In vitro developmental competence of bovine demi-embryos generated by blastomere separation and blastocyst bisection.

The efficiency of bovine in vitro embryo production can be significantly improved by splitting embryos at different stages. However, the blastocyst quality of in vitro-produced demi-embryos remains unexplored. The objective of this research was to compare embryo developmental rates and quality of bovine demi-embryos produced by two different strategies: (a) embryo bisection (BSEC) and (b) 2-cell blastomere separation (BSEP). To determine demi-embryos quality, we evaluated total blastocyst cell number and proportion of SOX2+ cells. Additionally, the expression of SOX2, NANOG, OCT4, CDX2, IFNT, BAX and BCL genes and let-7a and miRNA-30c Micro RNAs was analysed. BSEP resulted in improved blastocyst development, higher ICM cells and a significantly higher expression of IFNΤ than demi-embryos produced by BSEC. Let-7a, which is associated with low pregnancy establishment was detected in BSEC, while miRNA-30c expression was observed in all treatments. In conclusion, BSEP of 2-cell embryos is more efficient to improve in vitro bovine embryo development and to produce good quality demi-embryos based on ICM cell number and the expression pattern of the genes explored compared to BSEC.

Assessing Tn5 and Sleeping Beauty for transpositional transgenesis by cytoplasmic injection into bovine and ovine zygotes.

Transgenic domestic animals represent an alternative to bioreactors for large-scale production of biopharmaceuticals and could also provide more accurate biomedical models than rodents. However, their generation remains inefficient. Recently, DNA transposons allowed improved transgenesis efficiencies in mice and pigs. In this work, Tn5 and Sleeping Beauty (SB) transposon systems were evaluated for transgenesis by simple cytoplasmic injection in livestock zygotes. In the case of Tn5, the transposome complex of transposon nucleic acid and Tn5 protein was injected. In the case of SB, the supercoiled plasmids encoding a transposon and the SB transposase were co-injected. In vitro produced bovine zygotes were used to establish the cytoplasmic injection conditions. The in vitro cultured blastocysts were evaluated for reporter gene expression and genotyped. Subsequently, both transposon systems were injected in seasonally available ovine zygotes, employing transposons carrying the recombinant human factor IX driven by the beta-lactoglobulin promoter. The Tn5 approach did not result in transgenic lambs. In contrast, the Sleeping Beauty injection resulted in 2 lambs (29%) carrying the transgene. Both animals exhibited cellular mosaicism of the transgene. The extraembryonic tissues (placenta or umbilical cord) of three additional animals were also transgenic. These results show that transpositional transgenesis by cytoplasmic injection of SB transposon components can be applied for the production of transgenic lambs of pharmaceutical interest.

Efficient edition of the bovine PRNP prion gene in somatic cells and IVF embryos using the CRISPR/Cas9 system.

The recently developed engineered nucleases, such as zinc-finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease (Cas) 9, provide new opportunities for gene editing in a straightforward manner. However, few reports are available regarding CRISPR application and efficiency in cattle. Here, the CRISPR/Cas9 system was used with the aim of inducing knockout and knock-in alleles of the bovine PRNP gene, responsible for mad cow disease, both in bovine fetal fibroblasts and in IVF embryos. Five single-guide RNAs were designed to target 875 bp of PRNP exon 3, and all five were codelivered with Cas9. The feasibility of inducing homologous recombination (HR) was evaluated with a reporter vector carrying EGFP flanked by 1 kbp PRNP regions (pHRegfp). For somatic cells, plasmids coding for Cas9 and for each of the five single-guide RNAs (pCMVCas9 and pSPgRNAs) were transfected under two different conditions (1X and 2X). For IVF zygotes, cytoplasmic injection was conducted with either plasmids or mRNA. For plasmid injection groups, 1 pg pCMVCas9 + 0.1 pg of each pSPgRNA (DNA2X) was used per zygote. In the case of RNA, two amounts (RNA1X and RNA2X) were compared. To assess the occurrence of HR, a group additionally cotransfected or coinjected with pHRegfp plasmid was included. Somatic cell lysates were analyzed by polymerase chain reaction and surveyor assay. In the case of embryos, the in vitro development and the genotype of blastocysts were evaluated by polymerase chain reaction and sequencing. In somatic cells, 2X transfection resulted in indels and large deletions of the targeted PRNP region. Regarding embryo injection, higher blastocyst rates were obtained for RNA injected groups (46/103 [44.6%] and 55/116 [47.4%] for RNA1X and RNA2X) than for the DNA2X group (26/140 [18.6%], P < 0.05). In 46% (26/56) of the total sequenced blastocysts, specific gene editing was detected. The total number of genetic modifications (29) was higher than the total number of gene-edited embryos, as three blastocysts from the group RNA2X reported more than one type of modification. The modifications included indels (10/56; 17.9%) and large deletions (19/56; 33.9%). Moreover, it was possible to detect HR in 1/8 (12.5%) embryos treated with RNA2X. These results report that the CRISPR/Cas9 system can be applied for site-specific edition of the bovine genome, which could have a great impact on the development of large animals resistant to important zoonotic diseases.

Surveillance of adamantane resistance among influenza A H3 viruses isolated in Argentina between 2001 and 2007.

A dramatic rise in the frequency of resistance to adamantane drugs by influenza A H3 viruses, associated with a single amino acid replacement in the viral matrix M2 protein, has occurred in multiple countries worldwide in recent years. We investigated the frequency of adamantane-resistant influenza A H3 viruses in Argentina during the period 2001-2007. We used reverse transcription followed by polymerase chain reaction. The obtained products were sequenced for the detection of mutations of the M2 gere relevant to the resistance phenotypes. The HA1 sequences of the sensitive and resistant strains were also analyzed to clarify whether they had any relevance to the resistant mutations. Twenty out of 55 (36%) strains were identified with the resistance-conferring substitution at amino acid 31 (Serine 31 Asparagine). No resistant viruses were detected between 2001 and 2005. All strains isolated in 2006 and four out of five isolates from 2007 were resistant. None of the patients had received previous treatment with amantadine and/or rimantadine. The HA1 analysis showed that there were only two changes (Serine193 Phenylalanine and Aspartic acid 225 Asparagine) present in the strains with the M2 substitution at position 31. Our data indicate that since 2006 there has been a significant increase of adamantane-resistant influenza A H3 viruses, which raises concern over the spread of these viruses in Argentina.

Surveillance of adamantane resistance among influenza A H3 viruses isolated in Argentina between 2001 and 2007 / Vigilancia de la resistencia a los adamantanos entre los virus influenza A H3 aislados en Argentina entre 2001 y 2007

A dramatic rise in the frequency of resistance to adamantane drugs by influenza A H3 viruses, associated with a single amino acid replacement in the viral matrix M2 protein, has occurred in multiple countries worldwide in recent years. We investigated the frequency of adamantane-resistant influenza A H3 viruses in Argentina during the period 2001- 2007. We used reverse transcription followed by polymerase chain reaction. The obtained products were sequenced for the detection of mutations of the M2 gene relevant to the resistance phenotypes. The HA1 sequences of the sensitive and resistant strains were also analyzed to clarify whether they had any relevance to the resistant mutations. Twenty out of 55 (36%) strains were identified with the resistance-conferring substitution at amino acid 31 (Serine 31 Asparagine). No resistant viruses were detected between 2001 and 2005. All strains isolated in 2006 and four out of five isolates from 2007 were resistant. None of the patients had received previous treatment with amantadine and/or rimantadine. The HA1 analysis showed that there were only two changes (Serine193 Phenylalanine and Aspartic acid 225 Asparagine) present in the strains with the M2 substitution at position 31. Our data indicate that since 2006 there has been a significant increase of adamantane-resistant influenza A H3 viruses, which raises concern over the spread of these viruses in Argentina.

En los últimos años, se ha detectado un aumento de virus influenza A H3 resistentes a los adamantanos en distintos países, asociados mayoritariamente con el reemplazo de un único aminoácido de la proteína matriz M2. Se investigó la frecuencia de virus influenza A H3 resistentes a los adamantanos en Argentina entre 2001 y 2007. Se utilizó la transcripción reversa seguida de la reacción en cadena de la polimerasa y de la técnica de secuencia directa para la detección de mutaciones en el gen que codifica para la proteína M2, relevantes para los fenotipos de resistencia. También se analizó la secuencia de la porción HA1 de cepas resistentes y sensibles, para intentar establecer alguna relación con las mutaciones de M2. De un total de 55 cepas, 20 (36%) fueron resistentes debido a un cambio aminoacídico en la posición 31 (serina 31 asparagina). No se detectaron cepas resistentes entre 2001 y 2005. Las cepas aisladas en el 2006 y 4 de 5 cepas obtenidas en el 2007 fueron resistentes. Ninguno de los pacientes de los que se habían aislado esas cepas había recibido tratamiento antiviral con anterioridad. En la porción secuenciada de HA1 se encontraron dos cambios (serina 193 fenilalanina y ácido aspártico 225 asparagina), presentes sólo en las cepas que tuvieron la mutación en la posición 31 de M2. Desde el año 2006 se ha registrado en Argentina un aumento significativo de la circulación de virus influenza A H3 con genotipo resistente, lo que genera expectativa con respecto a su diseminación en nuestro país.

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.

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. (AU)

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. (AU)

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.

Regional perspectives on influenza surveillance in South America.

The implementation of influenza vaccination programs emphasize the necessity of an extended influenza surveillance in the countries of the region. As it is based on the activity of National Influenza Centers we intend to make a description of their work, their historical background and further development. Technical capacities in influenza South America laboratories, and networks in Argentina, Brazil and Chile are shown. Examples of different viral circulation in a unique country or in countries with common borders illustrate the importance of the information obtained by means of the virological surveillance. Specific characteristics of the region as long distances and the lack of modern information systems require a suitable fitting of the systems that are working in Northern Hemisphere countries. The contribution of motivated physicians and public health workers must not to be disregarded. The following actions are proposed: optimizing technical capacities of National Influenza Centers in order to improve the quality of data available; improving the communication of the information obtained by surveillance activities to all the participants; increasing the cooperation among the countries; motivate health authorities to become aware of influenza impact in public health.

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.

Multicentered study of viral acute lower respiratory infections in children from four cities of Argentina, 1993-1994.

This study describes the first multicentered study of acute lower respiratory infection viral etiology in young children from four different geographical areas of Argentina. A total of 1,278 children under 5 years of age, hospitalized in primary care centers from Buenos Aires, Córdoba, Santa Fé and Mar del Plata cities during a 2-year period were studied (1993-1994). Nasopharyngeal aspirates were investigated for respiratory syncytial virus (RSV), adenovirus, parainfluenza, and influenza A and B viruses by indirect immunofluorescence. Out of the patients studied, 946 (74%) were under 1 year of age. Viruses were detected in 399 patients (32%). RSV was observed in 25.3% of the samples, representing 78.2% of all viral positive cases. Adenoviruses were detected in 2.5% of the cases, parainfluenza in 2.2%, influenza A in 2.1%, and influenza B in 0.2%. Compared with other viruses, the higher RSV frequency was statistically significant (P < 0.000). Most RSV cases were detected between May and September with a significant peak in July (P < 0.000). Pneumonia was observed in 46% of the patients, bronchiolitis in 41% and other entities in 13%. The case fatality rate observed during the 2 year study was 0.73%. Most of the above respiratory viruses were detected in the four cities, however, the frequency of RSV and influenza were different in the southern city.

[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.

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.(AU)

Genetic characterization of wild-type measles viruses isolated during the 1998 measles epidemic in Argentina.

This study reports on genomic characterization of six measles virus (MV) isolates obtained from a measles epidemic in Argentina in 1998. Reverse transcription-polymerase chain reaction (RT-PCR) and nucleotide sequence analysis of the carboxyl-terminal region of the nucleoprotein (N) gene of these isolates classified all of them as wild type MV of D6 genotype. MVs of D6 genotype with identical nucleotide sequences in the region analyzed were also identified during the 1997 measles epidemic in Brazil and the 1999 measles outbreak in Uruguai. These results suggest that the MVs associated with the 1998 measles epidemic in Argentina might have originated from Brazil. As the D6 genotype is also widely distributed in Europe, it is possible that this genotype was brought to South America from Europe.

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.

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

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.

[Characterization of isolated adenovirus associated with acute lower respiratory infection in pediatrics]. / Caracterización de aislamientos de adenovirus asociados a infección respiratoria aguda baja en pediatría.

BACKGROUND: Acute respiratory infection (ARI) are a health care problem as the adenovirus (ADV) has shown to be one of the most frequent viral agents detected in children admitted for mild ARI in the authors medium. METHODS: Over a 7-year period (1988-1994) ADV isolated from patients under the age of 5, admitted for mild ARI in hospitals in the city of Buenos Aires (Argentina). All the strains were isolated in HEp-2 cell cultures from nasopharyngeal aspirates in which the presence of ADV was detected by indirect immunofluorescence with monoclonal antibodies. Antigenic characterization was performed by sero- and genome neutralization with restriction enzymes. RESULTS: The isolates corresponded to the genomic variants of ADV 7i, ADV 7c and to a greater number of ADV 7h. An increase was observed in the quantity of cases in the second half of the year. In the population studied, the most commonly infected were males (67.9%) and patients from 2 months to 1 year in age (89.2%). Sixty-six percent of the cases were severe infections with the length of hospitalization being greater than that of patients normally admitted for mild ARI by other virus and showed a high mortality. CONCLUSIONS: All the above events suggest that the genomic variants detected are highly pathogenic.