Two antibodies show broad,synergistic neutralization against SARS-CoV-2 variants by inducing conformational change within the RBD

Continual evolution of the severe acute respiratory syndrome coronavirus(SARS-CoV-2)virus has allowed for its gradual evasion of neutralizing antibodies(nAbs)produced in response to natural infection or vaccination.The rapid nature of these changes has incited a need for the development of superior broad nAbs(bnAbs)and/or the rational design of an antibody cocktail that can protect against the mutated virus strain.Here,we report two angiotensin-converting enzyme 2 competing nAbs—8H12 and 3E2—with synergistic neutralization but evaded by some Omicron subvariants.Cryo-electron microscopy reveals the two nAbs synergistic neutralizing virus through a rigorous pairing permitted by rearrangement of the 472-489 loop in the receptor-binding domain to avoid steric clashing.Bispecific antibodies based on these two nAbs tremendously extend the neutralizing breadth and restore neutralization against recent variants including currently dominant XBB.1.5.Together,these findings expand our understanding of the potential strategies for the neutralization of SARS-CoV-2 variants toward the design of broad-acting antibody therapeutics and vaccines.

Newcastle disease virus-based MERS-CoV candidate vaccine elicits high-level and lasting neutralizing antibodies in Bactrian camels

Middle East respiratory syndrome coronavirus （MERS-CoV）, a member of the Coronavifidae family, is the causative pathogen for MERS that is characterized by high fever, pneumonia, acute respiratory distress syndrome （ARDS）, as well as extrapul- monary manifestations. Currently, there are no approved treatment regimens or vaccines for MERS. Here~ we generated recombinant nonvirulent Newcastle disease virus （NDV） LaSota strain expressing MERS-CoV S protein （designated as rLa- MERS-S）, and evaluated its immunogenicity in mice and Bactrian camels. The results revealed that rLa-MERS-S showed similar growth properties to those of LaSota in embryonated chicken eggs, while animal immunization studies showed that rLa-MERS-S induced MERS-CoV neutralizing antibodies in mice and camels. Our findings suggest that recombinant rLa- MERS-S may be a potential MERS-CoV veterinary vaccine candidate for camels and other animals affected by MERS.

Transforming growth factor -β neutralizing antibodies inhibit subretinal fibrosis in a mouse model

AIM:To determine the involvement of the transforming growth factor(TGF)-β with the development of experimental subretinal fibrosis in a mouse model.· METHODS:Subretinal fibrosis was induced by subretinal injection of macrophage-rich peritoneal exudate cells(PECs) and the local expression of TGF-β isoforms was assessed by quantitative real-time reverse transcription-polymerase chain reaction(RT-PCR) and enzyme-linked immunosorbent assay(ELISA) at various time points.In addition,we investigated the effect of TFG-β-neutralizing antibodies(TGF-β NAb) on subretinal fibrosis development.· RESULTS:TGF-β1 and TGF-β2 mRNA level was significantly elevated at day 2 after subretinal fibrosis induction and increased further to 5 and 6.5-fold respectively at day 5,reaching the peak.TGF-β3 mRNA was not detected in the present study.The result of ELSIA showed that active TGF-β1 and TGF-β2 levels were upregulated to 10-fold approximately,while total TGF-β1 and TGF-β2 levels were even upregulated more than 10-fold and more than 20-fold respectively in subretinal fibrosis mice in comparison with na?觙ve mice at day 5.TGF-β NAb resulted in a reduced subretinal fibrosis areas by 65% compared to animals from control group at day 7.· CONCLUSION:Our results indicate that TGF-β signaling may contribute to the pathogenesis of subretinal fibrogenesis and TGF-β inhibition may provide an effective,novel treatment of advanced and late-stage neovascular age-related macular degeneration.·

Detection of HPV Types and Neutralizing Antibodies in Women with Genital Warts in Tianjin City,China

The serum samples and corresponding cervical swabs were collected from 50 women with genital warts from Tianjin city, China. The neutralizing antibodies against HPV-16, -18, -58, -45, -6 and -11 in serum samples were tested by using pseudovirus-based neutralization assays and HPV DNAs in cervical swabs were also tested by using a typing kit that can detect 21 types of HPV. The results revealed that 36% （18/50） of sera were positive for type-specific neutralizing antibodies with a titer range of 160-2560, of which 22%（11/50）, 12%（6/50）, 10%（5/50）, 4%（2/50）, 4%（2/50） and 2%（1/50） were against HPVs -6, -16, -18, -58, -45 and -1 l, respectively. Additionally, 60% （30/50） of samples were HPV DNA-positive, in which the most common types detected were HPV-68（18%）, HPV-16（14%）, HPV-58（12%）, HPV-33（8%） and HPV-6, HPV-11, HPV-18 and HPV-52 （6% each）. The concordance between HPV DNA and corresponding neutralizing antibodies was 56% （28/50） with a significant difference （P〈0.05）. The full-length sequences of five HPV types （HPV -42, -52, -53, -58 and -68） were determined and exhibited 98%-100% identities with their reported genomes. The present data may have utility for investigating the natural history of HPV infection and promote the development of HPV vaccines.

Neutralizing antibodies in hepatitis C virus infection

Hepatitis C virus (HCV) is a major cause of hepatitis world-wide. The majority of infected individuals develop chronic hepatitis which can then progress to liver cirrhosis and hepatocellular carcinoma. Spontaneous viral clearance occurs in about 20%-30% of acutely infected individuals and results in resolution of infection without sequaelae. Both viral and host factors appear to play an important role for resolution of acute infection. A large body of evidence suggests that a strong, multispecific and long-lasting cellular immune response appears to be important for control of viral infection in acute hepatitis C. Due too the lack of convenient neutralization assays, the impact of neutralizing responses for control of viral infection had been less defined. In recent years, the development of robust tissue culture model systems for HCV entry and infection has finally allowed study of antibody-mediated neutralization and to gain further insights into viral targets of host neutralizing responses. In addition, detailed analysis of antibody-mediated neutralization in individual patients as well as cohorts with well defined viral isolates has enabled the study of neutralizing responses in the course of HCV infection and characterization of the impact of neutralizing antibodiesfor control of viral infection. This review will summarize recent progress in the understanding of the molecular mechanisms of antibody-mediated neutralization and its impact for HCV pathogenesis.

Epitope Analysis of Anti-SARS-CoV-2 Neutralizing Antibodies

Coronavirus disease 2019 is threatening thousands of millions of people around the world.In the absence of specific and highly effective medicines,the treatment of infected persons is still very challenging.As therapeutics,neutralizing antibodies(NAbs)have great potential.Many NAbs have been reported,and most target various regions on the receptor-binding domain of the spike(S)protein,or the N-terminal domain.Several NAbs and NAb cocktails have been authorized for emergency use,and more arc in clinical trials or are under development.In this review,considering the angle of binding epitopes on the S protein,we summarize the functions and the underlying mechanisms of a set of well-recognized NAbs and provide guidance for vaccine design and the combinatorial use of these antibodies.In addition,we review the NAbs and NAb cocktails that have been approved for emergency use and discuss the effectiveness of these NAbs for combating severe acute respiratory syndrome coronavirus 2 mutants.

Safe and Objective Assay of Enterovirus 71 Neutralizing Antibodies via Pseudovirus

Current serum neutralization assays based on the inhibition of the cytopathic effect（Nt-CPE） need to ma nipulate live viruses, which are time-consuming, labor-intensive, and have the potential exposure to infectious agents, so a safe and objective assay via pseudovirus for the fast and efficient detection of enterovirus 71（EV71） neutralizing antibodies was developed. First, we generated EV71 pseudovirus containing firefly luciferase gene in place of the capsid gene P1 in EV71 genome. Vero cells infected with 200 CCID50（50% cell culture infective dose） of EV71 pseudovirus for 24 h were found to have the best performance. Seval sera were measured by EV71 pseudoparticle neutralization assay（Nt-PPN） and the conventional serological method Nt-CPE. Neutralizing antibody titers measured by Nt-PPN and those obtained by Nt-CPE demonstrate a high correlation between the two methods. Overall, the PPN assay represents a valid alternative to conventional serological methods for the evaluation of EV71 neutralizing anti bodies. This method can be used for detecting neutralizing antibodies of other picornaviruses, such as hepatitis A vi rus（HAV） and coxsackievirus 16（CVA16）, and make it possible to determine whether there is cross-reactivity be tween EV71 and CVA16.

Neutralizing Antibody Responses against Five SARS-CoV-2 Variants and T Lymphocyte Change after Vaccine Breakthrough Infections from the SARS-CoV-2 Omicron BA.1 Variant in Tianjin, China: A Prospective Study

Objective To investigate whether Omicron BA.1 breakthrough infection after receiving the SARS-CoV-2 vaccine could create a strong immunity barrier.Methods Blood samples were collected at two different time points from 124 Omicron BA.1 breakthrough infected patients and 124 controls matched for age,gender,and vaccination profile.Live virus-neutralizing antibodies against five SARS-CoV-2 variants,including WT,Gamma,Beta,Delta,and Omicron BA.1,and T-lymphocyte lymphocyte counts in both groups were measured and statistically analyzed.Results The neutralizing antibody titers against five different variants of SARS-CoV-2 were significantly increased in the vaccinated population infected with the Omicron BA.1 variant at 3 months after infection,but mainly increased the antibody level against the WT strain,and the antibody against the Omicron strain was the lowest.The neutralizing antibody level decreased rapidly 6 months after infection.The T-lymphocyte cell counts of patients with mild and moderate disease recovered at 3 months and completely returned to the normal state at 6 months.Conclusion Omicron BA.1 breakthrough infection mainly evoked humoral immune memory in the original strain after vaccination and hardly produced neutralizing antibodies specific to Omicron BA.1.Neutralizing antibodies against the different strains declined rapidly and showed features similar to those of influenza.Thus,T-lymphocytes may play an important role in recovery.

A SARS-CoV-2 neutralizing antibody discovery by single cell sequencing and molecular modeling

Although vaccines have been developed,mutations of SARS-CoV-2,especially the dominant B.1.617.2(delta)and B.1.529(omicron)strains with more than 30 mutations on their spike protein,have caused a significant decline in prophylaxis,calling for the need for drug improvement.Antibodies are drugs preferentially used in infectious diseases and are easy to get from immunized organisms.The current study combined molecular modeling and single memory B cell sequencing to assess candidate sequences before experiments,providing a strategy for the fabrication of SARS-CoV-2 neutralizing antibodies.A total of 128 sequences were obtained after sequencing 196 memory B cells,and 42 sequences were left after merging extremely similar ones and discarding incomplete ones,followed by homology modeling of the antibody variable region.Thirteen candidate sequences were expressed,of which three were tested positive for receptor binding domain recognition but only one was confirmed as having broad neutralization against several SARS-CoV-2 variants.The current study successfully obtained a SARS-CoV-2 antibody with broad neutralizing abilities and provided a strategy for antibody development in emerging infectious diseases using single memory B cell BCR sequencing and computer assistance in antibody fabrication.

Blockade of high mobility group box-1 protein attenuates experimental severe acute pancreatitis

AIM： To examine the effects of anti-high mobility group box 1 （HIGB1） neutralizing antibody in experimental severe acute pancreatitis （SAP）. METHODS： SAP was induced by creating closed duodenal loop inC3H/HeN mice. SAP was induced immediately after intrapedtoneal injection of anti-HMGB1 neutralizing antibody （200 pg）. Sevedty of pancreatitis, organ injury （liver, kidney and lung）, and bacterial translocation to pancreas was examined 12 h after induction of SAP. RESULTS： Anti-HHGB1 neutralizing antibody significantly improved the elevation of the serum amylase level and the histological alterations of pancreas and lung in SAR Anti-HHGB1 antibody also significantly ameliorated the elevations of serum alanine aminotransferase and creatinine in SAR However, anti-HHGB1 antibody worsened the bacterial translocation to pancreas. CONCLUSION： Blockade of HHGB1 attenuated the development of SAP and associated organ dysfunction, suggesting that HHGB1 may act as a key mediator for inflammatory response and organ injury in SAR

Neurotoxic role of interleukin-17 in neural stem cell differentiation after intracerebral hemorrhage

Interleukin 17(IL-17)and its main producer,T cell receptorγδcells,have neurotoxic effects in the pathogenesis of intracerebral hemorrhage(ICH),aggravating brain injuries.To investigate the correlation between IL-17 and ICH,we dynamically screened serum IL-17 concentrations using enzyme-linked immunosorbent assay and explored the clinical values of IL-17 in ICH patients.There was a significant negative correlation between serum IL-17 level and neurological recovery status in ICH patients(r=–0.498,P<0.01).To study the neurotoxic role of IL-17,C57 BL/6 mice were used to establish an ICH model by injecting autologous blood into the caudate nucleus.Subsequently,the mice were treated with mouse neural stem cells(NSCs)and/or IL-17 neutralizing antibody for 72 hours.Flow cytometry,brain water content detection,Nissl staining,and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling results indicated that NSC transplantation significantly reduced IL-17 expression in peri-hematoma tissue,but there was no difference in T cell receptorγδcells.Compared with the ICH group,there were fewer apoptotic bodies and more Nissl bodies in the ICH+NSC group and the ICH+NSC+IL-17 group.To investigate the potential effect of IL-17 on directional differentiation of NSCs,we cultured mouse NSCs(NE-4 C)alone or co-cultured them with T cell receptorγδcells,which were isolated from mouse peripheral blood mononuclear cells,for 7 days.The results of western blot assays revealed that IL-17 secreted by T cell receptorγδcells reduced the differentiation of NSCs into astrocytes and neurons,while IL-17 neutralization relieved the inhibition of directional differentiation into astrocytes rather than neurons.In conclusion,serum IL-17 levels were elevated in the early stage of ICH and were negatively correlated with outcome in ICH patients.Animal experiments and cytological investigations therefore demonstrated that IL-17 probably has neurotoxic roles in ICH because of its inhibitory effects on the directional differentiation of NSCs.The application of IL-17 neutralizing antibody may promote the directional differentiation of NSCs into astrocytes.This study was approved by the Clinical Research Ethics Committee of Anhui Medical University of China(For human study:Approval No.20170135)in December 2016.All animal handling and experimentation were reviewed and approved by the Institutional Animal Care and Use Committee of Anhui Medical University(approval No.20180248)in December 2017.

Recent Developments in SARS-CoV-2 Neutralizing Antibody Detection Methods

The ongoing Coronavirus disease 19 pandemic has likely changed the world in ways not seen in the past.Neutralizing antibody(NAb)assays play an important role in the management of the severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)outbreak.Using these tools,we can assess the presence and duration of antibody-mediated protection in naturally infected individuals,screen convalescent plasma preparations for donation,test the efficacy of immunotherapy,and analyze NAb titers and persistence after vaccination to predict vaccine-induced protective effects.This review briefly summarizes the various methods used for the detection of SARS-CoV-2 NAbs and compares their advantages and disadvantages to facilitate their development and clinical application.

Comparison of RFFIT Tests with Different Standard Sera and Testing Procedures

The World Health Organization （WHO） standard assay for determining antibody level is the rapid fluorescent focus inhibition test （RFFIT） and is used to determine the degree of immunity after vaccination against rabies. To compare the difference in RFFIT results between the laboratories of The National Institute of Infectious Disease in Japan （NIID） and the Chinese Centre for Disease Control （CCDC） as well the influence of the choice of standard serum （STD） for the detection, the two laboratories detection methods were simultaneously manipulated by RFFIT. The reference serums used in NIID and the WHO standard serum used in CCDC were compared in the same RFFIT detection to determine the titer of four sera samples C1, Sl, S2 and S4 in parallel, and the titers of the detected sera samples were calculated using the standard formula for neutralizing antibody titer. No significant difference was found in RFFIT methods from the two laboratories and the RFFIT testing procedures of the two laboratories have good consistency. However, different titers were obtained with the tentative internal standard serum （TI-STD） produced by adjusting to 2.0 IU of WHO standard serum in NIID and the WHO STD. The titer determined with the TI-STD was higher than that determined with WHO STD, This difference appears to be significant and requires further investigation

Convalescent plasma: A potential therapeutic option for COVID-19 patients

The new coronavirus disease(COVID-19)outbreak has challenged us to take unprecedented steps to bring this pandemic under control.In view of the urgency of this situation,convalescent plasma which was used in previous coronavirus outbreaks has emerged as one of the treatment options in this current pandemic.This is mainly due to the fact that convalescent plasma has been studied in a few case series with promising outcomes.In addition,on-going large clinical trials aimed to further evaluate the effectiveness,safety,and optimal dosage,duration and timing of administration of convalescent plasma are indeed revealing a certain level of promising results.Therefore,this article aims to provide an overview of possible mechanisms of actions of convalescent plasma,its benefits and its level of usage safeness by summarizing the existing evidence on the use of convalescent plasma in COVID-19 patients.

Virus-host Interactions during Hepatitis C Virus Entry-Implications for Pathogenesis and Novel Treatment Approaches

Hepatitis C virus (HCV) is a member of the Flaviviridae family and causes acute and chronic hepatitis. Chronic HCV infection may result in severe liver damage including liver cirrhosis and hepatocellular carcinoma. The liver is the primary target organ of HCV, and the hepatocyte is its primary target cell. Attachment of the virus to the cell surface followed by viral entry is the first step in a cascade of interactions between the virus and the target cell that is required for successful entry into the cell and initiation of infection. This step is an important determinant of tissue tropism and pathogenesis; it thus represents a major target for antiviral host cell responses, such as antibody-mediated virus neutralization. Following the development of novel cell culture models for HCV infection our understanding of the HCV entry process and mechanisms of virus neutralization has been markedly advanced. In this review we summarize recent developments in the molecular biology of viral entry and its impact on pathogenesis of HCV infection, development of novel preventive and therapeutic antiviral strategies.

Efficient Humoral and Cellular Immune Responses Induced by a Chimeric Virus-like Particle Displaying the Epitope of EV71 without Adjuvant

Objective To eliminate the side effects of aluminum adjuvant and His-tag,we constructed chimeric VLPs displaying the epitope of EV71（SP70） without His-tagged.Then evaluating whether the VLPs could efficiently evoke not only humoral but also cellular immune responses against EV71 without adjuvant.Methods The fusion protein was constructed by inserting SP70 into the MIR of truncated HBc Ag sequence,expressed in E.Coli,and purified through ion exchange chromatography and density gradient centrifugation.Mice were immunized with the VLPs and sera were collected afterwards.The specific antibody titers,Ig G subtypes and neutralizing efficacy were detected by ELISA,neutralization assay,and EV71 lethal challenge.IFN-γ and IL-4 secreted by splenocytes were tested by ELISPOT assay.Results HBc-SP70 proteins can self-assemble into empty VLPs.After immunization with HBc-SP70 VLPs,the detectable anti-EV71 antibodies were effective in neutralizing EV71 and protected newborn mice from EV71 lethal challenge.There was no significant difference for the immune efficacy whether the aluminum adjuvant was added or not.The specific Ig G subtypes were mainly IgG1 and IgG2 b and splenocytes from the mice immunized produced high levels of IFN-γ and IL-4.Conclusion The fusion proteins without His-tagged was expressed and purified as soluble chimeric HBc-SP70 VLPs without renaturation.In the absence of adjuvant,they were efficient to elicit high levels of Th1/Th2 mixed immune response as well as assisted by aluminum adjuvant.Furthermore,the chimeric VLPs have potential to prevent HBV and EV71 infection simultaneously.

Immunization Schedule of Liposomal Rabies Vaccine in Animals

The standard rabies vaccines recommended by WHO include Essen regimen, the Thai Red Cross two-site ID regimen and the eight-site ID regimen, and so on. The present schedules of rabies vaccine are all laborious and time consuming. We developed a new rabies vaccine with liposome as adjuvant（LipoRabV） and found that liposome could facilitate the inactivated rabies vaccine（RabV） to induce the more vigorous production of rabies virus neutralizing antibody（RVNA） in BALB/c mice and beagles. We established preliminary pre- and post-exposure prophylaxis schedules for LipoRabV. LipoRabV（0/14） could elicit similar RVNA level as RabV（0/7/28） by pre-exposure prophylaxis schedules in mice and beagles. LipoRabV（0/3/14） could elicit higher RVNA level vs. RabV（0/3/7/14/28） in BALB/c. The data indicate that the three-shot liposome-enhanced rabies vaccine could achieve a higher protection rate（survival rate 56.2%） by post-exposure prophylaxis compared with that of the RabV group（survival rate 40.6%） in mice. The data also indicate that the three-inoculation liposome-enhanced rabies vaccine could achieve a survival rate of 80.0% vs. RabV（70.0%） by post-exposure prophylaxis in beagles. The results show that the immunization schedule for LipoRabV could be preliminarily determined at 0 and 14 d for pre-exposure prophylaxis and at 0, 3 and 14 d for post-exposure prophylaxis.

Kinetic Characteristics of Neutralizing Antibody Responses Vary among Patients with COVID-19

Objective The coronavirus disease 2019(COVID-19) pandemic continues to present a major challenge to public health. Vaccine development requires an understanding of the kinetics of neutralizing antibody(NAb) responses to severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).Methods In total, 605 serum samples from 125 COVID-19 patients(from January 1 to March 14, 2020)varying in age, sex, severity of symptoms, and presence of underlying diseases were collected, and antibody titers were measured using a micro-neutralization assay with wild-type SARS-CoV-2.Results NAbs were detectable approximately 10 days post-onset(dpo) of symptoms and peaked at approximately 20 dpo. The NAb levels were slightly higher in young males and severe cases, while no significant difference was observed for the other classifications. In follow-up cases, the NAb titer had increased or stabilized in 18 cases, whereas it had decreased in 26 cases, and in one case NAbs were undetectable at the end of our observation. Although a decreasing trend in NAb titer was observed in many cases, the NAb level was generally still protective.Conclusion We demonstrated that NAb levels vary among all categories of COVID-19 patients. Longterm studies are needed to determine the longevity and protective efficiency of NAbs induced by SARS-CoV-2.

Neutralizing Antibody Titer Test of Ebola Recombinant Protein Vaccine and Gene Vector Vaccine pVR-GP-FC

Objective In previous studies, we immunized mice with Ebola recombinant protein vaccine and gene vector vaccine. Both stimulated high levels of humoral immunity. In this work, we constructed a pseudovirus containing Ebola membrane proteins to verify whether the two immunization strategies can induce neutralizing antibodies in mice. Methods A pseudovirus containing an Ebola virus membrane protein based on the HIV-1 viral gene sequence was constructed and evaluated using a known neutralizing antibody. The titer of the neutralizing antibody in the sera of mice immunized with the recombinant protein and the gene vector vaccine was examined using a neutralization test. Results Ebola pseudovirus was successfully prepared and applied for neutralizing antibody detection. Immunological experiments showed that recombinant protein GP-Fc and gene vaccine pVR-modGP-Fc had good immunogenicity. The titer of the bound antibody in the serum after 8 weeks of immunization in mice was more than 1：105, and the recombinant protein induced greater humoral immunity. The results of the neutralization test based on the Ebola pseudovirus system demonstrated that both vaccines induced production of protective antibodies, while the gene vaccine induced a higher titer of neutralizing antibodies. Conclusion An Ebola pseudovirus detection system was successfully established and used to evaluate two Ebola vaccines. Both produced good immunogenicity. The findings lay the foundation for the development of new Ebola vaccines and screening for neutralizing monoclonal antibodies.

Polyfunctional T Cell and Neutralizing Antibody Responses to ACAM2000TM Smallpox Vaccine Immunization in Primary-Vaccinated Individuals

Smallpox eradication was successful via prophylactic administration of live attenuated vaccinia virus. As a result of the discontinuation of the smallpox immunization program, many individuals are now susceptible to smallpox virus infection should it be used as a biological weapon. Presently, only individuals at high risk for exposure are required to receive smallpox vaccine, such as laboratory personnel that handle variola/vaccinia virus. This study endeavored to investigate a one-year period of vaccinia virus-specific T cell responses using polychromatic flow cytometry and neutralizing (Nt) antibody responses using plaque reduction neutralization test (PRNT) in individuals receiving primary immunization (n = 5) with ACAM2000TM smallpox vaccine. Functional and phenotypic profiles of vaccinia virus-specific T cell responses were characterized. Each single functional measurement {CD107a/b expression, production of interferon g (IFN-g), macrophage inflammatory protein 1b (MIP-1b), interleukin 2 (IL-2), and tumor necrosis factor a (TNF-a)} demonstrated that vaccinia virus-specific CD8+ T cells were functional at least one time point after vaccination (p ≤ 0.05). However, vaccinia virus-specific CD4+ T cells were functional only for MIP-1b production (p ≤ 0.05). Vaccinia virus-specific CD8+ T cells induced in these individuals showed increased polyfunctionality in at least 2 phenotypes relative to pre-vaccination (p ≤ 0.05). Although only three of five individuals (60%) showed positive Nt antibody (titer ≥ 20) at first month after vaccination, all five individuals (100%) demonstrated Nt antibody at 2 months, post-immunization. Interestingly, all vaccinees could retain the Nt antibody for 6 months after primary vaccination. In conclusion, ACAM2000TM smallpox vaccine induced both polyfunctional T cell-and Nt antibody-responses in primary immunized individuals.