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Wkly Epidemiol Rec. Antigenic and genetic characteristics of influenza A(H5N1) and influenza A(H9N2) viruses and candidate vaccine viruses developed for potential use in human vaccines ? February 2010
Antigenic and genetic characteristics of influenza A(H5N1) and influenza A(H9N2) viruses and candidate vaccine viruses developed for potential use in human vaccines ? February 2010 (Wkly Epidemiol Rec., edited)
[Source: World Health Organization, edited: LINK.]
Weekly epidemiological record - 12 march 2010, 85th year - No. 11, 2010, 85, 93?108
Antigenic and genetic characteristics of influenza A(H5N1) and influenza A(H9N2) viruses and candidate vaccine viruses developed for potential use in human vaccines ? February 2010
The development of representative A(H5N1) and A(H9N2) candidate influenza vaccine viruses, coordinated by WHO, remains an essential component of the overall global strategy for pandemic preparedness.
Comparisons of the candidate vaccine viruses with respect to their immunogenicity and their relationship to newly emerging viruses are ongoing, and the results will be updated periodically by WHO; a listing of continuing and completed clinical vaccine trials can be found at (LINK).
Influenza A(H5N1)
Since their re-emergence in 2003, influenza A(H5N1) viruses have become endemic in some countries, and they continue to cause outbreaks in poultry as well as sporadic human infections. The influenza A(H5N1) viruses have diversified both genetically and antigenically, leading to the need for multiple candidate vaccine viruses. Despite the emergence of pandemic influenza A(H1N1) 2009 virus, the zoonotic and pandemic threats posed by influenza A(H5N1) viruses remain. The following summary provides an update on the characterization of influenza A(H5N1) viruses isolated from birds and humans, and information on the status of the development of candidate influenza A(H5N1) vaccine viruses.
Influenza A(H5N1) activity, 23 September 2009?17 February 2010
Influenza A(H5N1) viruses continue to be detected in birds in Africa, Asia and the Middle East. Human infections have been reported to WHO from Cambodia, Egypt, Indonesia and Viet Nam: these countries have also declared outbreaks in birds (Table 1).
Antigenic and genetic characteristics
A nomenclature for phylogenetic relationships among the haemagglutinin (HA) genes of influenza A(H5N1) viruses was devised in consultation with representatives of the United Nations Food and Agriculture Organization, the World Organisation for Animal Health and WHO. This nomenclature is updated when novel genetic clades emerge; the nomenclature can be found at (LINK).
Viruses characterized from 23 September 2009 to 17 February 2010 belonged to the clades listed below.
Influenza A(H5N1) candidate vaccine viruses
Based on antigenic and epidemiological data, no new candidate influenza A(H5N1) vaccine viruses are proposed at this time. The available candidate influenza A(H5N1) vaccine viruses are listed in Table 3. On the basis of geographical spread, epidemiology, and antigenic and genetic properties of the influenza A(H5N1) viruses, national authorities may recommend the use of >1 of these for pilot-lot vaccine production, clinical trials and the subsequent stockpiling of vaccines.
Additional influenza A(H5N1) candidate vaccine viruses may be developed as the viruses evolve, and these candidates will be announced as they become available.
Institutions, companies and others interested in developing pandemic vaccines and that wish to receive candidate vaccine viruses should contact the WHO Global Influenza Programme at GISN@who.int or the institutions listed in announcements published at (LINK).
Influenza A(H9N2)
Influenza A(H9N2) viruses are endemic in poultry populations in parts of Asia and the Middle East. These viruses fall within a number of genetically defined HA lineages, with the majority of viruses belonging to the G1 and Y280 clades (Fig. 2). Since 1999 when the first human infection was detected, the isolation of influenza A(H9N2) viruses from humans and swine has been reported infrequently. In all human cases the associated disease symptoms have been mild, and there has been no evidence of human- to-human transmission.1
The following summary provides an update on the characterization of influenza A(H9N2) viruses isolated from humans and information on the status of the development of candidate influenza A(H9N2) vaccine viruses.
Human influenza A(H9N2) infection, 23 September 2009?17 February 2010
In 2009, 2 unrelated human infections with influenza A(H9N2) viruses were reported by Hong Kong SAR: 1 in October in an immunocompromised individual aged 47 years, and another in December in a 35-month-old child. Both had recently travelled to mainland China. These individuals presented with mild disease and both recovered.
Antigenic and genetic characteristics.
Genetically, the 2009 human isolates belong to the G1 lineage of influenza A(H9N2) viruses; they are closely related to each other (Fig. 2). Influenza A/Hong Kong/33982/2009 was antigenically characterized and reacted with postinfection ferret antiserum to influenza A/quail/Hong Kong/G1/97, although it had reduced reactivity to postinfection ferret antiserum to the available influenza A(H9N2) G1 lineage candidate vaccine virus A/Hong Kong/1073/99 (Table 4).
Influenza A(H9N2) candidate vaccine viruses
Candidate influenza A(H9N2) vaccine viruses are listed in Table 5. Based on antigenic and epidemiological data, the development of an influenza A/Hong Kong/33982/2009-like vaccine virus is proposed. On the basis of geographical spread, epidemiology, and antigenic and genetic properties of the influenza A(H9N2) viruses, national authorities may recommend the use of >1 of these for pilot-lot vaccine production, clinical trials and the subsequent stockpiling of vaccines.
Additional influenza A(H9N2) candidate vaccine viruses may be developed as the viruses evolve, and these candidates will be announced as they become available.
Institutions, companies and others interested in developing pandemic vaccines and that wish to receive candidate vaccine viruses should contact WHO?s Global Influenza Programme at GISN@who.int or the institutions listed in announcements published at (LINK).
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1 The World Organisation for Animal Health does not require notification of poultry infections with influenza A(H9N2) viruses.
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[Source: World Health Organization, edited: LINK.]
Weekly epidemiological record - 12 march 2010, 85th year - No. 11, 2010, 85, 93?108
Antigenic and genetic characteristics of influenza A(H5N1) and influenza A(H9N2) viruses and candidate vaccine viruses developed for potential use in human vaccines ? February 2010
The development of representative A(H5N1) and A(H9N2) candidate influenza vaccine viruses, coordinated by WHO, remains an essential component of the overall global strategy for pandemic preparedness.
Comparisons of the candidate vaccine viruses with respect to their immunogenicity and their relationship to newly emerging viruses are ongoing, and the results will be updated periodically by WHO; a listing of continuing and completed clinical vaccine trials can be found at (LINK).
Influenza A(H5N1)
Since their re-emergence in 2003, influenza A(H5N1) viruses have become endemic in some countries, and they continue to cause outbreaks in poultry as well as sporadic human infections. The influenza A(H5N1) viruses have diversified both genetically and antigenically, leading to the need for multiple candidate vaccine viruses. Despite the emergence of pandemic influenza A(H1N1) 2009 virus, the zoonotic and pandemic threats posed by influenza A(H5N1) viruses remain. The following summary provides an update on the characterization of influenza A(H5N1) viruses isolated from birds and humans, and information on the status of the development of candidate influenza A(H5N1) vaccine viruses.
Influenza A(H5N1) activity, 23 September 2009?17 February 2010
Influenza A(H5N1) viruses continue to be detected in birds in Africa, Asia and the Middle East. Human infections have been reported to WHO from Cambodia, Egypt, Indonesia and Viet Nam: these countries have also declared outbreaks in birds (Table 1).
Antigenic and genetic characteristics
A nomenclature for phylogenetic relationships among the haemagglutinin (HA) genes of influenza A(H5N1) viruses was devised in consultation with representatives of the United Nations Food and Agriculture Organization, the World Organisation for Animal Health and WHO. This nomenclature is updated when novel genetic clades emerge; the nomenclature can be found at (LINK).
Viruses characterized from 23 September 2009 to 17 February 2010 belonged to the clades listed below.
- Clade 1 viruses were detected in poultry in Cambodia. Genetic characterization of these viruses showed that they were closely related to clade 1 viruses previously circulating in the country (Fig. 1). No antigenic data are available.
- Clade 2.2 viruses were detected in poultry in Nepal. Genetically these viruses were very similar to viruses previously detected in the region (Fig. 1). No antigenic data are available.
- Clade 2.2.1 viruses continue to circulate in poultry in Egypt; there is sporadic transmission to humans. Viruses isolated during this period were genetically similar to those isolated during 2008 and 2009 (Fig. 1). Data are not available on the antigenic properties of the recent poultry viruses, but isolates from humans are antigenically similar to the clade 2.2.1 reference vaccine virus A/Egypt/321/2007 (Table 2) as measured by haemagglutination inhibition.
- Clade 2.3.2 viruses were detected in wild birds in China, Hong Kong Special Administrative Region (Hong Kong SAR); in the Russian Federation; and in poultry in Nepal and Viet Nam. These viruses were genetically similar to clade 2.3.2 viruses isolated in previous years (Fig. 1). Antigenically, the virus from Hong Kong SAR reacted to antiserum to the clade 2.3.2 reference vaccine virus A/Common Magpie/Hong Kong/5052/2007, albeit with reduced haemagglutination inhibition titres when compared with the homologous antigen (data not shown).
- Clade 2.3.4 viruses were detected in poultry in Viet Nam. These viruses formed 2 distinct genetic subclades within the 2.3.4 clade (Fig. 1). Viruses from 1 of these subclades reacted well to postinfection ferret antiserum raised against the reference vaccine virus A/Anhui/1/2005 (data not shown); antigenic data are not available for the other subclade.
Influenza A(H5N1) candidate vaccine viruses
Based on antigenic and epidemiological data, no new candidate influenza A(H5N1) vaccine viruses are proposed at this time. The available candidate influenza A(H5N1) vaccine viruses are listed in Table 3. On the basis of geographical spread, epidemiology, and antigenic and genetic properties of the influenza A(H5N1) viruses, national authorities may recommend the use of >1 of these for pilot-lot vaccine production, clinical trials and the subsequent stockpiling of vaccines.
Additional influenza A(H5N1) candidate vaccine viruses may be developed as the viruses evolve, and these candidates will be announced as they become available.
Institutions, companies and others interested in developing pandemic vaccines and that wish to receive candidate vaccine viruses should contact the WHO Global Influenza Programme at GISN@who.int or the institutions listed in announcements published at (LINK).
Influenza A(H9N2)
Influenza A(H9N2) viruses are endemic in poultry populations in parts of Asia and the Middle East. These viruses fall within a number of genetically defined HA lineages, with the majority of viruses belonging to the G1 and Y280 clades (Fig. 2). Since 1999 when the first human infection was detected, the isolation of influenza A(H9N2) viruses from humans and swine has been reported infrequently. In all human cases the associated disease symptoms have been mild, and there has been no evidence of human- to-human transmission.1
The following summary provides an update on the characterization of influenza A(H9N2) viruses isolated from humans and information on the status of the development of candidate influenza A(H9N2) vaccine viruses.
Human influenza A(H9N2) infection, 23 September 2009?17 February 2010
In 2009, 2 unrelated human infections with influenza A(H9N2) viruses were reported by Hong Kong SAR: 1 in October in an immunocompromised individual aged 47 years, and another in December in a 35-month-old child. Both had recently travelled to mainland China. These individuals presented with mild disease and both recovered.
Antigenic and genetic characteristics.
Genetically, the 2009 human isolates belong to the G1 lineage of influenza A(H9N2) viruses; they are closely related to each other (Fig. 2). Influenza A/Hong Kong/33982/2009 was antigenically characterized and reacted with postinfection ferret antiserum to influenza A/quail/Hong Kong/G1/97, although it had reduced reactivity to postinfection ferret antiserum to the available influenza A(H9N2) G1 lineage candidate vaccine virus A/Hong Kong/1073/99 (Table 4).
Influenza A(H9N2) candidate vaccine viruses
Candidate influenza A(H9N2) vaccine viruses are listed in Table 5. Based on antigenic and epidemiological data, the development of an influenza A/Hong Kong/33982/2009-like vaccine virus is proposed. On the basis of geographical spread, epidemiology, and antigenic and genetic properties of the influenza A(H9N2) viruses, national authorities may recommend the use of >1 of these for pilot-lot vaccine production, clinical trials and the subsequent stockpiling of vaccines.
Additional influenza A(H9N2) candidate vaccine viruses may be developed as the viruses evolve, and these candidates will be announced as they become available.
Institutions, companies and others interested in developing pandemic vaccines and that wish to receive candidate vaccine viruses should contact WHO?s Global Influenza Programme at GISN@who.int or the institutions listed in announcements published at (LINK).
-
-
1 The World Organisation for Animal Health does not require notification of poultry infections with influenza A(H9N2) viruses.
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