Antibodies to streptococcal opacity factor in a selected Indian population

Area of Science:

• Immunology
• Microbiology
• Epidemiology

Background:

• Group A Streptococcus (GAS) infections are linked to significant sequelae like rheumatic fever and acute glomerulonephritis.
• Streptococcal opacity factor (OF) is a virulence factor produced by certain GAS strains.
• Antibodies to OF can serve as potential markers for GAS exposure and related diseases.

Purpose of the Study:

• To investigate the prevalence of antibodies to various types of streptococcal opacity factor (OF) in a selected population.
• To determine the association between specific OF antibody types and clinical conditions such as rheumatic fever and acute glomerulonephritis.
• To evaluate the utility of the OF-inhibition test as an epidemiological tool for tracking prevalent GAS M-serotypes.

Main Methods:

• Serological testing using the OF-inhibition test was performed on 235 selected subjects.
• Antibody prevalence was analyzed across different age groups and in patients with specific streptococcal-related diseases.
• The frequency of antibodies against different OF M-serotypes was determined and ranked.

Main Results:

• Antibodies to at least one OF type were found in 39.0% of subjects, with 47.8% having antibodies to multiple types.
• Prevalence of OF antibodies was lower in children under 4 years old (21.6%).
• Common antibodies targeted OF from M-serotypes 25, 4, 22, 2, and 9. Rheumatic disease patients frequently had antibodies to OF from M-types 25, 22, 4, and 9, while acute glomerulonephritis patients showed antibodies to OF from M-types 48, 49, and 61.

Conclusions:

• Antibodies to streptococcal opacity factor are prevalent in the studied population, with varying specificities.
• Distinct patterns of OF antibodies are associated with rheumatic fever/rheumatic heart disease and acute glomerulonephritis.
• The OF-inhibition test shows potential as an epidemiological marker for GAS, though its limitations require consideration.