# Presentation: 566748

## Usefulness of Antibody Detection in the Diagnosis of Malaria Parasites

**Marianna Wilson**
**Reference Immunodiagnostic Lab**
**Division of Parasitic Diseases, CDC**

## Types of Serological Assays Malaria

**Antibody Detection**
**Indirect Fluorescent Antibody**
**Enzyme immunoassays**
**Antigen Detection**
**Immunochromatographic**

## Antibody Detection

## Antibody Detection

## Indirect Fluorescent Antibody (IFA)

**Microscope slide**

## Enzyme Immunoassay (EIA/ELISA)

## ELISA 

**ELISA **

**Notes:**
Eight of the 8-kDa antigens were chemically synthesized and tested with a panel of defined sera in a FAST-ELISA.

All sera were tested in triplicate against each synthetic protein.

This plate shows the substrate development for one protein.

For evaluation, the mean absorbance value for each serum was divided by the mean absorbance value for the positive reference serum to give a relative absorbance unit.

## Antigen Detection

## Antigen Detection

## Antigen DetectionMalaria Immunochromatographic Dipstick

**OptiMAL Assay**

**Control**

***Plasmodium***** pan specific**
**monoclonal antibody**

***P. falciparum***** specific**
**monoclonal antibody**

## Antigen DetectionMalaria Immunochromatographic DipstickProblems

**Low sensitivity with parasites density <100/ml**
**Currently only useful for detection of                 *****P. falciparum***** infections**
**Moody, Clin Microbiol Rev 2002;15:66-78**

## Diagnostic Toolsfor Human Infections with Malaria

- Blood film examination
- Serology - IFA
- PCR

## Malaria IFA Test

**Sensitivity   =  98%**
**Specificity   =  99.5%**
**Sulzer et al, Am J Trop Med Hyg 1969;18:199-205**
**Sulzer et al, Bull Wld Hlth Org 1971;45:375-379**

## P. malariae

***P. malariae***

## P. malariae

***P. malariae***

## P. malariae

## P. falciparum

***P. falciparum***

## P. falciparum

***P. falciparum***

## P. falciparum

## Malaria IFA TestInitial detection of antibodies

**Parasitemia precedes antibody**
***P. vivax*****  2-6 days**
***P. falciparum***** and *****P. malariae*****  4-6 days**
**If parasitemia is suppressed by treatment, may develop detectable antibody **

## Malaria IFA TestDetermination of Infecting Species

**Non-Immune**
**Samples drawn 0-14 days post onset: Highest titer was to the infecting species in 81%**
**Samples drawn 15-60 days post onset: Highest titer was to the infecting species in 96%  **

## Malaria IFA TestDetermination of Infecting Species

**Is possible in ****non-immune**** individuals with primary infection.**
**Is ****NOT**** possible in immune individuals because their antibody response reflects multiple infections with multiple species.**

## Malaria IFA TestAntibody Persistence after Treatment

-  **Non-Immunes (Vietnam Vets with Pv)**
** ****53%**** IFA negative at     ****6**** mo. post-Rx**
** ****59%**** IFA negative at   ****12**** mo. post-Rx**
** **
**Wilson et al, Am J Trop Med Hyg 1970;19:401-404**

## Malaria IFA TestAntibody Persistence

## Malaria IFA Results

| Patient #
  (infecting sp.) | P. vivax
Pos >1:16 | P. falciparum
Pos > 1:16 | P. malariae
Pos > 1:16
 | P. ovale
Pos > 1:16
 |
| --- | --- | --- | --- | --- |
| 1  (P. vivax,        non-immune) | 1:1024 | <1:16 | <1:16 | 1:16 |
| 2  (?, immune
          pattern) | 1:256 | 1:16,384 | 1:4096 | 1:4096 |
| 3  (?) | 1:64 | 1:256 | 1:256 | 1:256 |
| 4  (negative) | <1:16 | <1:16 | <1:16 | <1:16 |

## Sensitivity of Tools forDiagnosis of Malarial Infection

**Most sensitive:**
**	****	****  ****Antibody detection**
**2.****	****PCR**
**3.****	****Blood film examination**

## Diagnosis of  Untreated Acute Malaria

**Blood film examination**
**PCR**

## Diagnosis of  Treated Recent Malaria

**Serology**
**Blood film examination**
**PCR**

## Diagnosis of Chronic Malaria

**Screen with serology**
**If IFA positive:**
**May do blood film examination **
**May do PCR**