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Browsing by Author "Bowen, R. A., advisor"

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    Avian immunity to West Nile virus
    (Colorado State University. Libraries, 2008) Nemeth, Nicole M., author; Bowen, R. A., advisor; Spraker, Terry R., advisor
    As West Nile virus (WNV) becomes endemic throughout much of North America, it continues to have detrimental effects on countless birds of various taxonomic groups. However, many birds survive infection, mounting an effective immune response. This dissertation focuses on the avian immune response to WNV, including naturally and experimentally-induced antibody duration and passive transfer of immunity. In addition, persistent WNV infection is a potential factor in altering pathogenesis if immunity were to wane. The duration and protection provided by anti-WNV antibodies was documented in house sparrows (Passer domesticus) and raptors for 3-4 years. Antibody levels were relatively stable over time, and protected against viremia in the former and recurrence of clinical disease in the latter. Passive transfer of WNV immunity from hen to eggs and chicks was characterized in domestic chickens (Gallus gallus domesticus). Eggs from both seropositive and seronegative hens were either sacrificed to test for WNV antibody in yolks or chicks artificially inoculated to examine viremic and serologic responses. Concurrently, age-associated differences in response to WNV infection were documented. The passive transfer experiment was repeated in house sparrows to explore this phenomenon in a passerine species; passive transfer was less prevalent in sparrow versus chicken chicks, was of shorter duration, and was less protective. Persistent WNV shedding, viremia, and tissue infection was examined in house sparrows, with juveniles sampled more intensively on a shorter time scale (30-65 days) and adults sampled at 1, 6, 12, 18, and 24 months post-infection. Infectious WNV was isolated from an oral swab, spleen, and kidney of several individuals at 30 DPI, but not from sera after 6 DPI or swabs after 15 DPI. However, WNV was detected in an oral swab by RT-PCR at 44 DPI and was in multiple tissues from most sparrows at 30 DPI, and from kidney and spleen of two individuals at 65 DPI. These findings suggest that WNV infection in tissues may persist beyond the acute stage of infection, while implications for natural transmission and avian health remain unknown.
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    Cloning and expression of a porcine zona pellucida gene: an approach to immunocontraception
    (Colorado State University. Libraries, 1991) Fontenot, Gregory Kenneth, author; Bowen, R. A., advisor; Jonathan Carlson, committee member; Niswender, Gordon, committee member
    Immunization with native porcine zona pellucida (ZP) proteins has been shown to induce infertility in females of several species and is thus a potentially valuable method of contraception. However, more extensive testing and commercialization of such a vaccine has been hampered by the limited availability of ZP proteins from natural sources. Availability of recombinant ZP proteins should simplify production of a practical ZP vaccine. The objective of this research was to clone a porcine ZP gene and use it to develop a recombinant ZP vaccine for use in pet animals. Polyadenylated RNA isolated from swine ovary was used to generate a cDNA library in the bacteriophage lambda gt11. This library was screened immunologically for ZP sequences using a polyclonal antiserum raised against solubilized porcine ZP. One immunoreactive clone, PZP, contained an insert of approximately 2.6 kb and was characterized further. The three Eco RI fragments constituting PZP were isolated and subcloned into a plasmid vector. The amino acid sequence deduced from the nucleotide sequence of PZP is considered to represent 305 residues from the carboxyterminal end of the ZP protein. A putative N-glycosylation site is present at residue 288 of this polypeptide. Comparison of the deduced amino acid sequence of PZP with deduced protein sequences from all of the other ZP proteins published to date failed to reveal significant homology. To confirm that PZP represented a ZP mRNA, a 418 bp fragment of the cDNA was expressed as a fusion protein in E. coli and used to hyperimmunize a rabbit. Antibodies to the PZP fusion protein bound to ZP surrounding porcine oocytes, stained ZP in sections of porcine ovary and immunoprecipitated a porcine ZP protein that was tentatively identified as ZP2. The PZP fusion protein was preliminarily evaluated as a vaccine in rabbits. Two groups of four adult rabbits were immunized three or four times with PZP2 fusion protein emulsified in either one of two adjuvants. Reproductive function was evaluated eight and sixteen weeks after initial immunization. In comparison to control rabbits, no effect of vaccination on reproductive function was observed.
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    Pathogenesis and immunity of rabies virus infection in bats
    (Colorado State University. Libraries, 2007) Davis, April, author; Bowen, R. A., advisor; Blair, Carol D., advisor
    Rabies is one of the oldest known viral diseases and, with a >99% fatality rate, it is also one of the most deadly. Although a major public health concern, human deaths due to rabies in the developed world are rare. Worldwide, statistics are very different as rabies kills in excess of 50,000 humans per year, most often the result of canine rabies variants. During the 1950's, canine rabies cases began decreasing in the United States as a result of vaccination efforts, followed by a decrease in human rabies cases. Rabies in insectivorous bats was first reported in the US in the 1950's and has now been reported in most North American bat species. Over the last 20 years, 92% of the human rabies cases have been the result of a bat variant. This purpose of this work was to expand our knowledge of rabies variants associated with silver hair bats, Mexican free-tailed bats, and big brown bats. The goal of the first study was to characterize disease progression between two closely related big brown bat rabies variants. The data from this experiment indicated that changes in the rabies virus genome may have profound effects on infectivity and virulence. The second study was designed to determine if rabies virus could be transmitted to bats through the aerosol route. Outbred mice and two species of bats were exposed to three variants of rabies virus by aerosol exposure. Although all bats survived the aerosol exposure, 44% of the mice died of rabies. Following exposure, anti-rabies virus neutralizing antibodies were demonstrated in all bats. Following an intramuscular inoculation of rabies virus six months after the aerosol exposure, the number of seropositive bats that developed rabies was equal to the control bats. The third study examined the dynamics of rabies virus infection in bats from colonies in Texas and Colorado. The ability of healthy wild bats incubating rabies to transmit rabies virus was also examined. Rabies virus antigen was found in 50% of the salivary glands from rabid bats yet infectious rabies virus was isolated from less than 35% of rabid bats. Evaluation of of bats from both the field and in captive colonies demonstrated that approximately 0.5-2% of clinically healthy bats were in the incubation phase of rabies virus infection.