Analysis of the roles of antilipopolysaccharide and anti-cholera toxin immunoglobulin A (IgA) antibodies in protection against Vibrio cholerae and cholera toxin by use of monoclonal IgA antibodies in vivo

Abstract

Secretory immunoglobulin A (IgA) antibodies (sIgA) directed against cholera toxin (CT) and surface components of Vibrio cholerae are associated with protection against cholera, but the relative importance of specific sIgAs in protection is unknown. A monoclonal IgA directed against the V. cholerae lipopolysaccharide (LPS), secreted into the intestines of neonatal mice bearing hybridoma tumors, was previously shown to provide protection against a lethal oral dose of 107 V. cholerae cells. We show here that a single oral dose of 5 to 50 Lg of the monoclonal anti-LPS IgA, given within 2 h before V. cholerae challenge, protected neonatal mice against challenge. In contrast, an oral dose of 80 tLg of monoclonal IgA directed against CT B subunit (CTB) failed to protect against V. cholerae challenge. A total of 80 pg of monoclonal anti-CTB IgA given orally protected neonatal mice from a lethal (5-.g) oral dose of CT. Secretion of the same anti-CTB IgA antibodies into the intestines of mice bearing IgA hybridoma backpack tumors, however, failed to protect against lethal oral doses of either CT (5 jg) or V. cholerae (107 cells). Furthermore, monoclonal anti-CTB IgA, either delivered orally or secreted onto mucosal surfaces in mice bearing hybridoma tumors, did not significantly enhance protection over that provided by oral anti-LPS IgA alone. These results demonstrate that anti-LPS sIgA is much more effective than anti-CT IgA in prevention of V. chokerae-induced diarrheal disease.

Distribution of Monoclonal Antibodies in Intestinal and Urogenital Secretions of Mice Bearing Hybridoma ‘Backpack’ Tumours

“…In previous studies we observed that the rate of tumour growth in vivo tends to roughly parallel the rate of growth of the corresponding hybridoma cells in culture [4,5]. In this study, mice injected with IgA hybridoma cells began to show visible tumours at the injection site 2 days before those with IgG hybridoma cells.…”

“…It has been difficult to directly assess the contribution of secretory IgA to mucosal protection, however, because of the technical difficulties in collecting local mucosal secretions and the complexity of immune responses after oral immunization or microbial challenge. One approach to this problem has been to generate monoclonal, dimeric IgA antibodies that can be fed orally [4,5], delivered to the respiratory mucosa by nose drops [6], or applied directly to epithelial cells in culture [7,8]. Such studies have demonstrated that specific IgA antibodies can indeed protect against viral infection, bacterial invasion and toxin binding.…”

“…The hybridoma cells are injected subcutaneously on the upper backs of naive, syngeneic mice where they grow to form hybridoma tumours that release monoclonal, dimeric IgA into the circulation. The 'backpack' tumour method was used to demonstrate that secretion of a single monoclonal IgA antibody can protect mice against mucosal colonization and disease caused by Vibrio cholerae [4,5], and can protect against mucosal invasion and systemic disease caused by Salmonella typhimurium [11].…”

The ABCs (Antibody, B Cells, and Carbohydrate Epitopes) of Cholera Immunity: Considerations for an Improved Vaccine

“…The mechanism of protection in the mouse model is not known and may depend on the specificity of the antibody. The use of Fab fragments which do not fix complement and the efficacy of anti-LPS IgA which does not fix complement, suggests that complement is not required for protection in the infant mouse model (8,217). The prevention of colonization is a major finding in studies that examine the protective capacity of various antisera or antibodies.…”

Cervical Secretions in Pregnant Women Colonized Rectally with Group B Streptococci have High Levels of Antibodies to Serotype III Polysaccharide Capsular Antigen and Protein R

“…Mucosal antibodies may protect against invasive infections but still permit colonization, which is the case for commensal bacteria in the gut [31,32]. On the other hand, they may eradicate microbes from the mucosal surface, as demonstrated for Respiratory Syncytial Virus (RSV) and Haemophilus influenzae in the respiratory tract [33,34], or Vibrio cholera, Helicobacter felis and Salmonella typhimurium in the gut [35][36][37]. Although persistent colonization or eradication may be determined by the quantity of the local antibodies [38,39], there is also evidence that their specificity to the different microbial epitopes [40], as well as their avidity [41], is important.…”