In previous studies, our lab has characterized a number of highly mutated antibodies against structural epitopes of the human immunodeficiency virus (HIV) envelope protein. These antibodies were first isolated from long-term nonprogressors (LTNPs). We have previous mapped 6F5 to a novel structural epitope that encompasses areas in both heptad repeats of GP41, mapping to amino acids of 557, 654 and 657 of reference sequence HXB2. In these studies, three other antibodies that were <90% homologous to 6F5 also resolved amino acid 657. On sequence analysis, 6F5 and its relatives had the same gene usage and general structure. These similarities and the similar epitope mapping implied these were once distantly related to a single B-cell lineage. As fusion of the viral membrane to the target cell depends on these heptad repeat regions associating and forming a six-helix postfusion bundle, antibodies that can interfere in this may be highly useful. See results. Because 6F5 maps to 557 and 654/657 which are widely separated on the primary sequence, we explored if there was differential binding to the postfusion six-helix-bundle form. Two peptides (N36 and C34) each containing one of the heptad repeats can form the post-fusion six-helix-bundle in vitro. On sandwich ELISA testing, 6F11 and 7B6 did not bind any form. Interestingly, 4E4 specifically captured both peptides alone, but not the six-helix-bundle and 6F5 only bound the six-helix-bundle but not the other peptide. A small number of samples were obtained to assess the prevalence of these responses in LTNPs. Antibodies that compete 6F11 are much more prevalent in LTNPs than normal progressors (75% vs. 20%). Functionally, we found that despite being mapped to a similar portion of Gp41 (657), only 6F5 is shown to have significant ADCC activity, however relative 6F11 does not. If targeting these epitopes correlates with the LTNP state, then these sites may be highly significant as targets of therapeutics or in vaccine strategies. Further studies on a larger cohort of LTNPs are ongoing. Additionally, deep sequencing of antibody sequences are being done to explore the development of structural epitope targeting by this family of antibodies. All authors: No reported disclosures.
With recent reports showing clinical and laboratory overlap of multisystem inflammatory syndrome in children and Kawasaki disease (KD), we addressed the hypothesis that cross coronavirus humoral immunity leads to a parallel postinfectious phenomenon explaining similar pathologic findings in KD and multisystem inflammatory syndrome in children. We demonstrated no cross-reactivity in children with KD but observed some nonspecific interactions postintravenous immunoglobulin infusion.
Kawasaki disease (KD) is one of the leading causes of acquired heart disease in children in developed nations. Epidemiologic evidence suggests that KD is related to an infectious agent; however, the cause remains unknown. Yearly incidence in Japan has been steadily increasing, but few long-term databases of KD cases from North America have been reviewed.We reviewed the epidemiology of local cases over a 16-year period to study incidence with time and temporal and geographic clustering of cases in a representative cohort in North America.The yearly incidence in cases per population <5 years old per 100,000 was 20.2 and 15.9, using International Classification of Disease, ninth revision and detailed chart review, respectively. Using International Classification of Disease, ninth revision alone overestimates our incidence by 27%. We show a distinct seasonality of cases with winter predominance. Applying Kulldorff's spatial scan statistic revealed no significant clustering of cases with either purely spatial or space-time analyses. On purely nonconstrained temporal SaTScan analysis, there was a significant clustering of cases in a 67- to 68-week period in 2000-2001.Our analysis reveals an apparent outbreak of KD in our region in 2000-2001. In contrast to Japan, for the last 14 years, the incidence in our region has been stable.
The human antibody response against HIV-1 infection recognizes diverse antigenic subunits of the virion, and includes a high level of antibodies to the Gag protein. We report here the isolation and characterization of a subset of Gag-specific human monoclonal antibodies (mAbs) that were prevalent in the antibody repertoire of an HIV-infected individual. Several lineages of Gag-specifc mAbs were encoded by a single antibody heavy chain variable region, VH4-59, and a representative antibody from this group designated mAb 3E4 recognized a linear epitope on the globular head of the p17 subunit of Gag. We found no evidence that mAb 3E4 exhibited any function in laboratory studies aimed at elucidating the immunologic activity, including assays for neutralization, Ab-dependent cell-mediated virus inhibition, or enhanced T cell reactivity caused by Gag-3E4 complexes. The findings suggest this immunodominant epitope in Gag protein, which is associated with VH4-59 germline gene usage, may induce a high level of B cells that encode binding but non-functional antibodies that occupy significant repertoire space following HIV infection. The studies define an additional specific molecular mechanism in the immune distraction activity of the HIV virion.
