PubMed Health⌕ Search

Biomedical subjects

Patricia Greer

Publications and source records attributed to Patricia Greer.

5 recordsLinked to original sources
PubMed2006

Morphologic, immunologic, and molecular methods to detect bacillus anthracis in formalin-fixed tissues.

Due to the importance of Bacillus anthracis as a cause of naturally occurring infection among humans and as an agent of bioterrorism, there is a vital need for rapid and specific assays, including immunohistochemistry (IHC) and polymerase chain reaction (PCR) assays, to detect the bacterium in formalin-fixed tissues. Colorimetric IHC assays were developed using a multistep indirect immunoalkaline phosphatase method with anti-B. anthracis cell wall (EAII-6G6-2-3) and anti-B. anthracis capsule (FDF-1B9) mAbs to detect B. anthracis antigens in formalin-fixed, paraffin-embedded bacterial cultures and tissues. B. anthracis antigens were localized, using both antibodies, in samples from B. anthracis-infected animals and humans. The colorimetric IHC assay with both antibodies was expedient in diagnosing the presence of B. anthracis in formalin-fixed, paraffin-embedded tissue from bioterrorism-associated cases of inhalational and cutaneous anthrax and from a case of naturally occurring cutaneous anthrax. Using the same antibodies, confocal microscopy demonstrated the structure of replicating B. anthracis in tissues. B. anthracis-specific primers were successfully used with PCR to amplify and detect B. anthracis sequences derived from formalin-fixed tissues of anthrax cases. In this study, morphologic, immunologic, and molecular assays were used to study and diagnose 22 veterinary and human anthrax cases.

Animals↗
PubMed2005

CD8-mediated protection against Ebola virus infection is perforin dependent.

CD8 T cells have been shown to play an important role in the clearance and protection against fatal Ebola virus infection. In this study, we examined the mechanisms by which CD8 T cells mediate this protection. Our data demonstrate that all normal mice infected s.c. with a mouse-adapted Ebola virus survived the infection, as did 100% of mice deficient in Fas and 90% of those deficient in IFN-gamma. In contrast, perforin-deficient mice uniformly died after s.c. challenge. Perforin-deficient mice failed to clear viral infection even though they developed normal levels of neutralizing anti-Ebola Abs and 5- to 10-fold higher levels of IFN-gamma than control mice. Using MHC class I tetramers, we have also shown that perforin-deficient mice have 2- to 4-fold higher numbers of Ebola-specific CD8s than control mice. These findings suggest that the clearance of Ebola virus is perforin-dependent and provide an additional example showing that this basic immunologic mechanism is not limited to the clearance of noncytopathic viruses.

Animals↗
PubMed2004

Persistent infection with ebola virus under conditions of partial immunity.

Ebola hemorrhagic fever in humans is associated with high mortality; however, some infected hosts clear the virus and recover. The mechanisms by which this occurs and the correlates of protective immunity are not well defined. Using a mouse model, we determined the role of the immune system in clearance of and protection against Ebola virus. All CD8 T-cell-deficient mice succumbed to subcutaneous infection and had high viral antigen titers in tissues, whereas mice deficient in B cells or CD4 T cells cleared infection and survived, suggesting that CD8 T cells, independent of CD4 T cells and antibodies, are critical to protection against subcutaneous Ebola virus infection. B-cell-deficient mice that survived the primary subcutaneous infection (vaccinated mice) transiently depleted or not depleted of CD4 T cells also survived lethal intraperitoneal rechallenge for >/==" BORDER="0">25 days. However, all vaccinated B-cell-deficient mice depleted of CD8 T cells had high viral antigen titers in tissues following intraperitoneal rechallenge and died within 6 days, suggesting that memory CD8 T cells by themselves can protect mice from early death. Surprisingly, vaccinated B-cell-deficient mice, after initially clearing the infection, were found to have viral antigens in tissues later (day 120 to 150 post-intraperitoneal infection). Furthermore, following intraperitoneal rechallenge, vaccinated B-cell-deficient mice that were transiently depleted of CD4 T cells had high levels of viral antigen in tissues earlier (days 50 to 70) than vaccinated undepleted mice. This demonstrates that under certain immunodeficiency conditions, Ebola virus can persist and that loss of primed CD4 T cells accelerates the course of persistent infections. These data show that CD8 T cells play an important role in protection against acute disease, while both CD4 T cells and antibodies are required for long-term protection, and they provide evidence of persistent infection by Ebola virus suggesting that under certain conditions of immunodeficiency a host can harbor virus for prolonged periods, potentially acting as a reservoir.

Acute Disease↗
PubMed2003

The critical role of pathology in the investigation of bioterrorism-related cutaneous anthrax.

Cutaneous anthrax is a rare zoonotic disease in the United States. The clinical diagnosis traditionally has been established by conventional microbiological methods, such as culture and gram staining. However, these methods often yield negative results when patients have received antibiotics. During the bioterrorism event of 2001, we applied two novel immunohistochemical assays that can detect Bacillus anthracis antigens in skin biopsy samples even after prolonged antibiotic treatment. These assays provided a highly sensitive and specific method for the diagnosis of cutaneous anthrax, and were critical in the early and rapid diagnosis of 8 of 11 cases of cutaneous anthrax during the outbreak investigation. Skin biopsies were obtained from 10 of these 11 cases, and histopathological findings included various degrees of ulceration, hemorrhage, edema, coagulative necrosis, perivascular inflammation, and vasculitis. Serology was also an important investigation tool, but the results required several weeks because of the need to test paired serum specimens. Other tests, including culture, special stains, and polymerase chain reaction assay, were less valuable in the diagnosis and epidemiological investigation of these cutaneous anthrax cases. This report underscores the critical role of pathology in investigating potential bioterrorism events and in guiding epidemiological studies, a role that was clearly demonstrated in 2001 when B. anthracis spores were intentionally released through the United States postal system.

Adult↗