A real-time quantitative polymerase chain reaction assay for the detection of Chlamydia in the mouse genital tract model

Chlamydia trachomatis is a human pathogen that infects genital tracts in women. Disease control may be achieved through development of an efficacious vaccine. A mouse genital tract model serves as a tool for evaluation of vaccine candidates. Currently, assessment of infection in mice is performed by enumeration of inclusion-forming units (IFUs) through microscopic counting of fluorescently stained bacteria. We have developed a highly sensitive real-time quantitative polymerase chain reaction (RT-qPCR) assay for enumeration of Chlamydia from mouse genital tracts to increase assay sensitivity, remove subjectivity, and improve sample throughput. The qPCR assay uses a 16S ribosomal gene sequence that is conserved across Chlamydia species and serovars, resulting in detection of multiple serovars of C. trachomatis, as well as Chlamydia muridarum and Chlamydia pneumoniae. The PCR assay provided results similar to IFU enumeration (94% agreement between the 2 assays) and is highly sensitive and specific with less inherent subjectivity than traditional enumeration methods.

Memory T-cell response to rotavirus detected with a gamma interferon enzyme-linked immunospot assay

Measurements of serum-neutralizing antibody and anti-rotavirus immunoglobulin A (IgA) are the current standard for assessing immune responses following rotavirus vaccination. However, there is ongoing debate as to whether antibody titers correlate with protection against rotavirus gastroenteritis. Children recovering from rotavirus gastroenteritis have increased gamma interferon release from cultured peripheral blood mononuclear cells (PBMCs), suggesting that cell-mediated immunity (CMI) may play a role in viral clearance and protection from subsequent gastroenteritis. We have developed a gamma interferon enzyme-linked immunospot (ELISPOT) assay for evaluation of CMI responses to rotavirus using frozen PBMCs obtained from healthy adults. Responses to three different rotavirus antigen types were analyzed-a peptide pool based on the human VP6 sequence; reassortant human:bovine vaccine strains; and cell culture-adapted (CCA) human G1, G2, G3, G4, and bovine (WC3) G6 strains. The reassortant strains consist of a bovine WC3 genome background expressing the human rotavirus surface proteins VP7 (G1, G2, G3, or G4) or VP4 (P1). Responses to titrations of the peptide pool as well as CCA and reassortant strains were assessed. Gamma interferon ELISPOT responses were similar for CCA and reassortant strains, whether live or UV inactivated, and when tested either individually or pooled. For most subjects, responses to the VP6 peptide pool positively correlated with responses to CCA and reassortant strains. Cell depletion studies indicate the memory responses detected with these frozen adult PBMCs were primarily due to the CD4+ T-cell population. This gamma interferon ELISPOT assay provides a new tool to apply in clinical studies for the characterization of natural or vaccine-induced CMI to rotavirus.

Immunohistochemical characterization of the distribution of galectin-4 in porcine small intestine

Galectins are an evolutionarily conserved family of 15 different lectins found in various combinations in virtually every type of animal cell. One of the primary galectins expressed in intestinal epithelium is galectin-4, a tandem-repeat galectin with two carbohydrate-recognition domains in a single polypeptide chain. In the current study, we produced an anti-galectin-4 monoclonal antibody (MAb) for determining the distribution of galectin-4 in porcine small intestine to enhance our understanding of where galectin-4 performs its functions in the small intestine. In immunohistochemistry studies, this MAb detected galectin-4 primarily in the cytoplasm of absorptive epithelial cells lining intestinal villi. Mature epithelial cells at the villous tips stained the most intensely with this MAb, with progressively less intense staining observed along the sides of villi and into the crypts. In addition to its cytoplasmic localization, galectin-4 was also associated with nuclei in villous tip cells, indicating that some galectin-4 may migrate to the nucleus during terminal maturation of these cells. In intestinal crypts, a specific subset of cells, which may be enteroendocrine cells, expressed galectin-4 at a relatively high level. Galectin-4 distribution patterns were similar in all three regions (duodenum, jejunum, and ileum) of porcine small intestine.

Identification of galectin-4 isoforms in porcine small intestine

Lactose-binding proteins with molecular masses of 14-, 17-, 18-, 28-, and 34-kDa were identified in extracts from porcine small intestinal mucosa. Amino acid sequence analysis of peptides generated by CNBr cleavage of the 34-kDa protein, the most abundant of these proteins, identified this protein as porcine galectin-4. To determine if a porcine homolog of murine galectin-6 is expressed in small intestine, primers for a reverse transcriptase-polymerase chain reaction (RT-PCR) were developed that amplified across the linker region of galectin-4, which is the region that differs between murine galectins-4 and -6. Using these primers, this RT-PCR approach identified two galectin-4 isoforms that differed in the length of their linker region. The larger isoform, galectin-4.1, is nine amino acids longer in its linker region than the smaller isoform, galectin-4.2. Based on nucleotide sequence similarities, the two isoforms are likely splice variants of galectin-4 pre-mRNA and not products of separate genes like murine galectins-4 and -6.