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Biomedical subjects

C E Coto

Publications and source records attributed to C E Coto.

At least 37 records · Page 2Linked to original sources
PubMed1987

Antiviral effects of Melia azedarach L. leaves extracts on Sindbis virus-infected cells.

Partially purified extracts from leaves of Melia azedarach L. (MA) exert a broad range of antiviral effects on DNA and RNA viruses. The effect of MA on different stages of Sindbis virus replicative cycle in BHK cells was investigated. Under one-step growth conditions MA afforded a greater than 90% inhibition in virus yield if added to the cell cultures 2 h before or after infection, and when added 4 h after infection MA still caused a greater than 80% inhibition. Analysis of early events following Sindbis virus infection showed that MA did not affect viral adsorption to or penetration in BHK cell. In contrast, viral RNA and protein synthesis was almost totally inhibited in cells pretreated with MA 2 h before infection, while cellular macromolecular synthesis was similar in MA-treated and untreated cell cultures.

Antiviral Agents↗
PubMed1986

An antiviral factor from Melia azedarach L. prevents Tacaribe virus encephalitis in mice.

Treatment of neonatal mice with an antiviral factor, (AVF), obtained from the leaves of Melia azedarach L. protected them against lethal encephalitis caused by Tacaribe virus inoculation. The degree of protection obtained varied from 66% to 100% depending on the virus dose. Similarly, administration of AVF to nursing mothers protected their offspring from developing virus encephalitis. AVF does not directly inactivate Tacaribe virus; it inhibits an early step (s) in the replication process in cell cultures.

Animals↗
PubMed1986

Role of Calomys musculinus peritoneal macrophages in age-related resistance to Junin virus infection.

In nature, the cricetid Calomys musculinus is the principal host of Junin virus, the etiological agent of Argentine hemorrhagic fever. In the experimental infection, adult C. musculinus survived whereas newborns died after intraperitoneal inoculation with the XJ.Cl3 strain of Junin virus. The role of peritoneal macrophages in this age-related resistance was studied. Junin virus multiplied in cultivated macrophages from either neonatal or adult animals and, therefore, it was not possible to correlate the susceptibility of peritoneal macrophages to Junin virus infection with the age-dependent resistance. When adult and neonatal animals were treated with silica prior to Junin virus infection, deaths occurred in the adults, while a delay and decrease in the mortality rate were observed in neonatals. These results suggest that in neonatal C. musculinus macrophages could be permissive cells for Junin virus multiplication, whereas in adult cricetids, these cells would act as a barrier against viral infection by means of an extrinsic antiviral activity.

Aging↗
PubMed1986

Antigenic variants of Junín virus isolated from infected Calomys musculinus. Brief report.

Junín virus establishes a long-term persistent infection in its natural host, Calomys musculinus. Virus recovered from blood of infected animals from 14 to 61 days p.i. behaved antigenically distinct to parental virus, as shown by cross neutralization assays. The emergence of antigenic viral variants occurs during both the acute and persistent state of infection.

Animals↗
PubMed1986

Vero cells persistently infected with Tacaribe virus: role of interfering particles in the establishment of the infection.

Eight Vero cell sublines (Vero T) persistently infected with wild type Tacaribe virus replicated in different hosts were established. In order to unravel the mechanism involved in the initiation and maintenance of persistence, the properties of virus shed by the sublines and the presence of interfering particles (IP) were analyzed. During the course of infection, persistent virus (Tac-pi) underwent mutations although no consistent pattern of virus evolution was observed. ts mutants were isolated from two Vero T sublines, whereas a slow growth variant was shed by another. The remaining sublines released virus resembling wt parental virus. Except for Vero T1 sublines, Vero T cultures shed no detectable IP. These results emphasize the point that neither the emergence of virus mutants nor the synthesis of IP is essential for the maintenance of the persistent state. To define the role of IP in the initiation of persistence, coinfection experiments with a characterized inoculum were performed. For that purpose, attempts were made to obtain IP stocks free from pfu by serial transfers of undiluted virus. Neither enrichment nor amplification of IP occurred, and virus stocks were freed of infectious virus by UV irradiation. If normal Vero cells were infected with Tac-pi virus released by Vero T2, Vero T3, Vero T4, Vero T5, Vero T6, Vero T7 and Vero T10 sublines, a complete destruction of the monolayer without cell recovery was observed. In contrast, parental and Vero T1 viruses always originated persistently infected sublines. Similarly, the addition of IP to virus inocula constituted by Tac-pi viruses released by Vero T2, Vero T3, Vero T4, Vero T5, Vero T6, Vero T7 and Vero T10 sublines gave rise to persistently infected cultures. These results suggest that although IP are not important by themselves in the maintenance of persistence, they play a major role in initiation.

Animals↗
PubMed1986

Administration of antithymocyte serum modifies the response of Calomys musculinus to junin virus infection.

Approximately 80% of Calomys musculinus inoculated with an attenuated strain of Junin virus (JV) developed a lethal encephalitis. Antithymocyte serum, a potent suppressor of T-cell-mediated immunity, was studied for its effect on JV pathogenicity. Early administration of an anti-C. musculinus thymocyte serum (ACTS) to neonatal animals significantly diminished clinical disease and death and abrogated brain damage, which is usually associated with viral presence in the brain. Late ACTS administration did not modify the pattern of JV infection. These results suggest that immune mechanisms participate in the pathogenesis of JV infection for its main natural host.

Animals↗
PubMed1986

[Susceptibility of 11-day-old mice to infection with the Junin virus grown in different hosts].

Twelve clones derived from a stock of Junin virus grown in baby mouse brain were isolated in Vero cells. Some properties of those viral clones were determined and compared with parental virus in order to ascertain the degree of heterogenicity of the original population. No differences were observed among clones and parental virus when the degree of thermolability was measured by heating them at 50 degrees C for 30 min. (Table 1). Similarly no ts phenotype character was present among all viral isolates tested since ratios 40 degrees C/37 degrees C, alike parental virus, oscillated around 0.48 (Table 1). Also virulence for 2 days old mice, expressed as the ratio of PFU/LD50 varied between 5.27 to 25 while parental virus ratio was 4.56. A completely different picture was observed when virulence ratio was determined in 11 days old mice. The values found for viral clones were all above 47 being the maximum 210 (Table 1) whereas the ratio of parental virus was 2.65. Considering that the difference observed could be due to the last host where the virus multiplied, parental virus stock was passed once or two times in Vero or BHK21 cells before assaying virulence. Results quoted in Table 2 show that after one or two passages in cells, the ratio of virulence decreased, at least, 60 times independently of the virus stock or the type of cells used. Furthermore, the appearance of a viral population with an intermediate virulence index was detected by a passage through mouse embryo cells (Table 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1986

Partial characterization of two temperature-sensitive mutants of junin virus.

Two temperature sensitive (ts) mutants of Junin virus, a member of Arenaviridae, have been partially characterized. Both mutants, named ts-32 and ts-40, had a relative plating efficiency 40 degrees C/34 degrees C lower than 10(-3) an exhibited a leak yield below 10(-4). Standard growth curves showed that at 34 degrees C the viral mutants multiplied slower than wt virus and at high multiplicity did not display autointerference. No differences in thermolability were observed between wt and ts mutants. By contrast, when the pathogenic properties of the mutants were investigated they were significantly attenuated for mice. At the restrictive temperature both mutants were unable to synthesize viral-specific polypeptides, while at the permissive temperature the pattern was similar to wt virus. Shift-up and down experiments suggested that ts defect is expressed between 2 and 4 hours post-infection. It is concluded that ts-32 and ts-40 are early function mutants. The possible nature of their defect is discussed.

Animals↗
PubMed1985

Interactions of Junin and Tacaribe viruses during mixed infections.

The interaction between Junin virus (JV) and Tacaribe virus (TACV) during mixed infections of RK13 cells was examined. The effects of a prior infection with JV upon TACV replication depended on the time between the two inoculations. Simultaneous infection of RK13 cells with TACV and JV did not alter the plaquing efficiency of TACV; but if there was a 1- to 24-hour delay between JV preinfection and TACV superinfection, a variable increase of TACV replication was observed. The enhancement of TACV replication by preinfection with JV was dependent on several factors, such as the MOI of both viruses and the integrity of the JV genome. This effect was also highly specific, as the plaquing efficiencies of the arenavirus Pichinde and the unrelated vesicular stomatitis virus were not affected by preinfection with JV at any multiplicity assayed. The majority of the progeny formed in cells superinfected with TACV 1 or 24 h after JV infection was partially neutralized by antisera to both viruses. This suggested that phenotypic mixing, with JV or TACV genomes enclosed within an envelope containing TACV and JV glycoprotein, had occurred.

Animals↗
PubMed1985

[Assays of cytotoxicity and antiviral activity of crude and semipurified extracts of green leaves of Melia azedarach L].

Crude extracts from fresh green leaves of Melia azedarach L contain an antiviral factor (FAV) able to inhibit the replication of several animal viruses, e.g. Polio, VSV, HSV, FMDV, Sindbis, Junín, Pichinde and Tacaribe in Vero or BHK-21 cells. Crude preparations were subjected to different steps of purification like chromatography on Sephadex G-100 and DEAE-Sephadex. The antiviral activity of G-100 and DEAE fractions was fully conserved, whereas contaminating proteins were lost. Two types of cytotoxicity tests were performed with the different fractions. Two-fold serial dilutions of each of them were added to preformed monolayers of Vero or BHK-21 cells and cellular viability was tested. While crude extracts were toxic at low dilutions (less than or equal to 1:10), G-100 and DEAE fractions were not. The other cytotoxicity assay consisted in seeding the cells in the presence of different concentrations of each fraction. G-100 fraction affected cell growth at low dilutions (less than or equal to 1:5), while DEAE fraction did not. It should be remarked that the purification procedure rendered a partial purified DEAE fraction with an increased specific activity (antiviral activity/mg of protein). It is concluded that an antiviral factor devoid of toxicity exists in M. azedarach L extracts, which exhibited a broad spectrum of antiviral activity.

Antiviral Agents↗
PubMed1985

[Isolation of Junin virus from blood and peripheral lymphocytes of infected Calomys musculinus].

Neonatal Calomys musculinus experimental infection with Junín virus (JV) XJCl3 strain causes either death or a persistent infection in the major part of surviving animals. JV can be isolated from peritoneal macrophages early during infection, and from brain and salivary glands during the chronic state of disease. It was of interest to investigate the appearance of virus in blood of infected animals. For this purpose, we decided to study the development of viremia in inoculated cricetids. A high frequency of viremia was registered during the acute state of disease (figure 1), which became sporadic approximately from 20 days post-infection onwards. Considering the results above mentioned, the characteristic lymphotropism of arenaviruses and the well-known JV replication in human mononuclear cells, cultures of lympho-monocytes obtained from blood of infected C. musculinus were done in order to investigate the eventual detection of infectious virus in the supernatants. JV was isolated, although in low titres, from cultures established with mononuclear cells belonging to animals in the acute state of disease (table 1); in the case of chronically infected cricetids, attempts to isolate JV were negative. These results show that viremia is currently detected in experimentally infected C. musculinus and that circulating mononuclear cells are permissive for JV multiplication, during the acute state of disease.

Animals↗
PubMed1985

Substituted benzaldehyde thiosemicarbazone with antiviral activity against poliovirus.

A series of eight benzaldehyde thiosemicarbazone derivatives with a variable number of -OH substituents at different positions on the aromatic ring were prepared and evaluated for in vitro antiviral activity against poliovirus types I, II and III. Some of the compounds significantly inhibited the replication of poliovirus at a mean ED50 of 2, 5.7, 10.5 and 9.7 micrograms/ml. A comparison between chemical structure and biological activity suggests that the inhibitory effect depends on the relative position of the -OH and the thiosemicarbazone group. The compounds possess antiviral action only when the two groups are distant enough to prevent the formation of intramolecular hydrogen bonds.

Animals↗
PubMed1984

[Effect of the host cells in the crossed neutralization reactions between Junín and Tacaribe viruses ].

It has been previously reported that guinea pigs inoculated with Tacaribe virus grown in suckling mouse brain, develop specific anti-Junín neutralizing antibodies (NA) after 45 days of infection and a typical secondary response after Junín virus challenge. Since in these experiments both viruses were grown in suckling mouse brain doubt was raised about the specificity of NA, considering the possibility that they were raised against host-cell antigens. In order to test this interpretation the following experiments were performed. Stocks of Tacaribe and Junín viruses were prepared in sucking mouse brain, in monkey kidney cells (Vero) and in rabbit kidney cells (RK13). Different groups of guinea-pigs were inoculated with 1000 TC ID50 from each stock of Tacaribe virus. The animals were challenged on day 66 p.i. with 1000 LD50 of Junín virus grown in suckling mouse brain. Animals were bled at 30, 60 and 80 days after Tacaribe virus infection and sera were assayed in neutralization tests against Tacaribe and Junín viruses grown in Vero or RK13 cells or suckling mouse brain. Specific NA against Junín virus were found in all sera on day 60 post Tacaribe infection, discarding the possibility that the antibodies were not specifically directed against virus antigens. However, it was observed that the antibody titers were higher when neutralization was performed using immune sera prepared with virus grown in the host used for virus antigen. These results suggest that during the process of budding, viruses recruit cellular antigens which enhance the immune response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Response of cells persistently infected with arenaviruses to superinfection with homotypic and heterotypic viruses.

Vero cell cultures persistently infected with the arenaviruses Junin, Pichinde, Tacaribe, and Tamiami were established and designated Vero-Jun, Vero-Pic, Vero-Tac, and Vero-Tam, respectively. Two types of carrier cultures could be easily distinguished: Vero-Jun and Vero-Tac systems were characterized by a lack of infectious virus production after a few cell transfers, whereas a more productive state with continuous release of virus was observed in Vero-Pic and Vero-Tam cultures. These differences appeared to be related to resistance of the culture to viral superinfection. In fact, Vero-Jun and Vero-Tac cultures totally excluded only the replication of the serologically more closely related arenaviruses Amapari, Junin, or Tacaribe, while the refractoriness of Vero-Pic and Vero-Tam cultures was extended to most of the virus group members. The resistance of Vero-Jun cells to superinfection by Junin or Tacaribe virus could be ascribed to the production of specific uv-resistant Junin interfering particles, which showed a specific range of interference against Junin and Tacaribe viruses. Interfering particles against homotypic and heterotypic arenaviruses were isolated from Vero-Pic cultures. However, the degree of interference developed by these Pic-interfering particles was not enough to fully explain reinfecting virus exclusion from Vero-Pic cultures. Viral susceptibility of persistent cultures is proposed as a useful tool to examine relationships of members of the arenavirus group.

Animals↗
PubMed1983

[Induction of heat-sensitive mutants of Junín virus using 5-fluorouracil].

This paper presents results concerning production, selection and isolation of conditionally lethal mutants of Junin virus. Two temperature sensitive (ts) mutants of Junin virus, XJCl3 strain, were isolated from a virus population that had been mutagenized with 5-Fluorouracil (5-FU). A study of the behaviour of wild-type virus over a range of temperature from 34 degrees C to 40 degrees C was done. In Vero cells, the initial cloned Junin virus stock gave very turbid plaques at 34 degrees C, more clear plaques at 37 degrees C and lytic pinpoint plaques at 40 degrees C. The efficiency of plaquing (ratio of plaques formed at 40 degrees C to plaques formed at 37 degrees C) in Vero cells was 0.86. Moreover, the wild-type virus had similar growth curves at 34, 37 or 40 degrees C in Vero cells. To study the 5-FU inhibition of Junin virus multiplication, Vero cell cultures were infected with approximately 0.6 PFU per cell and incubated in the presence of various doses of mutagen. After 24 hs of infection the yields were titrated. The mutagen inhibited virus multiplication in a dose-dependent manner. A concentration of 100 micrograms/ml, which reduced virus yields to 1% of that obtained in cultures lacking 5-FU, was chosen to select ts mutants. A rapid screening procedure based on the ability of Junin virus to develop cytopathic effects in Vero cells at 37 degrees C and 40 degrees C was used to identify potential ts mutants among 90 randomly picked plaque isolates obtained from virus grown at 34 degrees C during 24 hs in the presence of the mutagen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗