Histopathologic and antibody responses of rabbits exposed to aerosols containing spores of Aspergillus fumigatus: comparison of single and multiple exposures.

Resistance to pulmonary aspergillosis was studied in groups of rabbits exposed to aerosolized spores of Aspergillus fumigatus for 15 minutes on successive days for a total of 10, 7, or 4 exposures or a single exposure. The results of the study demonstrated that exposure of rabbits to spores for 15 minutes on 10 successive days did not result in an accumulation of viable spores in excess of those present in the lungs of rabbits exposed a single time. The tissue response in the lungs of the rabbits exposed at multiple times was more intense than that in the rabbits exposed once, but resolution of the lesions occurred similarly in terms of time and completeness of resolution. The duration of the antibody response as determined by a passive hemagglutination test and by enzyme-linked immunosorbent assay correlated with the number of exposures to spores, in that rabbits exposed 10 or 7 times to aerosolized spores remained positive longer than did those exposed fewer times. The results of the precipitin tests in agar gel were negative in all the rabbits but one.

Cloning and overexpression of Moloney murine leukemia virus reverse transcriptase in Escherichia coli.

A pBR322-derived expression vector, plasmid pKD1, was constructed containing the strong leftward promoter (pL) of bacteriophage lambda, the ribosome-binding site (RBS) of the cII gene of lambda, and a unique downstream NdeI restriction site for construction of an ATG initiation codon. The section of the pol gene of Moloney murine leukemia virus (M-MLV) that codes for reverse transcriptase (RT) was cloned into the NdeI site of this vector generating the plasmid pRT103. Upon thermal induction, enzymatically active RT was expressed in Escherichia coli [pRT103]. The identity of this activity was confirmed by its template specificity and its sensitivity to inhibition by immunoglobulin G (IgG) prepared against authentic murine RT. RT represented 20% of the newly synthesized protein in these cells 20 min after induction.