Use of a Guinea Pig-Specific Transcriptome Array for Evaluation of Protective Immunity against Genital Chlamydial Infection following Intranasal Vaccination in Guinea Pigs

Abstract

Guinea pigs have been used as a second animal model to validate putative anti-chlamydial vaccine candidates tested in mice. However, the lack of guinea pig-specific reagents has limited the utility of this animal model in Chlamydia sp. vaccine studies. Using a novel guinea pig-specific transcriptome array, we determined correlates of protection in guinea pigs vaccinated with Chlamydia caviae (C. caviae) via the intranasal route, previously reported by us and others to provide robust antigen specific immunity against subsequent intravaginal challenge. C. caviae vaccinated guinea pigs resolved genital infection by day 3 post challenge. In contrast, mock vaccinated animals continued to shed viable Chlamydia up to day 18 post challenge. Importantly, at day 80 post challenge, vaccinated guinea pigs experienced significantly reduced genital pathology - a sequelae of genital chlamydial infections, in comparison to mock vaccinated guinea pigs. Sera from vaccinated guinea pigs displayed antigen specific IgG responses and increased IgG1 and IgG2 titers capable of neutralizing GPIC in vitro. Th1-cellular/inflammatory immune genes and Th2-humoral associated genes were also found to be elevated in vaccinated guinea pigs at day 3 post-challenge and correlated with early clearance of the bacterium. Overall, this study provides the first evidence of guinea pig-specific genes involved in anti-chlamydial vaccination and illustrates the enhancement of the utility of this animal model in chlamydial pathogenesis.

Guinea pig genital tract lipidome reveals in vivo and in vitro regulation of phosphatidylcholine 16:0/18:1 and contribution to Chlamydia trachomatis serovar D infectivity

“…Chlamydia caviae is the naturally infecting strain in guinea pigs and has been used by several laboratories to study chlamydial infection (Rank et al 2003; Wali et al 2014; Neuendorf et al 2015). However, given that Ct D and Ct E are strains infecting humans, the translational value of the guinea pig model has further increased by the report of de Jonge et al on establishment of Ct D and Ct E infection in guinea pigs (de Jonge et al 2011).…”

“…Histological images were obtained at ×200 or ×400 magnifications using an Olympus AX80 light microscope (Olympus, Center Valley, PA) and evaluated in a blind fashion for pathological damage (Wali et al 2014). The microscopic findings were either graded as follows: none/minimal (0), slight (1), moderate (2), or severe (3) histological alteration.…”

Chlamydial protease‐like activity factor mediated protection against C. trachomatis in guinea pigs

“…To achieve a sustained CT‐D infection in guinea pigs, all animals received a subcutaneous injection of 5 mg β‐estradiol (Sigma, St Louis, MO, USA) in 100 μl sesame oil (Sigma) on days −10 and −3 before challenge as described by de Jonge et al 31 All guinea pigs were anesthetized with 3% isoflurane before immunization and challenge procedures. Following challenge, vaginal swabs were collected at a 3‐day interval for 36 days from all groups of guinea pigs and plated onto HeLa cell monolayers to determine the chlamydial burden as described previously 28 …”

“…To measure antibody reactivity, microtiter plates were coated with 1 × 10 5 IFUs of UV‐inactivated CT‐D or 0.5 μg rCPAF and incubated at 4 °C overnight. ELISA was performed using serial twofold diluted sera (starting with 1:100) as described 28 to assess antibody reactivity. Following serial dilution of serum samples, plates were incubated for 2 h, followed by incubation with goat anti‐guinea pig total IgG conjugated to horseradish peroxidase (ABD Serotec, Raleigh, NC, USA).…”

Development of a vaccine for Chlamydia trachomatis: challenges and current progress

“…The general model used to evaluate vaccines has been the C. muridarum-mouse model, although continued excellent work is progressing using the guinea pig model. [145][146][147] Protection is usually assessed following live genital tract challenge and is measured by any improvements in infection load (either peak of infection, total infection burden, or days to clearance) or reduction in pathology (physical size of the hydrosalpinx). By all measures, the candidate vaccines have not been able to produce a protective response anywhere near close to elimination of the organism, as can be seen following live infection.…”