Systemic administration of a potent mouse monoclonal antibody provides multisite protection against HPV16 infection.

Although preventive vaccines for Human Papillomaviruses (HPV) are available, a definitive cure for the viral infection itself is currently lacking. There is a sizable population that remains inaccessible to HPV vaccination due to reasons such as high costs or lack of availability of the vaccines. Therefore, there remains a significant population susceptible to HPV infection. Persistent multisite infections with high-risk HPV types can cause cancer at several different anatomic sites.Especially HPV16 is a key etiologic factor for cervical, other ano-genital and oropharyngeal cancers. Therefore, it is imperative to develop pharmaceutical interventions for the treatment of viral infections. In this study, a panel of 9 neutralizing antibodies was screened using the hybridoma technique, with 20F6 being identified as the representative antibody. The purified 20F6 exhibited an IC50 of 0.0011 µg/ml against HPV16, demonstrating potent viral inhibitory activity. Moreover, it displayed cross-neutralizing efficacy towards other Alphapapillom 9 subtypes including HPV31, HPV33, HPV52, and HPV58 with respective IC50 values of 2.0 µg/ml, 7.3 µg/ml, 1.7 µg/ml, and 3.0 µg/ml. 20F6 recognizes the linear epitope MSLW, the first four amino-acids located at the very N-terminus of the HPV16 L1 protein. Administration of 20F6, 24 h prior to and following HPV16 pseudo-virion (PSV) challenge, conferred protection against infection in mice at doses as low as 1 mg/kg. Following intraperitoneal administration of 20F6, neutralizing antibodies were consistently detected at both oral and vaginal sites, indicating that prophylactic systemic administration of 20F6 may confer efficient protection against multiple susceptible mucosal sites.

Susceptibility to lenacapavir, fostemsavir and broadly neutralizing antibodies in French primary HIV-1 infected patients in 2020-2023.

Surveillance studies of Transmitted Drug Resistance (TDR) are crucial in tracking the evolution of HIV epidemiology. Our aim was to investigate TDR to nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), integrase inhibitors (INIs), as well as to new drugs: lenacapavir, fostemsavir. Predictive sensitivity was evaluated for maraviroc and broadly neutralizing antibodies (bNAbs) (zinlirvimab and teropavimab). Between 2020 and 2023, 85 people with HIV (PWH) were diagnosed with primary HIV-1 infection (PHI). Pol and env sequences were analyzed and TDR was characterized according to the French ANRS algorithm. The genotypic-based prediction of bNAbs sensitivity was based on HIV env amino acid signatures I108, I201, F353 for teropavimab and N325, N332, H330 for zinlirvimab. TDR to NRTIs, NNRTIs, PIs and INIs was evidenced in 8.2%, 12.9%, 4.7%, and 5.9% strains, respectively. Ten viruses were CXCR4/dual mix. All viruses were susceptible to lenacapavir (100%) and 52% harbored resistance to fostemsavir. The genotypic profile was associated with a predictive positive value (PPV) > 83% of susceptibility to both teropavimab and zinlirvimab for 23 viruses (31%), while 22 (29%) had a PPV between 62% and 75%, suggesting reduced susceptibility to both bNAbs as soon as primary infection. The surveillance of TDR evidenced at the time of PHI is important with regard to new strategies for HIV patients with virological failure and global implementation of PrEP using NRTI, INI such as recently approved injectable cabotegravir, and future long-acting drugs such as lenacapavir and bNAbs.

Detection of Neutralizing Antibodies in Serum Samples Using a SARS-CoV-2 Pseudotyped Virus Assay.

Conventional live virus research on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of coronavirus disease-19 (COVID-19), requires Biosafety Level 3 (BSL-3) facilities. SARS-CoV-2 pseudotyped viruses have emerged as valuable tools in virology, mimicking the entry process of the SARS-CoV-2 virus into human cells by expressing its spike glycoprotein in a surrogate system using recombinant plasmids. One significant application of this tool is in functional assays for the evaluation of neutralizing antibodies. Pseudotyped viruses have the advantage of being competent for only a single cycle of infection, providing better safety and versatility and allowing them to be studied in BSL-2 laboratories. Here, we describe three protocols for the detection of SARS-CoV-2 neutralizing antibodies through a pseudotyped virus assay. First, SARS-CoV-2 S pseudotyped viruses (PV SARS-CoV-2 S) are produced using a Moloney murine leukemia virus (MuLV) three-plasmid system. The plasmids are designed to express the GagPol packing proteins, enhanced green fluorescent protein (eGFP) as a readout system, and the SARS-CoV-2 S protein modified to remove the endoplasmic reticulum retention domain and to improve infection. Next, the internalization of PV SARS-CoV-2 S protein in human embryonic kidney 293T (HEK-293T) cells overexpressing angiotensin-converting enzyme 2 (HEK-293T-ACE2) is confirmed by fluorescence microscopy and quantified using flow cytometry. Finally, PV SARS-CoV-2 S is used to screen neutralizing antibodies in serum samples from convalescent COVID-19 patients; it can also be used for studying the cell entry mechanisms of different SARS-CoV-2 variants, evaluating antiviral agents, and designing vaccines. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Generation of PV SARS-CoV-2 S pseudotyped virus Basic Protocol 2: Assay of PV SARS-CoV-2 S internalization in target cells. Basic Protocol 3: Detection of neutralizing antibodies in serum samples.

Jamaican fruit bats mount a stable and highly neutralizing antibody response after bat influenza virus infection.

Antibodies are an essential component of the antiviral response in many species, but to date, there is no compelling evidence that bats are capable of eliciting a robust humoral immunity, including neutralizing antibodies. Here, we report that infection of Jamaican fruit bats with the bat influenza A virus H18N11 elicits a rapid and stable humoral immune response with a strong neutralizing capacity, associated with no detectable viral shedding after repeat challenge infection. Thus, the neutralizing antibody response of bats might play an important role in the bat immunity.

Targeting RSV-neutralizing B cell receptors with anti-idiotypic antibodies.

Respiratory syncytial virus (RSV) causes lower respiratory tract infections with significant morbidity and mortality at the extremes of age. Vaccines based on the viral fusion protein are approved for adults over 60, but infant protection relies on passive immunity via antibody transfer or maternal vaccination. An infant vaccine that rapidly elicits protective antibodies would fulfill a critical unmet need. Antibodies arising from the VH3-21/VL1-40 gene pairing can neutralize RSV without the need for affinity maturation, making them attractive to target through vaccination. Here, we develop an anti-idiotypic monoclonal antibody (ai-mAb) immunogen that is specific for unmutated VH3-21/VL1-40 B cell receptors (BCRs). The ai-mAb efficiently engages B cells with bona fide target BCRs and does not activate off-target non-neutralizing B cells, unlike recombinant pre-fusion (preF) protein used in current RSV vaccines. These results establish proof of concept for using an ai-mAb-derived vaccine to target B cells hardwired to produce RSV-neutralizing antibodies.

Adenoviral fiber-knob based vaccination elicits efficient neutralizing antibodies and T cell responses against adenovirus infection.

BACKGROUND: Human adenoviruses (HAdVs) frequently cause common respiratory or gastrointestinal infections among children, adults, individuals with immune deficiencies, and other vulnerable populations with varying degree of symptoms, ranging from mild to server, and in some cases, even fatalities. Despite the significant clinical impact of HAdVs, there is currently no approved vaccine available. METHODS: This study explores the potential of the adenovirus type 5 fiber knob (Ad5-FK) to stimulate the production of Ad-specific neutralizing antibodies and T-cell responses in mice. Based on structure predictions, we first expressed Ad5-FK in E. coli and confirmed the assembly of FK into its trimeric form. After testing the binding capability of the trimeric FK to susceptible cells, the immunogenicity of the protein in combination with the c-di-AMP adjuvant was assessed in BALB/c mice. RESULTS: The purified Ad5-FK exhibited self-trimerization and maintained correct conformation akin to the authentic FK structure. This facilitated effective binding to susceptible HEK293 cells. Notably, the protein demonstrated significant inhibition of HEK293 cells infection by rAd5-GFP. Immunization of BALB/c mice with Ad5-FK, or Ad5-FK mixed with c-di-AMP yielded FK-specific antibodies with potent neutralization capacity. Significantly, Ad5-FK was found to elicit a vigorous CD4+ T-cell response in the immunized mice. CONCLUSION: Our findings underscore the efficacy of FK-based vaccine in eliciting anti-Ad humoral immune response and CD4 T-cell immune reactions essential for protection against viral infections.

Corrigendum: Six-month humoral immune response to inactivated COVID-19 vaccine among people living with HIV.

[This corrects the article DOI: 10.3389/fimmu.2022.988304.].

Structural Basis for Evasion of New SARS-CoV-2 Variants from the Potent Virus-Neutralizing Nanobody Targeting the S-Protein Receptor-Binding Domain.

COVID-19 has caused millions of deaths and many times more infections worldwide, emphasizing the unpreparedness of the global health system in the face of new infections and the key role for vaccines and therapeutics, including virus-neutralizing antibodies, in prevention and containment of the disease. Continuous evolution of the SARS-CoV-2 coronavirus has been causing its new variants to evade the action of the immune system, which highlighted the importance of detailed knowledge of the epitopes of already selected potent virus-neutralizing antibodies. A single-chain antibody ("nanobody") targeting the SARS-CoV-2 receptor-binding domain (RBD), clone P2C5, had exhibited robust virus-neutralizing activity against all SARS-CoV-2 variants and, being a major component of the anti-COVID-19 formulation "GamCoviMab", had successfully passed Phase I of clinical trials. However, after the emergence of the Delta and XBB variants, a decrease in the neutralizing activity of this nanobody was observed. Here we report on the successful crystal structure determination of the RBD:P2C5 complex at 3.1 Å, which revealed the intricate protein-protein interface, sterically occluding full ACE2 receptor binding by the P2C5-neutralized RBD. Moreover, the structure revealed the developed RBD:P2C5 interface centered around residues Leu452 and Phe490, thereby explaining the evasion of the Delta or Omicron XBB, but not Omicron B.1.1.529 variant, as a result of the single L452R or F490S mutations, respectively, from the action of P2C5. The structure obtained is expected to foster nanobody engineering in order to rescue neutralization activity and will facilitate epitope mapping for other neutralizing nanobodies by competition assays.

A monoclonal antibody targeting the Nipah virus fusion glycoprotein apex imparts protection from disease.

Nipah virus (NiV) is a highly pathogenic paramyxovirus capable of causing severe respiratory and neurologic disease in humans. Currently, there are no licensed vaccines or therapeutics against NiV, underscoring the urgent need for the development of countermeasures. The NiV surface-displayed glycoproteins, NiV-G and NiV-F, mediate host cell attachment and fusion, respectively, and are heavily targeted by host antibodies. Here, we describe a vaccination-derived neutralizing monoclonal antibody, mAb92, that targets NiV-F. Structural characterization of the Fab region bound to NiV-F (NiV-F-Fab92) by cryo-electron microscopy analysis reveals an epitope in the DIII domain at the membrane distal apex of NiV-F, an established site of vulnerability on the NiV surface. Further, prophylactic treatment of hamsters with mAb92 offered complete protection from NiV disease, demonstrating beneficial activity of mAb92 in vivo. This work provides support for targeting NiV-F in the development of vaccines and therapeutics against NiV.IMPORTANCENipah virus (NiV) is a highly lethal henipavirus (HNV) that causes severe respiratory and neurologic disease in humans. Currently, there are no licensed vaccines or therapeutics against NiV, highlighting a need to develop countermeasures. The NiV surface displays the receptor binding protein (NiV-G, or RBP) and the fusion protein (NiV-F), which allow the virus to attach and enter cells. These proteins can be targeted by vaccines and antibodies to prevent disease. This work describes a neutralizing antibody (mAb92) that targets NiV-F. Structural characterization by cryo-electron microscopy analysis reveals where the antibody binds to NiV-F to neutralize the virus. This study also shows that prophylactic treatment of hamsters with mAb92 completely protected against developing NiV disease. This work shows how targeting NiV-F can be useful to preventing NiV disease, supporting future studies in the development of vaccines and therapeutics.

The combination of three CD4-induced antibodies targeting highly conserved Env regions with a small CD4-mimetic achieves potent ADCC activity.

The majority of naturally elicited antibodies against the HIV-1 envelope glycoproteins (Env) are non-neutralizing (nnAbs) because they are unable to recognize the Env trimer in its native "closed" conformation. Nevertheless, it has been shown that nnAbs have the potential to eliminate HIV-1-infected cells by antibody-dependent cellular cytotoxicity (ADCC) provided that Env is present on the cell surface in its "open" conformation. This is because most nnAbs recognize epitopes that become accessible only after Env interaction with CD4 and the exposure of epitopes that are normally occluded in the closed trimer. HIV-1 limits this vulnerability by downregulating CD4 from the surface of infected cells, thus preventing a premature encounter of Env with CD4. Small CD4-mimetics (CD4mc) sensitize HIV-1-infected cells to ADCC by opening the Env glycoprotein and exposing CD4-induced (CD4i) epitopes. There are two families of CD4i nnAbs, termed anti-cluster A and anti-CoRBS Abs, which are known to mediate ADCC in the presence of CD4mc. Here, we performed Fab competition experiments and found that anti-gp41 cluster I antibodies comprise a major fraction of the plasma ADCC activity in people living with HIV (PLWH). Moreover, addition of gp41 cluster I antibodies to cluster A and CoRBS antibodies greatly enhanced ADCC-mediated cell killing in the presence of a potent indoline CD4mc, CJF-III-288. This cocktail outperformed broadly neutralizing antibodies and even showed activity against HIV-1-infected monocyte-derived macrophages. Thus, combining CD4i antibodies with different specificities achieves maximal ADCC activity, which may be of utility in HIV cure strategies.IMPORTANCEThe elimination of HIV-1-infected cells remains an important medical goal. Although current antiretroviral therapy decreases viral loads below detection levels, it does not eliminate latently infected cells that form the viral reservoir. Here, we developed a cocktail of non-neutralizing antibodies targeting highly conserved Env regions and combined it with a potent indoline CD4mc. This combination exhibited potent ADCC activity against HIV-1-infected primary CD4 + T cells as well as monocyte-derived macrophages, suggesting its potential utility in decreasing the size of the viral reservoir.

Optimal Humanized Scg3-Neutralizing Antibodies for Anti-Angiogenic Therapy of Diabetic Retinopathy.

Secretogranin III (Scg3) is a diabetic retinopathy (DR)-restricted angiogenic factor identified in preclinical studies as a target for DR therapy. Previously, our group generated and characterized ML49.3, an anti-Scg3 monoclonal antibody (mAb) which we then converted into an EBP2 humanized antibody Fab fragment (hFab) with potential for clinical application. We also generated anti-Scg3 mT4 mAb and related EBP3 hFab. In this study, to identify the preferred hFab for DR therapy, we compared all four antibodies for binding, neutralizing and therapeutic activities in vitro and in vivo. Octet binding kinetics analyses revealed that ML49.3 mAb, EBP2 hFab, mT4 mAb and EBP3 hFab have Scg3-binding affinities of 35, 8.7, 0.859 and 0.116 nM, respectively. Both anti-Scg3 EBP2 and EBP3 hFabs significantly inhibited Scg3-induced proliferation and migration of human umbilical vein endothelial cells in vitro, and alleviated DR vascular leakage and choroidal neovascularization with high efficacy. Paired assays in DR mice revealed that intravitreally injected EBP3 hFab is 26.4% and 10.3% more effective than EBP2 hFab and aflibercept, respectively, for ameliorating DR leakage. In conclusion, this study confirms the markedly improved binding affinities of hFabs compared to mAbs and further identifies EBP3 hFab as the preferred antibody to develop for anti-Scg3 therapy.

Fetal Zika virus inoculation in macaques revealed control of the fetal viral load during pregnancy.

BACKGROUND: Early pregnancy Zika virus (ZIKV) infection is associated with major brain damage in fetuses, leading to microcephaly in 0.6-5.0% of cases, but the underlying mechanisms remain largely unknown. METHODS: To understand the kinetics of ZIKV infection during fetal development in a nonhuman primate model, four cynomolgus macaque fetuses were exposed in utero through echo-guided intramuscular inoculation with 103 PFU of ZIKV at 70-80 days of gestation, 2 controls were mock inoculated. Clinical, immuno-virological and ultrasound imaging follow-ups of the mother/fetus pairs were performed until autopsy after cesarean section 1 or 2 months after exposure (n = 3 per group). RESULTS: ZIKV was transmitted from the fetus to the mother and then replicate in the peripheral blood of the mother from week 1 to 4 postexposure. Infected fetal brains tended to be smaller than those of controls, but not the femur lengths. High level of viral RNA ws found after the first month in brain tissues and placenta. Thereafter, there was partial control of the virus in the fetus, resulting in a decreased number of infected tissue sections and a decreased viral load. Immune cellular and humoral responses were effectively induced. CONCLUSIONS: ZIKV infection during the second trimester of gestation induces short-term brain injury, and although viral genomes persist in tissues, most of the virus is cleared before delivery.

Evaluation of three alternative methods to the plaque reduction neutralizing assay for measuring neutralizing antibodies to dengue virus serotype 2.

BACKGROUND: Dengue is a global public health challenge which requires accurate diagnostic methods for surveillance and control. The gold standard for detecting dengue neutralizing antibodies (nAbs) is the plaque reduction neutralization test (PRNT), which is both labor-intensive and time-consuming. This study aims to evaluate three alternative approaches, namely, the MTT-based (or (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) microneutralization assay, the xCELLigence real-time cell analysis (RTCA), and the immuno-plaque assay-focus reduction neutralization test (iPA-FRNT). METHODS: Twenty-two residual serum samples were tested for DENV-2 nAbs using all four assays at three neutralization endpoints of 50%, 70% and 90% inhibition in virus growth. For each neutralization endpoint, results were compared using linear regression and correlation analyses. Test performance characteristics were further obtained for iPA-FRNT using 38 additional serum samples. RESULTS: Positive correlation of DENV-2 neutralization titers for the MTT-based microneutralization assay and the PRNT assay was only observed at the neutralization endpoint of 50% (r = 0.690). In contrast, at all three neutralization end points, a linear trend and positive correlation of DENV-2 neutralization titers for the xCELLigence RTCA and the PRNT assays were observed, yielding strong or very strong correlation (r = 0.829 to 0.967). This was similarly observed for the iPA-FRNT assay (r = 0.821 to 0.916), which also offered the added advantage of measuring neutralizing titers to non-plaque forming viruses. CONCLUSION: The xCELLigence RTCA and iPA-FRNT assays could serve as suitable alternatives to PRNT for dengue serological testing. The decision to adopt these methods may depend on the laboratory setting, and the utility of additional applications offered by these technologies.

Serum IgA antibody level against porcine epidemic diarrhea virus is a potential pre-evaluation indicator of immunization effects in sows during parturition under field conditions.

BACKGROUND: Porcine Epidemic Diarrhea (PED) is a highly contagious disease caused by Porcine Epidemic Diarrhea Virus (PEDV), resulting in a mortality rate of suckling piglets as high as 100%. Vaccination is the primary strategy for controlling PEDV infection, however, there is currently a lack of reliable methods for assessing the efficacy of vaccination. This study aimed to analyze serum and colostrum samples from 75 parturient sows with a specific vaccination strategy to measure levels of IgG, IgA, and neutralizing antibodies (nAbs) against PEDV, and to investigate the correlation between serum and colostrum antibody levels, as well as to identify potential biomarkers that can be used to evaluate immunization effects under field conditions. RESULTS: The findings of correlation analysis between antibody levels of IgA, IgG, and nAbs in serum or colostrum samples revealed that IgG demonstrated the most robust correlation with nAbs exhibiting a correlation coefficient of 0.64 in serum samples. Conversely, IgA exhibited the highest correlation with nAbs, with a correlation coefficient of 0.47 in colostrum samples. Additionally, the correlation analysis of antibody levels between serum and colostrum samples indicated that serum IgA displayed the strongest correlation with colostrum IgA, with a coefficient of 0.63, indicating that serum IgA may serve as a viable alternative indicator for evaluating IgA levels in colostrum samples. To further evaluate the suitability of serum IgA as a substitute marker for colostrum IgA, levels of IgA antibodies in serum samples from sows were examined both pre- and post-parturition. The findings indicated that serum IgA levels were initially low prior to the initial immunization, experienced a notable rise 21 days after immunization, and maintained a significant elevation compared to pre-immunization levels from 21 days pre-parturition to 14 days postpartum, spanning a total of 35 days. CONCLUSIONS: Serum anti-PEDV IgA antibody levels may serve as a valuable predictor for immunization effects, allowing for the assessment of colostrum IgA antibody levels up to 21 days in advance. This insight could enable veterinarians to timely adjust or optimize immunization strategies prior to parturition, thereby ensuring adequate passive immunity is conferred to piglets through colostral transfer postpartum.

Impact of anti leukemia inhibitory factor antibody on immune related gene expression in breast cancer Balb/c mouse model.

Leukemia inhibitory factor (LIF) is involved in the progression of different cancers. In this study, we investigated the effect of anti-LIF antibodies on immune-related gene expression in the Balb/c mouse model of breast cancer. To immunize mice against LIF, recombinant LIF with Freund adjuvant was injected into the test group, whereas the control group received phosphate-buffered saline with adjuvant. Tumor induction (4T1 cell line) was performed by increasing the antibody titer. The expression of immune-related genes was evaluated by real-time PCR. The anti-LIF titer was significantly increased in the immunized group. The expression of genes related to the differentiation of T helper (Th)-1, Th-2, and Th-17 cells was significantly higher in the immunized group than in the control group. In addition, anti-LIF did not have a significant effect on the expression of genes related to the differentiation of regulatory T cells, and immune checkpoint-associated genes. Additionally, the test group had higher survival and lower tumor development rates. The results demonstrated that the anti-LIF antibody may potentially play a role in the differentiation of immune cells or immune responses. However, further studies utilizing advanced techniques are necessary to validate its function.

Dynamics and implications of anti-drug antibodies against adalimumab using ultra-sensitive and highly drug-tolerant assays.

Background: Adalimumab induces the production of anti-drug antibodies (ADA) that may lead to reduced drug concentration and loss-of-response, posing significant clinical challenges. However, traditional immunoassays have limitations in terms of sensitivity and drug-tolerance, hindering the insights of ADA response. Methods: Herein, we developed an integrated immunoassay platform combining the electrochemiluminescence immunoassay with immunomagnetic separation strategy. A longitudinal cohort study involving 49 patients with ankylosing spondylitis was carried out to analyze the dynamic profiles of ADA and to investigate the impact of ADA on adalimumab pharmacokinetics using a population pharmacokinetic model. Additionally, cross-sectional data from 12 patients were collected to validate the correlation between ADA levels and disease relapse. Results: The ADA assay demonstrated high sensitivity (0.4 ng/mL) and drug-tolerance (100 µg/mL), while the neutralizing antibodies (NAB) assay showed a sensitivity of 100 ng/mL and drug-tolerance of 20 µg/mL. Analysis of the longitudinal cohort revealed that a majority of patients (44/49, 90%) developed persistent ADA within the first 24 weeks of treatment. ADA levels tended to plateau over time after an initial increase during the early immune response phase. Further, nearly all of the tested patients (26/27, 96%) were classified as NAB positive, with a strong correlation between ADA levels and neutralization capacity (R2 = 0.83, P < 0.001). Population pharmacokinetic modeling revealed a significant positive association between model-estimated individual clearance and observed ADA levels. Higher ADA levels were associated with adalimumab clearance and disease relapse in a cross-sectional cohort, suggesting a promising ADA threshold of 10 for potential clinical application. Moreover, the IgG class was the primary contributor to ADA against adalimumab and the apparent affinity exhibited an increasing trend over time, indicating a T-cell dependent mechanism for ADA elicitation by adalimumab. Conclusion: In summary, this integrated immunoassay platform shows promise for in-depth analysis of ADA against biologics, offering fresh insights into immunogenicity and its clinical implications.

Three families of CD4-induced antibodies are associated with the capacity of plasma from people living with HIV to mediate ADCC in the presence of CD4-mimetics.

CD4-mimetics (CD4mcs) are small molecule compounds that mimic the interaction of the CD4 receptor with HIV-1 envelope glycoproteins (Env). Env from primary viruses normally samples a "closed" conformation that occludes epitopes recognized by CD4-induced (CD4i) non-neutralizing antibodies (nnAbs). CD4mcs induce conformational changes on Env resulting in the exposure of these otherwise inaccessible epitopes. Here, we evaluated the capacity of plasma from a cohort of 50 people living with HIV to recognize HIV-1-infected cells and eliminate them by antibody-dependent cellular cytotoxicity (ADCC) in the presence of a potent indoline CD4mc. We observed a marked heterogeneity among plasma samples. By measuring the levels of different families of CD4i Abs, we found that the levels of anti-cluster A, anti-coreceptor binding site, and anti-gp41 cluster I antibodies are responsible for plasma-mediated ADCC in the presence of CD4mc. IMPORTANCE: There are several reasons that make it difficult to target the HIV reservoir. One of them is the capacity of infected cells to prevent the recognition of HIV-1 envelope glycoproteins (Env) by commonly elicited antibodies in people living with HIV. Small CD4-mimetic compounds expose otherwise occluded Env epitopes, thus enabling their recognition by non-neutralizing antibodies (nnAbs). A better understanding of the contribution of these antibodies to eliminate infected cells in the presence of CD4mc could lead to the development of therapeutic cure strategies.

Analytical Methods for Evaluating the Immunogenicity of Recombinant Rabies Virus Glycoprotein Expressed in the Yeast Komagataella phaffii.

BACKGROUND: Rabies is a fatal viral disease preventable by vaccination. The multiple-dose regimens, along with the high production costs of current rabies vaccines, limit their use in rabies-endemic countries with developing economies and consequently there is a need for new efficacious, low-cost rabies vaccines. This study investigates the immunogenicity of recombinant rabies virus glycoprotein (rRABVG), expressed in the yeast Komagataella phaffii (K. phaffii), as a candidate subunit rabies vaccine. METHODS: Monoclonal antibodies were used to confirm neutralizing epitopes presence on the rRABVG. The rRABVG potency was estimated by antigen quantification methods using ELISA and SRID. Serological methods, specifically ELISA and RFFIT, were applied to investigate the immune response of mice groups immunized with rRABVG varying doses, with or without adjuvant. RESULTS: The potency estimated by antigen quantification was dependent on the method employed. Active immunization assessment using ELISA was effective when the solid-phase antigen is the rRABVG. The RFFIT data indicated that a single adjuvanted dose of 20 µg rRABVG is sufficient for virus-neutralizing antibodies induction at a protective level of 0.5 IU/mL within 10 days post immunization. CONCLUSION: These data demonstrate that K. phaffii produced rRABVG is immunoactive and could be an attractive candidate to develop a low-cost subunit rabies vaccine.

CoronaVac-vaccinated kidney transplant recipients with hybrid immunity have strong neutralizing responses against Omicron and Mu variants of SARS-CoV-2.

Neutralizing antibody (nAb) responses against SARS-CoV-2 variants after inactivated virus vaccine (CoronaVac) in kidney transplant recipients (KTRs) with or without SARS-CoV-2 infection history remains unclear. We aimed to evaluate the neutralizing antibody responses against emerging SARS-CoV-2 variants after two doses of CoronaVac in these patients. 22.2% of participants had hybrid immunity. Anti-spike IgG antibodies were evidenced in 44% of the patients. nAbs against B.1.111, Mu, and Omicron were detected in 28.5%, 17.9%, and 21.4% of naïve KTRs, respectively. Furthermore, nearly 100% of KTRs with hybrid immunity had nAbs against the variants evaluated. Thus, a significant proportion of infection-naïve KTRs had no detectable nAb titers against Mu and Omicron variants after two doses of the CoronaVac vaccine. However, the nAb titers were significantly higher in patients with hybrid immunity, and it was no association between the immunosuppressive regimen and the seropositivity rate of anti-SARS-CoV-2 neutralizing antibodies. Therefore, hybrid KTRs are protected against COVID-19 by emerging variants able to escape from vaccine-elicited nAbs such as Mu and Omicron.

Influence of previous COVID-19 exposure and vaccine type (CoronaVac, ChAdOx1 nCov-19 or BNT162b2) on antibody and cytokine (Th1 or Th2) responses.

To achieve global herd immunity, widespread vaccination is the most effective strategy. Vaccines stimulate the immune system, generating cytokines and chemokines, isotype antibodies, and neutralizing antibodies; all these molecules collectively provide a more comprehensive characterization of the immune response post-vaccination. We conducted a longitudinal study in northwestern Mexico, involving 120 individuals before vaccination and after the first dose of the SARS-CoV-2 vaccine, and 46 individuals after their second dose. Our findings reveal that antibody levels stabilize over time; cytokine levels generally increase following the first dose but decrease after the second dose and higher than normal levels in IgG1 and IgG3 concentrations are present. Most of the innate cytokines determined in this study were higher after the first dose of the vaccine. Regardless of previous infection history, this finding suggests that the first dose of the vaccine is crucial and may stimulate immunity by enhancing the innate immune response. Conversely, increased levels of IL-4, indicative of a Th2 response, were found in individuals without prior exposure to the virus and in those vaccinated with CoronaVac. These results suggest that the immune response to COVID-19 vaccines is multi-faceted, with preexisting immunity potentiating a more robust innate response. Vaccine type plays a critical role, with genetic vaccines favoring a Th1 response and inactivated vaccines like CoronaVac skewing toward a Th2 profile.