Ehrlichia chaffeensis, Anaplasma phagocytophilum and Anaplasma platys are obligatory intracellular Gram-negative bacteria belong to the family Anaplasmataceae.
E. chaffeensis had lost lipopolysaccharide and peptidoglycan which are pathogen-associated molecular patterns (PAMPs) but kept other PAMPs, such as lipoproteins. In my dissertation research, using the specific inhibitor in lipoprotein processing, I showed that lipoproteins were essential for ehrlichial survival in vitro. The majority of putative lipoproteins can be detected expressed in cell culture. An E. chaffeensis infected dog developed antibodies against selected three lipoproteins and a strong delayed type hypersensitivity (DTH) to more than half of the putative lipoproteins.
The lipid moieties of lipoproteins are strong adjuvants for both humoral and cellular immunity. E. chaffeensis infected dogs developed strong cellular immunity to lipoproteins indicated by DTH. Selected lipoproteins with strong DTH reactions in E. chaffeensis infected dogs were used to immunize dogs in a DNA vaccine format. After immunization, vaccination group dogs developed humoral immunity and cellular immunity. Upon challenge with E. chaffeensis, immunized group dogs were transiently infected with E. chaffeensis at the same levels as the placebo immunized dogs. Thus, the lipoprotein DNA vaccine constructs was not protective against challenge.
P44s are A. phagocytophilum major outer membrane proteins encoded by a multi-gene family. They are always expressed in various systems, although different species of P44s are expressed. P44s are rich in â-strand structure. They have heat modifiability, a common feature of porin and other outer membrane proteins. The outer membrane of A. phagocytophilum has porin activity determined by proteoliposome swelling assay. The purified P44 protein has pore-forming activity.
Very little was known about prevalence of A. platys in endemic area, Venezuela and diversity around the world. By 16S rRNA PCR screening we found that around 16% of dogs samples tested was A. platys positive. By comparing 16S rRNA and groEL sequences of A. platys in Venezuela with other available sequences from all over the world, we conclude that divergence of A. platys around the world is quite small.