Rationalizing Random Walks: Replicating Protective Antibody Trajectories

mRNA-LNP HIV-1 trimer boosters elicit precursors to broad neutralizing antibodies

Germline-targeting (GT) HIV vaccine strategies are predicated on deriving broadly neutralizing antibodies (bnAbs) through multiple boost immunogens. However, as the recruitment of memory B cells (MBCs) to germinal centers (GCs) is inefficient and may be derailed by serum antibody-induced epitope masking, driving further B cell receptor (BCR) modification in GC-experienced B cells after boosting poses a challenge. Using humanized immunoglobulin knockin mice, we found that GT protein trimer immunogen N332-GT5 could prime inferred-germline precursors to the V3-glycan-targeted bnAb BG18 and that B cells primed by N332-GT5 were effectively boosted by either of two novel protein immunogens designed to have minimum cross-reactivity with the off-target V1-binding responses. The delivery of the prime and boost immunogens as messenger RNA lipid nanoparticles (mRNA-LNPs) generated long-lasting GCs, somatic hypermutation, and affinity maturation and may be an effective tool in HIV vaccine development.

Structure-guided stabilization improves the ability of the HIV-1 gp41 hydrophobic pocket to elicit neutralizing antibodies

The hydrophobic pocket found in the N-heptad repeat (NHR) region of HIV-1 gp41 is a highly conserved epitope that is the target of various HIV-1-neutralizing monoclonal antibodies. Although the high conservation of the pocket makes it an attractive vaccine candidate, it has been challenging to elicit potent anti-NHR antibodies via immunization. Here, we solved a high-resolution structure of the NHR mimetic IQN17, and, consistent with previous ligand-bound gp41 pocket structures, we observed remarkable conformational plasticity of the pocket. The high malleability of this pocket led us to test whether we could improve the immunogenicity of the gp41 pocket by stabilizing its conformation. We show that the addition of five amino acids at the C terminus of IQN17, to generate IQN22, introduces a stabilizing salt bridge at the base of the peptide that rigidifies the pocket. Mice immunized with IQN22 elicited higher avidity antibodies against the gp41 pocket and a more potent, albeit still weak, neutralizing response against HIV-1 compared with IQN17. Stabilized epitope-focused immunogens could serve as the basis for future HIV-1 fusion-inhibiting vaccines.

Application of IgG antibody titer and subtype in diagnosis and severity assessment of hemolytic disease of the newborn

BACKGROUND

To analyze the effect of different times of pregnancy of type O pregnant women on the occurrence of ABO hemolytic disease of the newborn (ABO-HDN).

METHODS

From December 2018 to December 2021, 725 pregnant women with O blood group (husbands with non-O blood group) who met the inclusion criteria were collected. There were 116 cases of ABO-HDN, which were summarized and analyzed. The pregnant women were divided into primigravida and non-primigravida groups. The influence of the number of pregnancies on the occurrence of ABO-HDN was compared, and the antibody titer of pregnant women with type O blood was monitored. The relationship between antibody titer and HDN in pregnant women was analyzed by hemolysis test and indirect bilirubin concentration.

RESULTS

In the primigravida group, 0 patients with HDN had a titer ≤1:64, 8 (8/26) had a titer of 1:128, 9 (9/20) had a titer of 1:256, 2 (2/4) had a titer of 1:512, and 2 (2/3) had a titer >1:512. In the non-primigravida group, there were 0 cases with a titer ≤1:64, 32 cases (32/78) with a titer of 1:128, and 26 cases (26/46) with a titer of 1:256. The number of cases of ABO incompatibility in maternal and infant groups with different titers of IgG anti-A (B) antibody were 377 cases in the <1:64 group, 130 cases in the 1:64 group, 104 cases in the 1:128 group, 66 cases in the 1:256 group, 32 cases in the 1:512 group, and 16 cases in the >1:512 group. The positive rates of ABO-HDN were 0.0% (0/0), 0.0% (0/0), 38.5% (40/104), 53.0% (35/66), 81.3% (26/32) and 93.8% (15/16), respectively, and the difference was statistically significant (P<0.05).

CONCLUSIONS

The occurrence of ABO-HDN was not significantly related to the blood type of the pregnant woman's husband. Therefore, in order to reduce the degree of hemolysis and avoid the occurrence of bilirubin encephalopathy or even death, pregnant women with antibody titer >1:64 in second or subsequent pregnancies should be closely monitored.

Persistent immunogenicity of integrase defective lentiviral vectors delivering membrane-tethered native-like HIV-1 envelope trimers

Integrase Defective Lentiviral Vectors (IDLVs) represent an attractive vaccine platform for delivering HIV-1 antigens, given their ability to induce specific and persistent immune responses in both mice and non-human primates (NHPs). Recent advances in HIV-1 immunogen design demonstrated that native-like HIV-1 Envelope (Env) trimers that mimic the structure of virion-associated Env induce neutralization breadth in rabbits and macaques. Here, we describe the development of an IDLV-based HIV-1 vaccine expressing either soluble ConSOSL.UFO.664 or membrane-tethered ConSOSL.UFO.750 native-like Env immunogens with enhanced bNAb epitopes exposure. We show that IDLV can be pseudotyped with properly folded membrane-tethered native-like UFO.750 trimers. After a single IDLV injection in BALB/c mice, IDLV-UFO.750 induced a faster humoral kinetic as well as higher levels of anti-Env IgG compared to IDLV-UFO.664. IDLV-UFO.750 vaccinated cynomolgus macaques developed unusually long-lasting anti-Env IgG antibodies, as underlined by their remarkable half-life both after priming and boost with IDLV. After boosting with recombinant ConM SOSIP.v7 protein, two animals developed neutralization activity against the autologous tier 1B ConS virus mediated by V1/V2 and V3 glycan sites responses. By combining the possibility to display stabilized trimeric Env on the vector particles with the ability to induce sustained humoral responses, IDLVs represent an appropriate strategy for delivering rationally designed antigens to progress towards an effective HIV-1 vaccine.

Individualized VDJ recombination predisposes the available Ig sequence space

The process of recombination between variable (V), diversity (D), and joining (J) immunoglobulin (Ig) gene segments determines an individual's naive Ig repertoire and, consequently, (auto)antigen recognition. VDJ recombination follows probabilistic rules that can be modeled statistically. So far, it remains unknown whether VDJ recombination rules differ between individuals. If these rules differed, identical (auto)antigen-specific Ig sequences would be generated with individual-specific probabilities, signifying that the available Ig sequence space is individual specific. We devised a sensitivity-tested distance measure that enables inter-individual comparison of VDJ recombination models. We discovered, accounting for several sources of noise as well as allelic variation in Ig sequencing data, that not only unrelated individuals but also human monozygotic twins and even inbred mice possess statistically distinguishable immunoglobulin recombination models. This suggests that, in addition to genetic, there is also nongenetic modulation of VDJ recombination. We demonstrate that population-wide individualized VDJ recombination can result in orders of magnitude of difference in the probability to generate (auto)antigen-specific Ig sequences. Our findings have implications for immune receptor-based individualized medicine approaches relevant to vaccination, infection, and autoimmunity.