The major determinant of attenuation in mice of the Candid1 vaccine for Argentine hemorrhagic fever is located in the G2 glycoprotein transmembrane domain.

Candid1, a live-attenuated Junin virus vaccine strain, was developed during the early 1980s to control Argentine hemorrhagic fever, a severe and frequently fatal human disease. Six amino acid substitutions were found to be unique to this vaccine strain, and their role in virulence attenuation in mice was analyzed using a series of recombinant viruses. Our results indicate that Candid1 is attenuated in mice through a single amino acid substitution in the transmembrane domain of the G2 glycoprotein. This work provides insight into the molecular mechanisms of attenuation of the only arenavirus vaccine currently available.

Chapare virus, a newly discovered arenavirus isolated from a fatal hemorrhagic fever case in Bolivia.

A small focus of hemorrhagic fever (HF) cases occurred near Cochabamba, Bolivia, in December 2003 and January 2004. Specimens were available from only one fatal case, which had a clinical course that included fever, headache, arthralgia, myalgia, and vomiting with subsequent deterioration and multiple hemorrhagic signs. A non-cytopathic virus was isolated from two of the patient serum samples, and identified as an arenavirus by IFA staining with a rabbit polyvalent antiserum raised against South American arenaviruses known to be associated with HF (Guanarito, Machupo, and Sabiá). RT-PCR analysis and subsequent analysis of the complete virus S and L RNA segment sequences identified the virus as a member of the New World Clade B arenaviruses, which includes all the pathogenic South American arenaviruses. The virus was shown to be most closely related to Sabiá virus, but with 26% and 30% nucleotide difference in the S and L segments, and 26%, 28%, 15% and 22% amino acid differences for the L, Z, N, and GP proteins, respectively, indicating the virus represents a newly discovered arenavirus, for which we propose the name Chapare virus. In conclusion, two different arenaviruses, Machupo and Chapare, can be associated with severe HF cases in Bolivia.

Studies on in vivo gene transfer in pituitary tumors using herpes-derived and adenoviral vectors.

Suicide gene therapy has met limited success for the treatment of rat pituitary tumors. In order to determine the cause of primary pituitary tumor resistance to suicide gene therapy, we studied the transgene expression of an adenoviral (Ad.RSV.beta gal.nls) and a herpes simplex virus-derived (tsK/beta-gal) vector, both harboring the beta-galactosidase reporter gene in rat prolactinomas. Rats carrying experimental prolactinomas received bilateral 1 microl intrapituitary injections of either saline (saline group), 5 x 10(5) plaque-forming units (pfu) tsK/beta-gal (HSV Group) or 5 x 10(5) pfu Ad.RSV.beta gal.nls (RAd Group). Two or seven days later the tumors were examined. Macroscopic inspection of glands injected with either vector showed that the tissue expressing beta-gal was concentrated at the ventral area around the site reached by the tip of the needle. Almost no transgene expression was observed in other sites. Cellularity and lactotrophic cell density was not affected by saline or virus injection. In the injected areas, apoptotic levels were (x +/-S.E.M.): 9.3+/-0.5, 22.1+/-1.1 and 31.7+/-1.4%, for the saline, RAd and HSV groups, respectively. Serum prolactin and growth hormone levels were not affected by virus injection. We conclude that the low diffusibility of viral suspensions in the pituitary tissue may constitute a significant obstacle for achieving full remission of in situ pituitary tumors in rats.