Detect Immunoglobulin G Antibodies Research Articles

Temporal pattern of humoral immune response in mild cases of COVID-19.

Understanding the humoral response pattern of coronavirus disease 2019 (COVID-19) is one of the essential factors to better characterize the immune memory of patients, which allows understanding the temporality of reinfection, provides answers about the efficacy and durability of protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and consequently helps in global public health and vaccination strategy. Among the patients who became infected with SARS-CoV-2, the majority who did not progress to death were those who developed the mild COVID-19, so understanding the pattern and temporality of the antibody response of these patients is certainly relevant. To investigate the temporal pattern of humoral response of specific immunoglobulin G (IgG) in mild cases of COVID-19. Blood samples from 191 COVID-19 real-time reverse transcriptase-polymerase chain reaction (RT-qPCR)-positive volunteers from the municipality of Toledo/ Paraná/Brazil, underwent two distinct serological tests, enzyme-linked immunosorbent assay, and detection of anti-nucleocapsid IgG. Blood samples and clinicoepidemiological data of the volunteers were collected between November 2020 and February 2021. All assays were performed in duplicate and the manufacturers' recommendations were strictly followed. The data were statistically analyzed using multiple logistic regression; the variables were selected by applying the P < 0.05 criterion. Serological tests to detect specific IgG were performed on serum samples from volunteers who were diagnosed as being positive by RT-qPCR for COVID-19 or had disease onset in the time interval from less than 1 mo to 7 mo. The time periods when the highest number of participants with detectable IgG was observed were 1, 2 and 3 mo. It was observed that 9.42% of participants no longer had detectable IgG antibodies 1 mo only after being infected with SARS-CoV-2 and 1.57% were also IgG negative at less than 1 mo. At 5 mo, 3.14% of volunteers were IgG negative, and at 6 or 7 mo, 1 volunteer (0.52%) had no detectable IgG. During the period between diagnosis by RT-qPCR/symptoms onset and the date of collection for the study, no statistical significance was observed for any association analyzed. Moreover, considering the age category between 31 and 59 years as the exposed group, the P value was 0.11 for the category 31 to 59 years and 0.32 for the category 60 years or older, showing that in both age categories there was no association between the pair of variables analyzed. Regarding chronic disease, the exposure group consisted of the participants without any comorbidity, so the P value of 0.07 for the category of those with at least one chronic disease showed no association between the two variables. A temporal pattern of IgG response was not observed, but it is suggested that immunological memory is weak and there is no association between IgG production and age or chronic disease in mild COVID-19.

Reduced antibody response to SARS-CoV-2 in COVID-19 patients with newly diagnosed diabetes: a retrospective observational study

BackgroundThe coronavirus disease 2019 (COVID-19) pandemic has dramatically impacted global health, and patients with type 2 diabetes have been identified as a high-risk group for COVID-19 infection and the development of severe disease. In response, this study aimed to evaluate whether patients with type 2 diabetes infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could develop antibody responses in the same manner as patients without diabetes, and whether there is a difference in antibody response to SARS-CoV-2 between patients with diabetes diagnosed prior to hospitalization, and those with newly diagnosed diabetes.MethodsSARS-CoV-2-specific immunoglobulin G (IgG) levels were quantified using two iFlash 3000 Chemiluminescence Immunoassay analyzer kits (Shenzhen YHLO Biotech Co., Ltd.) to detect IgG antibodies specific for nucleocapsid protein (IgG-N), and specific for the S1 subunit of the spike protein (IgG-S1). In 124 hospitalized patients with COVID-19, 40 patients with type 2 diabetes were matched to 40 patients without diabetes using propensity score matching (PSM).ResultsThere was no difference in IgG-N and IgG-S1 levels between the patients with diabetes and those without. Of patients with diabetes, 31 patients had known diabetes and nine patients had newly diagnosed diabetes. The median levels of IgG-N at 7–13 days in patients with newly diagnosed diabetes were significantly lower than those in patients with known diabetes (IgG-N; 10.9 vs. 31.0 AU/mL, p = 0.031, IgG-S1; 7.5 vs. 24.4 AU/mL, p = 0.023).ConclusionsEven after adjusting for covariates using PSM, COVID-19 patients with type 2 diabetes had comparable antibody responses to patients without diabetes. Patients with newly diagnosed diabetes had lower IgG-N and IgG-S1 production in the second week of the disease compared with those with previously known diabetes.

Seroprevalence of infection-induced SARS-CoV-2 antibodies among health care users of Northern Italy: results from two serosurveys (October-November 2019 and September-October 2021)

ObjectivesThe objective was to estimate the seroprevalence of SARS-CoV-2 in autumn 2019 (before case zero was identified in Italy) and 2021 among residual sera samples from health care users in the Piedmont region of northwestern Italy. MethodsTwo serosurveys were conducted. Using a semiquantitative method, samples were tested for the presence of immunoglobulin G (IgG) antibodies against the S1 domain of the spike protein. Samples with positive test results from the 2019 survey were independently retested using a multiplex panel to detect IgG antibodies against the receptor binding domain, S1 and S2 domains, and nucleocapsid. Samples with positive test results from the 2021 survey underwent repeat testing with enzyme-linked immunosorbent assay to detect anti-nucleocapsid IgG antibodies. Prevalence rates according to gender and age groups, together with their respective 95% confidence intervals (CIs), were calculated. ResultsOverall, the proportion of samples with positive test results was 2/353 in 2019 and 22/363 in 2021, with an estimated seroprevalence of 0.27% (95% CI 0-1.86) and 6.21% (95% CI 3.9-9.31) in 2019 and 2021 respectively. ConclusionResults of this study support the hypothesis that the virus was circulating in Italy as early as autumn 2019. The role of these early cases in broader transmission dynamics remains to be determined.

Detectable Respiratory Viruses IgM and IgG Antibodies among Children with Acute Respiratory Tract Infections in Owo, Ondo State, Nigeria

Globally, in children, less than 5 years of age, acute respiratory tract infections (ARTIs) are a major cause of morbidity and mortality. Long-lasting immunity is not induced by respiratory infections as reinfection can occur throughout life. This study aimed to determine the seroprevalence of six respiratory viruses specific immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in children with ARTIs in Owo, Ondo State. The sera samples of two hundred (200) subjects who consented to participate in the study were collected and tested using serum-specific Enzyme-Linked Immunosorbent Assay (ELISA) kits, anti-immunoglobulin M (IgM) and anti-immunoglobulin G (IgG) antibodies to the influenza A virus (FLU-A), respiratory syncytial virus (RSV), parainfluenza virus (PIV), coronavirus (CoV), rhinovirus (RV) and adenovirus (AdV) respectively (IgM and IgG ELISA Kits; Melsin Medical Co., China). The mean age of the subjects tested was 3.49±1.41. The total IgM seropositivity was detected in 83% of the children with the highest being AdV 91 (45.5%), followed by PIV 89 (44.5%), FLU-A and RV with 88 (44%) respectively, CoV 85 (42.5%), and RSV 80 (40%). The total IgG seropositivity was detected in 87.5% of the children with the highest being PIV 152 (76%), followed by RSV 135 (67.5%), RV 93 (46.5%), AdV 81 (40.5%), CoV and FLU A 76 (38%) respectively. The study revealed the presence of primary and secondary infection of respiratory viruses in Owo and the need for preventive and control measures against respiratory tract viruses are suggested.

Seroprevalence and infection fatality rate of the SARS-CoV-2 Omicron variant in Denmark: A nationwide serosurveillance study.

SummaryBackgroundIntroduction of the Omicron variant caused a steep rise in SARS-CoV-2 infections despite high vaccination coverage in the Danish population. We used blood donor serosurveillance to estimate the percentage of recently infected residents in the similarly aged background population with no known comorbidity.MethodsTo detect SARS-CoV-2 antibodies induced due to recent infection, and not vaccination, we assessed anti-nucleocapsid (anti-N) immunoglobulin G (IgG) in blood donor samples. Individual level data on SARS-CoV-2 RT-PCR results and vaccination status were available. Anti-N IgG was measured fortnightly from January 18 to April 3, 2022. Samples from November 2021 were analysed to assess seroprevalence before introduction of the Omicron variant in Denmark.FindingsA total of 43 088 donations from 35 309 Danish blood donors aged 17–72 years were screened. In November 2021, 1·2% (103/8 701) of donors had detectable anti-N IgG antibodies. Adjusting for test sensitivity (estimates ranging from 74%–81%) and November seroprevalence, we estimate that 66% (95% confidence intervals (CI): 63%–70%) of the healthy, similarly aged Danish population had been infected between November 1, 2021, and March 15, 2022. One third of infections were not captured by SARS-CoV-2 RT-PCR testing. The infection fatality rate (IFR) was 6·2 (CI: 5·1–7·5) per 100 000 infections.InterpretationScreening for anti-N IgG and linkage to national registers allowed us to detect recent infections and accurately assess assay sensitivity in vaccinated or previously infected individuals during the Omicron outbreak. The IFR was lower than during previous waves.FundingThe Danish Ministry of Health.

Detection of IgG Antibodies to Glycosylphosphatidylinositol (GPI) as a Biomarker of Immune Status to Plasmodium species

Finding new ways to eliminate malaria is critical and this would greatly be influenced by developing indicators of exposure as well as distribution of effective vaccines against Plasmodium. This study was aimed at detecting Immunoglobulin G(IgG) antibodies, to glycosylphosphatidylinositol (GPI) as a biomarker of immune status to Plasmodium species. In this study, blood samples were gotten from apparently healthy individuals and patients having symptoms of malaria attending Ahmadu Bello University Teaching Hospital, Zaria. Thick and thin blood smears were prepared and stained with Giemsa stain. The smears were observed microscopically. Parasite densities were estimated on positive slides. Samples positive and some negative for Plasmodium were further tested to detect IgG antibodies to GPI among both the Asymptomatic and Symptomatic participants using ELISA. The prevalence of Plasmodium infection among both asymptomatic and symptomatic participants in this study was 18.9% and the prevalence of asymptomatic malaria was 15.6%. There was a significant association between the level of parasitemia and concentration of IgG antibodies to GPI among the asymptomatic participants and a no significant association among symptomatic participants. Type of housing amongst other risk factors was the only factor significantly associated with malaria in this study. This study suggests PGPI as a biomarker of immunity to Plasmodium and may be a vaccine candidate for programs of malaria control.

SARS-CoV-2 antibodies in Ontario health care workers during and after the first wave of the pandemic: a cohort study.

Background:Health care workers have a critical role in the pandemic response to COVID-19 and may be at increased risk of infection. The objective of this study was to assess the seroprevalence of SARS-CoV-2 immunoglobulin G (IgG) antibodies among health care workers during and after the first wave of the pandemic.Methods:We conducted a prospective multicentre cohort study involving health care workers in Ontario, Canada, to detect IgG antibodies against SARS-CoV-2. Blood samples and self-reported questionnaires were obtained at enrolment, at 6 weeks and at 12 weeks. A community hospital, tertiary care pediatric hospital and a combined adult–pediatric academic health centre enrolled participants from Apr. 1 to Nov. 13, 2020. Predictors of seropositivity were evaluated using a multivariable logistic regression, adjusted for clustering by hospital site.Results:Among the 1062 health care workers participating, the median age was 40 years, and 834 (78.5%) were female. Overall, 57 (5.4%) were seropositive at any time point (2.5% when participants with prior infection confirmed by polymerase chain reaction testing were excluded). Seroprevalence was higher among those who had a known unprotected exposure to a patient with COVID-19 (p < 0.001) and those who had been contacted by public health because of a nonhospital exposure (p = 0.003). Providing direct care to patients with COVID-19 or working on a unit with a COVID-19 outbreak was not associated with higher seroprevalence. In multivariable logistic regression, presence of symptomatic contacts in the household was the strongest predictor of seropositivity (adjusted odds ratio 7.15, 95% confidence interval 5.42–9.41).Interpretation:Health care workers exposed to household risk factors were more likely to be seropositive than those not exposed, highlighting the need to emphasize the importance of public health measures both inside and outside of the hospital.

Seroprevalence of antibodies to SARS-CoV-2 and predictors of seropositivity among employees of a teaching hospital in New Delhi, India.

ObjectivesHealthcare workers (HCWs) are at a high risk of contracting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) due to the increased likelihood of clinical exposure during patient management. The study objective was to determine the seroprevalence of antibodies to SARS-CoV-2 and its predictors among hospital employees.MethodsThe cross-sectional study was conducted at a teaching hospital from August 2020 to September 2020 among 1,401 employees, including 1,217 HCWs, in New Delhi, India. The serum samples were examined for immunoglobulin G (IgG) antibodies to SARS-CoV-2 using the COVID Kavach-Anti-SARS-CoV-2 IgG Antibody Detection enzyme-linked immunosorbent assay kit. Data were collected electronically using the EpiCollect mobile platform. A p < 0.05 was considered to indicate statistical significance.ResultsA total of 169 participants (12.1%) had detectable IgG antibodies to SARS-CoV-2. The highest seropositivity rate was observed in the administrative staff (20.1%), while it was lowest among medical doctors (5.5%, p < 0.001). Male sex and ever having lived in a containment zone were independently associated with past infection with SARS-CoV-2.ConclusionThe seroprevalence of SARS-CoV-2 infection in health workers may be lower than in the general population in New Delhi. However, nonpharmaceutical interventions were not associated with a reduction in the risk of acquisition of SARS-CoV-2.

Immunoadsorption and Plasma Exchange in Seropositive and Seronegative Immune-Mediated Neuropathies.

The inflammatory neuropathies are disabling conditions with diverse immunological mechanisms. In some, a pathogenic role for immunoglobulin G (IgG)-class autoantibodies is increasingly appreciated, and immunoadsorption (IA) may therefore be a useful therapeutic option. We reviewed the use of and response to IA or plasma exchange (PLEx) in a cohort of 41 patients with nodal/paranodal antibodies identified from a total of 573 individuals with suspected inflammatory neuropathies during the course of routine diagnostic testing (PNAb cohort). 20 patients had been treated with PLEx and 4 with IA. Following a global but subjective evaluation by their treating clinicians, none of these patients were judged to have had a good response to either of these treatment modalities. Sequential serology of one PNAb+ case suggests prolonged suppression of antibody levels with frequent apheresis cycles or adjuvant therapies, may be required for effective treatment. We further retrospectively evaluated the serological status of 40 patients with either Guillain-Barré syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP), and a control group of 20 patients with clinically-isolated syndrome/multiple sclerosis (CIS/MS), who had all been treated with IgG-depleting IA (IA cohort). 32 of these patients (8/20 with CIDP, 13/20 with GBS, 11/20 with MS) were judged responsive to apheresis despite none of the serum samples from this cohort testing positive for IgG antibodies against glycolipids or nodal/paranodal cell-adhesion molecules. Although negative on antigen specific assays, three patients’ pre-treatment sera and eluates were reactive against different components of myelinating co-cultures. In summary, preliminary evidence suggests that GBS/CIDP patients without detectable IgG antibodies on routine diagnostic tests may nevertheless benefit from IA, and that an unbiased screening approach using myelinating co-cultures may assist in the detection of further autoantibodies which remain to be identified in such patients.

Adaptive Immune Responses in Humans During Nipah Virus Acute and Convalescent Phases of Infection.

Nipah virus (NiV) is 1 of 10 potential causes of imminent public health emergencies of international concern. We investigated the NiV outbreak that occurred in May 2018 in Kerala, India. Here we describe the longitudinal characteristics of cell-mediated and humoral immune responses to NiV infection during the acute and convalescent phases in 2 human survivors. Serial blood samples were obtained from the only 2 survivors of the NiV outbreak in Kerala. We used flow cytometry to determine the absolute T-lymphocyte and B-lymphocyte counts and the phenotypes of both T and B cells. We also detected and quantitated the humoral immune response to NiV by virus-specific immunoglobulin M (IgM) and immunoglobulin G (IgG) enzyme-linked immunosorbent assay. Absolute numbers of T lymphocytes remained within normal limits throughout the period of illness studied in both survivors. However, a marked elevation of activated CD8 T cells was observed in both cases. More than 30% of total CD8 T cells expressed Ki67, indicating active proliferation. Proliferating (Ki-67+) CD8 T cells expressed high levels of granzyme B and PD-1, consistent with the profile of acute effector cells. Total B-lymphocyte, activated B-cell, and plasmablast counts were also elevated in NiV survivors. These individuals developed detectable NiV-specific IgM and IgG antibodies within a week of disease onset. Clearance of NiV RNA from blood preceded the appearance of virus-specific IgG and coincided with the peak of activated CD8 T cells. We describe for the first time longitudinal kinetic data on the activation status of human B- and T-cell populations during acute NiV infection. While marked CD8 T-cell activation was observed with effector characteristics, activated CD4 T cells were less prominent.

Frequency of seropositivity against infectious agents amongst pemphigus vulgaris patients: a case-control study on Strongyloides stercoralis, Helicobacter pylori, Toxoplasma gondii, Leishmania major, and Epstein-Barr virus.

Environmental and genetic factors may contribute to the pathogenesis of pemphigus vulgaris (PV) as an autoimmune disease. We aimed to determine rates of seropositivity for immunoglobulin G (IgG) antibodies against a number of infectious agents in untreated and treated PV patients and in healthy individuals. Eighty-two newly diagnosed untreated PV patients (34 men and 48 women; mean ± standard deviation [SD] age: 44.18 ± 14.43 years) and 36 previously diagnosed patients under immunosuppressive therapy (16 men and 20 women; mean ± SD age: 38.53 ± 9.96 years) were enrolled in the study. The clinical diagnosis of PV was confirmed by histopathology and direct immunofluorescence findings. As a control group, 131 healthy individuals (68 men and 63 women; mean ± SD age: 42.56 ± 19.69 years) were recruited. In all patients and controls, serum IgG antibodies against Strongyloides stercoralis, Helicobacter pylori, Epstein-Barr virus (EBV) capsid antigen, and Leishmania major were measured using enzyme-linked immunosorbent assays. The indirect immunofluorescence test was used to detect IgG antibodies against Toxoplasma gondii. Newly-diagnosed untreated PV patients had significantly higher rates of seropositivity of IgG antibodies against S. stercoralis and H. pylori compared with the control group (69.5% vs. 16.0% [P < 0.001] and 79.3% vs. 59.5% [P = 0.004], respectively). For the other agents, namely T. gondii, L. major, and EBV capsid antigen, the differences between groups in seropositivity for IgG antibodies were not statistically significant. Significant associations between S. stercoralis and H. pylori seropositivity rates and untreated disease led to the hypothesis that these pathogenic agents may contribute to the pathogenesis of PV.

PneumococcalHaemophilus influenzaeProtein D Conjugate Vaccine Induces Antibodies That Inhibit Glycerophosphodiester Phosphodiesterase Activity of Protein D

Haemophilus influenzae outer membrane protein D (PD) is a glycerophosphodiester phosphodiesterase (GlpQ) activity-possessing virulence factor and a promising vaccine antigen, providing 35.3% efficacy against acute otitis media caused by nontypeable H. influenzae (NTHI) when it was used as a carrier protein in a novel pneumococcal PD conjugate (Pnc-PD) vaccine. To study if PD-induced protection against NTHI could be due to antibodies that inhibit or neutralize its enzymatic activity, a GlpQ enzyme inhibition assay was developed, and serum samples collected from Finnish infants before and after Pnc-PD vaccination were analyzed for enzyme inhibition and anti-PD immunoglobulin G (IgG) antibody concentration. Before vaccination at age 2 months, the majority (84%) of infants (n = 69) had no detectable anti-PD IgG antibodies, and all were enzyme inhibition assay negative (inhibition index, <20). At age 13 to 16 months, all infants receiving three or four doses of Pnc-PD had detectable anti-PD IgG antibodies and 36% (8/22 infants) of the infants receiving three doses and 26% (6/23 infants) of the infants receiving four doses of Pnc-PD were inhibition assay positive (inhibition index, >/=20). No significant rise in anti-PD IgG antibodies or enzyme inhibition among control vaccinees (n = 24) receiving three doses of hepatitis B vaccine was detected. A modest correlation (r(s), approximately 0.66) between anti-PD IgG concentration and enzyme inhibition was detected; however, their kinetics were clearly different. These data suggest that measurement of antibody responses that inhibit PD's enzymatic activity could be a useful tool for assessing Pnc-PD vaccine-induced protective immunity against NTHI.

T-Cell-Stimulating Protein A Elicits Immune Responses during Meningococcal Carriage and Human Disease

In recognition of the need for immunological memory-inducing components for future Neisseria meningitidis group B vaccines, we previously searched the proteome of N. meningitidis and identified T-cell-stimulating protein A (TspA). This study was designed to confirm the immunogencity of TspA and to examine the subset of T-helper cell responses to the protein in patients and nasopharyngeal carriers. The tspA gene was reconstructed, cloned, and expressed in Escherichia coli, and the recombinant TspA (rTspA) protein was affinity purified. T-cell proliferative responses to rTspA were detected in the peripheral blood mononuclear cells (PBMCs) of convalescent patients and carriers, confirming that TspA-specific T-cell responses were stimulated by invasive disease and nasopharyngeal colonization. Following stimulation of PBMCs with meningococcal lysate, increased frequencies of both Th1 and Th2 cells were observed, indicating that, as during carriage, invasive meningococcal disease induced an unbiased T-helper subset response. A similar unbiased T-helper response was also detected against rTspA in the PBMCs of convalescent patients. The response of PBMCs from the carriers to TspA stimulation, however, was very weak, and the frequencies of cytokine-positive CD4 cells were not significantly greater than the frequencies in unstimulated control cultures. All of the patients and carriers responded with serum antimeningococcal immunoglobulin G (IgG) antibodies, while four of six samples from patients and 5 of 14 samples from carriers contained detectable anti-rTspA IgG antibodies. Taken together, the results of this study confirmed the immunogenicity of TspA in humans during natural meningococcal infection, and therefore, TspA is worthy of further investigation as a possible T-cell stimulating component of future vaccines.

Tear IgA and serum IgG antibodies against Acanthamoeba in patients with Acanthamoeba keratitis.

Exposure to Acanthamoebaspecies appears to be ubiquitous, as 50% to 100% of healthy human subjects display anti-Acanthamoebaantibodies. However, the presence of specific anti-Acanthamoebaantibodies in the serum and tears of patients has not been investigated. The prevalence of serum immunoglobulin G (IgG) and tear IgA against three species of Acanthamoebawas assessed in healthy subjects and patients with Acanthamoebakeratitis. The level of specific serum IgG and tear IgA against A. castellanii, A. astronyxis, and A. culbertsoniin the sera of 23 patients and 25 healthy subjects was tested by enzyme-linked immunosorbent assays. Total serum IgM, IgG, and IgA concentrations were measured by nephelometry. Acanthamoebakeratitis was diagnosed clinically and confirmed by in vivo confocal microscopy. In some patients, corneal biopsies were also performed and trophozoites were cultured on lawns of Escherichia colion non-nutrient agar. All healthy subjects and patients with Acanthamoebakeratitis had detectable serum IgG antibodies against all Acanthamoebaantigens. However, patients with Acanthamoebakeratitis had significantly higher anti-AcanthamoebaIgG antibody titers than healthy subjects. In contrast, Acanthamoeba-specific tear IgA was significantly lower in patients with Acanthamoebakeratitis in comparison with healthy subjects. Total serum immunoglobulins did not differ significantly between healthy subjects and patients with Acanthamoebakeratitis. The results suggest that a low level of anti-AcanthamoebaIgA antibody in the tears appears to be associated with Acanthamoebakeratitis.

Immunoglobulin G subclass antibodies against excretory/secretory antigens of Ancylostoma caninum in human enteric infections.

Most patients with proven or suspected enteric infection with the common hookworm of dogs, Ancylostoma caninum, produce immunoglobulin G (IgG) and IgE antibodies to an immunodominant excretory/secretory antigen (Ac68) of the parasite. These antibodies were detected in both enzyme-linked immunosorbent assay (ELISA) and Western blots; the Western blot to detect IgG antibodies to Ac68 was the most specific and sensitive. The subclasses of IgG of the antibody response to the parasite were analyzed using Western blots with anti-IgG subclass-specific monoclonal antibodies as marker systems in an attempt to further improve the specificity of the assay. Eight patients with confirmed enteric infections with A. caninum (positive controls) were tested; six had antibodies in all IgG subclasses against Ac68. Twenty sera from patients with suspected enteric infection with A. caninum (manifested as eosinophilic enteritis or unexplained abdominal pain with peripheral eosinophilia) were tested; 16 had total IgG antibodies to Ac68, while IgG1, IgG2, IgG3, and IgG4 responses were found in 11, 10, 9, and 12 of these sera, respectively. Small numbers of sera from groups of patients infected with other helminths and from healthy blood donors had various combinations of IgG, IgG1, IgG2, and IgG3 antibodies to Ac68, but none of these sera had IgG4 antibodies to Ac68. Sera from all nine patients with human hookworm infection had IgG, IgG1, IgG2, and IgG3 antibodies to Ac68 and eight of the nine were also positive for IgG4 antibodies. These results indicate the Western blot to detect IgG4 antibodies to Ac68 is the most reliable immunodiagnostic test yet described for enteric infection with A. caninum, although this test does not discriminate between infections with human and canine hookworms.

Detection of antibodies to human immunodeficiency virus in vaginal secretions by immunoglobulin G antibody capture enzyme-linked immunosorbent assay: application to detection of seminal antibodies after sexual intercourse.

In order to evaluate a commercial immunoglobulin G (IgG) antibody capture enzyme-linked immunoassay (ELISA) (Wellcozyme HIV1 + 2 Gacelisa; Murex Diagnostics Limited, Dartford, United Kingdom) for the detection of antibodies to human immunodeficiency virus (HIV) in vaginal secretion samples (VS) from HIV-seropositive and -seronegative women, serum samples (S) and VS were obtained from 129 African women living in the Central African Republic, a country of high HIV prevalence. Sera were tested for HIV by routine second-generation ELISA with confirmatory Western blot (immunoblot) (WB). By the Gacelisa IgG immuno-capture assay, 45 VS were positive and 84 were negative, whereas by WB, 44 VS were confirmed positive and 85 were confirmed negative. Considering WB as a reference, the IgG immunocapture assay in VS was 97.7% sensitive (43 of 44 positive samples) and 97.6% specific (83 of 85 negative samples). Of 42 HIV-seropositive women, 41 (97.6%) had S and VS that both were HIV positive (S+ VS+), and of 87 HIV-seronegative women, 83 (95.4%) had S and VS that both were HIV negative (S- VS-). Five women had discordant results for S and VS. One (S+ VS-) possibly had a false-negative VS result. Two (S- VS+) had similar indeterminate patterns for S and VS in WB. Two (S- VS+) had a typical HIV-positive pattern on WB of VS, whereas S results in WB were indeterminate in one case and negative in the other case; for both women, detection of prostatic acid-phosphatase was positive in VS, strongly suggesting recent sexual intercourse with an HIV-positive man. Because all HIV-infected men have detectable IgG antibodies to HIV in the seminal fluid, an HIV-seronegative rape victim with HIV-positive VS (S- VS+) should receive short-term antiviral therapy to prevent possible HIV transmission.