Antibody-Mediated Elimination of the Obligate Intracellular Bacterial PathogenEhrlichia chaffeensisduring Active Infection

Abstract

It is generally accepted that cellular, but not humoral immunity, plays an important role in host defense against intracellular bacteria. However, studies of some of these pathogens have provided evidence that antibodies can provide immunity if present during the initiation of infection. Here, we examined immunity against infection by Ehrlichia chaffeensis, an obligate intracellular bacterium that causes human monocytic ehrlichiosis. Studies with mice have demonstrated that immunocompetent strains are resistant to persistent infection but that SCID mice become persistently and fatally infected. Transfer of immune serum or antibodies obtained from immunocompetent C57BL/6 mice to C57BL/6 scid mice provided significant although transient protection from infection. Bacterial clearance was observed when administration occurred at the time of inoculation or well after infection was established. The effect was dose dependent, occurred within 2 days, and persisted for as long as 2 weeks. Weekly serum administration prolonged the survival of susceptible mice. Although cellular immunity is required for complete bacterial clearance, the data show that antibodies can play a significant role in the elimination of this obligate intracellular bacterium during active infection and thus challenge the paradigm that humoral responses are unimportant for immunity to such organisms.

A Variable-Length PCR Target Protein of Ehrlichia chaffeensis Contains Major Species-Specific Antibody Epitopes in Acidic Serine-Rich Tandem Repeats

“…Recently, a number of studies demonstrated that humoral immunity plays an essential role in host defenses against ehrlichial pathogens (10,33,34,36). Furthermore, a small subset of E. chaffeensis proteins, many of which contain tandem repeats (TRs), appear to be the primary targets of the humoral immune response and are considered to be the major immunoreactive proteins (4,5,15,30).…”

Farmacocinética y efectos adversos de la doxiciclina en el tratamiento de la Ehrlichiosis: fundamentos teóricos para ensayos clínicos en caninos

“…Los linfocitos B (CD21+) aumentan luego del tratamiento, sin embargo posterior y de manera gradual disminuyen a valores normales. La respuesta inmune humoral no se ha considerado un mecanismo protector contra la infección por Ehrlichia canis, por lo tanto el aumento inicial de linfocitos B podría estar relacionada con la eficacia terapéutica (36). Adicionalmente, el aumento de beta-globulinas luego del tratamiento con doxiciclina podría asociarse con el aumento de los linfocitos B (5).…”

“…Therefore, the initial increase in B lymphocytes may be related to therapeutic efficacy (36). Additionally, the increase in beta-globulins following doxycycline treatment could be associated with increased B lymphocytes (5).…”

Dinâmica da infecção experimental de cães por Ehrlichia canis: aspectos clínicos, laboratoriais e resposta imune humoral e celular

“…Como em todas as infecções por agentes infecciosos intracelulares, a extinção da infecção está intimamente ligada à imunidade celular, não se minimizando a importância da imunidade humoral WINSLOW et al, 2000). Na EMC há persistência da riquétsia no organismo hospedeiro, a despeito do alto título de anticorpos desenvolvidos , existindo evidências de que, para a adequada destruição intracelular do agente infeccioso há necessidade da interação entre a resposta humoral e celular do hospedeiro .…”

“…A resposta humoral na fase precoce da infecção por E. chaffeensis (WINSLOW et al, 2000) bem como a ativação das células T CD4+, resultam na imunidade do hospedeiro a E.…”