Surrogate Markers Of Protection Research Articles

KIR2DL1 gene is a surrogate marker of protection against infection-related hospitalization among HIV-1 unexposed versus exposed uninfected infants in Cameroon

BackgroundHIV-exposed uninfected infants (HEU) appear more vulnerable to infections compared to their HIV-unexposed uninfected (HUU) peers, generally attributed to poor passive immunity acquired from the mother. This may be due to some genetic factors that could alter the immune system. We thus sought to determine the distribution of Killer Cell Immunoglobulin-Like Receptors (KIRs) genes in HEU versus HUU and study their associations with the occurrence of infection-related hospitalization.MethodsA cohort study was conducted from May 2019 to April 2020 among HEU and HUU infants, including their follow-up at weeks 6, 12, 24, and 48, in reference pediatric centers in Yaoundé-Cameroon. The infant HIV status and infections were determined. A total of 15 KIR genes were investigated using the sequence-specific primer polymerase chain reaction (PCR-SSP) method. The KIR genes that were significantly associated with HIV-1 status (HEU and HUU) were analyzed for an association with infection-related hospitalizations. This was only possible if, and to the extent that, infection-related hospitalizations varied significantly according to status. Multivariate logistic regression analyses were conducted to determine the association between KIR gene content variants and HIV status, while considering a number of potential confounding factors. Furthermore, the risk was quantified using relative risk, odds ratio, and a 95% confidence interval. The Fisher exact test was employed to compare the frequency of occurrences. A p-value of less than 0.05 was considered statistically significant.ResultsIn this cohort, a total of 66 infants participated, but only 19 acquired infections requiring hospitalizations (14.81%, 04/27 HUU and 38.46%, 15/39 HEU, p = 0.037). At week 48 (39 HEU and 27 HUU), the relative risk (RR) for infection-related hospitalizations was 2.42 (95% CI: 1.028–5.823) for HEU versus HUU with OR 3.59 (1.037–12.448). KIR2DL1 gene was significantly underrepresented in HEU versus HUU (OR = 0.183, 95%CI: 0.053–0.629; p = 0.003), and the absence of KIR2DL1 was significantly associated with infection-related hospitalization (p < 0.001; aOR = 0.063; 95%CI: 0.017–0.229).ConclusionCompared to HUU, the vulnerability of HEU is driven by KIR2DL1, indicating the protective role of this KIR against infection and hospitalizations.

Chapter 14: TBE-Prevention: Vaccines and Immunoglobulins

Worldwide there are 6 different TBE vaccines – two from Western Europe, three from Russia and one from China. The two western European vaccines and one of the Russian vaccines have an adult and a pediatric formulation. The products names are FSME IMMUN and FSME-IMMUN Junior; Encepur adults and Encepur children, Klesch-E-Vac, EnceVir and EnceVir Neo, Dry lyophilized TBE Moscow and Sen Tai Bao All TBE vaccines except the one from China have similar but not identical immunization schedules with primary immunization (&gt;3 doses) and regular booster vaccinations. For FSME-IMMUN, Encepur and EnceVir rapid immunization schedules are also licensed. The Chinese vaccine is given with 2 primary doses 2 weeks apart followed by annual boosters. All vaccines induce significant immune responses. In the absence of a formal correlate of protection, the presence of neutralizing antibodies is used as a surrogate marker for protection. Recent clinical studies show long-term seropersistence of TBE antibodies after the first booster vaccination (dose 4) with the two European vaccines. An effectiveness of approximately 99% (years 2000–2006) and 98.7% (years 2000-2011) was calculated for regularly vaccinated persons in Austria, a country with established high vaccination uptake. Whereas in Western Europe post-exposure prophylaxis with immunoglobulins was discontinued in the late 1990s, in the highly endemic regions of Russia it continues to be common practice. Both – FSME-IMMUN and Encepur are well tolerated with a well-established safety profile. TBE-Moscow and EnceVir appear to be somewhat more reactogenic.

Chapter 14: Prevention: vaccines and immunoglobulins

Worldwide there are 6 different TBE vaccines – two from Western Europe, three from Russia and one from China. The two western European vaccines and one of the Russian vaccines have an adult and a pediatric formulation. The products names are FSME IMMUN and FSME-IMMUN Junior; Encepur adults and Encepur children, Klesch-E-Vac, EnceVir and EnceVir Neo, Dry lyophilized TBE Moscow and Sen Tai Bao All TBE vaccines except the one from China have similar but not identical immunization schedules with primary immunization (&gt;3 doses) and regular booster vaccinations. For FSME-IMMUN, Encepur and EnceVir rapid immunization schedules are also licensed. The Chinese vaccine is given with 2 primary doses 2 weeks apart followed by annual boosters. All vaccines induce significant immune responses. In the absence of a formal correlate of protection, the presence of neutralizing antibodies is used as a surrogate marker for protection. Recent clinical studies show long-term seropersistence of TBE antibodies after the first booster vaccination (dose 4) with the two European vaccines. An effectiveness of approximately 99% (years 2000–2006) and 98,7% (years 2000-2011) was calculated for regularly vaccinated persons in Austria, a country with established high vaccination uptake. Whereas in Western Europe post-exposure prophylaxis with immunoglobulins was discontinued in the late 1990s, in the highly endemic regions of Russia it continues to be common practice. Both - FSME-IMMUN and Encepur are well tolerated with a well-established safety profile. TBE-Moscow and EnceVir appear to be somewhat more reactogenic.

Optimising SARS-CoV-2 vaccination schedules

Optimising SARS-CoV-2 vaccination schedules

Chapter 14: Prevention: vaccines and immunoglobulins

Worldwide there are 6 different TBE vaccines – two from Western Europe, three from Russia and one from China. The two western European vaccines and one of the Russian vaccines have an adult and a pediatric formulation. The products names are FSME IMMUN and FSME-IMMUN Junior; Encepur adults and Encepur children, Klesch-E-Vac, EnceVir and EnceVir Neo, Dry lyophilized TBE Moscow and Sen Tai Bao. All TBE vaccines except the one from China have similar but not identical immunization schedules with primary immunization (&gt;3 doses) and regular booster vaccinations. For FSME-IMMUN, Encepur and EnceVir rapid immunization schedules are also licensed. The Chinese vaccine is given with 2 primary doses 2 weeks apart followed by annual boosters. All vaccines induce significant immune responses. In the absence of a formal correlate of protection, the presence of neutralizing antibodies is used as a surrogate marker for protection. Recent clinical studies show long-term seropersistence of TBE antibodies after the first booster vaccination (dose 4) with the two European vaccines. An effectiveness of approximately 99% (years 2000–2006) and 98.7% (years 2000-2011) was calculated for regularly vaccinated persons in Austria, a country with established high vaccination uptake. Whereas in Western Europe post-exposure prophylaxis with immunoglobulins was discontinued in the late 1990s, in the highly endemic regions of Russia it continues to be common practice. Both – FSME-IMMUN and Encepur are well tolerated with a well-established safety profile. TBE-Moscow and EnceVir appear to be somewhat more reactogenic.

Potential biomarkers of immune protection in human leishmaniasis.

Leishmaniasis is a vector-borne neglected tropical disease endemic in over 100 countries around the world. Available control measures are not always successful, therapeutic options are limited, and there is no vaccine available against human leishmaniasis, although several candidate antigens have been evaluated over the last decades. Plenty of studies have aimed to evaluate the immune response development and a diverse range of host immune factors have been described to be associated with protection or disease progression in leishmaniasis; however, to date, no comprehensive biomarker(s) have been identified as surrogate marker of protection or exacerbation, and lack of enough information remains a barrier for vaccine development. Most of the current understanding of the role of different markers of immune response in leishmaniasis has been collected from experimental animal models. Although the data generated from the animal models are crucial, it might not always be extrapolated to humans. Here, we briefly review the events during Leishmania invasion of host cells and the immune responses induced against Leishmania in animal models and humans and their potential role as a biomarker of protection against human leishmaniasis.

Chapter 14: Prevention: vaccines and immunoglobulins

Worldwide there are 6 different TBE vaccines – two from Western Europe, three from Russia and one from China. The two western European vaccines and one of the Russian vaccines have an adult and a pediatric formulation. The products names are FSME IMMUN and FSME-IMMUN Junior; Encepur adults and Encepur children, Klesch-E-Vac, EnceVir and EnceVir Neo, Dry lyophilized TBE Moscow and Sen Tai Bao All TBE vaccines except the one from China have similar but not identical immunization schedules with primary immunization (&gt;3 doses) and regular booster vaccinations. For FSME-IMMUN, Encepur and EnceVir rapid immunization schedules are also licensed. The Chinese vaccine is given with 2 primary doses 2 weeks apart followed by annual boosters. All vaccines induce significant immune responses. In the absence of a formal correlate of protection, the presence of neutralizing antibodies is used as a surrogate marker for protection. Recent clinical studies show long-term seropersistence of TBE antibodies after the first booster vaccination (dose 4) with the two European vaccines. An effectiveness of approximately 99% (years 2000–2006) and 98.7% (years 2000-2011) was calculated for regularly vaccinated persons in Austria, a country with established high vaccination uptake. Whereas in Western Europe post-exposure prophylaxis with immunoglobulins was discontinued in the late 1990s, in the highly endemic regions of Russia it continues to be common practice. Both – FSME-IMMUN and Encepur are well tolerated with a well-established safety profile. TBE-Moscow and EnceVir appear to be somewhat more reactogenic.

Comparison of whole blood and spleen transcriptional signatures over the course of an experimental malaria infection

Although the spleen is broadly accepted as the major lymphoid organ involved in generating immune responses to the erythrocytic stages of the malaria parasite, Plasmodium, human splenic tissue is not readily available in most cases. As a result, most studies of malaria in humans rely on peripheral blood to assess cellular immune responses to malaria. The suitability of peripheral blood as a proxy for splenic immune responses is however unknown. Here, we have simultaneously analysed the transcriptomes of whole blood and spleen over 12 days of erythrocytic stage Plasmodium chabaudi infection in C57BL/6 mice. Using both unsupervised and directed approaches, we compared gene expression between blood and spleen over the course of infection. Taking advantage of publicly available datasets, we used machine learning approaches to infer cell proportions and cell-specific gene expression signatures from our whole tissue transcriptome data. Our findings demonstrate that spleen and blood are quite dissimilar, sharing only a small amount of transcriptional information between them, with transcriptional differences in both cellular composition and transcriptional activity. These results suggest that while blood transcriptome data may be useful in defining surrogate markers of protection and pathology, they should not be used to predict specific immune responses occurring in lymphoid organs.

Respiratory Syncytial Virus Vaccines: Are We Making Progress?

Respiratory Syncytial Virus Vaccines: Are We Making Progress?

Chapter 14: Prevention – Vaccines + Immunoglobulins

• Worldwide there are 6 different TBE vaccines – two from Western Europe, three from Russia and one from China. The two western European vaccines and one of the Russian vaccines have an adult and a pediatric formulation. • The products names are FSME IMMUN and FSME-IMMUN Junior; Encepur adults and Encepur children, Klesch-E-Vac, EnceVir and EnceVir Neo, Dry lyophilized TBE Moscow and Sen Tai Bao • All TBE vaccines except the one from China have similar but not identical immunization sched-ules with primary immunization (&gt;3 doses) and regular booster vaccinations. For FSME-IMMUN, Encepur and EnceVir a rapid immunization schedules is also licensed. The Chinese vaccine is giv-en with 2 primary doses 2 weeks apart followed by annual boosters. • All vaccines induce significant immune responses. In the absence of a formal correlate of pro-tection, the presence of neutralizing antibodies is used as a surrogate marker for protection. • Recent clinical studies show long-term seropersistence of TBE antibodies after the first booster vaccination (dose 4) with the two European vaccines. • An effectiveness of approximately 99% (years 2000–2006) and 98,7% (years 2000-2011) was calculated for regularly vaccinated persons in Austria, a country with established high vaccina-tion uptake. • Whereas in Western Europe post-exposure prophylaxis with immunoglobulins was discontinued in the late 1990s, in the highly endemic regions of Russia it continues to be common practice. • Both - FSME-IMMUN and Encepur are well tolerated with a well-established safety profile. TBE-Moscow and EnceVir appear to be somewhat more reactogenic.

2027. Immune Correlates of Protection Against Herpes Zoster (HZ) in People Living with HIV (PLWH)

BackgroundHZ has high morbidity in immune-compromised hosts, including PLWH. Two vaccines against HZ are available, but their efficacy in PLWH is unknown. A surrogate marker of protection against HZ would facilitate efficacy studies of HZ vaccines in PLWH, as compared with HZ clinical outcome studies. To this goal, our study investigated the association of cytotoxic T lymphocytes (CTL) and regulatory T cells (Treg) with incident HZ in PLWH.MethodsThe study used peripheral blood mononuclear cells (PBMC) cryopreserved at mean (SD) of 2.7 (2.5) months before HZ from 31 PLWH cases on ART with plasma vRNA < 200 c/mL, and CD4 counts ≥200 cells/µL. 31 non-HZ controls were matched to cases by CD4 count, age, sex, race, parent study, and ART duration. T cell subsets were measured by flow cytometry after ex vivo VZV- and mock-restimulation and in freshly thawed unstimulated PBMC using the following markers: CD3, CD8, CD25, CD28, CD39, CD57, CD127, CTLA4, FOXP3, IFNg, IL10, KLRG1, LAG3, PD1, perforin, TGFb, TIM3 and TNFa. Data were analyzed by paired t-tests.ResultsAt PBMC collection, PLWH had mean (SD) age 41 (10) years; 16 females; 28 White and 22 Black non-Hispanics; mean (SD) CD4 counts 501 (222) cells/µL; 56 (90%) vRNA < 50 c/mL; median ART duration 50 weeks. In unstimulated PBMC, HZ cases had higher %FOXP3+CD25+(CD4+) Treg compared with controls (P = 0.08). Cases generally had lower responses to ex vivo VZV-restimulation (after subtraction of mock) compared with controls, including %perforin+(CD8+) CTL (P = 0.07) and %IL10+(CD4+) (P = 0.04) and %TGFb+(CD4+) Treg (P = 0.07). %FOXP3+CD25+(CD4+) Treg in unstimulated PBMC did not correlate with VZV-specific %perforin+(CD8+) or %IFNg+(CD4+) effector T cells, but the VZV-specific effector T cell percentages correlated with each other (r = 0.24, P = 0.05).ConclusionAlthough limited by small numbers, this study showed that before development of HZ, PLWH had marginally increased number of Treg in blood and decreased VZV-specific responses. VZV-specific Treg and CTL were equally lower in cases compared with controls, suggesting that a general low VZV-specific T cell responsiveness precedes HZ in PLWH. The lack of association between circulating Treg and VZV-specific T cell responses suggests independent mechanisms of action.Disclosures All authors: No reported disclosures.

Predicting vaccine efficacy against tuberculosis using immunologic and radiologic measures in the non-human primate model

Abstract The only licensed vaccine (BCG) for tuberculosis (TB) has variable efficacy and does not protect against pulmonary TB. New vaccines are in development and in human clinical trials. However, vaccine trials are long and expensive without useful surrogate markers of protection. A problem thus emerges: what does a protective response to TB look like? This project’s goal is to identify markers of vaccine efficacy that can further be developed as new clinical endpoints. We posit that exploiting differences in vaccine outcome (protected vs. unprotected) will identify novel markers that correlate with outcome, and that serial PET/CT will predict outcome early in infection, as well as identify sites of protection. Cynomolgus macaques vaccinated with BCG and a multistage vaccine (H56 in CAF01) have more sterile thoracic lymph nodes (LN) 6 months post-Mtb challenge, compared to unvaccinated controls, indicating that LN play an important role in H56-conferred protection. BCG/H56 prevents dissemination but not establishment of infection; vaccinated animals also have fewer CFU per granuloma than controls. Total FDG avidity by PET scan in lungs (a surrogate for inflammation and disease) and individual granuloma FDG avidity of vaccinated animals are significantly lower than controls at both early and late time points. Total FDG avidity can also be used to predict vaccine efficacy, as the animals protected by BCG/H56 had less FDG in lungs than unprotected vaccinated and latent controls at early time points post challenge, and will be further developed as a surrogate marker of protection at early time points in pre-clinical trials.

A large portion of meningococcal antigen typing system-negative meningococcal strains from spain is killed by sera from adolescents and infants immunized with 4CMenB.

A new vaccine (the 4CMenB 4-component protein vaccine [Bexsero], which includes PorA, factor H-binding protein [fHbp], neisserial heparin-binding antigen [NHBA], and Neisseria adhesin A [NadA]) against serogroup B meningococci has recently been approved for use in people older than age 2 months in Europe, Australia, and Canada. Preapproval clinical efficacy studies are not feasible for invasive meningococcal disease because its incidence is low/very low, and the serum bactericidal antibody (SBA) titer (or the human SBA [hSBA] titer when human complement is used in the assay) has been used as a surrogate marker of protection. However, the hSBA assay cannot be used on a large scale, and therefore, a meningococcal antigen typing system (MATS) was developed. MATS combines conventional PorA genotyping with an enzyme-linked immunosorbent assay (ELISA) that quantifies both the expression and the cross-reactivity of antigenic variants. The assay has been used to evaluate the potential of the 4CMenB meningococcal group B vaccine to cover group B strains in several countries. Some recent data suggest that MATS is a conservative predictor of strain coverage. We used pooled sera from adolescents and infants to test by the hSBA assay 10 meningococcal group B strains isolated in Spain that were negative for the 3 antigens (n = 9) or that had very low levels of the 3 antigens (n = 1) by MATS. We found that all strains were killed by sera from adolescents and that 5 of the 10 strains were also killed, although at a low titer, by sera from infants. Our data confirm that MATS underestimates vaccine coverage.

Predicting vaccine efficacy against tuberculosis using immunologic and radiologic markers in the non-human primate model (VAC7P.974)

Abstract The only licensed vaccine (BCG) for tuberculosis (TB) has variable efficacy and does not protect against pulmonary TB. New vaccines are in development and in human clinical trials. However, vaccine trials are long and expensive without useful surrogate markers of protection. A problem thus emerges: what does a protective response to TB look like? This project’s goal is to identify markers of vaccine efficacy that can further be developed as new clinical endpoints. We posit that exploiting differences in vaccine outcome (protected vs. unprotected) will identify novel immunologic markers that correlate with outcome, and serial PET/CT will predict outcome early in infection. Vaccine-induced protection could work at any point in early infection: movement of bacilli from airway to parenchyma; formation of primary lesions; migration of bacteria to LN; and development of secondary lesions. In both our rhesus and cynomolgus macaque models of infection, prime-boost vaccination with BCG followed by viral-expressed or protein antigens protects against TB disease better than BCG alone or no vaccine. However, granuloma formation is not prevented and the vaccines do not reduce initial granuloma numbers. However, total PET signal, as a surrogate for inflammation and disease, in lungs of vaccinated animals is significantly lower at early time points. Future work will develop the predictive markers to elucidate early immune mechanisms that confer protection in the lungs.

Advances and controversies in yellow fever vaccination.

Ever since its development in 1937, the live-attenuated 17D yellow fever (YF) vaccine has been one of the most effective vaccines available to man. In this review we highlight the major steps in the development of 17D YF vaccine. We discuss the use of neutralizing antibodies as a surrogate marker for protection, and explore the strengths and weaknesses of the current plaque reduction neutralization test (PRNT), a technique developed in the 1960s that continues to be superior to every modern test in both sensitivity and specificity. The neutralizing antibodies demonstrated by the PRNT can be detected for several decades after vaccination, possibly even for the remainder of the recipient's natural life. We review the available evidence on the duration of protection after primary vaccination, a topic that has been the subject of controversy over the last few months. For persons who are immunocompromised due to disease, medication or advancing age, the duration of protection may be shorter: they should always have their vaccine response checked by PRNT. Due to the higher risk of severe adverse events after vaccination with 17D YF in this group, the development of a new, inactivated vaccine will have substantial benefits in this population.

Expression of TNF-Alpha-Dependent Apoptosis-Related Genes in the Peripheral Blood of Malagasy Subjects with Tuberculosis

The majority of Mycobacterium tuberculosis (Mtb) infections remain asymptomatic with only up to 10% progressing to clinical tuberculosis. However, the constituents of the effective “protective immunity” against tuberculosis responsible for containing most infections remain unknown. Evaluating gene transcriptional profiles in tuberculosis clinical cohorts is one approach to understanding the spectrum of tuberculosis progression. It is clear that apoptosis plays a role in the control of tuberculosis but the utility of apoptosis-related genes as surrogate markers of protection against tuberculosis has not been well investigated. To characterize potential surrogate markers that could discriminate different phases of the clinical tuberculosis spectrum, we investigated gene expression of several TNF-alpha dependent apoptotic genes (TNFR1, TNFR2, FLICE, FLIPs) by real-time RT-PCR of peripheral blood cells from cohorts of individuals with active tuberculosis or potential exposure to tuberculosis.Newly diagnosed tuberculosis patients (n = 23), their close household contacts (n = 80), and community controls (n = 46) were tested at intervals over a period of up to two years. Latent infection or previous Mtb contact was assessed by ELISPOT and TST and complete blood counts were performed during the follow up.Results showed significant upregulation of FLIPs expression by infected individuals regardless of clinical status at entry to the study. A higher percentage of lymphocytes was found in the infected household contacts that remained healthy. In contrast, in individuals with active TB, a significant upregulation of TNFR2 expression, a significantly higher percentage of monocytes and a significantly decreased lymphocyte count were seen, compared to subjects that remained healthy. Moreover, the household contacts who subsequently developed signs of TB also had a significantly high number of monocytes.These data suggest tuberculosis may be associated with decreased T-cell survival (perhaps due to apoptosis) while inhibition of apoptosis in monocytes could lead to a relative increase in these cells: a situation predicted to favour Mtb.

Immunization with Cholera Toxin B Subunit Induces High-Level Protection in the Suckling Mouse Model of Cholera

Cholera toxin (CT) is the primary virulence factor responsible for severe cholera. Vibrio cholerae strains unable to produce CT show severe attenuation of virulence in animals and humans. The pentameric B subunit of CT (CTB) contains the immunodominant epitopes recognized by antibodies that neutralize CT. Although CTB is a potent immunogen and a promising protective vaccine antigen in animal models, immunization of humans with detoxified CT failed to protect against cholera. We recently demonstrated however that pups reared from mice immunized intraperitoneally (IP) with 3 doses of recombinant CTB were well protected against a highly lethal challenge dose of V. cholerae N16961. The present study investigated how the route and number of immunizations with CTB could influence protective efficacy in the suckling mouse model of cholera. To this end female mice were immunized with CTB intranasally (IN), IP, and subcutaneously (SC). Serum and fecal extracts were analyzed for anti-CTB antibodies by quantitative ELISA, and pups born to immunized mothers were challenged orogastrically with a lethal dose of V. cholerae. Pups from all immunized groups were highly protected from death by 48 hours (64–100% survival). Cox regression showed that percent body weight loss at 24 hours predicted death by 48 hours, but we were unable to validate a specific amount of weight loss as a surrogate marker for protection. Although CTB was highly protective in all regimens, three parenteral immunizations showed trends toward higher survival and less weight loss at 24 hours post infection. These results demonstrate that immunization with CTB by any of several routes and dosing regimens can provide protection against live V. cholerae challenge in the suckling mouse model of cholera. Our data extend the results of previous studies and provide additional support for the inclusion of CTB in the development of a subunit vaccine against V. cholerae.

Pneumococcal vaccine and opsonic pneumococcal antibody

Streptococcus pneumoniae is a major human pathogen responsible for the majority of bacterial pneumonia cases as well as invasive pneumococcal diseases with high mortality and morbidity. Use of conjugate vaccines targeting the pneumococcal capsule has dramatically reduced the incidence of invasive diseases, and there are active efforts to further improve the conjugate vaccines. However, in children new pneumococcal vaccines can no longer be tested with placebo-based clinical trials because effective vaccines are currently available. Thus, vaccine studies must depend on surrogate markers of vaccine efficacy. Although traditional antibody levels (e.g., ELISA) are useful as a surrogate marker of protection, they have limitations, and a bioassay measuring the capacity of antibodies to opsonize pneumococci has been developed. This opsonophagocytosis assay (OPA) replicates the in vivo mechanism of antibody protection and should therefore better reflect protection by vaccine-induced antibodies. Technical improvements of OPA have made this bioassay rapid, multiplexed, and practical for analyzing small samples including those from children. Strong correlations between ELISA and OPA have been observed in many studies of young children. However, poor correlations have been found in some important clinical situations (such as determination of protection by cross-reactive antibodies) and populations (such as elderly adults and immunodeficient patients). In these settings, OPA has become a useful supplementary measure of pneumococcal vaccine immunogenicity. Current efforts to standardize OPA will further expand its uses.

CCR7+ Central and CCR7− Effector Memory CD4+ T Cells in Human Cutaneous Leishmaniasis

The profile of central (=T(CM)) and effector (=T(EM)) memory CD4(+) T cell subsets and the possible role as surrogate markers of protection is studied in the volunteers with history of cutaneous leishmaniasis (HCL). Profile of T cell subsets based on CCR7/CD45RA expressions and phenotypic changes after soluble Leishmania antigen (SLA) stimulation were analyzed. Then, sorted CD4(+)CD45RO(-)CD45RA(+) naïve T, CD4(+)CD45RO(+)CD45RA(-)CCR7(-) T(EM,) CD4(+)CD45RO(+)CD45RA(-)CCR7(+) T(CM) subsets were cultured with SLA for proliferation, cytokine production and intracellular cytokine assays. In the HCL and control volunteers, the mean frequencies of CD4(+)CD45RA(+)CCR7(+) naïve T cells and CD4(+)CD45RA(-)CCR7(-) T(EM) cells were higher than the other subsets before culture. Frequency of naïve T cells and CD4(+)CD45RA(-)CCR7(+) T(CM) cells was significantly decreased (P=0.01 for naïve T and P<0.05 for T(CM) cells) and frequency of T(EM) cells was significantly increased after SLA stimulation compared to before culture (P<0.001). By CFSE labeling, CD4(+)CD45RO(+)CD45RA(-)CCR7(+) T(CM) cells showed more proliferation potential than CD4(+)CD45RO(+)CD45RA(-)CCR7(-) T(EM) cells. Stimulation of the T(EM) cells in HCL volunteers induced a significantly higher IFN-γ production (P=0.04) with higher number of intracellular IFN-γ positive cells (P=0.032) than the same cells from controls. A significantly higher number of T(CM) cells produced IL-2 in HCL volunteers compared with controls (P<0.05). Most of the intracellular IFN-γ positive T(EM) cells were proliferating CFSE-dim populations (P<0.05). A combination of Leishmania-reactive IFN-γ producing CD4(+)CD45RO(+)CD45RA(-)CCR7(-) T(EM) and Leishmania-reactive IL-2 producing CD4(+)CD45RO(+)CD45RA(-)CCR7(+) T(CM) are identified in individuals with history of CL which might play a role in protective recall immune response against Leishmania infection.

Antibodies Against Neutralization Epitopes of Human Cytomegalovirus gH/gL/pUL128-130-131 Complex and Virus Spreading May Correlate with Virus Control In Vivo

Recently, human cytomegalovirus (HCMV) UL128-131 locus gene products have been found to be associated with glycoprotein H (gH) and glycoprotein L (gL) to form a pentameric glycoprotein complex gH/gL/pUL128-130-131, which is present in the virus envelope and elicits production of neutralizing antibodies. Purpose of this study was to verify whether in vitro activities of these antibodies may correlate with protection in vivo. By using potently neutralizing human monoclonal antibodies (mAbs) targeting 10 different epitopes of the pentameric complex, a competitive ELISA assay was developed, in which the pentamer bound to the solid-phase was reacted competitively with human sera and murinized human mAbs. In addition, inhibition of virus spreading (plaque formation and leukocyte transfer) by neutralizing human mAbs and sera was investigated. In the absence of any reactivity of sera from HCMV-seronegative subjects, antibodies to all 10 epitopes were detected in HCMV-seropositive individuals. During primary HCMV infection in pregnancy antibodies to some epitopes showed a trend towards an earlier appearance in mothers not transmitting the virus to the fetus as compared to transmitting mothers. In addition, the activity of neutralizing human mAbs and sera in blocking virus cell-to-cell spreading and virus transfer to leukocytes from infected endothelial cells was shown to develop during the convalescent phase of primary infection. Dissection of the neutralizing/inhibiting activities of human sera may be helpful in the study of their protective role in vivo. In particular, neutralizing antibodies to the pentamer may be a surrogate marker of protection in vivo.