A novel deletion mutant of hepatitis B virus surface antigen.

HBsAg is the most important serological marker for acute or chronic hepatitis B. Nevertheless, there are reports of HBsAg-negative virus carriers, either with anti-HBc as the only marker for hepatitis B virus (HBV) infection or even positive for anti-HBs and anti-HBc. We report isolates from a patient, in which a deletion in the HBs-gene was associated with persisting viremia in the presence of anti-HBs. The 62-year-old female, infected most likely by her husband, had detectable markers of chronic active hepatitis B, such as HBsAg, HBeAg, and anti-HBc-IgM, for 2 years. The patient then seroconverted to anti-HBs, although HBeAg and anti-HBc-IgM remained detectable. At this time, semiquantitative polymerase chain reaction showed about 10(4) viral genomes per milliliter of serum. Direct sequencing of the amplified products revealed a major population of DNA molecules with a deletion of nucleotide 31 of the HBs-gene, which up to now has not been described. This deletion led to a frame-shift and introduced a stop-codon after 21 amino acids of the sHBsAg. We suspect that this deletion, and the resulting HBsAg lacking the major epitopes recognized by specific antibodies, could favor ongoing viral replication, despite the presence of anti-HBs. However, because the reading frame of the polymerase was also severely damaged by this deletion, it is assumed that a minor population of intact genomes was present to help in the formation of virus particles.

Evaluación de precisión y exactitud de laboratorios en determinaciones de química clínica / Evaluation of precision and accuracy of results clinical chemistry

En el año 1990, el Instituto de Investigaciones en Ciencia de la Salud y la Asociación de Bioquímicos del Paraguay, realizaron un diagnóstico de la magnitud de la confiabilidad de los resultados emitidos por los laboratorios en Química Clínica, a través de una evaluación serológica, de precisión en el 37 por ciento (60/163) de los laboratorios registrados en la Asociación de Bioquímicos, el Ministerio de Salud Pública y firmas comerciales de ventas de reactivos; de exactitud en el 24 por ciento (39/163) de los laboratorios registrados, y un cuestionario sobre los factores que influyen en los resultados emitidos por los laboratorios. Los que remitieron sus resultados, en cuanto a su ubicación geográfica, 40//fueron de la capital del país (44/110) y del interior del país 30 por ciento (16/53). En cuanto a dependencia administrativa, 49 por ciento (17/35) fueron laboratorios públicos y 34 por ciento (43/128) privados. No se dispone de mayor información que permita caracterizar a los laboratorios que no remitieron sus resultados, debido al caracter anónimo de la encuesta. En cuanto a la evaluación de precisión, los coeficientes de variación se encontraban alejados de los publicados internacionalmente en un porcentaje que oscila entre el 38 y 84 por ciento, en todos los analitos estudiados. Y el 4l por ciento de los laboratorios tuvieron rendimiento insatisfactorio, utilizando el criterio del Colegio de Patólogos Americanos (CAP), en la evaluación serológica de exactitud. Este estudio revela la situación de la exactitud y precisión de los resultados emitidos en bioquímica clínica de los laboratorios que respondieron nuestra encuentra, que si bien no son representativos de la población total de los laboratorios existentes en el país, representa a aquellos que tuvieron mayor interés en participar. Por lo tanto, se ve la necesidad urgente de implementar Programas Educativos en Control de Calidad en los laboratorios de nuestro país

Evaluación de precisión y exactitud de laboratorios en determinaciones de química clínica / Evaluation of precision and accuracy of results clinical chemistry

En el año 1990, el Instituto de Investigaciones en Ciencia de la Salud y la Asociación de Bioquímicos del Paraguay, realizaron un diagnóstico de la magnitud de la confiabilidad de los resultados emitidos por los laboratorios en Química Clínica, a través de una evaluación serológica, de precisión en el 37 por ciento (60/163) de los laboratorios registrados en la Asociación de Bioquímicos, el Ministerio de Salud Pública y firmas comerciales de ventas de reactivos; de exactitud en el 24 por ciento (39/163) de los laboratorios registrados, y un cuestionario sobre los factores que influyen en los resultados emitidos por los laboratorios. Los que remitieron sus resultados, en cuanto a su ubicación geográfica, 40//fueron de la capital del país (44/110) y del interior del país 30 por ciento (16/53). En cuanto a dependencia administrativa, 49 por ciento (17/35) fueron laboratorios públicos y 34 por ciento (43/128) privados. No se dispone de mayor información que permita caracterizar a los laboratorios que no remitieron sus resultados, debido al caracter anónimo de la encuesta. En cuanto a la evaluación de precisión, los coeficientes de variación se encontraban alejados de los publicados internacionalmente en un porcentaje que oscila entre el 38 y 84 por ciento, en todos los analitos estudiados. Y el 4l por ciento de los laboratorios tuvieron rendimiento insatisfactorio, utilizando el criterio del Colegio de Patólogos Americanos (CAP), en la evaluación serológica de exactitud. Este estudio revela la situación de la exactitud y precisión de los resultados emitidos en bioquímica clínica de los laboratorios que respondieron nuestra encuentra, que si bien no son representativos de la población total de los laboratorios existentes en el país, representa a aquellos que tuvieron mayor interés en participar. Por lo tanto, se ve la necesidad urgente de implementar Programas Educativos en Control de Calidad en los laboratorios de nuestro país

Evaluation of a simple screening test for the quality of drinking water systems.

A simple and inexpensive assay for detection of H2S producing bacteria in drinking water was evaluated in Paraguay. Using an improved preparation procedure, results were basically temperature independent in the range of 22-37 degrees C and correlated well with the presence of total coliform bacteria (96%, 28 degrees C). The assay was not suitable for control of surface water and dug well water due to the frequent presence of non-faecal coliforms. However, it was very suitable for routine control of high quality water systems, like treated community water systems or deep-tube well water, where complete absence of coliforms is required. The H2S-test is very inexpensive and does not require a laboratory technician or special equipment. Its use permits a cost-effective routine control of high quality community water systems in developing countries. In addition, this test turned out to be an effective educational tool for heightening the awareness of people towards dangers of unclean drinking water.

A seroepidemiological survey of antibodies to HTLV-I/HTLV-II in selected population groups in Paraguay.

Between March 1987 and November 1989 a cross-sectional serological survey was conducted on 884 residents of Paraguay to obtain data on the prevalence of antibodies to human T-cell leukemia virus type I/II (HTLV-I/II). Sera from 8/884 individuals (0.9%) were positive, confirmed by Western blotting and radioimmunoprecipitation (RIPA). This study shows that HTLV-I/II is very rare (or absent) among the general (healthy) population (0/338) and ethnic Japanese (0/227) in Paraguay. However, it can be detected at a rate of 2-3% in prostitutes (4/178) and homosexuals (4/117), suggesting sexual transmission as an important route for spread of HTLV-I/II in Paraguay.

Mycotic keratitis in Paraguay.

Patients with corneal ulcer, residing mainly in rural areas of Paraguay, were controlled for mycotic eye infections. In 26 cases out of 45 (58%) presence of filamentous fungi was observed (Fusarium sp. (11), Aspergillus sp. (5), Cladosporium sp. (3), Alternaria sp. (2), Acremonium sp. (1), Curvularia sp. (1), culture negative (3)). In 17 cases also pathogenic bacteria were present. Most of the patients were farmers and belonged to the low income class. These data indicate that mycotic keratitis may be a frequent cause for eye infections in developing countries.

IgG antibody reactivity with Trypanosoma cruzi and Leishmania antigens in sera of patients with Chagas' disease and leishmaniasis.

Sera from 38 Paraguayans with positive skin tests to Leishmania braziliensis panamensis and 51 sera from Paraguayan patients in different stages of Chagas' disease were analyzed by Western blotting using antigen from Trypanosoma cruzi Y strain epimastigotes and from L. b. panamensis promastigotes. Using a single serum sample, distinctive patterns of IgG antibody response to both antigens were identified allowing the differentiation between T. cruzi infection, Leishmania infection, and probable double infection. Sera from patients with T. cruzi infections consistently recognized bands of approximately 25 kDa, 38 kDa, and greater than 97 kDa in T. cruzi antigen lysates and recognized a band of 38 kDa of 66 kDa in Leishmania antigen lysates but did not consistently recognize any bands using T. cruzi antigen. Sera from patients with probable double infections recognized all bands normally detected by individual sera from patients infected with either T. cruzi or Leishmania. In our study population, T. cruzi infection among leishmaniasis patients was as frequent as among individuals free of leishmaniasis.

Seroprevalence of human parvovirus B19 infection in Sao Tomé and Principe, Malawi and Mascarene Islands.

The prevalence of antibodies to human parvovirus B19 (anti-B19 IgG) in sera (n = 577) from Sao Tomé and Principe, Malawi and Mascarene Islands (Mauritius and Rodriguez Islands) was determined by antibody capture ELISA. The B19 prevalence was 51.5% on Sao Tomé and Principe, 58.4% in Malawi, and 55.0% on the Mauritius mainland and 2.2% on Rodriguez Island, indicating that B19 virus is highly prevalent not only in Europe, Japan and the Americas but also in the African region. Rodriguez Islands has a very low B19 prevalence.

Detection of Chlamydia trachomatis by isolation in cell culture and enzyme amplified immunoassay.

188 (139 female; 49 male) genital swabs from patients with urogenital complaints (greater than 6 weeks), 69 (33 female; 36 male) conjunctival swabs from patients with chronic conjunctivitis and 14 swabs from newborns with acute conjunctivitis were tested for the presence of Chlamydia trachomatis (Ct) by inoculation in cell culture and visualisation by indirect immunofluorescence (IFT) with a monoclonal antibody and enzyme immunoassay (ELISA). Of the 271 specimens 20 (7.4%) were Ct positive by cell culture (IFT) and 18 (6.6%) were positive by ELISA. In 184 (97.9%) urogenital specimens results between cell culture (IFT) and ELISA agreed. With ELISA 4 further genital specimens were found to be Ct positive. In 59 (85.5%) conjunctival swabs of patients with chronic conjunctivitis results between cell culture (IFT) and ELISA agreed. By inoculation of cell culture (IFT) 6 (8.7%) more Ct positive specimens could be identified which were negative in ELISA. There was complete agreement between positive and negative Ct detection with cell culture (IFT) and ELISA in the cases of acute conjunctivitis.

Reactogenicity and immunogenicity of the newly developed purified chick embryo cell (PCEC)-rabies vaccine in man.

Purified Chick Embryo Cell (PCEC) rabies vaccine was given to 88 healthy adults according to six different vaccination schedules. Local side effects were reported on reactivity forms after 16.4% of PCECV injections, general symptoms were recorded after 15.1% of the 292 doses administered. IgE antibodies specific for chicken proteins determined by the Radio Allergo Sorbens Test (RAST) could not be shown before and after the vaccinations. With no exception, all 88 vaccinees developed high titres of complement-fixing and neutralizing antibodies as determined by the Rapid Fluorescent Focus Inhibition Test and Serum Mouse Neutralization Test. For the first time, induction of serum interferon by PCEC rabies vaccine has been shown in man. In rabies vaccination, PCEC vaccine seems to be as effective as Human Diploid Cell Strain (HDCS) vaccine.

Different immune responses after intradermal and intramuscular administration of vaccine against tick-borne encephalitis virus.

A single multisite intradermal (ID) administration of the same dose used for regular intramuscular (IM) immunisation with vaccine against tick-borne encephalitis virus (TBEV) resulted in seroconversion of all vaccinees within three weeks: with the regular IM schedule, two vaccinations were necessary for all vaccinees to seroconvert. After the first ID vaccination, antibodies of the IgM class against TBEV (anti-TBEV-IgM) were observed in all vaccinees; after the first IM vaccination, only three out of nine vaccinees showed an IgM response. The geometric mean titer (GMT) of anti-TBEV-IgM in seropositives was 5-20-fold higher in the ID group and similar to that after natural infection. The GMT of antibodies of the IgG class against TBEV (anti-TBEV-IgG) was also higher in the ID group but with a less marked difference. Hemagglutination-inhibiting (HI) antibodies appeared earlier and persisted longer after one or two ID injections; after a third vaccination, HI antibody levels were similar in both groups. Side effects after ID vaccination were limited to local reactions. These results indicate that follow-up injections may be omitted or at least reduced after ID administration of the vaccine dose usually used for IM vaccination schedules. However, additional studies in larger groups of vaccinees are necessary before ID vaccination can be recommended for general use.

[Increase in the prevalence of antibodies against LAV/HTLV III in drug addicts in West Germany]. / Zunahme der Prävalenz von Antikörpern gegen LAV/HTLV III bei Drogenabhängigen in der Bundesrepublik Deutschland.

Sera obtained from 927 drug addicts in 1983 to 1985 were tested for antibodies against LAV/HTLV-III. There was a steadily rising proportion of positive results: 10.1% in 1983, 17.6% in 1984 and 23.9% in 1985. In each year the prevalence of anti-LAV/HTLV-III was higher among female than male addicts. No increased proportion of positive results was demonstrable in relation to age. Among 152 sera from 1983/84, hepatitis-B markers were found in 72 (43.7%), of whom 10 (14%) were also anti-LAV/HTLV-III positive. Among hepatitis-B marker-negative sera there were 8 (6%) which were also anti-LAV/HTLV-III positive. The prevalence of anti-LAV/HTLV-III in drug addicts in prisons, rehabilitation centres, hospitals and medical practices was similar. There is a danger that prostitution by addicts for obtaining drugs will cause a penetration of LAV/HTLV-III in the rest of the population.

Epidemiological studies on the prevalence of hepatitis Delta virus infections in the Federal Republic of Germany.

This study evaluated the prevalence of hepatitis Delta virus (HDV) infections in various groups of HBsAg carriers including drug addicts and patients with hemophilia in the Federal Republic of Germany. HDV was found only occasionally (less than 1%) in individuals found HBsAg positive during an examination as potential blood donors or in hemodialysis patients, but in 3% in patients with chronic hepatitis and up to 50% in drug addicts and hemophilia patients. These findings are in agreement with data reported from other European countries. Presence of antibodies to HDV in two hemodialysis patients indicates the presence of HDV in this group and screening for HDV infections in hemodialysis units is indicated to prevent outbreaks of this disease in HBsAg-positive patients with possibly serious consequences.

Laboratory markers of immunity to varicella-zoster virus.

Clinical and subclinical reinfection with varicella-zoster virus (VZV) in healthy persons may occur despite detectable neutralizing antibodies in serum. Subclinical reinfection is not uncommon, but clinical reinfection is rare. Therefore, detectable anti-VZV antibody correlates with a subclinical course after reinfection rather than with immunity to reinfection. Cell-mediated immunity (CMI) to VZV appears to be a better indicator of immunity. Skin testing may be a simple and reliable test for CMI, but this must be further evaluated.

Markers of hepatitis viruses A and B: direct comparison between whole serum and blood spotted on filter-paper.

The use of blood spotted on filter-paper is a cheap and convenient method for collecting, storing and transporting samples for analysis of markers of hepatitis virus B. Vaccine against viral hepatitis B is now available but is expensive, and, in order to make the best use of it, large-scale screening programmes need to be carried out in endemic areas prior to immunization campaigns. The sensitivity of the filter-paper method was compared with that of the analysis of whole serum, and the epidemiological data produced by the two methods were analysed. It was found that analysis of eluates of blood spotted on filter-paper cannot be recommended if accurate results are wanted, since large numbers of seropositive persons are likely to be missed; however, it may be a suitable method for detecting HBsAg-carriers and most anti-HBs-positive individuals prior to an immunization campaign.