ABSTRACT
We used the recombinant trimeric spike (S) glycoprotein in the prefusion conformation to immunize horses for the production of hyperimmune globulins against SARS-CoV-2. Serum antibody titers measured by ELISA were above 1:106, and the neutralizing antibody titer against authentic virus (WT) was 1:14,604 (average PRNT90). Plasma from immunized animals was pepsin digested to remove the Fc portion and purified, yielding an F(ab')2 preparation with PRNT90 titers 150-fold higher than the neutralizing titers in human convalescent plasma. Challenge studies were carried out in hamsters and showed the in vivo ability of equine F(ab')2 to reduce viral load in the pulmonary tissues and significant clinical improvement determined by weight gain. The neutralization curve by F(ab')2 was similar against the WT and P.2 variants, but displaced to higher concentrations by 0.39 log units against the P.1 (Gamma) variant. These results support the possibility of using equine F(ab')2 preparation for the clinical treatment of COVID patients.
ABSTRACT
Leptospirosis is a zoonotic disease of global importance, and has a worldwide distribution. Equine leptospirosis is commonly manifested by recurrent uveitis, reproductive disorders, as abortions, embryonic absorption, stillbirth and the birth of weak foals. The aim of this study was to verify the presence of Leptospira sp or its DNA in genital tract of mares with reproductive problems. A total of 38 mares with reproductive problems were studied. All the mares were sampled for blood (for serology), urine (for culturing and qPCR), vaginal fluid-VF and endometrial biopsy-EB (for culturing, qPCR and indirect immunofluorescence). PCRs products were sequenced for secY gene. Seventeen (44.7%) serum samples were reactive, predominantly against serogroups Australis (76.4%) and Pomona (23.6%). No positive culture was obtained, but DNA was detected by qPCR on urine samples (26.3%), VF (44.7%) and EB (18.4%) collected 2 months or longer following diagnosis of early fetal death and endometritis. Leptospira cell aggregations were visible by indirect immunofluorescence on 57.1% (4/7) EBs and 17.6% (3/17) VFs. A total of 18 amplicons showed interpretable sequences. Out of those 18 amplicons, 15 presented 100% of identity with the species L. interrogans (sv Bratislava and Pomona), while three were L. borgpertersenii. This study suggests the presence of leptospires in the uterus of mares with reproductive problems. Moreover, serology was shown not to be indicated for the diagnosis of presumptive Leptospira infection in early gestation. The most common agent of the genital infection in those mares was L. interrogans, most probably sg Australis.
