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

Prior to plasma transfusion and experimental infection (day 0), all cats in both groups tested Mhf PCR-negative. All cats in groups A and B became Mhf PCR-positive within 7-31 days and 7-38 days pi, respectively ( Figures 1A and B) , except for one cat (JHW3) in group B. Cat JHW3 remained PCR-negative throughout the 100-day follow-up period ( Figure 1B ) but became Mhf PCR-positive after the end of the experiment (day 154 pi, data not shown). Peak hemoplasma loads (group A: 2.3 × 10 8 -1.7 × 10 9 copies/mL blood; group B 1.8 × 10 8 -8.6 × 10 8 copies/mL blood) were reached between days 17 and 49 pi in group A and days 17 and 63 pi in group B. There was no significant difference in Mhf blood loads between the two groups during the 100-day follow-up period, except for day 100 pi, when group A showed significantly higher Mhf blood loads (p MWU = 0.0280; Figure 1C ); this difference was not significant when the PCR-negative cat JHW3 in group B was excluded from the analysis (p MWU = 0.0759).