Síndrome respiratorio agudo grave. El laboratorio de salud pública frente a una emergencia global / Severe acute respiratory syndrome: the public health laboratory in a global emergency

By the end of year 2002 there was an outbreak of atypical pneumonia in Southeast Asia which soon spread to other continents. This new severe acute respiratory syndrome (SARS) was produced by a novel coronavirus. Due to the severity of the situation and risk of introduction of this pathology in our country, the need to arrange specific laboratory diagnostic tests arose. Classic techniques, such as the electron microscopy and molecular biology test such as retrotranscription followed by the polymerase chain reaction (RT-PCR) were implemented. The araldit included cells infected with bovine coronavirus which allowed the viral particles to be visualized easily but it took more time in comparison with the negative staining of free particles from viral cultures. RT-PCR was able to detect RNA of isolated viruses from cases in Hong Kong and Germany.

A fines del año 2002 se inicia un brote de neumonía atípica en el Sudeste asiático el cual se extiende posteriormente a otros continentes. El nuevo síndrome respiratorio agudo grave (SARS) era producido por un coronavirus novedoso. Debido a la gravedad de la situación y al riesgo de introducción de esta patología en Argentina, se implementaron técnicas de diagnóstico clásicas como la microscopía electrónica, y moleculares como una reacción de retrotranscripción seguida de una reacción en cadena de la polimerasa (RT-PCR). La inclusiónen araldita de células infectadas con un coronavirus bovino permitió visualizar más fácilmente las partículas virales, pero requirió más tiempo en comparación con la coloración negativa de partículas libres de cultivos virales.La RT-PCR implementada fue capaz de detectar ARN de cepas de casos de Hong Kong y de Alemania.

Influenza circulating strains in Argentina exhibit differential induction of cytotoxicity and caspase-3 in vitro.

BACKGROUND: Human influenza infections are a significant cause of morbidity worldwide. Though damage to the respiratory epithelium and has been related to apoptosis, which occurs subsequent to influenza virus infection, little information is available regarding cell cytotoxicity of human strains. OBJECTIVE: To study cytotoxicity performed in vitro by various circulating strains in Argentina. The study sample consisted of three vaccine strains (H1N1, H3N2, and B) administered during 1999-2000 in South America and three strains isolated from clinical samples, one, NAC (H1N1) obtained from an adult inpatient with human pneumonia; and the other two (T) and (T2) (H3N2) with influenza syndrome. Viral antigen was detected by an immunofluorescence test, conducted prior to viral isolation in MDCK cells. Strains were subtyped by the hemmaglutination inhibition test. Cytotoxic properties were determined by lactate dehydrogenase reaction (LDH), crystal violet staining and Hoechst staining. Caspase-3 activity, morphological changes of apoptosis, and viral yields were measured in MDCK infected cells. RESULTS AND CONCLUSIONS: Cells infected by each of the strains exhibited apoptosis morphology by Hoechst staining and caspase-3 activity was high for both H1N1 strains. Further, high levels of LDH activity were detected for NAC and H3N2 strains tested, indicating the possible role of different viral proteins or functions on cell cytotoxicity. The NAC strain, isolated from human pneumonia and antigenically related to A/New Caledonia /20/99 (H1N1), was the highest cytotoxic strain and an excellent inducer of caspase-3 activity. In turn, no parameter was related to different viral yields. We conclude that human strains studied in this paper may be useful tools in the characterization of molecular determinants involved in viral cytopathogenicity.

Antigenic and genomic relation between human influenza A (H3N2) viruses circulating in Argentina during 1998 and the H3N2 vaccine component.

OBJECTIVE: Due to the lack of correlation from 1994 to 1997 between the A H3N2 component of the influenza vaccine recommended for this period and the circulating viruses in Argentina, we decided to study the antigenic and genomic relationships of the 1998 A H3N2 Argentine circulating strains with the corresponding vaccine component for that year as recommended by the World Health Organization (WHO). METHODS: We selected 18 influenza A H3N2 strains isolated in Argentina during 1998 to carry out an antigenic and genomic study of their hemagglutinin (HA) and neuraminidase (NA) proteins. For the genomic study we added 3 isolates from Uruguay. We compared the Argentine and Uruguayan strains with available reference strains. RESULTS: We found that all 18 strains from Argentina were similar to the A/Sydney/5/97 (H3N2) strain, as opposed to the A/Wuhan/359/95 (H3N2) strain, which was the vaccine component. This result was confirmed by the genomic study. CONCLUSIONS: The approach that we applied in Argentina has improved the quality and quantity of information about influenza in the country. This type of work should be encouraged in other countries in order to help choose the most appropriate vaccine components each year and provide individuals with the best possible protection against influenza.

[Comparison of 2 techniques for the laboratory diagnosis of influenza virus infections]. / Comparación de dos técnicas para el diagnóstico de laboratorio de infecciones por el virus influenza.

The clinical or epidemiological influenza diagnosis require fast, sensitive and accessible techniques for small laboratories. In order to investigate the sensitivity of the methods currently used in Argentina, the rapid diagnosis by indirect immunofluorescent assay (IF) was compared to the rapid viral culture in MDCK cells. The diagnosis of influenza virus infection was performed on 81 nasal and pharyngeal swabs collected from outpatients with upper respiratory infection, influenza-like syndrome. The samples were collected during 1998 winter season and both techniques were tested. The IF specificity and sensitivity obtained were 91.9% and 59.5%, respectively. In the selection of the assay to be used for influenza diagnosis, the limitations of the simplest techniques such as IF should be considered. Furthermore, it is advisable to set up an optimized culture method in complex laboratories since culture is the only technique which allows the reference centers to perform the full characterization of the isolates.

Comparación de dos técnicas para el diagnóstico de laboratorio de infecciones por el virus influenza / Comparison of 2 techniques for the laboratory diagnosis of influenza virus infections

The clinical or epidemiological influenza diagnosis require fast, sensitive and accessible techniques for small laboratories. In order to investigate the sensitivity of the methods currently used in Argentina, the rapid diagnosis by indirect immunofluorescent assay (IF) was compared to the rapid viral culture in MDCK cells. The diagnosis of influenza virus infection was performed on 81 nasal and pharyngeal swabs collected from outpatients with upper respiratory infection, influenza-like syndrome. The samples were collected during 1998 winter season and both techniques were tested. The IF specificity and sensitivity obtained were 91.9 and 59.5, respectively. In the selection of the assay to be used for influenza diagnosis, the limitations of the simplest techniques such as IF should be considered. Furthermore, it is advisable to set up an optimized culture method in complex laboratories since culture is the only technique which allows the reference centers to perform the full characterization of the isolates.

[Antigenic relationship between influenza A (H3N2) strains circulating in Argentina and vaccine strains]. / Estudio antigenico de cepas de influenza A (H3N2) circulantes en la Argentina y su relacion con las cepas vacunales.

Influenza epidemic season occurs usually from May to September in Argentina, so that the vaccine produced in the northern hemisphere to be administered during October-November may be out of phase for Argentina. In order to determine if the locally circulating strains in Argentina are antigenically close by related to the vaccine strains administered, they were compared with the influenza viruses isolated from May 1994 to December 1997. Clinical samples (9866) were nasopharyngeal aspirates from children hospitalized for acute lower respiratory tract infection and nasal-pharyngeal swabs from adults with influenza syndrome. Initial laboratory diagnosis was performed by immunofluorescence assay, followed by isolation in MDCK cells. Influenza A viruses (242) were detected and subtyped by hemagglutination inhibition (HAI) with WHO FLU Reagent Kit. A subset of the isolated viruses was antigenically analyzed by the WHO Collaborating Center at CDC, Atlanta, USA. Influenza A (H3N2) viruses characterized as circulating in Argentina during the last four years matched partially with the antigens present in the vaccines administered during 1994-97 period. These antigenic variants sometimes circulate late in the year (October 1994 and 1997) initiating the following influenza season and becoming prevalent. They were present 2 years later in the vaccine formula administered in the southern hemisphere. The HAI results of our isolates show that they are highly specific with the homologous antiserum and much less specific with antibodies against vaccine strains. The difference is 16 to 64 fold different. These results demonstrate the need to intensify influenza laboratory surveillance in order to obtain the best possible vaccine.

[Rabies vaccine inactivated with ethylenimine. Duration of the immunity in dogs]. / Vacuna antirrábica inactivada con etilenimina. Duración de immunidad en perros.

The duration-of-immunity afforded by the ethylenimine inactivated rabies vaccine produced in BHK cells with the PV strain, was studied in dogs. One hundred per cent of the dogs became serologically positive 7 days after vaccination; the same percentage was still positive 3 years after vaccination with one dose of the vaccine. A good correlation was observed between the antibody profiles as determined by the titers obtained with the mouse neutralization and fluorescent field inhibition techniques. The correlation was not as good when the number of international units per ml was determined by both tests. The best correspondence between serological response and resistance to challenge was observed when the antibodies were determined by the number of international units per ml, using the neutralization test in mice. All the dogs challenged 12 and 25 months after vaccination resisted challenge; 89% (8/9) were protected 36 months after vaccination. Inactivated vaccines can be as effective to control rabies as those prepared with modified live virus; moreover, the inactivated vaccines are more stable and safer than the latter.

Ethylenimine-inactivated rabies vaccine of tissue culture origin.

The replication of seven rabies virus strains (CVS, HEP, PV, ERA, WIRAB, CPZ and BOLIVAR) in BHK cells and the inactivation dynamics of these strains by beta-propiolactone, acetylethylenimine, and ethylenimine were studied to find the most immunogenic strain and the most economic and stable inactivating agent for the production of an inactivated tissue culture rabies vaccine for animal use. The seven strains reached the peak of virus production 3 to 5 days after inoculation of the cell culture; PV yielded the highest virus titer (10(9) plaque-forming units/ml). The infectivity of virus suspensions containing 10(7) to 10(8) plaque-forming units/0.1 ml was inactivated by beta-propiolactone in 0.5 h, acetylethylenimine in 3.0 h, and ethylenimine in 1.0 h. Most of the vaccine lots prepared with the different strains and inactivating agents passed a modified National Institutes of Health potency test. The vaccines prepared with the PV strain had consistently higher antigenic values (equal or better than four) than the other six strains. This difference was highly significant (F6,12=59.8), whereas there were no statistically significant differences among the antigenic values of the vaccine lots prepared with the three inactivating agents. Batches of lyophilized and liquid vaccine stored at 4 C maintained potency for over 1 year. Ten dogs vaccinated with a vaccine prepared with the PV strain and inactivated with ethylenimine developed a good antibody response and resisted challenge 60 days after vaccination, while seven of eight nonvaccinated controls died of rabies. This information indicates that an inactivated, stable, economic, and easy-to-prepare rabies vaccine can be produced in BHK cells by using the PV strain and ethylenimine as an inactivating agent.

[Inactivation of rabies virus by chemical agents]. / Inactivacion del virus rabico por agentes quimicos

To study the virucidal activity of several chemical agents available locally in Argentina for rabies virus, was considered to be very useful for physicians treating persons bitten by rabid dogs and for those responsible for the sterilization of rabies contaminated areas. CVS fixed rabies virus suspensions were treated for one minute at room temperature with soaps of different quality, anionic (most of them derivates of dodecyl-bencene-sulfonic acid) and cationic (dodecyl, tetradecyl, hexadecyl-trimethyl-ammonium bromide) detergents, lemon juice, vinegar, hydrochloric acid, sodium carbonate, etc. Most of these agents inactivated 4 logarithms of virus (99.99%) which is approximately the amount of virus present in the saliva of experimentally infected dogs. It is noteworthy that a popular treatment for animal bites in several latin America countries is lemon juice, while the scientific community may still recommend the use of nitric acid which has a definitive necrotic and scarring effect on the treated wound. The need to eliminate organic matter prior to sterilization of contaminated areas because of interference with the virucidal activity of the agents was also confirmed.

Sensitivity of bhk-21 cells supplemented with diethylaminoethyl-dextran for detection of street rabies virus in saliva samples.

A tissue culture system for detecting rabies virus from saliva samples of suspected animals was developed and compared to suckling mouse inoculation. Swab samples were obtained from the mouth of the animal heads received for rabies diagnosis; these swabs were submerged in maintenance medium. The maintenance medium was inoculated intracerebrally into suckling mice and onto BHK-21 cells with diethylaminoethyl (DEAE)-dextran (BHK/DEAE) and without (BHK). Rabies immunofluorescence was performed on the brain of the mice dying during the observation period and also on both tissue culture systems every day after infection. The BHK-DEAE system detected 28 positive samples obtained from 48 rabid animals and the BHK system detected 18. By suckling mouse inoculation only 11 of the same positive samples were detected. A total of 90 samples was studied by the three methods. Rabies virus was detected by the tissue culture methods earlier than by suckling mouse inoculation. The BHK-DEAE method was an economic and fast method for rabies virus detection in saliva samples, which could be used for ecological and pathogenesis studies, as well for rabies diagnosis before the death of the suspected animal.