Current serological assays for species-specific detection of anti-Chlamydia species antibodies suffer from well-known shortcomings in specificity and ease of use. Due to the high prevalences of both anti-C. trachomatis and anti-C. pneumoniae antibodies in human populations, species-specific serology is unreliable. Therefore, novel specific and simple assays for chlamydial serology are urgently needed. Conventional antigens are problematic due to extensive cross-reactivity within Chlamydia spp. Using accurate B cell epitope prediction and a robust peptide ELISA methodology developed in our laboratory, we identified immunodominant C. trachomatis B cell epitopes by screening performed with sera from C. trachomatis-infected women. We discovered 38 novel human host-dependent antigens from 20 immunodominant C. trachomatis proteins, in addition to confirming 10 host-independent mouse serum peptide antigens that had been identified previously. This extended set of highly specific C. trachomatis peptide antigens can be used in simple ELISA or multiplexed microarray formats and will provide high specificity and sensitivity to human C. trachomatis serodiagnosis.

Feline infectious peritonitis (FIP), caused by feline coronavirus (FcoV), is considered one of the most enigmatic diseases in cats. Developing effective drugs for FIP is crucial due to its global prevalence and severity. In this study, six antiviral drugs were tested for their cytotoxicity, cell viability, and antiviral efficacies in Crandell-Reese feline kidney cells. A cytotoxicity assay demonstrated that these drugs were safe to be used with essentially no cytotoxicity with concentrations as high as 250 µM for ruxolitinib; 125 µM for GS441524; 63 µM for teriflunomide, molnupiravir, and nirmatrelvir; and 16 µM for ritonavir. GS441524 and nirmatrelvir exhibited the least detrimental effects on the CRFK cells, with 50% cytotoxic concentration (CC50) values of 260.0 µM and 279.1 µM, respectively, while ritonavir showed high toxicity (CC50 = 39.9 µM). In the dose–response analysis, GS441524, nirmatrelvir, and molnupiravir demonstrated promising results with selectivity index values of 165.54, 113.67, and 29.27, respectively, against FIPV. Our study suggests that nirmatrelvir and molnupiravir hold potential for FIPV treatment and could serve as alternatives to GS441524. Continued research and development of antiviral drugs are essential to ensure the well-being of companion animals and improve our preparedness for future outbreaks of coronaviruses affecting animals and humans alike.