Lawrence T. Wang

Current HIV vaccines designed to stimulate CD8 ⁺ T cells have failed to induce immunologic control upon infection. The functions of vaccine-induced HIV-specific CD8 ⁺ T cells were investigated here in detail. Cytotoxic capacity was significantly lower than in HIV controllers and was not a consequence of low frequency or unaccumulated functional cytotoxic proteins. Low cytotoxic capacity was attributable to impaired degranulation in response to the low antigen levels present on HIV-infected targets. The vaccine-induced T cell receptor (TCR) repertoire was polyclonal and transduction of these TCRs conferred the same reduced functions. These results define a mechanism accounting for poor antiviral activity induced by these vaccines and suggest that an effective CD8 ⁺ T cell response may require a vaccination strategy that drives further TCR clonal selection.

Combinations of monoclonal antibodies (mAbs) against different epitopes on the same antigen synergistically neutralize many viruses. However, there are limited studies assessing whether combining human mAbs against distinct regions of thePlasmodium falciparum(Pf) circumsporozoite protein (CSP) enhancesin vivoprotection against malaria compared to each mAb alone or whether passive transfer of PfCSP mAbs would improve protection following vaccination against PfCSP. Here, we isolated a panel of human mAbs against the subdominant C-terminal domain of PfCSP (C-CSP) from a volunteer immunized with radiation-attenuated Pf sporozoites. These C-CSP-specific mAbs had limited binding to sporozoitesin vitrothat was increased by combination with neutralizing human “repeat” mAbs against the NPDP/NVDP/NANP tetrapeptides in the central repeat region of PfCSP. Nevertheless, passive transfer of repeat- and C-CSP-specific mAb combinations did not provide enhanced protection againstin vivosporozoite challenge compared to repeat mAbs alone. Furthermore, combining potent repeat-specific mAbs (CIS43, L9, and 317) that respectively target the three tetrapeptides (NPDP/NVDP/NANP) did not provide additional protection againstin vivosporozoite challenge. However, administration of either CIS43, L9, or 317 (but not C-CSP-specific mAbs) to mice that had been immunized with R21, a PfCSP-based virus-like particle vaccine that induces polyclonal antibodies against the repeat region and C-CSP, provided enhanced protection against sporozoite challenge when compared to vaccine or mAbs alone. Collectively, this study shows that while combining mAbs against the repeat and C-terminal regions of PfCSP provide no additional protectionin vivo, repeat mAbs do provide increased protection when combined with vaccine-induced polyclonal antibodies. These data should inform the implementation of PfCSP human mAbs alone or following vaccination to prevent malaria infection.

Rare and potent monoclonal antibodies (mAbs) against the Plasmodium falciparum (Pf) circumsporozoite protein (CSP) on infective sporozoites (SPZ) preferentially bind the PfCSP junctional tetrapeptide NPDP or NVDP minor repeats while cross-reacting with NANP central repeats in vitro. The extent to which each of these epitopes is required for protection in vivo is unknown. Here, we assessed whether junction-, minor repeat- and central repeat-preferring human mAbs (CIS43, L9 and 317 respectively) bound and protected against in vivo challenge with transgenic P. berghei (Pb) SPZ expressing either PfCSP with the junction and minor repeats knocked out (KO), or PbCSP with the junction and minor repeats knocked in (KI). In vivo protection studies showed that the junction and minor repeats are necessary and sufficient for CIS43 and L9 to neutralize KO and KI SPZ, respectively. In contrast, 317 required major repeats for in vivo protection. These data establish that human mAbs can prevent malaria infection by targeting three different protective epitopes (NPDP, NVDP, NANP) in the PfCSP repeat region. This report will inform vaccine development and the use of mAbs to passively prevent malaria.

L9 is a potent human monoclonal antibody (mAb) that preferentially binds two adjacent NVDP minor repeats and cross-reacts with NANP major repeats of the Plasmodium falciparum circumsporozoite protein (PfCSP) on malaria-infective sporozoites. Understanding this mAb’s ontogeny and mechanisms of binding PfCSP to neutralize sporozoites will facilitate vaccine development. Here, we isolated mAbs clonally related to L9 and showed that this B-cell lineage has baseline NVDP affinity and evolves to acquire NANP reactivity. Pairing the L9 kappa light chain (L9κ) with clonally-related heavy chains resulted in chimeric mAbs that cross-linked two NVDP, cross-reacted with NANP, and more potently neutralized sporozoites compared to their original light chain. Structural analyses revealed that chimeric mAbs bound the minor repeat motif in a type-1 β-turn seen in other repeat-specific antibodies. These data highlight the importance of L9κ in binding NVDP on PfCSP to neutralize SPZ and suggest that PfCSP-based immunogens might be improved by presenting ≥2 NVDP.

A functional human IgA response to malaria targets a conserved epitope in the N terminus of the Plasmodium falciparum circumsporozoite protein.

Malaria is a leading cause of paediatric morbidity and mortality in Uganda. More than half of febrile children in rural areas initially seek care at private clinics and drug shops. These shops are generally unregulated and the quality of clinical care is variable, with the potential for misdiagnosis and the development of drug resistance. There is thus an urgent need to identify rural drug shops and coordinate their malaria treatment efforts with those of the public sector. The objective of the study was to identify all drug shops in the Bugoye sub-county of Western Uganda and assess their anti-malarial dispensing practices. This study is a cross-sectional survey of drug shops in a rural sub-county of Western Uganda. In the first phase, shop locations, licensing and shopkeeper’s qualifications, and supply and pricing of anti-malarials were characterized. In the second phase, the proportion of anti-malarials dispensed by private drug shops was compared to public health facilities. A total of 48 drug shops were identified. Only one drug shop (1 of 48, 2%) was licensed with the sub-county’s records office. The drug shops stocked a variety of anti-malarials, including first-line therapies and less effective agents (e.g., sulfadoxine/pyrimethamine). Almost all drug shops (45 of 48, 94%) provided parenteral anti-malarials. Of the 3900 individuals who received anti-malarials during the study, 2080 (53.3%) purchased anti-malarials through the private sector compared to 1820 (46.7%) who obtained anti-malarials through the public sector. Drug shops were the primary source of parenteral anti-malarials. Inadequate dosing of anti-malarials was more common in drug shops. Drug shops are major sources of parenteral anti-malarials, which should be reserved for cases of severe malaria. Strengthening malaria case management and incorporating drug shops in future interventions is necessary to optimize malaria control efforts in the sub-county, and in similarly endemic regions.

Study Design: This is a cadaveric biomechanical study evaluating the biomechanical properties of a novel spinopelvic fixation technique with percutaneous lumbo-sacro-iliac (LSI) screws in an unstable total sacrectomy model. Objective: To compare standard posterior dual rod spinopelvic fixation alone with dual rod fixation supplemented with LSI screw fixation. Summary of Background Data: Primary or metastatic tumors of the sacrum requiring a total sacrectomy can result in spinopelvic instability if inadequate fixation is achieved. Many fixation techniques have been proposed to address this instability. However, to date, an optimal fixation technique has not been established. Materials and Methods: Ten fresh-frozen cadaveric spinopelvic specimens were randomized according to bone mineral density (BMD) to either posterior rod fixation (control group) or posterior rod fixation with supplemental LSI screws (LSI group). After fixation, a total sacrectomy of each specimen was performed. Specimens where then potted and axially loaded in a caudal direction. Stiffness, yield load, energy absorbed at yield load, ultimate load, and energy absorbed at ultimate load were computed. A Student t test was used for statistical analysis with significance set at PP=0.255; BMD: P=0.810). After normalizing for BMD, there were no significant differences detected for any of the biomechanical parameters measured between the 2 fixation techniques: stiffness (P=0.857), yield load (P=0.219), energy at yield load (P=0.293), ultimate load (P=0.407), and energy at ultimate load (P=0.773). However, both fixation techniques were able to withstand physiological loads. Conclusions: Our study did not demonstrate any biomechanical advantage for supplemental LSI screw fixation in our axial loading model. However, given the theoretical advantage of this percutaneous technique, further studies are warranted that take into account forward bending and sagittal stability.