The level of naturally occurring anti-αGal antibody predicts antibody response to polysaccharide vaccination in HIV-infected adults.

In clinical practice, the capacity for producing anti-carbohydrate antibodies is regarded as an entity, but supportive evidence is lacking. We hypothesized that the outcome of the gold standard test for clinical assessment of this capacity, antibody response to polysaccharide vaccination, correlated with the level of the abundant naturally occurring anti-carbohydrate antibody, anti-αGal. To perform an exploratory study, 47 HIV-infected adults were recruited from a vaccine trial. Participants received a 23-valent pneumococcal capsular polysaccharide vaccine. Plasma samples obtained just before and median 4 weeks after the vaccination were quantified for IgG anti-αGal antibody and IgG antibodies to polysaccharides present in the vaccine (serotypes 1, 7F and 19A) by solid-phase type immunoassays. The vaccination responses were assessed as a categorical variable (based on criteria defined by The American Academy of Allergy, Asthma & Immunology and the American College of Allergy, Asthma & Immunology) and as three different continuous variables (antibody increment, geometrical average and standard normal deviates of the achieved antibody concentrations). The baseline anti-αGal level predicted the vaccine response as a categorical variable (ROC-curve analysis, AUC = 0.71; 95%CI: 0.55-0.86) and as the three continuous variables (eg slope of linear regression of geometrical average = 0.37; 95%CI: 0.15-0.59). The correlation between the anti-αGal level and antibody responses to polysaccharide vaccination fits with a shared underlying capacity. Thus, the present study supports the notion of a measurable capacity for the production of anti-carbohydrate antibodies in each individual. Firm conclusions on the generalizability and clinical utility require further studies.