Accumulation and persistence of hepatitis A virus in mussels.

Accumulation and persistence of hepatitis A virus (HAV) in the mussel Mytilus chilensis was evaluated. Under optimal filtration activity of mussels (temperature 12 degrees C, salinity 3%, feeding twice a day with Dunaliella marina), HAV was concentrated 100-fold from the surrounding water. Similar concentrations of HAV were reached in the filtration apparatus and in the digestive system (hepatopancreas). HAV persisted for about 7 days in mussels. Elimination of HAV from mussels was slower than elimination of poliovirus. Without feeding of mussels (causing low filtration activity), there was no measurable uptake of HAV into mussels, and depuration of HAV from mussels was slower. The ability of mussels to concentrate HAV was used successfully to monitor fecally contaminated river water for the presence of HAV.

[Post-transfusion hepatitis iin Chile: the reference parameters]. / Hepatitis postransfusional en Chile: parámetros de referencia.

Most cases of post-transfusion hepatitis correspond to infection by non-A non-B virus. Indirect test (ALT elevation, anti-HBc titers) have been used to detect the presence of this virus. We screened 692 blood donors and health personnel, measuring anti-HBc (n = 572), HBs antigen (340), and ALT serum levels (190). Positive results were obtained for anti-HBc in 1.7% and HBs in 0%. ALT levels were 25 +/- 12 u/l in males and 18 +/- 14 in females (p < 0.01). ALT levels above 45 u/l were found in 6% of subjects. ALT levels were not related to anti-HBc positiveness nor to alcohol intake. The possible risk of posttransfusion hepatitis related to increased ALT levels remains to be clarified by specific markers.

In vitro exposure of the early mouse embryo to Herpes Simplex Virus-1 strain Wal.

The causes of early embryonic death are not clearly understood, but one of them may be viral infection. To study the interaction between the virus and the undifierentiated cell, early mouse embryos in morula and blastocyst stages were exposed to Herpes Simplex Virus-1 WAL (HSV-1 WAL). In one group of a total of 167 embryos, 108 were exposed to HSV-1 WAL; the rest were maintained as controls. After washing in culture medium, these embryos were cultured on a murine fetal fibroblast monolayer for viral isolation. None showed cytopathic effects in the susceptible monolayer. In a second group, 140 empryos were exposed and 106 were maintained as controls. These embryos were cultured without a monolayer or washing to permit continuous viral contact. Eighty-seven of the exposed embryos and 74 control empryos developed normally 2 to 3 d post hatching with no morpnological differences between the two groups. No statistical differences were observed when the proportion of natched and degenerated embryos was compared. Our results indicated that the cells of early mouse embryos are not susceptible to HSV-1 WAL. We concluded that possibly the susceptibility of empryonic cells to viral agents partially depends on stage of differentiation.

Transmission of bovine leukemia virus (BLV) to immunocompromised monkeys: evidence for persistent infection.

Splenectomized or irradiated adult and untreated baby macacques were infected with bovine leukemia virus from continuously virus producing fetal lamb kidney cell cultures. Persisting high antibody titers were followed for 4 years in the adult and 16 months in the baby monkeys, using an ELISA technique. With the exception of a persistent leukocytosis in one adult monkey, the animals remained healthy throughout the observation period. Transfer of lymphocytes from this animal to a seronegative recipient led to anti-BLV seroconversion with a lag of 5 months. All other transfer experiments showed a negative result. Virus could be recovered from the newly infected baby macacques by means of lymphocyte/fetal lamb kidney cell cocultivation for up to 4 weeks after inoculation. All other attempts to recover virus from the infected animals at a later point were unsuccessful.

[Smallpox vaccine, then and now. From the "cow lymphe" to the cell-culture vaccine]. / Pocken-Impfstoff, einst und jetzt. Von der "Kuhlymphe" zur Zellkultur-Vakzine

There have been few changes in the preparation of smallpox vaccine since Eduard Jenner described his method of preventive inoculation in 1798. Jenner's vaccine, "the matter", was maintained in man by arm to arm passage. The only major achievement in production methods was the introduction of an animal host for virus propagation. The skin of living calves or sheep was inoculated with seed virus and the "pulp" harvested three to four days later. The disadvantages of this procedure are evident: massive bacterial contamination in spite of rigorous cleanliness and excessive amounts of undesired tissue debris in the crude material to be used for vaccine production. In spite of these obvious disadvantages the method is still in use all over the world. Advances in tissue culture techniques have led to the production of all modern vaccines for use in animals and in the human from this substrate with low initial content of foreign protein and of primary sterility. The only exception today is conventional smallpox vaccine. Sporadic attempts to produce smallpox vaccine in tissue culture have been recently and successfully made in England, Holland and Yugoslavia. The Bavarian State Institute of Vaccination has adopted Vaccinia strain Elstree to primary cultures of chick embryo fibroblasts. The virus propagation in roller bottles permits the economical production of a high titered vaccine with a stability equal to that of calf origin. The cell culture harvest is bacteriologically steril and has a minimal content of foreign protein. Within the past two years this cell culture vaccine has totally replaced the old "calf lymph". Vaccination takes are equal, complications have so far not come to our attention.

[Determination of autohemolysin formation using the plaque test. Demonstration of autoimmune phenomena following vaccinations and infections].

A simple and sensitive modification of the plaque assay for the evaluation of autohaemolysin-producing cells (APC) in the peripheral blood is described: Very small chambers, (volume less than or equal to 0.03 cc) made out of glass slides (75 X 25 mm), are filled with a diluted (1:7) blood cell suspension. After incubation for 26 hours the haemolytic plaques produced by APC in the thin monolayer of blood cells can be counted under the microcope at a magnification up to 320-fold. The number of APC in guinea pigs immunized with cholera vaccine and in monkeys infected with variola-virus was evaluated by means of this method. Cholera vaccination significantly raised the APC up to 7 days after immunization. In monkeys these cells increased markedly between 4 and 7 days after infection with variola-virus. The increase was less pronounced in animals partially protected by prior vaccination with attenuated vaccinia-virus (MVA-strain) and showing a mild course of variola. Autoimmune mechanisms may exist in apparently normal organisms. They may rise after tissue destruction or cell alteration by infectious or other exogenous agents. The method described might be useful to determine the degree of reactogenicity of bacterial and viral vaccines.

Oral immunization against smallpox.

Attenuated vaccinia strain penetrates the mucous membranes of the oral and pharyngeal cavity; local lesions are not produced, even if high doses of attenuated virus are applied. Attenuated vaccinia virus thus offers the possibility of oral and nasal immunization against smallpox in man. Several groups of monkeys were immunized by the oral and nasal route. The subsequent challenge with virulent smallpox virus resulted in strongly mitigated clinical symptoms as compared to non-immunized controls. In the human, oral immunization with live attenuated virus was affected by the administration of virus-containing tablets. The procedures caused no untoward effect in primary vaccinees. Subsequent skin testing and conventional cutaneous vaccination resulted in accelerated takes, demonstrating successful oral pre-immunization.