Quantitative Antibody Response Research Articles

Antibody Responses After Oxford Astrazeneca (Covishield) Vaccine Among Healthcare Workers in Dhaka Medical College, Dhaka, Bangladesh

Background: Oxford AstraZeneca (Covishield) vaccine is the 1st vaccine administered in Bangladesh to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We assessed the antibody response after 1st and 2nd dose of this vaccine in health care workers of Dhaka Medical College hospital, Bangladesh.Methods: Health care workers (teachers, clinicians and medical staff) of Dhaka Medical College Hospital who participated in this study were asked to collect blood sample after 28 days of 1st vaccination and 14 days after 2nd vaccination. Quantitative post-vaccination antibody responses were measured using the chemiluminescent immunoassay, ADVIA Centaur (Siemens, Munich, Germany) SARS-CoV-2 IgG (COV2G) assay (output index was ≥1·00).Findings: Among 308 participants 197(64%) were male and 111(36%) were female. The mean age was 45·08 years (±9·2 years). 35·06% participants were previously COVID-19 positive confirmed by RT- PCR. Vaccine related antibody was found in 126(41%) participants after 1st dose of AstraZeneca vaccine. After 2nd dose of vaccine reactive level of antibody was found in 172(93%) participants. Antibody responses were significantly higher in previously infected participants compared to participants who had no history of previous COVID-19 after1st dose (51·92±50·85 vs 23·67±41·07, p=0·001) as well as 2nd dose of vaccine (64·12±97·76 vs 35·04±64·84, p=0·001). No difference in antibody response was observed among participants with or without comorbidities.Interpretation: Oxford AstraZeneca Covishield vaccine induces a strong immune response after two doses of vaccination.Funding Information: The study was funded by the office of Directorate General of Health Services, Ministry of Health and Family Welfare, Bangladesh.Declaration of Interests: We wish to confirm that there are no known conflicts of interest associated with this publication.Ethics Approval Statement: All the participants provided written informed consent and the protocol was approved by ethical review committee of Dhaka Medical College.

Group B Streptococcus (GBS) vaccine

Intrapartum antibiotic prophylaxis (IPA) during labor for women identified as having recto-vaginal Groups B Streptococcus (GBS) colonization, has been successful in preventing early-onset invasive (<7 days of age) disease in new-borns in high income countries where implemented. Nevertheless, GBS remains a leading cause of neonatal sepsis in high-income settings, and is now also the leading cause of bacterial meningitis in USA. Also, the incidence of invasive GBS disease remains high in sub-Saharan African countries, where IAP is not feasible, whilst its contribution to neonatal sepsis is uncertain in South Asia. Furthermore, recent data indicate that the burden of GBS associated stillbirths might be similar to that for EOD in some African countries. Recent advances in the prevention of invasive GBS disease during early infancy, including the potential to prevent late onset disease (7-89 days age) which is not preventable by IAP, is the development of polyvalent polysaccharide protein conjugate vaccines. Recent studies have reported on the safety and immunogenicity of a trivalent (serotypes Ia, Ib and III) GBS polysaccharide protein conjugate vaccine (GBS-3CV). This vaccine elicits immune responses in pregnant women vaccinated during the last trimester, albeit less so among women in whom the pre-vaccination antibody titers were less than the lower detection limit of the assay. The ratio of antibody transfer to the newborns’ of these women was approximately 0.5-0.7, indicating less efficient transplacental transfer of polysaccharide targeted IgG than is observed for IgG targeted at protein antigens. Furthermore, vaccination of HIV-infected women, elicited lower quantitative antibody responses than in HIV-uninfected women, suggesting the need for different vaccine schedules in these women. Also, the GBS conjugate vaccine appears to be more immunogenic in African than European/North American women. The licensure of a GBS vaccine for pregnant women aimed at protection against invasive GBS disease of their newborns will, however, require sample size in excess of 70,000 participants for an invasive disease endpoint. An alternate licensure pathway, as is the case for meningococcal vaccine, could be premised on establishing a sero-correlate of protection against invasive disease and using this to license the vaccine based on immunogenicity and safety.

Quantitative and Functional Antibody Responses to the 13-Valent Conjugate and/or 23-Valent Purified Polysaccharide Vaccine in Aging HIV-Infected Adults.

The number of aging human immunodeficiency virus-infected (HIV+) individuals living in the United States has substantially grown over the past two decades. Advanced age and HIV infection both increase susceptibility to Streptococcus pneumoniae infection due to B cell dysfunction. The combined impact of these factors on pneumococcal vaccine responses remains unknown. We assessed serum immunoglobulin (Ig) G and IgM levels and opsonophagocytic killing assay (OPA) titers to pneumococcal serotypes 14 and 23F in HIV+ subjects and HIV-uninfected (HIV-) controls 50-65 years old. HIV+ individuals with CD4+ T cells/μl (CD4) >200 and ≥1 year of antiretroviral therapy (ART) received either a dose of the 13-valent pneumococcal conjugate vaccine followed by the 23-valent pneumococcal polysaccharide vaccine 8 weeks later (PCV/PPV) as currently recommended (n=15) or a single dose of PPV only (n=22). HIV- controls received PCV/PPV (n=14). HIV+ PCV/PPV and PPV groups exhibited similar increases in IgG levels and OPA titers for both serotypes after immunization. Postvaccination IgM levels for serotype 23F, but not 14, were significantly higher in HIV+ PCV/PPV compared to PPV groups. IgG and IgM levels for serotype 14 and OPA titers to serotype 23F were significantly reduced in HIV+ compared to HIV- PCV/PPV groups. Serotype-specific IgG levels correlated with OPA titers for all groups. Our data suggest that the recommended PCV/PPV regimen may not significantly improve quantitative or functional antibody responses compared to PPV only in aging HIV+ subjects. Continued efforts aimed at improving vaccine responses in this high risk population are warranted.

Quantitative and Qualitative Antibody Responses to Immunization With the Pneumococcal Polysaccharide Vaccine in HIV-Infected Patients After Initiation of Antiretroviral Treatment: Results From a Randomized Clinical Trial.

Pneumococcal vaccination is recommended for human immunodeficiency virus-infected (HIV+) persons; the best timing for immunization with respect to initiation of antiretroviral therapy (ART) is unknown. Double-blind, placebo-controlled trial in HIV+ with CD4(+) T cells/µL (CD4) ≥ 200 randomized to receive the 23-valent pneumococcal polysaccharide vaccine (PPV23) or placebo at enrollment, followed by placebo or PPV23, respectively, 9-12 months later (after ≥6 months of ART). Capsular polysaccharide-specific immunoglobin (Ig) G and IgM levels to serotypes 1, 3, 4, 6B, and 23F, and opsonophagocytic killing activity (OPA) to serotypes 6B and 23F were evaluated 1 month postvaccination. One hundred seven subjects were enrolled, 72 (67.3%) were evaluable (36/group). Both groups had significant increases in pre- to 1-month postvaccination IgG levels, but negligible to IgM, and significant increases in OPA titers to serotype 6B but not to 23F. There were no significant differences between groups in serotype-specific IgM or IgG levels or OPA titers. For the combined groups, there was a significant correlation between serotype-specific IgG and OPA titers to 23F but not to 6B. There was no correlation between CD4, viral load and IgG responses. In HIV+ with CD4 ≥ 200, delaying PPV23 until ≥6 months of ART does not improve responses and may lead to missed opportunities for immunization.

Antibody-mediated immunity induced by engineered Escherichia coli OMVs carrying heterologous antigens in their lumen

BackgroundOuter membrane vesicles (OMVs) from Gram-negative bacteria are gaining increasing attention as vaccine platform for their built-in adjuvanticity and for their potential use as carriers of heterologous antigens. These 2 properties offer the opportunity to make highly effective, easy to produce multi-valent vaccines. OMVs can be loaded with foreign antigens by targeting protein expression either to the outer membrane or to the periplasm of the OMV-producing strain. Periplasmic expression is simple and relatively efficient but leads to the accumulation of recombinant antigens in the lumen of OMVs and the ability of OMVs carrying internalized antigens to induce antigen-specific antibody responses has been only marginally investigated and is considered to be sub-optimal.MethodsWe have systematically analyzed in qualitative and quantitative terms antibody responses induced by OMVs carrying different heterologous antigens in their lumen. Group A Streptococcus (GAS) Slo, SpyCEP, Spy0269 and Group B Streptococcus (GBS) SAM_1372 were fused to the OmpA leader sequence for secretion and expressed in Escherichia coli. OMVs from the recombinant strains were purified and tested for immunogenicity and protective activity.ResultsAll proteins were incorporated into the OMVs lumen in their native conformation. Upon mice immunization, OMVs induced high functional antibody titers against the recombinant proteins. Furthermore, immunization with Slo-OMVs and SpyCEP-OMVs protected mice against GAS lethal challenge.ConclusionsThe efficiency of antigen delivery to the vesicular lumen via periplasmic expression, and the surprisingly high immunogenicity and protective activity of OMVs carrying internalized recombinant antigens further strengthens the potential of OMVs as vaccine platform.

Use of vaccines in the evaluation of presumed immunodeficiency

The assessment of the humoral immune response is a critical component in the evaluation of patients suspected of having a primary immune deficiency disease (PIDD). [1] Bonilla F.A. Bernstein I.L. Khan D.A. Chinen J. Frank M. Kobrynski L. Practice parameter for the diagnosis and management of primary immunodeficiency. Ann Allergy Asthma Immunol. 2005; 94: S1-S63 Abstract Full Text PDF PubMed Scopus (437) Google Scholar In fact, more than 50% of the patients with immune deficiency have some impairment in the ability to make specific antibodies and/or have a quantitative deficiency of antibodies. Although there are a number of laboratory tools that are helpful in the evaluation of patients suspected of having an antibody deficiency disorder, such as quantitative serum immunoglobulin analysis, analysis of lymphocyte subpopulations by flow cytometry, or even genetic diagnoses of single-gene mutations, the evaluation of a patient's response to immunization with a vaccine and the production of specific antibodies are extremely important. The assessment of qualitative antibody responses is not only important in confirming a specific antibody immune deficiency but is also important in the decision-making process for using immunoglobulin replacement therapy. 2 Stiehm E. The four most common peditric immunodefiencies. J Immunotoxicol. 2008; 5: 227-234 Crossref PubMed Scopus (59) Google Scholar , 3 Stiehm E. Orange J. Ballow M. Lehman H. Therapeutic use of immunoglobulins. Adv Pediatr. 2010; 57: 185-218 Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar If on initial evaluation patients demonstrate a deficient quantitative antibody response, an antigen challenge or booster vaccine immunization with existing Food and Drug Administration (FDA)–approved vaccines can determine whether the patient has the ability to generate an adequate qualitative antibody response. In an effort to provide guidance in the evaluation of patients for a humoral PIDD, a working group of the Basic and Clinical Immunology Interest Section of the American Academy of Allergy, Asthma and Immunology (AAAAI) published a report in September 2012. [4] Orange J. Ballow M. Stiehm E. Ballas Z. Chinen J. De La Morena M. Use and interpretation of diagnostic vaccination in primary immunodeficiency: a working group report of the Basic and Clinical Immunology Interest Section of the American Academy of Allergy, Asthma and Immunology. J Allergy Clin Immunol. 2012; 130: S1-S24 Abstract Full Text Full Text PDF PubMed Scopus (289) Google Scholar This article discusses some of the topics related to the use and interpretation of vaccine responses in the evaluation of patients for a possible PIDD.

Chronic Mycoplasma conjunctivitis in house finches: Host antibody response and M. gallisepticum VlhA expression

Previous studies have shown that house finch field isolates of Mycoplasma gallisepticum (MG) vary in virulence and ability to induce an antibody response. After experimental inoculation, MG causes persistent, severe disease in a subset of individuals. In this study, we further characterized MG infection using five field isolates, with an emphasis on chronically diseased birds. After experimental inoculation of house finches, MG load was measured by quantitative PCR and anti-MG antibody responses were measured by ELISAs. Birds with chronic disease had significantly higher pathogen loads and antibody responses than did birds without chronic disease. Using a monoclonal antibody (MAb86) specific for a variant of the MG VlhA adhesin and immunodominant surface protein, we show that VlhA expression differs among MG isolates in this study, and that in vivo VlhA changes occur in house finches infected with MG. Overall, our results suggest that chronic MG disease has a strong pathogen-mediated component.

Inferior quantitative and qualitative immune responses to pneumococcal conjugate vaccine in infants with nasopharyngeal colonization by Streptococcus pneumoniae during the primary series of immunization

Background Heightened immunogenicity, measured one month after the primary series of pneumococcal conjugate vaccine (PCV), in African children was previously hypothesized to be due to increased rates of nasopharyngeal pneumococcal colonization during early infancy. Methods We analyzed the effect of selected vaccine-serotype (6B, 19F and 23F) nasopharyngeal colonization prior to the first PCV dose or when colonized for the first time prior to the second or third (2nd/3rd) PCV dose on serotype quantitative and qualitative antibody responses. Results Colonization prior to receiving the first PCV was associated with lower geometric mean antibody concentrations (GMCs) one month after the third dose of PCV and six months later to the colonizing-serotype. Colonized infants also had lower geometric mean titers (GMTs) on opsonophagocytosis activity assay (OPA) and a lower proportion had titers ≥8 against the colonizing serotypes (19F and 23F) post vaccination. Colonization occurring only prior to the 2nd/3rdPCV dose was also associated with lower GMCs and OPA GMTs to the colonizing-serotype. The effect of colonization with serotypes 19F and 23F prior to PCV vaccination had a greater effect on a lower proportion of colonized infants having OPA titers ≥8 than the effect of colonization on the lower proportion with antibody ≥0.35 μg/ml. Conclusion Infant nasopharyngeal colonization at any stage before completing the primary series of PCV vaccination was associated with inferior quantitative and qualitative antibody responses to the colonizing-serotype.

Effect of HIV Infection Status and Anti‐Retroviral Treatment on Quantitative and Qualitative Antibody Responses to Pneumococcal Conjugate Vaccine in Infants

Serotype-specific antibody concentration and opsonophagocytic activity (OPA) were evaluated after 3 doses of pneumococcal conjugate vaccine. Groups included human immunodeficiency virus (HIV)-positive infants with CD4(+) cell percentages > or =25% who initiated immediate antiretroviral treatment (the HIV+/ART+ group) or whose antiretroviral treatment was deferred until clinically or immunologically indicated (the HIV+/ART- group). Immune responses were also evaluated in HIV-noninfected infants born to HIV-seronegative (M-/I-) or HIV-positive mothers (M+/I-). Antibody concentrations were similar between HIV+/ART+ and HIV+/ART- infants. However, antibody concentrations were lower in M-/I- infants than in M+/I- infants. Nevertheless, M-/I- infants had superior OPA responses, compared with those in HIV+/ART+ infants, who in turn had better OPA responses, compared with those in HIV+/ART- infants.

Association of the novel serologic anti-glycan antibodies anti-laminarin and anti-chitin with complicated Crohnʼs disease behavior

We tested a panel of novel serological anti-glycan antibodies including the previously unpublished anti-laminarin IgA (Anti-L) and anti-chitin IgA (Anti-C) carbohydrate antibodies for the presence in Crohn's disease (CD) patients, diagnosis and differentiation of CD, association with complicated disease behavior, and marker stability over time. The presence of Anti-L, Anti-C, anti-chitobioside IgA (ACCA), anti-laminaribioside IgG (ALCA), anti-mannobioside IgG (AMCA), and anti-Saccaromyces cervisiae IgG (gASCA) carbohydrate antibodies were tested in serum samples from 824 participants (363 CD, 130 ulcerative colitis [UC], 74 other gastrointestinal diseases, and 257 noninflammatory bowel/gastrointestinal disease controls) of the German IBD-network by enzyme-linked immunosorbent assay (ELISA; Glycominds, Lod, Israel) and for perinuclear antineutrophil cytoplasmic antibody (pANCA) by immunofluorescence. In all, 77.4% of the CD patients were positive for at least 1 of the anti-glycan antibodies. gASCA or the combination of gASCA/pANCA remained most accurate for the diagnosis of CD, but the combined use of the antibodies improved differentiation of CD from UC. Several single markers as well as an increasing antibody response were independently linked to a severe disease phenotype, as shown for the occurrence of complications, CD-related surgery, early disease onset, and ileal disease location. This was observed for both quantitative and qualitative antibody responses. The antibody status remained stable over time in most IBD patients. A panel of anti-glycan antibodies including the novel Anti-L and Anti-C may aid in differentiation of CD from UC, is associated with complicated CD behavior and IBD-related surgery, and is stable over time in a large patient cohort.

Antibody Response in Children Infected with Giardia intestinalis before and after Treatment with Secnidazole

We examined 364 school children for intestinal parasites in a sub-urban zone of Caracas, Venezuela. Giardia intestinalis was the most prevalent parasite in stool samples from 34 children. Levels of IgA and IgG antibodies to G. intestinalis were assessed by enzyme-linked immunosorbent assay and Western blot before and after treatment with secnidazole. All patients were cured with a reduction of IgA antibody levels in 26 of 34 children and a reduction in IgG-specific antibody levels in 18 of 34 children. Serum of infected patients reacted with proteins of 14 kD to 137 kD. Some patients did not show a change in IgA serum reactivity for parasite proteins by Western blot after treatment. Seventeen children showed reduction of the reactivity or disappearance of protein reactivity (mainly the 14-kD, 122-kD, and 137-kD proteins). Antibody response was not related to clinical status, but quantitative and qualitative serum antibody response against G. intestinalis infection could be used to assess levels of new protein markers that decrease or disappear with successful chemotherapy.

A simplified immunoprecipitation method for quantitatively measuring antibody responses in clinical sera samples by using mammalian-produced Renillaluciferase-antigen fusion proteins

BackgroundAssays detecting human antigen-specific antibodies are medically useful. However, the usefulness of existing simple immunoassay formats is limited by technical considerations such as sera antibodies to contaminants in insufficiently pure antigen, a problem likely exacerbated when antigen panels are screened to obtain clinically useful data.ResultsWe developed a novel and simple immunoprecipitation technology for identifying clinical sera containing antigen-specific antibodies and for generating quantitative antibody response profiles. This method is based on fusing protein antigens to an enzyme reporter, Renilla luciferase (Ruc), and expressing these fusions in mammalian cells, where mammalian-specific post-translational modifications can be added. After mixing crude extracts, sera and protein A/G beads together and incubating, during which the Ruc-antigen fusion become immobilized on the A/G beads, antigen-specific antibody is quantitated by washing the beads and adding coelenterazine substrate and measuring light production.We have characterized this technology with sera from patients having three different types of cancers. We show that 20–85% of these sera contain significant titers of antibodies against at least one of five frequently mutated and/or overexpressed tumor-associated proteins. Five of six colon cancer sera tested gave responses that were statistically significantly greater than the average plus three standard deviations of 10 control sera. The results of competition experiments, preincubating positive sera with unmodified E. coli-produced antigens, varied dramatically.ConclusionThis technology has several advantages over current quantitative immunoassays including its relative simplicity, its avoidance of problems associated with E. coli-produced antigens and its use of antigens that can carry mammalian or disease-specific post-translational modifications. This assay should be generally useful for analyzing sera for antibodies recognizing any protein or its post-translational modifications.

Quantitative and Qualitative Antibody Response to Pneumococcal Conjugate Vaccine Among African Human Immunodeficiency Virus-Infected and Uninfected Children

To determine the quantitative and qualitative antibody responses to a pneumococcal conjugate vaccine (PnCV) in human immunodeficiency virus (HIV)-exposed infected and uninfected children. Children were randomized to receive either a PnCV or placebo at 6, 10 and 14 weeks of age. PnCV serotype-specific antibody concentrations were measured by a standard enzyme immunoassay (EIA) and a 22F modified EIA (22F EIA) on single serum samples drawn at 21-42 days post-dose 3. Functional activities of the serotype-specific antibody to serotypes 6B, 19F and 23F were measured with an opsonophagocytic assay (OPA). The geometric mean antibody concentrations (GMC) were similar in HIV-infected and HIV-uninfected PnCV recipients for 7 of the 9 vaccine serotypes. In placebo recipients, the GMCs were significantly higher in HIV-infected than in uninfected children for 7 of the serotypes. In HIV-infected PnCV recipients, the GMCs were lower for 5 of the serotypes in children with severe acquired immunodeficiency syndrome than in children who were asymptomatic or mildly symptomatic with acquired immunodeficiency syndrome. HIV-infected PnCV recipients were less likely to have measurable functional antibody (OPA titer > or =1/8) to all 3 studied serotypes (6B, 19F and 23F) than in HIV-uninfected children. HIV-infected children required a higher concentration of anticapsular antibody to achieve 50% of the maximum uptake of labeled Streptococcus pneumoniae in the OPA assay than HIV-uninfected children for 2 of the 3 serotypes, although this was significant only for serotype 6B (P = 0.0005). HIV-infected children have similar quantitative antibody responses but poorer qualitative antibody responses to the PnCV.

Role of CD8+ T cells in control of West Nile virus infection.

Infection with West Nile virus (WNV) causes fatal encephalitis more frequently in immunocompromised humans than in those with a healthy immune system. Although a complete understanding of this increased risk remains unclear, experiments with mice have begun to define how different components of the adaptive and innate immune response function to limit infection. Previously, we demonstrated that components of humoral immunity, particularly immunoglobulin M (IgM) and IgG, have critical roles in preventing dissemination of WNV infection to the central nervous system. In this study, we addressed the function of CD8(+) T cells in controlling WNV infection. Mice that lacked CD8(+) T cells or classical class Ia major histocompatibility complex (MHC) antigens had higher central nervous system viral burdens and increased mortality rates after infection with a low-passage-number WNV isolate. In contrast, an absence of CD8(+) T cells had no effect on the qualitative or quantitative antibody response and did not alter the kinetics or magnitude of viremia. In the subset of CD8(+)-T-cell-deficient mice that survived initial WNV challenge, infectious virus was recovered from central nervous system compartments for several weeks. Primary or memory CD8(+) T cells that were generated in vivo efficiently killed target cells that displayed WNV antigens in a class I MHC-restricted manner. Collectively, our experiments suggest that, while specific antibody is responsible for terminating viremia, CD8(+) T cells have an important function in clearing infection from tissues and preventing viral persistence.

Recognition patterns of Neospora caninum tachyzoite antigens by bovine IgG at different IFAT titres.

This study describes qualitative and quantitative antibody response in cows naturally infected with Neospora caninum. The study was carried out with 269 serum samples obtained from 24 cows over a period of 15 weeks. Prior to sample collection, the cows were tested with ELISA. The 269 samples were screened with IFAT and categorized into seven IFAT titre groups (< 1 : 80, 1 : 80, 1 : 200, 1 : 600, 1 : 1000, 1 : 2000, > 1 : 2000). The samples were finally analysed by Western blotting. Seven immunodominant antigens (approximately 18-, approximately 25-, approximately 33-, approximately 35-36-, approximately 45-46-, approximately 47-, approximately 60-62 kDa) and five minor antigens (approximately 25, approximately 51, approximately 64, approximately 77, approximately 116 kDa) were recognized by cow sera. The recognition of approximately 46 kDa antigen by cow sera was common to samples with IFAT titre 1 : 80 and above. Another common antigen was the approximately 18 kDa antigen, which was recognized by samples with IFAT titre 1 : 200 and above. The most remarkable observation was the presence of the 45-46 kDa, the 77 kDa, and absence of the 18 kDa antigenic bands in samples with IFAT titre 1 : 80. This observation was consistent even in the face of fluctuating antibody titre where serum antibody titres from an animal exceeded then failed to reach 1 : 80. Antibody fluctuation was observed across all cows (pregnant and aborted) with no discernible fluctuation pattern. However, the fluctuation in antibody titre observed appeared to be most remarkable in initially ELISA-negative pregnant cows, and to a lesser extent in ELISA-positive pregnant cows, and ELISA-positive aborted cows. Although there was fluctuation in antibody titre, the banding patterns of N. caninum tachyzoite antigens by cows within the same IFAT titre group remained similar.

Experimental reproduction of postweaning multisystemic wasting syndrome in cesarean-derived, colostrum-deprived piglets inoculated with porcine circovirus type 2 (PCV2): investigation of quantitative PCV2 distribution and antibody responses.

Sixteen cesarean-derived, colostrum-deprived piglets were inoculated intranasally with porcine circovirus type 2 (PCV2), originally isolated from a pig affected with postweaning multisystemic wasting syndrome (PMWS). At 1 day postinoculation (PI), 3 of the 5 piglets in the uninoculated control group were moved to the room of inoculated piglets for contact exposure. Porcine circovirus type 2 was detected by polymerase chain reaction (PCR) in swabs from inoculated piglets from 1 day PI and from contact piglets from 2 days after cohabitation. Porcine circovirus type 2 was also detected in all serum samples but not in control piglets 7 days PI. Until the end of study, PCV2 was detected in swabs and serum samples by PCR but not in the control piglets. One inoculated piglet died suddenly without clinical signs 19 days PI. Beginning at 14 days PI, 5 piglets, including 1 contact piglet, had clinical signs of depression, anorexia, and icterus, and 1 inoculated piglet died 21 days PI. Most of the piglets exhibiting the above clinical signs became moribund and were necropsied 21 and 28 days PI. In the piglets that showed clinical signs, gross lesions, including icterus of liver and hemorrhage in stomach, and typical histopathological lesions of PMWS, such as lymphoid depletion and basophilic intracytoplasmic inclusion bodies in lymph nodes and other tissues, were observed. Porcine circovirus type 2 was detected by PCR in all tissue samples except in those of the control piglets. Porcine circovirus type 2 was recovered from several tissue samples of the piglets necropsied until 35 days PI. In particular, PCV2 was recovered in high titer from most of the tissue samples of the piglets exhibiting clinical signs. Serum antibody against PCV2 was mostly detected in inoculated piglets and in contact piglets 14 and 21 days PI by an indirect fluorescence antibody test but was not detected in the piglets exhibiting clinical signs until 28 days PI. These results indicate that PCV2 was able to induce clinical PMWS in the absence of other swine pathogens and that there were significant differences in both the quantitative PCV2 distribution in tissues and the antibody response between the piglets that were infected and developed PMWS and those that were infected but remained healthy.

Randomized trial of the quantitative and functional antibody responses to a 7-valent pneumococcal conjugate vaccine and/or 23-valent polysaccharide vaccine among HIV-infected adults

In a double-blinded, randomized trial, human immunodeficiency virus (HIV)-infected adults with ≥200 CD4 cells/μl received placebo (PL), 7-valent conjugate, or 23-valent pneumococcal polysaccharide (PS) vaccine in one of the following two-dose combinations given 8 weeks apart: conjugate–conjugate, conjugate–polysaccharide, placebo–polysaccharide, placebo–placebo. A total of 67 persons completed the study. Neither significant increases in HIV viral load nor severe adverse reactions occurred in any group. After controlling for confounders, when compared with persons receiving placebo–polysaccharide, persons receiving conjugate–conjugate and conjugate–polysaccharide had higher antibody concentrations (serotypes 4, 6B, 9V and serotype 23F, respectively) and opsonophagocytic titers (functional antibody assay, serotypes 9V, 23F and serotypes 4, 6B, 9V, respectively) after the second dose ( P<0.05). The second dose with either conjugate or polysaccharide following the first conjugate dose, however, produced no further increase in immune responses.

Genetic regulation of acquired immune responses to antigens of Mycobacterium tuberculosis: a study of twins in West Africa.

The role of genetic factors in clinical tuberculosis is increasingly recognized; how such factors regulate the immune response to Mycobacterium tuberculosis in healthy individuals is unclear. In this study of 255 adult twin pairs residing in The Gambia, West Africa, it is apparent that memory T-cell responses to secreted mycobacterial antigens (85-kDa antigen complex, "short-term culture filtrate," and peptides from the ESAT-6 protein), as well as to the 65-kDa heat shock protein, are subject to effective genetic regulation. The delayed hypersensitivity response to intradermal tuberculin also demonstrates significant genetic variance, while quantitative T-cell and antibody responses to the 38-kDa cell membrane protein appear to be determined largely by environmental factors. Such findings have implications for vaccine development.

Quantitative antibody responses to structural (Core) and nonstructural (NS3, NS4, and NS5) hepatitis C virus proteins among seroconverting injecting drug users: impact of epitope variation and relationship to detection of HCV RNA in blood.

To gain insight into the natural history of hepatitis C virus (HCV), 13 human immunodeficiency virus (HIV)-seronegative injecting drug users were studied who seroconverted for HCV as determined by third-generation enzyme-linked immunosorbent assay, showed an ensuing antibody response to HCV, and were not treated with any antiviral drugs during follow-up. Subjects included 13 untreated HIV-negative individuals, of whom 5 (38.5%) apparently cleared HCV and were polymerase chain reaction (PCR)-negative in at least 3 consecutive samples, 3 (23.1%) showed transient viremia and were PCR-negative in 1 sample during the study period, and the other 5 (38.5%) showed persistent viremia. Viremia was determined longitudinally by reverse-transcription PCR (RT-PCR) and quantified by branched DNA (bDNA). HCV genotypes were determined on serial samples during follow-up. Quantitative antibody levels to core, NS3, NS4, and NS5 were determined using the Chiron RIBA HCV-titering Strip Immunoblot Assay, which is based on HCV genotype 1. The antibody responses to core, NS3, NS4, and NS5 were erratic. In individuals infected with HCV genotype 1, significantly higher median antibody responses to core (P =.02) and to NS4 (P =.04) were found as compared with those infected with other genotypes, showing a significant impact of HCV genotype specificity of the assay. In groups infected with HCV genotype 1, significantly higher median NS3 antibody titers (2.61 relative intensity [RI] vs. 0.38 RI; P =.003) were found in the individuals with persistent viremia than in those with apparent resolution of HCV RNA in blood. In groups infected with genotypes other than genotype 1, significantly higher median NS3 antibody titers (0.89 RI vs. 0.03 RI; P =.0004) and NS5 antibody titers (1.86 RI vs. 0.01 RI; P =.006) were found in the individuals with persistent viremia than in those with apparent resolution of HCV RNA in blood. Individuals with viral persistence had higher HCV-RNA loads with higher antibody responses as compared with individuals with apparent viral clearance from blood. Apparent viral clearance from blood was observed in an unexpectedly high percentage (38.5%), associated with a significant decrease of antibodies to NS3, independent of HCV genotype, as compared with individuals with persistent viremia (P <.005). Apparent viral clearance from blood with gradual loss of antibodies to various HCV proteins, independent of HCV genotype, was observed in 4 of the 5 individuals within approximately 1 year after HCV seroconversion, whereas 1 of these individuals apparently cleared the virus from blood, with complete seroreversion.

The Immunogenicity of Haemophilus influenzae Type B Conjugate Vaccines in Children Born to HIV-Infected Women † 899

Although immunocompromise due to HIV-1 (HIV) infection increases the importance of receipt of routine childhood vaccines, such vaccines appear to have decreased immunogenicity in these children. The study's objectives were to evaluate the immunogenicity of Haemophilus influenzae type B(Hib) conjugate vaccines among HIV-infected children according to clinical and immunologic disease progression as well as viral load. The concentration of antibody to polyribosylribitolphosphate (PRP) was measured at approximately nine and 24 months of age in plasma specimens from children of HIV-infected women enrolled in the Women and Infants Transmission Study. Of 227 children at the 9-month visit known to have received age-appropriate immunization with a Hib conjugate vaccine, the geometric mean antibody concentration (GMAC) was lower among 35 HIV-infected children (1.64 μg/ml) as compared to uninfected children (2.70 μg/ml), although the difference was not statistically significant. The proportion of children with antibody concentrations ≥ 1.0μg/ml did not differ significantly according to HIV infection status (73% uninfected, 74% infected). Neither the GMAC nor the proportion of children with antibody concentrations ≥ 1.0 μg/ml varied significantly among these HIV-infected children with predominantly mild-moderate disease progression according to clinical category, immunologic stage, or viral load(p ≥ 0.37). Similar results were obtained among 127 children (17 HIV-infected) eligible for analysis at the 24-month study visit. Changes in antibody concentrations over time did not differ significantly among HIV-infected as compared to uninfected children (p = 0.87). These results suggest that HIV-infected children with mild-moderate disease progression may have an adequate quantitative antibody response to Hib conjugate vaccines during the first two years of life. Additional investigations of the immune response to Hib conjugate vaccines, including the qualitative antibody response to immunization, should be pursued.