Publications

Classical swine fever (CSF) was induced in 20 pigs by inoculation with a virulent strain of CSF virus to determine sequential changes (2, 4, 7, 10 and 14 days post-inoculation) in the number and morphology of splenic macrophages (red pulp and lymphoid marginal zone) and thus to assess the role of these cells in the pathogenesis of the disease. The first splenic cells to be infected with CSF virus were macrophages in the marginal zone followed by other macrophage populations. The initial phase of CSF was associated with an increase in splenic macrophage numbers in the marginal zone and a decrease in the red pulp. Subsequently, the numbers in the red pulp increased. The study suggested that infection, mobilization and apoptosis of splenic macrophages play an important role in the spread of CSF virus in vivo. Moreover, the secretory changes that occurred in macrophages in the initial phase of the infection suggested that macrophages release chemical mediators capable of modulating pathogenesis, (C) 2001 Harcourt Publishers Ltd.

Onchocerciasis is a debilitating parasitic infection caused by the filarial nematode Onchocerca volvulus. Infections are chronic, and persistence of the parasites for several years argues for highly adapted mechanisms of immune evasion. Due to the restricted host repertoire of O. volvulus, we have used the cattle parasite Onchocerca ochengi to investigate the nature of immunomodulation underpinning these long-term infections. Cattle were infected with a single inoculation of 350 infective-stage larvae under laboratory conditions (n = 6). Intradermal nodules containing immature adult worms were detected from 110 days postinfection, and microfilariae in skin were detected from day 280 postinfection. Parasite-specific responses during early infection were nonpolarized with respect to the major Th cytokines (interleukin-4 [IL-4], IL-2, and gamma interferon [IFN-gamma]) produced by antigen-stimulated peripheral blood mononuclear cells (PBMC) or serum antibody isotypes. Antigen-induced proliferation of PBMC peaked shortly after exposure and remained high during the prepatent infection. As the parasites matured and animals developed patent infections, there was a profound down-regulation of lymphoproliferation, accompanied by sharp falls in the expression of both IL-4 and IFN-gamma and a gradual decline in IL-2. Levels of immunoglobulin G2 (IgG2) fell, while those of IgG1 remained high. We conclude that neither a classical Th2 response nor a simple Th1-to-Th2 switch is sufficient to explain the immunomodulation associated with patent Onchocerca infections. Instead, there is an initial Th0 response, which matures into a response with some, but not all of the features of a Th2 response. The natural host-parasite relationship of O. ochengi in cattle may be useful as both a descriptive and predictive tool to test more refined models of immunomodulation in onchocerciasis.

Monokines are glycoproteins, synthesised by macrophages, which exert various effects on the organism. The most important monokines are interleukin (IL)-1 alpha, IL-1 beta, tumor necrosis factor (TNF)-alpha and IL-6. This paper reports on immunohistochemical techniques developed for the detection of IL-alpha, IL-1 beta, IL-6 and TNF-alpha in fixed and paraffin-embedded pig tissues (spleen, lymph nodes, thymus, liver and kidney). Different fixatives (buffered formalin, acetic formalin, paraformadehyde-lysine-periodate and Bouin solution), and antigen unmasking techniques (permeabilisation with Tween 20, pronase enzymatic digestion and microwave-citrate buffer) were used. We describe different protocols for detection of monokines using polyclonal antibodies against the studied monokines. No signal was obtained with monoclonal antibodies against pig-TNF-alpha and human IL-1 alpha. Bouin solution was shown to be the best fixative for immunohistochemical detection of IL-1 alpha, TNF-alpha, and IL-6, using permeabilisation with Tween 20 as an unmasking antigen method. Acetic formalin was shown to be the best fixative for IL-1 beta detection, not needing antigen retrieval techniques. Macrophages were identified as the main cytokine-producing cells, although other types of cells also stained positively to some cytokines. These techniques represent valuable tools for studies of the pathogenesis of viral and bacterial diseases, and of the immune system of the pigs.

The CD45 antigen is essential for normal antigen receptor-mediated signalling in lymphocytes, and different patterns of splicing of CD45 are associated with distinct functions in lymphocytes. Here we show that abnormal CD45 splicing caused by a C77G transversion in exon A of the gene encoding CD45 (PTPRC) is associated with increased susceptibility to HIV-1 infection.