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Biomedical subjects

K E Hooper-McGrevy

Publications and source records attributed to K E Hooper-McGrevy.

4 recordsLinked to original sources
PubMed2005

Virulence-associated protein-specific serum immunoglobulin G-isotype expression in young foals protected against Rhodococcus equi pneumonia by oral immunization with virulent R. equi.

The purpose of this study was to determine whether foals immunized orally from 2 days of age with virulent Rhodococcus equi developed a protective pulmonary immune response and to characterise the antibody response of the immunized foals to the virulence-associated proteins (Vaps) of the bacterium. Two groups of foals were used. One (n=4) was given live R. equi ATCC 33701 orally at 2, 7, and 14 days of age. The second group comprised three non-immunized foals age-matched to the vaccinates. At 3 weeks of age, 1 week after the final immunization, both groups were challenged intrabronchially with virulent R. equi ATCC 33701 and observed for 2 weeks post-challenge. Unvaccinated foals became clinically pneumonic and had high fever with increased heart and respiratory rates and severe pneumonia evident at necropsy. Foals of the immunized group remained healthy and lung lesions were not found post-mortem. Thus, it is possible to immunize young foals orally to protect them by 3 weeks of age against lung challenge with R. equi, even in the presence of maternal antibodies. The antibody response of the immunized foals confirmed that VapA and VapC are highly immunogenic. The immunoglobulin G isotype-related serum antibody response of immunized compared to non-immunized foals had an IgGT bias and a relatively low IgGa:IgGb ratio, both features different from what has been previously observed in immune adults and immune foals. This suggests that the serum IgG isotype profile of antibody cannot be used as a measure of evidence of protection against R. equi pneumonia.

Administration, Oral↗
PubMed2001

Evaluation of equine immunoglobulin specific for Rhodococcus equi virulence-associated proteins A and C for use in protecting foals against Rhodococcus equi-induced pneumonia.

OBJECTIVE: To determine whether purified equine immunoglobulin specific for Rhodococcus equi virulence-associated proteins A and C (VapA and VapC) can confer passive protection against R. equi-induced pneumonia in foals. ANIMALS: Twenty-eight 3-week-old mixed-breed pony foals. PROCEDURE: 7 foals received IV injections of equine hyperimmune plasma (HIP) against whole-cell R. equi, and 7 received purified equine immunoglobulin specific for VapA and VapC 1 day prior to intrabronchial infection with R. equi strain 103+. Eleven foals were not treated prior to infection, and 3 control foals were neither treated nor infected. Heart rate, respiratory rate, and rectal temperature were recorded twice daily, and serum fibrinogen concentration and WBC count were determined every other day following infection. Foals were euthanatized 14 days following infection, and lung lesions and concentration of R. equi in lungs were assessed. RESULTS: The onset of clinical signs of pneumonia was significantly delayed in the HIP- and immunoglobulin-treated groups, compared with the untreated infected group. Moreover, pulmonary lesions were less severe in the treated groups, and significantly fewer R. equi organisms were cultured from the lungs of treated foals. CONCLUSIONS AND CLINICAL RELEVANCE: Degree of protection against R. equi-induced pneumonia provided by purified immunoglobulin specific for VapA and VapC was similar to that provided by commercially available HIP. Results not only suggest that immunoglobulin is the primary component of HIP that confers protection against R. equi-induced pneumonia in foals but also indicate that antibodies against R. equi VapA and VapC are protective.

Actinomycetales Infections↗
PubMed1998

Alterations in bovine platelet function and acute phase proteins induced by Pasteurella haemolytica A1.

Platelet function was assessed by aggregometry in 10 Holstein calves before and after exposure to Pasteurella haemolytica (biotype A, serotype 1) by intrabronchial challenge. At 24 h after exposure the platelets had become more reactive to stimulation with known platelet agonists such as adenosine diphosphate (ADP) and platelet-activating factor (PAF) and the platelet aggregates that formed were more resistant to disaggregation. The activation of platelets was an early response in the challenged calves as platelet function had returned to pretreatment levels 72 h after exposure to the bacteria while the acute phase reactant proteins, haptoglobin and fibrinogen, were approaching their peak values and alpha 2-macroglobulin levels had also risen significantly (P < 0.05) at this time. The plasma levels of these proteins were still elevated and albumin levels were depressed 6 d post-treatment. At post-mortem all calves exhibited pneumonic tissue damage. When P. haemolytica leukotoxin was added directly to bovine platelet suspensions both spontaneous aggregation and an increase in the aggregation response to ADP and PAF stimulation were observed. The morphological appearance of the platelet aggregates exhibited the typical pattern for bovine platelets with 2 distinct zones of cells being visible within each aggregate. One zone contained platelets in which the cytoplasmic granules were still evident and the other zone contained irregularly shaped platelets devoid of granular content. In the latter zone, discrete gaps, or pores, were evident in the plasma membrane of numerous platelets. This pore formation is characteristic of leukotoxin action and is not observed in ADP or PAF induced aggregates.

Acute-Phase Proteins↗