Passive immunization does not provide protection against experimental infection with Mycoplasma haemofelis

Sugiarto, Sarah; Spiri, Andrea M.; Riond, Barbara; Novacco, Marilisa; Oestmann, Angelina; de Miranda, Luisa H. Monteiro; Meli, Marina L.; Boretti, Felicitas S.; Hofmann-Lehmann, Regina; Willi, Barbara

For passive immunization, a total of 118 mL of plasma was collected from the three cats that had overcome previous Mhf infection (HBU2, HBZ2 and HCD2) [28] . The plasma was collected from these cats on day 538 post Mhf inoculation. HBU2 had cleared the infection without treatment, whereas HBZ2 and HCD2 had received antibiotic treatment to clear the infection (HBZ2: 10 mg/kg/day doxycycline for 44 days; HCD2: 10 mg/ kg/day doxycycline for 27 days, followed by 2 mg/kg/ day marbofloxacin for 23 days); in the latter two cats, antibiotic treatment was stopped 59-129 days prior to plasma collection. All cats tested negative for Mhf for at least eight consecutive weeks following antibiotic treatment and prior to the plasma collection, as determined using weekly collected blood samples that were analyzed in triplicate with a Mhf-specific qPCR assay [12] . For plasma transfusion of the control cats, a total of 70 mL of plasma from two adult naïve SPF cats (GCN5 and JCR4) was collected. Prior to plasma collection, the two cats were confirmed to be negative for all three feline hemoplasmas using qPCR [12] and to be free from all commonly known feline pathogens, as described [19] .