AHL LabNote 29-Summary of Influenza A virus testing

STEP 1

VIRUS DETECTION TESTING

ANTIBODY DETECTION TESTING

Test

Real-time PCR - matrix gene

ELISA, Multi-Screen

Agar gel immunodiffusion

Sample

Swabs in VTM (swine-nasal, birds-cloacal/tracheal), oral fluids, tissues

Serum

Use/advantage

Primary screening test targeting a conserved influenza virus gene.

Detects all common Influenza A virus subtypes in multiple animal species, very sensitive, fast.

Primary screening test, detects antibody from all common Influenza A virus subtypes in multiple animal species.

Screening test used for avian samples.

Disadvantage

Cannot determine the subtype of the virus.

Cannot determine the subtype of the virus to which animals were exposed. Cannot be used on paired samples to determine a 4-fold titer change/seroconversion.

STEP 2

VIRUS SUBTYPING

ANTIBODY SUBTYPING

Sample

PCR positive sample

Serum

Test

PCR typing for specific subtypes

Hemagglutinin gene sequencing

Hemagglutination inhibition test

(E.g., H1N1, H3N2, H3N8 – other subtypes may be available upon request)

Use/advantage

Swine: H1N1& H3N2

Turkeys: H5& H7, also H1N1& H3N2

All other avian species: H5 & H7

Simpler, faster than sequencing.

Covers all common

Influenza A virus subtypes.

Allows strain identification and comparison of various viruses.

Use on paired samples to determine a 4-fold titer change/seroconversion.

Disadvantage

Detects only H1N1, H3N2, H5 & H7 subtypes

Weak positives may not have enough virus for typing.

Weak positives may not have enough virus for typing.

Subtype/strain specific-depending on antigen used.

OTHER TESTS

Test

Immunohistochemistry

Sample

Formalin-fixed tissues

Use/advantage

Used on fixed tissues when fresh tissues are not available, or as a part of postmortem procedures. Detects all common Influenza A virus subtypes.

Disadvantage

Cannot determine the virus subtype.