Seroprevalence of IgM and IgG antibodies to toxoplasma infection in human immunodeficiency virus-positive antiretroviral therapy-naive individuals

Saloni Garg; Babita Sharma; Rameshwari Bithu; Nitya Vyas

doi:10.4103/mjmsr.mjmsr_6_18

ORIGINAL ARTICLE

Year : 2019 | Volume : 10 | Issue : 1 | Page : 8-12

Seroprevalence of IgM and IgG antibodies to toxoplasma infection in human immunodeficiency virus-positive antiretroviral therapy-naive individuals

Saloni Garg¹, Babita Sharma², Rameshwari Bithu², Nitya Vyas²
¹ Department of Laboratory Medicine, Artemis Hospitals, Gurgaon, Haryana, India
² Department of Microbiology, Sawai Man Singh Medical College and Attached Hospitals, Jaipur, Rajasthan, India

Date of Web Publication

29-May-2019

Correspondence Address:
Dr. Saloni Garg
#450, Ground Floor, Saraswati Vihar, Gurgaon - 122 002, Haryana
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/mjmsr.mjmsr_6_18

Abstract

Introduction: Toxoplasmosis, a zoonotic disease infecting about one-third of the world's population, is caused by intracellular parasite Toxoplasma gondii. It is a major health concern in immunocompromised individuals as in human immunodeficiency virus (HIV)-positive patients. The aim of the study was to determine the seroprevalence of T. gondii infection among HIV-infected antiretroviral therapy-naive individuals attending Integrated Counseling and Testing Center. Materials and Methods: It was a cross-sectional observational study conducted at a tertiary care hospital between April 2015 and March 2016 on 400 HIV-positive patients and 100 HIV-negative healthy adults. Anti-toxoplasma IgM and IgG antibodies were detected using a commercially available enzyme-linked immunosorbent assay kit. Sociodemographic and associated risk factors for T. gondii infection were obtained and the data were analyzed using SPSS version 17.0. Results: Seroprevalence of anti-toxoplasma antibodies among 400 HIV-positive patients and 100 HIV-negative healthy adults was 19.75% and 11%, respectively. Majority of seropositive individuals were in the childbearing age groups. Out of 79 toxoplasma-seropositive cases, 10 were clinically confirmed cases of toxoplasma encephalitis (TE). The mean CD4+ T-lymphocyte count of HIV-positive patients was 255.32 ± 221.19 cells/cmm. Conclusion: The seroprevalence of toxoplasma infection is significantly higher in HIV-positive patients than in HIV-negative healthy individuals. It is important to test all HIV-positive patients for toxoplasma antibodies to prevent life-threatening complication and TE in these patients.

Keywords: Antibodies, antiretroviral therapy naive, human immunodeficiency virus, toxoplasma

How to cite this article:
Garg S, Sharma B, Bithu R, Vyas N. Seroprevalence of IgM and IgG antibodies to toxoplasma infection in human immunodeficiency virus-positive antiretroviral therapy-naive individuals. Muller J Med Sci Res 2019;10:8-12

How to cite this URL:
Garg S, Sharma B, Bithu R, Vyas N. Seroprevalence of IgM and IgG antibodies to toxoplasma infection in human immunodeficiency virus-positive antiretroviral therapy-naive individuals. Muller J Med Sci Res [serial online] 2019 [cited 2023 Mar 23];10:8-12. Available from: https://www.mjmsr.net/text.asp?2019/10/1/8/259255

Introduction

Toxoplasmosis is a globally distributed zoonosis caused by an obligate intracellular protozoan parasite, Toxoplasma gondii. This parasite was first discovered in 1908 by Nicolle and Manceaux. Transmission of T. gondii may occur through ingestion of infectious oocysts in water, food, or soil, by eating raw or undercooked meat containing tissue cysts, or by transplacental transmission.^[1] It infects approximately one-third of world's population^[2] because of its worldwide distribution, high infection rates, and ability to maintain benign existence in its host.^[3] Toxoplasma infections are generally subclinical and asymptomatic, but in immunocompromised states such as acquired immunodeficiency syndrome (AIDS) patients, T. gondii is the most common opportunistic infection causing severe life-threatening debilitating disease.^[4] In these patients, reactivation of latent T. gondii as a result of conversion of the bradyzoites to the proliferative tachyzoite stage may occur leading to toxoplasma encephalitis (TE).^[5] TE may manifest as headache, confusion, lethargy, focal brain lesions, coma, and even death in untreated patients.

Diagnosis of toxoplasma depends on direct demonstration of the parasite, imaging, and immunologic methods. Direct demonstration is hazardous to the worker and labor intensive, needs several weeks for results, and is often not conclusive of acute infection,^[6] whereas imaging modalities such as computed tomography (CT) and magnetic resonance imaging are less specific. Therefore, serological tests are the mainstay of correct diagnosis, especially in resource-limited countries like India where it is the most available and affordable means of detecting the presence of T. gondii antibodies (toxoplasma IgG and IgM antibodies). Among the serological tests, indirect hemagglutination is less sensitive and more labor intensive,^[7] indirect fluorescent antibody test gives false-positive results with rheumatoid factor, and Sabin–Feldman dye test titers do not correlate with the severity of the illness.^[8] Enzyme-linked immunosorbent assay (ELISA) is the most acceptable and easy to perform and can be used for diagnosis and prognosis.

Seroprevalence of toxoplasma varies greatly in geographical regions within a country and within different ethnic groups according to different environments, social customs, and habits of different populations. Very few studies have been conducted in India to know the seroprevalence in different geographical regions. Therefore, this study was conducted to determine the seroprevalence of T. gondii infection among human immunodeficiency virus (HIV)-infected antiretroviral therapy-naive individuals attending Integrated Counseling and Testing Center (ICTC).

Materials and Methods

It is a hospital-based cross-sectional observational study conducted at a tertiary care hospital between April 2015 and March 2016 after approval from the institute's Ethics Committee. Four hundred HIV-positive individuals were included in this study. These individuals were unaware about their HIV status. The HIV status of these patients was confirmed at ICTC. One hundred HIV-negative individuals were also included as control group. At enrollment, informed consent was obtained from patients and a proforma was filled which consisted of sociodemographic and personal details of patients, history of contact with any pets, and any neuropsychiatric signs and symptoms. Any HIV-positive person who had taken any treatment for HIV was excluded from the study. Blood samples were collected from all the patients. The HIV status of individuals was confirmed as per Strategy III of National AIDS Control Organization guidelines. The samples were tested for the presence of IgM and IgG antibodies against T. gondii using ELISA kits (Diapro Diagnostic Bioprobes Srl, Milano, Italy) as per manufacturer's instructions. The results were interpreted qualitatively as positive or negative based on the optical density of the sample obtained. CD4+ T-lymphocytes were analyzed by FACSCalibur flow cytometry (Becton Dickinson Immunocytometry Systems, San Jose, CA, USA).

Statistical analysis was done with the Statistical Package for the Social Sciences (SPSS Inc., Chicago, USA) version 17.0 (). The categorical data were presented as percent and were compared among groups using Chi-square test. Groups were compared for demographic data and were presented as mean and standard deviation and were compared using Student's t-test. Significance level was set at P < 0.05.

Results

The mean age of study group was 36.65 ± 11.94 years. Males were more than females. Most individuals in study group were in 31–40 years' age group [Table 1]. The HIV infection was more common in patients with low education status [Figure 1] and majority of the patients were housewives (27.5%). Anti-toxoplasma antibodies were detected in 79 (19.75%) HIV-infected patients. Twenty-four patients (6%) were positive for anti-toxoplasma IgM antibodies while 51 (12.75%) were positive for anti-toxoplasma IgG antibodies. Only 4 patients (1%) were positive for both IgM and IgG antibodies. In HIV-positive patients, IgG antibody response was more as compared to HIV-negative individuals, but it was not statistically significant [Table 2]. In the present study, the mean CD4+ T-lymphocyte count was 255.32 ± 221.19 cells/cmm. Two hundred and eight patients (52%) had CD4+ T-cell count <200 cells/cmm [Table 3].

Table 1: Sociodemographic characteristics of study group

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Figure 1: Distribution of cases according to educational status

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Table 2: Distribution of IgM and IgG antibody responses to toxoplasmosis in human immunodeficiency virus-positive and human immunodeficiency virus-negative individuals

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Table 3: Association between CD4+ T-lymphocyte count and Toxoplasma gondii seroprevalence in human immunodeficiency virus-positive patients

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Out of 79 toxoplasma-positive patients, 10 were clinically confirmed cases of TE. Fever (90%) was the most common symptom in these clinically confirmed cases of TE followed by headache (80%) and focal neurological signs (80%) [Table 4].

Table 4: Clinical symptoms in Toxoplasma gondii seropositive individuals in study group

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Discussion

Toxoplasmosis is one of the common parasitic illnesses affecting all age groups. It is self-limiting in immunocompetent hosts but manifests as severe encephalitis and chorioretinitis in immunocompromised states such as HIV-infected patients. In these patients, IgM antibody is often not detectable due to profound immunosuppression. IgG antibody is detectable in about 97% of the patients infected with T. gondii in the past. In the present study, both toxoplasma-specific IgG and IgM antibody levels were analyzed using ELISA.

Seroprevalence studies vary according to geographic location. The global seroprevalence of toxoplasma is reported to be 46.1%.^[9] In India, the exact seroprevalence of T. gondii is not known. Various studies in India reported seroprevalence as low as 1% and high as 80% in adults.^[10] This may be because different studies used various diagnostic tests to detect toxoplasma seroprevalence which have not been compared. This may also indicate different prevalence rates in different parts of the country.

In the present study, seropositivity of toxoplasma in HIV-infected group was 19.75%. In this group, 12.75% were IgG positive and 6% were IgM positive. In healthy control group, toxoplasma antibodies were detected from 11% of individuals only (6% were IgG positive and 5% IgM positive). The difference in the seroprevalence of anti-toxoplasma antibodies among both the groups was statistically significant (P< 0.05).

In the present study, toxoplasma IgG was detected from 51 HIV-positive patients (12.75%) and 6 healthy individuals (6%), respectively. Our findings are comparable with studies conducted by Sucilathangam et al.^[11] (15%), Bhatia et al.^[12] (12%), Malla et al.^[13] (12%), Shen et al.^[14] (9.7%), Mohraz et al.^[15] (18.2%), and Amuta et al.^[16] (10.8%). However, this is in contrast to studies by Anuradha andPreethi^[17] (34.78%), Shafiei et al.^[18] (38.01%), Walle et al.^[19] (87.4%), Daryani et al.^[20] (77.4%), and Nissapatorn et al.^[21] (44.8%) who reported higher IgG seropositivity of toxoplasmosis among HIV-infected patients. These reports indicate that frequency of toxoplasma infection varies according to geographical areas. The lower prevalence in our study might be related to climatic conditions such as warm and dry weather in our region.^[20]

Only 1% of the HIV-infected individuals exhibited both IgM and IgG antibodies against T. gondii, i.e., reactivation of toxoplasma infection whereas none of the HIV-negative individuals had both IgM and IgG antibodies. In studies conducted by Meisheri et al.^[22] and Bamba et al.,^[23] none of the patients with IgG seropositivity were positive for IgM antibodies.

In 51 positive cases for anti-toxoplasma IgG antibodies, 74.5% were males and 25.5% were females. Our findings are consistent with studies by Muco et al.^[24] who also reported higher IgG seropositivity in males (66.3%) than in females (33.69%). This is in contrast to study conducted by Shen et al.^[14] where higher prevalence was detected in 15.9% females than in 7.7% males. Higher male predilection in our study can be due to factors such as occupational exposure to soil and pets.^[25]

In the present study, majority of toxoplasma IgM and IgG seropositive individuals belonged to rural areas, but the difference was not statistically significant. However, in a study conducted by Walle et al.,^[19] 73.5% of toxoplasma-seropositive patients were from rural areas. However, Muluye et al.^[26] showed 91.5% seroprevalence in urban areas.

In our study, majority of toxoplasma-seropositive individuals did not have any contact with cat. This may be because cat is not a common pet in India. Similar results were shown by studies conducted in areas where cat contact is very common,^[19],[27] but no association of presence of cat with T. gondii seropositivity was found. This is in contrast to study by John et al.^[28] who suggested strong association of toxoplasma seropositivity with cat contact.

In the present study, majority of individuals had exposure to soil because of their occupation, but no statistically significant difference was found between seropositivity of toxoplasma antibodies in individuals with or without exposure to soil.

In the present study, the mean CD4+ T-lymphocyte count of HIV-infected patients was 255.32 ± 221.19 cells/cmm. Analysis of CD4+ T-lymphocyte count revealed the highest prevalence of anti-toxoplasma IgG antibodies in CD4+ T-lymphocyte count <100 cells/cmm followed by 101–200 cells/cmm. These patients would have a higher chance to develop TE than others who had CD4+ T-lymphocyte count >200 cells/cmm. In clinical practice, CD4+ T-lymphocyte count is considered to be a prognostic marker to monitor the progression of HIV infection. In the present study, 10 HIV-positive patients were clinically confirmed cases of TE and the diagnostic criteria included clinical presentations, CT scan finding, serological evidence of anti-toxoplasma IgG antibody, and response to anti-toxoplasma therapy. Two out of 10 cases of TE were both IgM and IgG positive. The role of IgM antibody test in the diagnosis of toxoplasmosis in patients with HIV is doubtful as it may give false-negative result because of immunodeficiency in patients with low CD4+ T-lymphocyte count or where testing was carried out several months after infection has been acquired. CD4+ T-lymphocyte count of all the cases of TE was <100 cells/cmm and 5 out of these 10 cases had CD4+ T-lymphocyte count <50 cells/cmm. As per literature, TE is reported to occur at CD4 count <200 cells/cmm + high IgG titers ≥150 IU/ml^[29] and 35 times more common in those with CD4 <50 cells/μl.^[30]

Conclusion

From our study, it can be concluded that there is a significant difference between seropositivity of T. gondii antibodies among HIV-positive and HIV-negative individuals. It may vary according to different geographical regions and does not have significant association with any risk factors. We recommend that all HIV patients should be tested for T. gondii antibodies as there is a high risk of reactivation of latent toxoplasmosis leading to TE in HIV/AIDS patients with CD4+ T-lymphocyte count <200 cells/cmm.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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