PubMedDate not supplied

Active replication of hepatitis B virus (HBV) in HIV type 1 and in HIV type 2 infected patients.

To evaluate the effect of concurrent infection by HIV on HBV infection or immunity, we have studied a group of 66 HIV1+ symptomatic Caucasian patients and another of 38 African HIV2+ asymptomatic individuals, concerning their HBV status: serological markers of infection and presence of HBV-DNA in serum, the last taken as sign of hepatitis B virus active replication, were monitored. HIV+ groups were compared with seronegative controls, adequately matched for age, sex and ethnological background. HBV DNA was found in 7.6% of HIV1+ Caucasian patients and 3.2% of seronegative controls; in African HIV2+ individuals 2.6% were also HBV DNA+, a percentage close to that found in HIV2 seronegative controls (2.9%). No correlation was found between HIV infection and HBV active replication. Immunodepression that follows HIV infection over time may be compatible with a degree of T cell function capable of avoiding reinfection with or reactivation of HBV, even in symptomatic stages of acquired immunodeficiency syndrome. Our findings are relevant to the choice of preventive strategies in populations at risk for HIV and HBV infection.

Acquired Immunodeficiency Syndrome↗